Climate Neutrality Strategies for the Chemical Industry Using a Novel Carbon Boundary: An Austrian Case Study

Abstract

The chemical industry is a key driver of economic growth and innovation but remains one of the largest contributors to greenhouse gas (GHG) emissions. Achieving sustainability demands advancements in green chemistry and cleaner production methods. This study investigates emission reduction strategies across Scope 1, Scope 2, and Scope 3 by applying both top-down and bottom-up approaches within four system boundaries. The Austrian chemical sector, with a focus on ammonia, methanol, and olefins, serves as a case study. Results highlight the potential of abatement technologies and alternative feedstocks—such as low-carbon hydrogen and methanol—to significantly reduce emissions. Hydrogen-based production for ammonia and methanol, along with low-carbon methanol in olefin production, could reduce Scope 1 and Scope 2 emissions by approximately 80% compared to conventional methods. However, Scope 3 emissions remain challenging due to embedded carbon in feedstocks and CO₂ use in production, particularly in product use and end-of-life phases. A comprehensive life cycle assessment is crucial to addressing these impacts. To evaluate Scope 3 emissions, this study explores three decarbonization scenarios: the reference scenario—relies on fossil-based production with high emissions; the geogenic scenario—integrates abatement technologies and geogenic CO₂ feedstock, reducing emissions by about 46%; and the bio-based scenario—combines abatement technologies with biogenic CO₂ feedstock, achieving an 80% reduction in total emissions at the national level. The findings emphasize the need for a system-wide approach that integrates bio-based solutions and circular economy strategies to achieve climate neutrality. However, uncertainties in climate policy, bio-resource availability, and data gaps in Scope 3 emissions must be addressed to ensure effective decarbonization and alignment with climate goals.

1. Introduction

The energy transition and emission reduction in the chemical industry are among the top global priorities in addressing climate change. As a significant energy-intensive sector, the chemical industry accounts for approximately 30% of global industrial energy consumption [1]. Its primary energy sources—oil and natural gas (NG)—serve both as energy carriers and as a feedstock for chemical production. Due to its heavy reliance on fossil fuels, the chemical industry is a major contributor to greenhouse gas (GHG) emissions, responsible for about 10% of global carbon dioxide (CO₂) emissions and 14.5% of direct industrial emissions. This makes the chemical industry the third-largest source of industrial pollutant emissions, following the iron and steel and cement subsectors [2].

Reducing emissions in the chemical industry—an essential pillar of global manufacturing and a key supplier of critical materials across multiple sectors—has gained increasing attention in recent years. This growing focus is primarily driven by the urgent need to mitigate environmental impacts and accelerate the transition toward more sustainable products and processes. Numerous studies have explored emission reduction strategies in the chemical sector, addressing the associated challenges, opportunities, and both technical and economic considerations [3,4,5,6,7,8]. At the international level, the International Energy Agency (IEA) [1,2] has published reports evaluating technological mitigation options for key primary chemicals, including ammonia, methanol, and high-value chemicals (HVCs) or olefins. These reports examine various future scenarios—including stated policies and sustainable development pathways—covering the period from 2019 to 2070. Through these analyses, the IEA assesses potential strategies for reducing emissions in the chemical industry and underscores the role of technological advancements in achieving long-term sustainability goals.

At the European Union (EU) level, several comprehensive reports have been published which outline technological solutions for reducing emissions in the European chemical industry. The Joint Research Center (JRC) has analyzed the potential energy saving and GHG emission reductions achievable through cost-effective technological improvements in the chemical and petrochemical industries by 2050, considering approximately 50 of the best available technologies (BAT) and cross-cutting technologies [9]. The European Chemical Industry Council (Cefic) and Ecofy have also introduced a roadmap to assess the impacts, opportunities, and risks of various energy and technology development scenarios for the European chemical industry from 2020 to 2050 [10]. Additionally, a study by Dechema examined innovative technologies that could enable the European chemical sector to reduce CO₂ emissions [11]. This study quantitatively assessed future low-carbon technologies, evaluated their potential to lower CO₂ emissions, and identified existing technological and financial barriers.

Table 1. Technological options for the emission reduction in the chemical industry.

Category	Technology	Description	Emission Scope	Emission Reduction Impact	Max Emission Reduction (%)	References
Energy Efficiency and Process Optimization	Process Integration and Heat Recovery	Reuses waste heat to improve energy efficiency.	Scope 1 and 2	Low	5–15%	[9,10]
	Catalytic Process Improvements	Enhances catalysts to increase yield, reducing emissions.	Scope 1	Low	10–20%	[12,13]
Carbon Capture and Utilization (CCU)	Post-Combustion Carbon Capture	Captures CO2 from flue gases for storage or reuse.	Scope 1	High	85–95%	[9,14,15,16]
	Carbon Utilization (CO2 to Chemicals)	Converts CO2 into useful chemicals or fuels.	Scope 1 and 3	High	40–70%	[9,14,15,16]
Alternative Feedstocks and Green Chemistry	Biomass-Based Feedstocks (Biochemicals)	Uses renewable feedstocks instead of fossil fuels.	Scope 1 &3	Moderate/High	30–85%	[10,11,15,17]
	Renewable	Use of green hydrogen produced via electrolysis with renewable energy.	Scope 1 and 2	High	70–90%	[11,18,19]
	Hydrogen
	Solvent Substitution	Replaces high-emission solvents with green alternatives.	Scope 1 and 3	Low/Moderate	10–25%	[20,21]
Electrification	Electrification of Processes	Replace fossil fuel-based heating with electricity.	Scope 1 and 2	Moderate	15–35%	[3,22]
Circular Economy and Waste Reduction	Chemical Recycling and Waste Valorization	Convert plastic and chemical waste into new raw materials.	Scope 3	High	50–80%	[10,23,24,25]
	Industrial Symbiosis	Shares energy and materials between industries.	Scope 1 and 3	Moderate	---	[26,27]

Emission reduction effect: Low < 20%, 20% < Moderate < 60%, High > 60%.

provides an overview of the key technologies discussed in the literature, categorized into five distinct groups.

Traditionally, emission reduction efforts within the chemical industry, as illustrated in Table 1, have primarily focused on Scope 1 emissions—those generated from direct operations, including on-site energy use and chemical processes—and Scope 2 emissions, which encompass indirect emissions from purchased electricity and heat. In contrast, Scope 3 emissions—accounting for approximately two-thirds of the chemical industry’s carbon footprint [28] and resulting from activities across the entire value chain, both upstream and downstream—have often been overlooked in current emission reduction strategies.

Certain chemical products are inherently dependent on carbon, either directly or indirectly. For example, CO₂ is used directly as a feedstock in urea production, whereas naphtha—the primary raw material for olefin production—contains carbon that is indirectly embedded in the final product. This carbon remains stored within the material temporarily but is ultimately released back into the atmosphere as CO₂ when the material is treated, processed, or used in other sectors such as agriculture, transportation, and energy.

These emissions represent an additional source of CO₂ within the chemical product value chain that is not accounted for in Scope 1 and Scope 2 reporting. Such emissions fall under Scope 3, as they originate from activities beyond the company’s system boundaries. Specifically, Scope 3 emissions are associated with upstream processes, such as raw material production and transportation, and downstream activities, including the use phase and end-of-life disposal of chemical products in other sectors.

The CO₂ used as a feedstock for direct incorporation into chemical products is primarily derived from the gasification of fossil fuels—such as in methanol production—or as a byproduct of fossil-based processes, such as steam reforming in ammonia production for urea synthesis. However, with the ongoing implementation of emission reduction strategies in the chemical industry and the progressive shift from fossil-based materials to low-carbon alternatives, the demand for CO₂ as a feedstock is expected to increase significantly. This transition will likely require sourcing CO₂ from external resources, including carbon capture and utilization (CCU) from other industrial processes, bio-based resources, or direct air capture (DAC).

As these transformations take place, the evaluation and management of CO₂ emissions categorized under Scope 3 will become increasingly critical in the industry’s decarbonization efforts. Upstream and downstream emissions contribute significantly to the industry’s overall carbon footprint. Addressing these emissions will be essential for developing comprehensive and effective decarbonization strategies in the future.

A comprehensive assessment of the total emissions across the chemical industry’s value chain, with a particular emphasis on Scope 3 emissions, remains a relatively underexplored area of research. The role of embedded carbon in chemical products and its impact on the entire value chain has received limited attention in existing studies. In particular, the influence of different CO₂ feedstock sources—including fossil-based, biogenic, and captured CO₂—on the industry’s overall carbon footprint remains insufficiently examined in the literature. This gap highlights the need for further research to better understand and quantify the environmental implications of various feedstock choices within the context of industrial decarbonization.

To address this knowledge gap, the present study proposes a comprehensive framework for assessing CO₂ emissions across the entire chemical value chain by adopting an expanded carbon system boundary. This framework considers both direct and indirect emissions under Scope 1 and Scope 2 while also incorporating the impact of embedded carbon and the utilization of CO₂ as a feedstock within Scope 3 emissions. Integrating these components provides a holistic approach to evaluating and mitigating emissions across the entire value chain of the chemical industry.

This research underscores the critical need for a systematic assessment of emissions at every stage of the chemical production cycle. Such a comprehensive approach is essential for identifying emission reduction opportunities and developing effective strategies to advance climate neutrality.

This research examines the Austrian chemical industry as a case study to examine key aspects of emission reduction and sustainability. The study evaluates the potential for emission reductions by analyzing the current and projected status of production processes and primary material consumption within the sector. A significant focus is placed on assessing the sustainability implications of different CO₂ feedstock sources—fossil-based, biogenic, or captured—within a nationwide system boundary.

Through this comprehensive analysis, the study aims to clarify how various CO₂ sources contribute to the chemical industry’s overall carbon footprint. It offers valuable insights into pathways toward climate-neutral chemical production at the national level. The findings are intended to serve as a foundational reference for discussions on the transformation and decarbonization of the Austrian chemical industry, supporting informed decision-making and policy development.

Objective and Structure

This paper outlines the following objectives to address the bottlenecks mentioned in the introduction, which have received limited attention in previous studies:

• Identifying key technologies crucial for reducing emissions and transitioning primary chemicals to low-carbon products.
• Adjusting the carbon boundary for the chemical industry and evaluating emission reduction throughout the chemical commodity value chain—from production to consumption and end-of-life—with a special focus on downstream Scope 3 emissions.
• Clarifying the role of cross-sectoral approaches and lifecycle assessments in achieving climate neutrality by addressing emissions beyond the chemical industry’s system boundaries.
• Analyzing the impact of CO₂ feedstock sources—fossil, geogenic, or biogenic—for chemical products on national-level emissions within an extended system boundary.

To achieve these goals, the analysis in this study relies on the system boundary shown in Figure 1, which serves as the foundation for evaluating the impact of emission reductions across the entire energy system. Based on a bottom-up approach, four system boundaries are defined to address the complexity of calculating CO₂ emissions and tracking the CO₂ flows within the chemical industry. These boundaries aim to consider various factors, such as CO₂ used as a feedstock, dependence on fossil-based feedstocks, and carbon-embedded products. These defined system boundaries facilitate a better understanding of the intricacies of tracking and measuring CO₂ emissions in chemical industry processes.

The first system boundary analyzes four major chemical industry products—ammonia, urea, methanol, and olefins—individually examining each in terms of energy consumption, CO₂ emissions, and potential technologies and alternatives for reducing emissions specific to these products.

The second system boundary evaluates the chemical industry’s conventional production processes and those utilizing decarbonization technologies. This boundary investigates the impact of applying alternative decarbonization methods to specific products on the chemical industry’s emission and energy intensity indicators.

The third system boundary is designed to account for the emission flows across industrial subsectors. In the subsequent sections, this paper presents scenarios to demonstrate the CO₂ recycling and utilization approach. According to these scenarios, CO₂ emissions from other industrial subsectors, such as cement or paper manufacturing, can be repurposed as a feedstock for chemical industry products like urea or methanol. CO₂ recycling or utilization represent a promising strategy for reducing the overall carbon intensity of the industrial sector, and this impact is assessed within the third system boundary.

While CO₂ recycling and utilization reduce the carbon intensity of the industrial sector (as considered in system boundary 3), the CO₂ is typically re-released when chemical products are used, decomposed, or incinerated. For example, urea fertilizer decomposes in agriculture, and methanol is burned as fuel in the transportation or energy sector. Therefore, this study traces the carbon flow from material production to the end of the product’s life cycle during the consumption phase across all sectors, as outlined in system boundary 4.

This approach encompasses emissions from all life cycle stages and ensures that no emissions related to chemical industry products are overlooked or double-counted at the national level.

Based on the preceding strategy, this paper is structured as follows: Section 2 provides a detailed description of the methodology used in this study. Section 3 outlines the existing manufacturing processes for selected chemicals and explores potential future alternatives for reducing emissions in their production. Section 4 analyzes the current state of the Austrian chemical industry, presenting an energy flow diagram and associated emissions. Section 5 examines the implications of adopting various emission reduction technologies and alternative feedstocks within the chemical industry’s system boundary. This section extends the analysis to assess the impact of different CO₂ feedstock sources beyond the chemical industry’s system boundary at the national level using three defined scenarios. Finally, Section 6 concludes the paper by summarizing the key findings for achieving climate-neutral chemicals.

2. Methodology

This section outlines the methodology employed to structure the essay, which focuses on analyzing the chemical industry’s efforts to achieve climate neutrality.

Given the sector’s diversity and complexity, a top-down approach has been adopted as an initial step to identify the fundamental chemical building blocks for this study. Based on data from both open and classified sources provided by industry experts and the scientific community at both the global level and in Austria, ammonia (and urea), methanol, and high-value chemicals (HVCs) or olefins (including ethylene and propylene) collectively represent the primary energy consumers and CO₂ emitters within the chemical industry [29,30,31]. These products are referred to as “basic chemicals” in this study.

The second step employs a bottom-up approach to evaluate the previously identified basic chemicals. The first key performance indicator (KPI) used for this evaluation is energy intensity, represented by Specific Energy Consumption (SEC, MWh/t product), as shown in Equation (1). Therefore, determining the total energy consumption (TWh), as outlined in Equation (2), is essential. The total energy consumption for the chemical industry includes both final energy use (TWh) and final non-energy use (TWh). Final energy refers to the quantity of energy required to operate machinery such as compressors, pumps, and reformers, including fossil fuels, electricity, and heat [32]. In contrast, final non-energy use, which is more significant for the chemical sector, refers to energy used as a feedstock, not as an energy source, and is calculated based on the energy equivalent of feedstock. Examples include naphtha for olefin production and natural gas for ammonia production [32].

$$\mathrm{S}\mathrm{E}\mathrm{C}={\displaystyle \frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l} \mathrm{E}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y} \mathrm{C}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{u}\mathrm{m}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n} \mathrm{i}\mathrm{n} {\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}}_{\mathrm{x}} \left[\mathrm{M}\mathrm{W}\mathrm{h}\right]}{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l} \mathrm{p}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t} \mathrm{i}\mathrm{n} {\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}}_{\mathrm{x}} \left[\mathrm{t}\right]}}$$

(1)

$$\begin{array}{l}\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l} \mathrm{E}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y} \mathrm{C}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{u}\mathrm{m}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\left[\mathrm{T}\mathrm{W}\mathrm{h}\right]\\ \hspace{1em}\hspace{1em} \hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}=\mathrm{F}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l} \mathrm{E}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y}\left[\mathrm{T}\mathrm{W}\mathrm{h}\right]+\mathrm{F}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l} \mathrm{N}\mathrm{o}\mathrm{n}-\mathrm{E}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y} \left[\mathrm{T}\mathrm{W}\mathrm{h}\right]\end{array}$$

(2)

The second KPI used to evaluate chemical products is Specific Carbon Emission (SCE, ${\displaystyle \frac{\mathrm{t} {\mathrm{C}\mathrm{O}}_2}{\mathrm{t} \mathrm{p}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}}}$), as shown in Equation (3). While measuring and tracking pollutants and GHGs released during chemical production is crucial for accurately assessing and managing the environmental impact, the complexity of these processes poses significant challenges.

$$\mathrm{S}\mathrm{C}\mathrm{E}={\displaystyle \frac{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l} {\mathrm{C}\mathrm{O}}_2 \mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n} \mathrm{i}\mathrm{n} {\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}}_{\mathrm{x}} \left[\mathrm{t}\right]}{\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l} \mathrm{p}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t} \mathrm{i}\mathrm{n} {\mathrm{y}\mathrm{e}\mathrm{a}\mathrm{r}}_{\mathrm{x}} \left[\mathrm{t}\right]}}$$

(3)

This study employs a holistic carbon footprint framework to calculate total emissions, accounting for all emissions across each stage of the chemical products’ value chain by considering three scopes of emissions based on GHG Protocol guidelines [33], as shown in Equation (4).

$$\begin{array}{l}\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l} {\mathrm{C}\mathrm{O}}_2 \mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}\left[\mathrm{K}\mathrm{t}\right]\\ \hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}=\mathrm{S}\mathrm{c}\mathrm{o}\mathrm{p}\mathrm{e} 1\left(\mathrm{d}\mathrm{i}\mathrm{r}\mathrm{e}\mathrm{c}\mathrm{t} \mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}, \mathrm{f}\mathrm{u}\mathrm{e}\mathrm{l} \mathrm{a}\mathrm{n}\mathrm{d} \mathrm{p}\mathrm{r}\mathrm{o}\mathrm{c}\mathrm{e}\mathrm{s}\mathrm{s}-\mathrm{r}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{d}\right)\\ \hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}+ \mathrm{S}\mathrm{c}\mathrm{o}\mathrm{p}\mathrm{e} 2\left(\mathrm{i}\mathrm{n}\mathrm{d}\mathrm{i}\mathrm{r}\mathrm{e}\mathrm{c}\mathrm{t} \mathrm{e}\mathrm{m}\mathrm{i}\mathrm{s}\mathrm{s}\mathrm{i}\mathrm{o}\mathrm{n}, \mathrm{E}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{r}\mathrm{i}\mathrm{c}\mathrm{i}\mathrm{t}\mathrm{y}-\mathrm{r}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{d}\right)\\ \hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}\hspace{1em}+ \mathrm{S}\mathrm{c}\mathrm{o}\mathrm{p}\mathrm{e} 3 \left(\mathrm{U}\mathrm{p}\mathrm{s}\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{a}\mathrm{m}\right)+\mathrm{S}\mathrm{c}\mathrm{o}\mathrm{p}\mathrm{e} 3\left(\mathrm{D}\mathrm{o}\mathrm{w}\mathrm{n}\mathrm{s}\mathrm{t}\mathrm{r}\mathrm{e}\mathrm{a}\mathrm{m}\right)\end{array}$$

(4)

Scope 1 emissions encompass those arising from direct fuel consumption as final energy and emissions generated during chemical reactions in production processes, such as NG reforming for ammonia production. Emissions from fuel consumption are calculated using the specific fuel type and its corresponding emission factor, which varies depending on the type of fuel used (e.g., NG, coal, or oil). Additionally, process-related emissions are determined based on established reference values for each chemical process.

Scope 2 accounts for indirect emissions from purchased energy, such as electricity or heat from external sources. The electricity emission factor used in this study is based on the latest European grid emission factor, which is 0.210 t CO₂/MWh for the base year 2023 [34]. Since electricity consumption in Austria is influenced by multiple factors, including national and international energy market policies, energy imports, and the availability of low-carbon electricity, the projected carbon footprint for electricity generation in the future is estimated at 0.019 t CO₂/MWh, according to the European electricity mix scenario for 2050 [35]. In future scenarios, Scope 2 also includes emissions from energy production for electricity-driven processes, such as hydrogen production through electrolysis for ammonia or methane synthesis.

Scope 3 encompasses all emissions from upstream and downstream activities (see Figure 2). In the chemical industry, approximately two-thirds of emissions fall under Scope 3 [28]. Unlike other industrial subsectors, where emission calculations are more straightforward and primarily focus on Scope 1 and 2 emissions, Scope 3 emissions play a critical role in the chemical industry. As illustrated in Figure 2, Scope 3 emissions encompass fifteen categories. This paper focuses on three key categories of emissions within the chemical industry’s value chain: purchased goods and services in upstream processes, the use of sold products, and the end-of-life treatment of sold products in downstream processes.

The chemical industry predominantly relies on fossil-based feedstocks, such as naphtha for olefins and natural gas for methanol. Emissions associated with the production of these feedstocks, classified as “purchased goods and services”, fall under Scope 3 upstream emissions. These feedstocks also contain bound carbon, which remains stored in end products. This embedded carbon is retained within the end products until their eventual incineration or other end-of-life treatments. As a result, additional CO₂ emissions are accounted for under Scope 3 downstream emissions, particularly within the categories of “End-of-Life Treatment of Sold Products” and “Use of Sold Products”. In this study, these downstream emissions are specifically analyzed for urea, olefins, and methanol.

Crucial factors that influence Scope 3 downstream emissions include the use of fossil resources for non-energy applications, the lifespan of the end products, and the recycling rates of materials—especially plastics—at their end-of-life stage. These elements are essential for accurately determining the chemical industry’s carbon footprint and identifying key opportunities to reduce emissions across the entire value chain.

The role of CO₂ used as a feedstock becomes increasingly important in future strategies, primarily as low-emission approaches are implemented for ammonia, urea, and methanol production. This study examines how different sources of CO₂—whether derived from fossil fuels, biogenic sources, direct air capture (DAC), or carbon recycling approaches—affect the overall carbon footprint. By focusing on the national level within system boundary 4, the analysis evaluates the impact of these CO₂ sources for the chemical products on the national emissions. This forward-looking approach highlights the importance of CO₂ feedstock selection in moving the industry toward climate neutrality.

In Step 3, emission reduction technologies are assessed for each basic chemical, and the key technologies contributing to climate neutrality are selected. Three indicators are used to determine the most relevant technologies: emission reduction potential, energy-saving potential, and technological readiness level (TRL). Finally, in Step 4, the impact of implementing low-carbon technologies and alternatives is examined in terms of SEC and SCE under the defined scenarios. The results are presented for each system boundary, with a particular focus on Austria as a case study.

3. Chemical Industry

3.1. Structure of the Chemical Industry

The chemical and petrochemical industry has traditionally been a fundamental component of the global economy. According to the NACE classification, this sector is divided into two main categories: the first category (NACE 20.1) includes the production of basic organic and inorganic chemicals, fertilizers, and nitrogen compounds, as well as plastics and rubber in primary forms. The second category (NACE 21.2) includes the manufacturing of pharmaceuticals and medicinal chemicals and botanical products, which contribute approximately 45% and 30% of the sector’s added value in Europe, respectively [36,37]. Additionally, the industry comprises the production of pesticides, agrochemicals, paints, coatings, soaps, detergents, cleaning and polishing agents, synthetic fibers, and other related products [37]. This wide range of products and processes, as well as the non-energetic use of fossil fuels in chemical production, makes this sector one of the most diverse and complex industrial subsectors.

The chemical industry is the world’s largest industrial energy consumer, accounting for approximately 30% of total industrial energy use. The aforementioned basic chemicals, including ammonia, methanol, and olefins, are particularly energy-intensive products and account for about two-thirds of the total energy consumption of the chemical industry globally [1].

According to the European Environment Agency (EEA) [38], CEFIC [26], and IEA [1] reports, the chemical industry is responsible for approximately 16% of direct industrial emissions both in Europe and globally [39]. Among these emissions, around 60% are attributed to the production of basic chemicals, mainly due to energy-intensive processes such as steam reforming and steam cracking, which are essential for the production of ammonia and olefins, respectively [38,40]. Consequently, this study focuses primarily on these major chemical building blocks, examining potential emission reduction pathways in more detail.

3.2. Ammonia and Urea

3.2.1. Current Production Process

Ammonia (NH₃) production is a crucial sub-process within the chemical industry, acting as the starting material for the manufacturing of all nitrogen-based fertilizers [9,13]. Approximately 70% of ammonia production is dedicated to meeting the increasing agricultural demand driven by population growth [41]. According to the IEA Stated Policies Scenario, this demand is projected to increase by almost 40% by 2050 [42].

The remaining NH₃ production is used in various industrial applications, such as plastics, explosives, and synthetic fibers [42]. Within the context of transitioning to clean energy, the potential for using NH₃ as a fuel source is promising [41,42]. However, it should be noted that this application is still at an early stage and is not addressed in this paper.

The synthesis of NH₃ requires large amounts of hydrogen. At present, hydrogen production is highly reliant on fossil fuels derived from heavy oil and coal via partial oxidation or from natural gas via the Steam Methane Reforming (SMR) processes [43,44]. In the EU, over 90% of hydrogen is produced from NG by steam reforming [9].

This process consumes approximately 7.8 to 9.7 MWh of NG per ton of NH₃, of which 5.8 to 6.9 MWh/t NH₃ is used as a feedstock for the reaction with steam (H₂O) to produce hydrogen. The remaining energy is used to heat the steam from 400 to 500 °C [11]. The SMR process releases CO and CO₂ as by-products, resulting in Scope 1 emissions of 1.8 tons of CO₂ per ton of NH₃. Of this total, 1.3 tons of CO₂ result from process-related emissions, while 0.5 tons are associated with energy-related emissions [11] (see Figure 3).

In the next step, hydrogen reacts with nitrogen, which is extracted from the atmosphere using air separation units, through the ammonia synthesis process via the Haber–Bosch method to produce ammonia (Equation (5)). This process requires approximately 0.205 MWh of electricity per ton of NH₃, leading to Scope 2 electricity-related emissions. On a global scale, the specific CO₂ emissions from ammonia production are approximately 2.4 tons of CO₂ per ton of NH₃, including both Scope 1 and Scope 2 emissions. This emission intensity is nearly double that of the direct emissions from crude steel (CS) production (1.4 tons of CO₂ per ton of CS) and four times that of cement production (0.6 tons of CO₂ per ton of cement) [42].

$${\mathrm{N}}_2+3{\mathrm{H}}_2\leftrightarrow 2{\mathrm{N}\mathrm{H}}_3\hspace{1em}\hspace{1em}∆{\mathrm{H}}_{298\mathrm{K}}^{°}=-92.28\mathrm{k}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}$$

(5)

In conventional ammonia production using SMR, Scope 3 emissions also arise from upstream and downstream activities. Upstream emissions are generated during the extraction and processing of NG, which serves as the critical feedstock for SMR. These emissions primarily result from methane leaks during NG extraction, along with carbon dioxide emissions from other parts of the feedstock supply chain, such as the transportation of feedstock to the ammonia production unit. The total upstream emissions vary significantly, ranging from 0.19 to 2.40 tons of CO₂eq per ton of NH₃ [19], with an average of approx. 0.63 tons of CO₂eq per ton of NH₃ [45].

The Scope 3 downstream emissions from NH₃ production are mostly associated with its use in various applications, including fertilizers, explosives, plastics, and other chemicals. Estimating these emissions depends on how the NH₃ is used after production. The most significant downstream emissions are associated with fertilizer use, which consumes about 70–80% of total ammonia production, especially for urea [42]. Emissions in this category are highly variable but significant, mainly due to the chemical processes involved in fertilizer application and interactions with the soil.

Urea production accounts for 55% of global ammonia consumption [41]. The urea synthesis process requires ammonia (0.57 t NH₃t Urea) and CO₂ (0.73 t CO₂t Urea) as raw materials [9,11]. These substances react under high temperature and pressure to form urea (Equations (6) and (7)). Urea production is typically integrated with ammonia production plants. As a result, the CO₂ generated from ammonia production, particularly from the SMR process, which yields pure CO₂, is directly utilized in urea production plants [41].

$${2{\mathrm{N}\mathrm{H}}_3+\mathrm{C}\mathrm{O}}_2\leftrightarrow \mathrm{N}{\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{N}{\mathrm{H}}_4$$

(6)

$$\mathrm{N}{\mathrm{H}}_2\mathrm{C}\mathrm{O}\mathrm{O}\mathrm{N}{\mathrm{H}}_4\leftrightarrow {\left(\mathrm{N}{\mathrm{H}}_2\right)}_2\mathrm{C}\mathrm{O}+{\mathrm{H}}_2\mathrm{O}$$

(7)

Estimating the energy requirements for urea production poses a challenge due to the interconnected nature of the urea and ammonia processes [11]. In an integrated plant, approximately 0.91 MWh of steam—sourced from excess steam generated by ammonia plants—and 58 kWh of electricity are needed to produce one ton of urea [9,11]. Conversely, in a stand-alone urea production facility, the energy demand and carbon footprint of the ammonia required as the feedstock must be taken into account [11].

Regarding CO₂ emissions, process- and electricity-related emissions from urea production range from 0.3 to 0.47 tons of CO₂ per ton of urea [9]. On the other hand, as previously mentioned, urea production consumes 0.73 tons of CO₂ per ton of urea as a raw material, which is stored within the urea and can contribute to reducing overall emissions in the chemical industry. However, when fertilizers are applied in agriculture, direct CO₂ and nitrous oxide (N₂O) emissions are released into the atmosphere. The estimated emissions during the use phase account for more than 70% of the total life cycle GHG emissions of nitrogen fertilizers [42].

3.2.2. Emission Reduction Technology

In recent years, ammonia plants, particularly those in the EU, have improved their energy efficiency, reducing the SEC to 8.9 MWht NH3 [10]. Continuing this trend through measures such as optimizing waste heat recovery systems and upgrading energy monitoring and management systems could further reduce the SEC to a benchmark of 7.8 MWht NH3 [10].

While enhancing the performance of existing equipment is essential, it may not be sufficient on its own to achieve the necessary emissions reduction. Additional measures and strategies will likely be needed to meet emission-reduction targets effectively.

According to the recent literature, the most critical methods for low-emission ammonia production include continuing fossil-based routes such as SMR with NG integrated with CCS/CCU technologies, methane pyrolysis, and water electrolysis to produce the hydrogen required for ammonia synthesis (Other technologies for low-emission ammonia production also exist, including SMR, biological enzyme processes, low-temperature catalytic synthesis, etc. However, as these technologies currently have a TRL of less than 4, they require significant further development before they can be considered commercially viable. For this reason, they are not included in the scope of the technologies discussed in this paper) [42].

In the fossil-based approach, the use of NG will continue, supplemented by the integration of CCS/CCU technologies [46]. This approach allows for the effective capture of CO₂ emissions generated during the SMR process, which are classified as Scope 1 (process-related) emissions. Captured CO₂ can then be partially utilized in other processes, such as urea production [18], or redirected to applications, including enhanced oil recovery or methanol production [41]. Fossil-based ammonia production combined with CCS remains a viable option in regions where natural gas prices are relatively low, including North Africa, North America, and the Middle East [41].

In this technological framework, replacing fossil fuels with bioenergy as an energy source can also help reduce Scope 1 energy-related emissions [18]. However, despite the economic and technical challenges associated with CCS/CCU, it is essential to note that captured CO₂ is not permanently sequestered, particularly in the case of the agricultural use of urea. Therefore, from a life-cycle perspective, this approach may not be considered fully sustainable [10], emphasizing the need for additional measures to achieve net-zero ammonia production.

Since hydrogen production is the most emission-intensive aspect of ammonia processing, the use of zero-emission hydrogen production methods is critical to achieving climate-neutral ammonia. Several methods for low-carbon hydrogen production, such as water electrolysis and methane pyrolysis, are under investigation. Among these, water electrolysis is emerging as the leading technology [42,47]. However, due to its high electricity demand, the total emissions from ammonia production are strongly influenced by the electricity source, whether derived from fossil fuels or renewable energy [11].

Currently, given the composition of the existing electricity mix, water electrolysis does not lead to a significant reduction in carbon emissions from ammonia production. However, if the electricity required for electrolysis is sourced entirely from renewable energy sources, it would be possible to achieve a near-total reduction in future CO₂ emissions associated with ammonia production [42].

Methane pyrolysis represents an innovative and promising technology for hydrogen production, with potential applications in ammonia synthesis. This process thermally decomposes methane (CH₄) into hydrogen and solid carbon (C), thereby eliminating the CO₂ emissions typically associated with conventional hydrogen production methods such as SMR [48]. Given that hydrogen is a crucial input for the Haber–Bosch process used to produce ammonia, methane pyrolysis offers a more environmentally sustainable pathway for both hydrogen generation and ammonia production [49].

A key advantage of methane pyrolysis is its compatibility with the existing industrial infrastructure for ammonia production, which enhances its feasibility as a near-term solution for reducing emissions in this sector [49]. Additionally, it has the potential to be more energy-efficient compared to green hydrogen production methods, such as water electrolysis, which require significant amounts of renewable electricity.

Despite these benefits, this technology faces challenges that must be addressed to ensure its widespread adoption. These include the effective management and utilization of the solid carbon by-product and the need to meet the high-temperature requirements of the process, which exceed 1000 °C [48].

The implementation of the aforementioned technologies holds the potential to reduce emissions beyond Scope 1, including Scope 3 emissions that occur outside the direct ownership or control of companies. Upstream Scope 3 emissions associated with NG extraction, processing, and transportation to ammonia plants could be eliminated. Additionally, downstream emissions from ammonia-derived products, particularly fertilizers and their application, can be mitigated through the use of low-carbon ammonia. For example, since ammonia and CO₂ are key feedstocks for urea synthesis, the carbon footprint of urea production can be minimized by integrating low-carbon ammonia with CO₂ sourced from carbon-neutral sources [11].

Captured CO₂ from various industrial facilities, such as cement or steel plants, power plants, or plastics incinerators, could also be used in urea production as part of carbon recycling strategies [11]. However, as mentioned above, if the CO₂ supplied to the urea plant comes from non-biogenic sources, using urea as a fertilizer would ultimately result in CO₂ emissions into the atmosphere, which would then be accounted for within the agricultural sector.

Therefore, to fully decarbonize the urea value chain, the CO₂ must be sourced from a biogenic carbon cycle, such as Bioenergy with Carbon Capture and Storage (BECCS) or DAC [41]

Table 2. Comparative summary of various ammonia production methods.

NH3 Production Method	Feedstock	Energy Demand * (MWh /t NH3)	Carbon Footprint (t CO2/t NH3)	TRL [42]	Advantage	Disadvantage
SMR **	NG	7.8–9.7 of NG (Feedstock + Final Energy) [11]	1.8–2.4 Scope 1 + 2 [11,42]	9	Established technology. High efficiency in converting methane to hydrogen. Low cost of natural gas.	High carbon emissions. Dependent on fossil fuels.
Water Electrolysis	Hydrogen	10.8–13.6 [11]	0 (if renewable energy is used)	8	No direct emissions technology. Potential for green ammonia.	High energy demand. Higher capital and operating costs.
Methane Pyrolysis	Methane	3.3–4.4	0.2–0.5 0.23 [49] Scope 1	7	Low carbon emissions. Produces solid carbon. Lower energy demand compared to SMR.	Scale-up challenges. Needs further research. High temperature demand.
SMR + CCS ***	NG	7.8–9.7 (like SMR)	0.3–0.9 Depends on CCS efficiency	7–8	Reduces carbon emissions significantly. Uses existing SMR infrastructure.	High cost of CCS technology. Long-term of captured CO2 needs infrastructure.

* Energy demand including energy content of feedstock and final energy, ** SMR: Steam Methane Reforming, *** CCS: Carbon Capture and Storage.

provides a comparative summary of the energy demand, carbon footprint, and TRL, as well as the advantages and disadvantages of various ammonia production methods.

3.3. Methanol

3.3.1. Current Production Process

Methanol (CH₃OH), also known as methyl alcohol, is not only a vital feedstock for various chemical products (such as acetic acid, formaldehyde, and plastics like polyethylene terephthalate, polypropylene, and polyvinyl chloride) but also provides significant environmental benefits. Methanol plays a role in the transport sector, where it is added to gasoline to enhance its octane rating. It is a key component of biodiesel, a renewable fuel that can be used either independently or blended with traditional diesel fuel [50]. Furthermore, methanol is directly utilized in methanol fuel cells [51,52], which contributes to a cleaner and more sustainable energy future.

In the energy sector, the demand for methanol as a fuel for industrial boilers is growing, as it provides heat and steam for various industrial processes [53]. This trend is particularly evident in the rising use of methanol for domestic heating, especially in China [54]. This shift reflects a global transition toward adopting more sustainable energy sources.

Methanol is synthesized on a large scale using synthesis gas, a mixture of carbon monoxide (CO), CO₂, and hydrogen. These synthesis gases are derived from various materials, including fossil fuels such as coal, petroleum, NG, and naphtha, through steam reforming, partial oxidation, and autothermal reforming processes. Additionally, it can be sourced from renewable feedstocks, including agricultural residues, biogas, waste, and wood, through gasification techniques [55,56].

Afterward, the synthesis gas undergoes purification to remove impurities, such as sulfur compounds and CO₂. During the methanol synthesis phase, the purified gas is directed over a catalyst, typically a combination of copper, zinc oxide (CuO/ZnO), and alumina (Al₂O₃), under elevated temperature and pressure conditions, typically within the temperature range of 200–300 °C and pressure range of 50–100 atmospheres. This process involves two principal reactions (Equations (8) and (9)) [9,51]:

$$\mathrm{C}\mathrm{O}+2{\mathrm{H}}_2\to \mathrm{C}{\mathrm{H}}_3\mathrm{O}\mathrm{H}$$

(8)

$$\mathrm{C}{\mathrm{O}}_2+3{\mathrm{H}}_2\to \mathrm{C}{\mathrm{H}}_3\mathrm{O}\mathrm{H}+{\mathrm{H}}_2\mathrm{O}$$

(9)

In Europe, methanol is predominantly derived from NG through SMR processes [9]. Generating one ton of methanol requires approximately 7–9 MWh of NG as a feedstock in the reformer, where synthesis gases are produced [11]. Additionally, about 3.86 MWh of fossil energy and 0.16 MWh of electricity are needed as energy sources to produce one ton of methanol [11].

Furthermore, methanol production is an exothermic process, yielding around 0.56 MWh of energy in the form of steam per ton of methanol [11]. This steam is integrated into the internal heat network and can be used in the methanol synthesis reaction or for other purposes, such as preheating feedstocks, heating buildings, or generating electricity [11].

The production of methanol results in CO₂ emissions in three categories. Scope 1 emissions arise due to the chemical reactions occurring during the reforming process and the utilization of fossil fuels as energy sources, ranging from 0.4 to 0.52 tons of CO₂ per ton of methanol [11,57]. Indirect Scope 2 emissions are associated with electricity consumption during methanol production and depend on the grid electricity’s emission factors.

Furthermore, methanol production is linked to considerable Scope 3 emissions from upstream and downstream activities, which constitute over 80% of methanol’s total life cycle emissions [57]. Upstream emissions are primarily due to methane leaks during NG extraction, as well as emissions from flaring and the energy required for NG production. These emissions contribute approximately 0.367 tons of CO₂ per ton of methanol [57]. Downstream emissions, which account for approximately 62% of total life cycle emissions, occur when methanol is combusted as a fuel [57].

Figure 4 illustrates the distribution of emissions across methanol’s life cycle.

3.3.2. Emission Reduction Technology

Approximately 10% of CO₂ emissions from the chemical and petrochemical industries originate from methanol production [1]. Therefore, mitigating emissions from methanol production is crucial to reducing the environmental impact and carbon intensity of traditional processes.

Since hydrogen (189 kg hydrogen per ton of methanol) and CO/CO₂ (1.373 t CO₂ per ton of methanol [11]) are the primary feedstock for methanol synthesis, low-emission methanol production is feasible if these inputs are sourced from emission-free resources.

Low-emission methanol can be produced using renewable energy and feedstocks via two main routes, namely bio-methanol derived from biomass such as forest and agricultural waste and biogas from landfills, or even, though a less common route, black liquor from the pulp and paper industry [58]. Green e-methanol is synthesized using green hydrogen (as in ammonia production) and CO₂ captured from emission-free sources like BECCS or DAC.

For methanol to qualify as renewable, all feedstock and energy sources must come from sustainable sources, such as biomass, solar, wind, hydro, or geothermal energy.

However, both methods face challenges. Scaling up bio-methanol production requires a reliable and consistent feedstock supply, which depends on the availability and cost of biomass feedstock. While some projects can source biomass locally, others will require extensive supply chains [58]. Large-scale green e-methanol production hinges on the affordability of green hydrogen and CO₂, as well as the capital costs of the production facilities. Key cost factors include the price of renewable energy for hydrogen production and the utilization rates of electrolyzers [58].

In addition to bio-methanol and green e-methanol, an innovative approach to methanol production involves using syngas derived from the chemical recycling of plastic waste [24,59]. This process simultaneously addresses plastic waste pollution while supporting the growing demand for sustainable chemical production.

Integrating plastic waste recycling into methanol production can play a significant role in fostering a more circular and sustainable economy while also reducing the overall carbon footprint when considering lifecycle emissions.

Table 3. Comparative summary of various methanol production methods.

Methanol Production Method	Feedstock	Energy Demand (MWh/t Methanol) [9,11,58]	Carbon Footprint (t CO2/t Methanol) [9,11,58]	TRL [1]	Advantage	Disadvantage
Natural Gas Reforming	NG	~8.3–11.1 of NG (Feedstock + Final Energy)	0.3–0.5 Scope 1 + 2	9	Established technology. High efficiency in low cost of natural gas.	High carbon emissions. Depends on fossil fuels.
Coal Gasification	Coal	11.1–13.9	2–3	9	Abundant coal reserves. Mature technology.	Extremely high carbon emissions.
Biomass Gasification	Biomass	9.7–13.9	0.1–0.3	5–7	Renewable feedstock. Potential for a negative carbon footprint.	High energy demand. Limited scalability.
Hydrogenation of CO2	Hydrogen + CO2 captured	12.5–16.7	0 (if renewable energy is used)	6–8	Uses captured CO2. Can be low-carbon if H2 is green.	Requires large-scale green H2 production.

presents a comparative summary of the key factors—including feedstock and energy consumption, emission footprint, TRL, and other relevant parameters—for low-emission methanol production processes compared to conventional methods.

3.4. Olefin

3.4.1. Current Production Process

Olefins, also known as alkenes, are hydrocarbons that contain at least one carbon–carbon double bond (C=C) within their molecular structure. These compounds are fundamental to the petrochemical industry, serving as key raw materials for the production of various chemical and polymer-based products. Ethylene, propylene, and butadiene are among the most important olefins, widely used in the manufacturing of plastics, detergents, adhesives, rubber, and food packaging [60].

The production of olefins primarily relies on steam cracking, a petrochemical process in which saturated heavy hydrocarbons—such as naphtha, liquid petroleum gas (LPG), and ethane—are exposed to high temperatures (ranging from 600 °C to 900 °C) in gas-fired furnaces before being rapidly cooled. This thermal decomposition breaks down the heavy hydrocarbons into shorter-chain hydrocarbons in the presence of steam [60,61].

The severity of the cracking process determines the primary product, which can be either olefins or aromatic. Under higher-severity conditions, olefins such as ethylene are predominantly produced, whereas lower-severity conditions favor the formation of propylene and other aromatics, including benzene, toluene, and xylene [62].

The steam cracking process for olefin production is one of the most energy-intensive operations in the global chemical industry, accounting for approximately 8% of the sector’s total primary energy consumption [61]. In Europe, naphtha is the predominant feedstock used in steam crackers, representing approximately 78% of the total feedstock consumption [62]. The remaining feedstock consists of ethane, gas oil, and LPG (a mixture of ethane, ethylene, propane, propylene, butane, and butylene) [61]. On average, a steam cracker consumes about 2.7 tons of naphtha to produce one ton of ethylene or propylene [9].

Naphtha steam crackers are largely self-sufficient in terms of energy, with approximately 95% of their process energy demand met by the energy content of naphtha itself. This efficiency is achieved by utilizing fuel by-products, which contribute around 20–25% of naphtha’s energy, in combination with flue gases and waste heat [9]. A small proportion of the required electricity, approximately 0.44 MWh per ton of ethylene, is sourced from external providers. The combustion of naphtha supplies the necessary energy, ranging from 7.2 to 8.6 MWh per ton of ethylene [9,61].

The production of ethylene by naphtha cracking is not only highly energy-intensive but also a significant source of GHG emissions across all three scopes. For Scope 1, emissions arise from on-site fuel combustion and chemical reactions during the cracking process, averaging approximately 1.73 tons of CO₂ per ton of ethylene or propylene produced, with a range of 1.5–2.0 tons of CO₂ per ton of ethylene [9]. Scope 2 emissions are linked to the electricity consumption for essential operations such as compression, separation, and cooling systems. The extent of these emissions depends heavily on the carbon intensity of the local electricity grid.

The Scope 3 upstream emissions in ethylene production include the CO₂ emissions associated with crude oil extraction, refining processes to produce naphtha, and its transportation to the ethylene production facility. On average, these emissions amount to around 0.3 tons of CO₂ per ton of naphtha [63], with variations based on extraction location methods used.

Scope 3 downstream emissions from ethylene and propylene production result from their processing and end-use. As key precursors for various products like plastics, their end-of-life disposal—whether through recycling, incineration, or landfilling—leads to significant CO₂ emissions. The complete combustion of ethylene or propylene releases approximately 3 tons of CO₂ per ton of these chemicals, while plastic derived from them emits an average of 2.7 tons of CO₂ per ton of plastic [25].

However, emissions fluctuate based on regional regulations, like EU policies that emphasize recycling and energy recovery [64]. Such policies play a crucial role in shaping Scope 3 downstream emissions and the total carbon footprint.

3.4.2. Emission Reduction Technology

In contrast to the processes previously discussed for ammonia and methanol, the direct decarbonization of olefins is currently hindered by low TRL [11]. Nevertheless, several emerging technologies hold the potential to transform the production of intermediates and low-emission feedstocks for olefin synthesis.

The replacement of fossil-derived naphtha with sustainable alternatives, along with the use of renewable energy sources to meet processing energy requirements, coupled with the adaption of technologies, such as the Fischer–Tropsch-to-Olefin (FTO) process and the Methanol-to-Olefins (MTO) process, offers a promising strategy to produce low-emission olefins. These approaches not only reduce emissions but also promote the transition towards a more sustainable future in chemical processes.

This section provides a detailed examination of these technologies, emphasizing their potential to drive significant transformations within the industry (Additionally, various other technologies can be employed, including the electrification of the steam cracker (utilizing electricity, preferably derived from renewable sources, to provide the necessary heat), advanced process control, enhanced process design, etc. [9] As these technologies primarily impact energy-related emissions and do not significantly reduce emissions across the entire value chain, they are not considered in this essay).

Using sustainable naphtha or bio-naphtha [65], which is produced from various biomass sources—including palm oil [66], corn, sugarcane, and lignocellulosic biomass—via processes such as pyrolysis, gasification, and fermentation, offers a viable approach to lowering the carbon footprint of olefin production. The chemical and physical properties of fossil-based and bio-naphtha are highly similar, making them interchangeable without requiring significant changes to existing infrastructure. The utilization of sustainable naphtha is crucial in supporting the transition from fossil carbon to renewable carbon in polymers and plastics production [66]. However, the main challenge associated with this approach is the restricted availability and high production cost of environmentally sustainable naphtha.

The Fischer–Tropsch-to-Olefin (FTO) process is a series of chemical reactions that convert syngas—a mixture of carbon monoxide and hydrogen—into liquid hydrocarbons and valuable olefins. This process typically utilizes iron- or cobalt-based catalysts and occurs at temperatures ranging from 200 °C to 350 °C under pressures of 10 to 40 bar [67]. The objective of the FTO process is to maximize light olefin production while minimizing methane selectivity and reducing the excess CO₂ generation [68].

The FTO process has gained increasing attention due to its ability to transform syngas derived from various sources—including coal, natural gas, and biomass—into valuable olefins. Even though the FTO process is a mature technology and offers a promising alternative for olefin production, particularly from non-petroleum-based raw materials, it still represents a relatively small proportion of global olefin production. Currently, the process is employed by Sasol in South Africa and at Shell’s gas-to-liquids (GTL) plant in Bintulu, Malaysia [69].

The principal challenges associated with the FTO process include the high cost of catalysts, their gradual deactivation [70], and the need for precise process control to optimize olefin selectivity while minimizing unwanted by-products such as methane and CO₂. Additionally, integrating renewable energy sources is crucial for mitigating these challenges and making FTO a more feasible alternative in olefin production.

The Methanol-to-Olefin (MTO) process is a well-established technology that produces olefins using methanol as the primary feedstock. As previously stated in Section 3.3, methanol can be derived from NG, coal, or biomass. The MTO process relies on zeolite-based catalysts, which enable the conversion of methanol into light olefins. Methanol is fed into a reactor containing a zeolite catalyst, where the reaction occurs at elevated temperatures ranging from 300 to 500 °C and under moderate pressure. Stoichiometric analysis shows that the MTO process requires approximately 2.28 tons of methanol to produce 1 ton of ethylene or propylene [11].

Currently, MTO units—particularly those in China—primarily rely on fossil-based feedstocks, with coal being the dominant source, to manufacture the methanol required for the process. In 2020, approximately 25% of global methanol consumption was attributed to the MTO process, and olefin production via methanol is expected to rise through 2028, particularly in China [58].

Furthermore, several initiatives and projects are focused on producing olefins from bio-methanol as part of a broader effort to develop more sustainable and low-carbon chemicals. Nevertheless, challenges such as catalyst deactivation and the high energy intensity of low-emission methanol production (see

Table 4. Comparative summary of various olefin production methods.

Olefin Production Method	Feedstock	Energy Deman (MWh/t Ethylene)	Carbon Footprint (t CO2/ t Ethylene)	TRL	Advantage	Disadvantage
Steam Cracking	Naphtha	15–25 (Feedstock + Final Energy) [9,11]	1.5–2 [9,11]	9	Established technology. Large-scale production capability.	High carbon emissions. Dependent on fossil fuels. Energy-intensive.
Steam Cracking	Ethane	10–15 [9]	0.5–1.2	9	Lower energy demand and CO2 emissions compared to naphtha.	Limited to regions with cheap ethane supply. Fossil fuel dependency.
Methanol-to-Olefins (MTO)	Methanol Fossil based	20–30	1–1.5	8–9	Flexible feedstock (methanol can be produced from natural gas, coal, or biomass).	High energy demand. High CO2 emissions.
Methanol-to-Olefins (MTO)	Methanol Emission-free	20–30 [11]	0	6–8	Uses captured CO2. Low carbon emissions if H2 is green.	Requires large-scale green H2 production.
Fischer-Tropsch (FT) [68,69,70]		30–50	2–3	7–8	Can use biomass (reduces net CO2). Integration with existing refineries.	High energy demand. CO2-intensive if based on fossil feedstocks. Complex process.

) must be addressed.

In addition to the technologies mentioned above, a notable shift in olefin production involves the transition towards a circular economy. This strategy includes the reuse of plastics and polymers derived from olefins, as well as the recycling and recovery of carbon from end-of-life materials.

Currently, a considerable portion of end-of-life plastics is either sent to landfills or incinerated for energy recovery, both of which contribute to CO₂ emissions. Globally, less than 20% of plastics are recycled due to challenges such as low collection rates and the technical difficulties associated with sorting and processing [71].

Beyond climate impacts, this inefficiency also results in the loss of valuable resources and raw materials that could otherwise be recovered and reused. The circular economy approach prioritizes preparing post-consumer plastics for recycling and recovery instead of incineration. This strategy not only reduces the demand for virgin raw material in polymer production but also helps lower CO₂ emissions [25,72].

Post-consumer plastic waste can be recovered using both mechanical and chemical recycling techniques. In mechanical recycling, plastic waste is processed into recycled polymers for use in new plastic products without depolymerization. The energy required for the mechanical recycling of clean, easily collected waste streams is 25% to 60% lower than that needed to produce virgin polymers [10,72].

In contrast, chemical recycling depolymerizes plastics into their monomers or hydrocarbons, which serve as feedstocks for petrochemical plants or refineries through thermal processing [10]. This method is primarily applied to impure or complex waste streams containing multiple plastic types that are not suitable for mechanical recycling. Plastic waste that cannot be sustainably recycled is instead utilized for energy recovery.

Table 4 provides a comparison between conventional olefin production via naphtha steam cracking and other promising olefin production routes.

To complete this section, Figure 5 illustrates the material and CO₂ flow diagram for the corresponding basic chemicals produced by both conventional and low-emission methods.

4. Austrian Chemical Industry

The Austrian chemical industry is a key energy-intensive sector, representing about 24% of total industrial energy demand [73]. Despite its high energy intensity, it ranks as the second-largest industrial consumer of final energy, accounting for approximately 14% of Austria’s total industrial final energy consumption [73].

This sector relies heavily on fossil-based raw materials, primarily crude oil and NG, which make up nearly 12% of Austria’s total raw material consumption. Additionally, a significant portion of these fossil fuels are imported, emphasizing the industry’s reliance on external sources [31].

Basic chemicals, including ammonia (and urea), methanol, and olefins, account for approximately 60% of the total energy consumption in the Austrian chemical industry [73]. The primary raw materials used for producing these chemicals are naphtha and NG. Naphtha is the main fossil feedstock in steam crackers, where it is used to produce olefins such as ethylene and propylene. These olefins are typically manufactured in a single integrated production facility operated by OMV company [74].

Natural gas is the second most important fossil fuel used in basic chemical production, particularly in steam reformers for synthesizing ammonia and methanol. Beyond serving as a feedstock, NG is also utilized as an energy source, often in combination with smaller amounts of other fossil fuels, such as oil and coal, to meet process heat and steam demands. Furthermore, electrical energy is essential in basic chemical production, primarily for powering industrial furnaces and stationary engines.

Figure 6 illustrates a Sankey diagram representing energy flow, providing a detailed breakdown of the consumption of various fuel types as both feedstock and energy sources in the production of primary chemicals. This visualization emphasizes the relative contributions of different fuels to the sector’s total energy demand.

Regarding CO₂ emissions, the Austrian chemical industry ranks as the third-largest emitter after the iron and steel industry and cement production [39]. In recent years, the industry has made significant steps in reducing energy consumption and CO₂ emissions in response to growing environmental concerns. Key initiatives include the adoption of energy-efficient technologies, the implementation of Combined Heat and Power (CHP) plants utilizing low-emission fuels, and the integration of waste heat recovery systems to improve energy efficiency [31]. As a result of these efforts, CO₂ emissions from the Austrian chemical industry have decreased by an impressive 50% between 1990 and 2022 [75].

The chemical industry currently accounts for approximately 13% of direct industrial emissions in Austria, with basic chemicals contributing to more than two-thirds of these emissions [75]. Figure 7 illustrates the emissions generated by basic chemicals across the three emission scopes in the base year 2022. Scope 3 upstream and downstream CO₂ emissions have been estimated using reference values to provide a comprehensive overview.

Additionally, the CO₂ used as a feedstock (e.g., in urea) and the carbon embedded in olefin products—both of which may be emitted in other sectors during their use or end-of-life phase—are also included in Scope 3 downstream emissions. In Austria, ammonia and urea are produced at an integrated facility. Therefore, emissions from these two processes are shown in a single column.

5. Emission Reduction Strategies and Emission Balance Using Novel Carbon Boundary for the Austrian Chemical Industry

To fulfill the objectives of this paper, the current section evaluates the impact of adopting low-carbon technologies on the energy consumption and carbon footprint of the chemical industry, with a particular focus on the Austrian context. The analysis is based on well-defined assumptions and the development of three distinct scenarios that model various potential pathways for achieving significant emissions reductions in the chemical sector. These scenarios undergo rigorous analysis to assess their implications across the three emission scopes, with particular emphasis on Scope 3 emissions—the most challenging to quantify and mitigate—as these occur throughout the value chain.

The assumptions underlying this paper are based on the decarbonization scenarios developed by the innovation network New Energy for Industry (NEFI) [29]. These scenarios outline strategic pathways for decarbonizing the Austrian industrial energy system and offer a structured framework for assessing the potential impact of various low-carbon technologies and energy transitions on industrial emissions.

In line with the NEFI scenarios, this paper assumes that all fossil fuels currently used for energy production in the chemical industry are replaced by carbon-neutral alternatives. These alternatives, such as hydrogen, biomethane, and synthetic methane (CH₄), are derived from renewable or low-carbon sources. This substitution ensures that Scope 1 direct energy-related emissions from fossil fuel combustion are effectively reduced.

To address process-related Scope 1 emissions, this study evaluates the most promising technological alternatives that have the greatest potential to reduce emissions in basic chemical production processes. Ammonia production will transition entirely to a low-carbon method, utilizing hydrogen synthesized exclusively through water electrolysis powered by renewable energy. Similarly, urea synthesis will rely on low-emission ammonia and captured CO₂, ensuring a fully decarbonized production cycle. Methanol production will also follow a sustainable approach, using zero-emission hydrogen and capture CO₂ as feedstocks. Moreover, olefins, which play a critical role in the chemical industry, will be produced from green methanol through the MTO process, marking a significant step towards decarbonized production.

The projected production volumes of ammonia, urea, and olefins in Austria are expected to follow historical growth trends, maintaining a steady trajectory aligned with past data. In contrast, methanol production is expected to experience a substantial increase. This growth is attributed not only to its historical growth rate but also to the additional demand stemming from its essential role as a key precursor in the MTO process for olefin production.

The Scope 2 electricity-related emissions for 2050 are estimated using an emission factor of 0.019 (t CO₂/MWh), derived from the projected EU energy mix scenario, as described in the methodology section [35]. This low-emission electricity serves as the primary energy source for the electrolysis process, enabling the production of emission-free hydrogen. The electrolyzer is assumed to operate at 60% efficiency, ensuring the effective conversion of electricity into hydrogen while minimizing associated emissions.

The Scope 3 upstream emissions associated with NG extraction will be eliminated by transitioning the feedstock from NG to low-emission hydrogen. This shift not only removes the carbon-intensive processes involved in natural gas extraction but also aligns with the broader decarbonization strategy. Figure 7 illustrates the CO₂ emissions of the chemical industry under system boundaries 1 and 2, comparing the conventional methods used in 2022 with the adoption of new decarbonization technologies projected for 2050. As shown, the total CO₂ emissions in Scopes 1 and 2, as well as Scope 3 upstream emissions from the chemical industry, are expected to decrease by approximately 80% by 2050 compared to 2022 levels.

Figure 7 also depicts the CO₂ emissions from Scope 3 downstream activities, which are not included within the chemical industry’s system boundary but have the potential to be re-emitted in other sectors. These emissions represent the downstream life cycle impacts of chemical products and highlight the interconnectedness of the chemical industry with broader economic sectors. The effects of these emissions beyond the system boundary of the chemical industry are considered in the three scenarios discussed in the following paragraphs.

The application of decarbonization technologies and the transition from fossils to low-emission energy sources will significantly increase the energy demand for basic chemicals. In 2022, the energy demand for conventional processes was approximately 27 TWh. By 2050, with the adoption of new low-carbon processes, this demand is expected to rise to around 46 TWh (see Figure 8).

While part of this increase is driven by growth in material demand, around 80% of the additional energy requirement is attributed to the new technologies implemented, mainly replacing fossil feedstock with hydrogen for ammonia and methanol synthesis. This shift leads to a significant increase in electricity consumption, as hydrogen must be produced through water electrolysis. Methanol production, a key input for the MTO process, is a major driver, accounting for over 80% of hydrogen consumption and the associated energy demand.

As previously discussed, the Scope 3 downstream emissions in the chemical industry are primarily linked to the CO₂ feedstock used in urea production and the embedded carbon in naphtha feedstock for end products in the conventional production methods. By adopting new technologies and replacing fossil feedstocks with low-emission alternatives, these embedded emissions are effectively eliminated. However, the demand for CO₂ as a feedstock increases, particularly for the MTO process.

To meet the increased demand for CO₂ as a feedstock for the MTO process, as well as the demand for CO₂ in urea production—which is currently supplied through ammonia synthesis—an external CO₂ source must be identified. This presents a significant challenge for the industry, as it requires the establishment of sustainable CO₂ capture and supply systems.

To address and account for CO₂ demand and associated Scope 3 downstream emissions, this paper considers three scenarios: the reference scenario (Ref–S), geogenic scenario (Geo-S), and bio-based scenario (Bio-S), which are detailed below.

Ref-S evaluates the future of the chemical industry without the adoption of new technologies. In this scenario, emissions are calculated based on the base year 2022, assuming no significant changes in feedstocks, production processes, and energy sources. This scenario serves as a benchmark to compare the potential benefits of innovative decarbonization strategies.

In the remaining two scenarios, innovative technologies are implemented for producing basic chemicals, but the key distinction between these scenarios is the source of the CO₂ feedstock. By 2050, the chemical industry is projected to require approximately 4600 Kt of CO₂ as a feedstock to support the production of urea and methanol.

As detailed in Section 3.2.1, urea production uses 0.73 tons of CO₂ as a feedstock for each ton of urea produced. In 2050, this corresponds to an estimated 320 Kt of CO₂ required for urea production. Similarly, to produce olefins through the MTO process, the demand for CO₂ is indirectly driven by methanol consumption. Each ton of ethylene produced by the MTO process requires 2.28 tons of methanol, and each ton of methanol produced consumes 1.37 tons of CO₂ as a feedstock (see Section 3.3.2 and Section 3.4.2). Consequently, the chemical industry is expected to require an additional 4280 Kt of CO₂ to meet the methanol demand for both the MTO process and the production of methanol.

To support the CO₂ feedstock requirements of the chemical industry, two alternative scenarios—Geo-S and Bio-S—are considered.

The geogenic scenario is based on the use of geogenic and fossil-derived CO₂ sources. In this scenario, a portion of the CO₂ required for chemical production is supplied by geogenic sources, such as the cement industry. Cement production inherently emits CO₂ as a by-product of limestone calcination, making it a viable source of geogenic CO₂. By capturing and utilizing these emissions, the chemical industry can reduce its dependence on additional fossil-based CO₂ sources while partially closing the carbon loop for industrial processes.

According to the NEFI-ZEM scenario, the Austrian cement industry is expected to decarbonize through the adoption of carbon capture technology, specifically the oxyfuel process [29]. This technology is designed to capture geogenic Scope 1 CO₂ emissions directly at the source. By 2050, the implementation of oxyfuel technology is expected to enable the Austrian cement industry to capture approximately 2500 Kt of CO₂ annually [29], which could then be redirected to the chemical sector as a feedstock.

To meet the remaining CO₂ demand, additional sources will be explored, including CO₂ captured from other nonmetallic mineral products, such as lime, magnesia, and refractory manufacturing (see Figure 9).

Furthermore, CO₂ can be captured from plastic waste incinerators equipped with carbon capture systems. Currently, around 25% of Austrian plastic production is recycled through mechanical recycling [76]. In the coming decades, the Austrian plastics industry aims to increase the share of recycled plastics to 50%, with 40% undergoing mechanical recycling and 10% being recycled chemically [76]. This shift is expected to reduce the demand for virgin plastic production significantly, thus substantially lowering the CO₂ feedstock demand.

Despite advancements in recycling technologies, approximately 50% of plastic waste is still expected to be sent to incineration plants for thermal energy recovery. This process releases a substantial amount of CO₂, which can be captured, purified, and repurposed as a feedstock for methanol production in the MTO process. In Austria, common polymers such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polyethylene terephthalate (PET)—all derived from polyolefins—play a vital role in daily life and various industrial applications. These polymers are used across multiple sectors, with significant portions allocated to consumer plastics (34%), packaging material (16%), semi-finished products like fibers, pipes, and rods (37%), and construction materials (13%) [77].

Once these materials reach the end of their lifecycle, they are collected for recycling, energy recovery, or landfill disposal. Plastics, packaging material, and semi-finished products, which typically have shorter lifespans, constitute a significant portion of plastic waste. Approximately 50% of this waste is sent to incineration plants for thermal energy recovery. This process is estimated to emit 1500 to 1845 Kt of CO₂ annually, which can be captured, purified, and repurposed as a valuable feedstock for the chemical industry.

However, since this CO₂ is derived from fossil fuels, it presents a challenge to national emission reduction targets. Fossil-derived CO₂, even when captured and reused, still contributes to the overall carbon budget, complicating efforts to achieve net-zero emissions. Nonetheless, if fossil-based CO₂ is managed within a closed-loop system—captured during incineration, reused in plastic production, and then recaptured at the end of the plastic lifecycle—it could have a positive environmental impact. This approach would minimize net emissions by recycling the same carbon atoms through the production system, thereby reducing the need for additional fossil-based inputs.

In Bio-S, innovative technologies for chemical production will utilize biogenic CO₂ as a feedstock. This CO₂ can be sourced from industrial processes such as those in the pulp and paper industry, as well as from biomass resources. Among these sources, the pulp and paper industry stands out as a key contributor due to its established reliance on black liquor as an energy source.

Black liquor, a by-product of the chemical pulping process, is produced during the breakdown of lignin and other wood components during paper production. It has a calorific value ranging from 2.4 [75] to 3.4 [78] MWh per ton, making it a highly efficient and valuable energy resource. The Austrian pulp and paper industry currently consumes approximately 9.4 TWh of black liquor as an energy source annually [73]. The combustion of one MWh of black liquor releases approximately 0.35 tons of CO₂ [75]. Notably, this CO₂ is biogenic, meaning it originates from the natural carbon cycle and does not contribute to a net increase in atmospheric CO₂ levels, thereby mitigating climate impacts.

Based on the NEFI-ZEM scenario, the Austrian pulp and paper industry aims to undergo a significant transition towards complete dependence on bioenergy, increasing its current bioenergy share from 60% to 100% by 2050. Within this bioenergy mix, approximately 60% is projected to come from black liquor, with the remainder being sourced from solid biomass, biogas, and other renewable materials [29]. By 2050, this shift is expected to enable the pulp and paper industry to supply around 3500 Kt of bio-based CO₂ annually through the combustion of black liquor alone (see Figure 9).

The remaining CO₂ requirements that are not fulfilled by black liquor gasification will be met through a combination of biogenic resources, such as waste wood and biomass residues sourced from pulp and paper manufacturing, agriculture, forestry, and other bio-based industries. Additionally, DAC technology may be utilized to extract CO₂ directly from the atmosphere. By integrating DAC with biogenic resources, the chemical industry can ensure a stable and environmentally sustainable CO₂ supply, significantly reducing its reliance on fossil-derived CO₂ sources and accelerating its decarbonization objectives.

As previously discussed, the chemical industry should not be analyzed in isolation when addressing emissions. Many chemical products play essential roles in various sectors, such as agriculture, transportation, and energy. Therefore, this study expands its emission assessment by considering system boundaries 3 and 4, extending beyond the direct boundaries of the chemical industry. This approach provides a more comprehensive understanding of the chemical sector’s indirect and downstream emissions, highlighting its interconnection within the broader industrial system.

Figure 10 presents the results of CO₂ emission reductions across the three emission scopes under the three proposed scenarios at the national level. The analysis builds upon the previously outlined assumptions. It evaluates the impact of various decarbonization strategies, including changes in feedstock sources, transitions to renewable energy, and modifications to production processes within the chemical industry.

According to the Austrian National Inventory Report [75], urea serves two primary purposes. First, it is used as a fuel additive in the transportation sector, commercially known as “AdBlue”. This application is crucial for reducing nitrogen oxide emissions in diesel engines. Second, urea is extensively applied as a fertilizer in agricultural soils to enhance crop productivity. Consequently, the CO₂ emissions resulting from urea consumption are reported in both the agriculture and transport sectors, as shown in Figure 10, consistent with the national emissions inventories.

As previously mentioned, by 2050, approximately 50% of plastics in Austria are expected to be recycled, while the remaining portion will be directed to incineration plants for energy recovery [79]. Based on these assumptions, it can be inferred that nearly half of the CO₂ used as a feedstock for methanol (and subsequently used for olefin production) will be re-released into the energy sector. This is depicted in Figure 10 under “Scope 3 downstream—Use of Plastic Waste in the Energy Sector”. The remaining CO₂ used as the feedstock for methanol production in the geo- and bio-scenarios, as well as carbon bound in the naphtha raw material in the Ref-S, will remain embedded in the material for an extended period, as shown in Figure 10 under “CO₂ Embedded”.

A comparison between the REF- and geo-scenarios in Figure 10 highlights that implementing new technologies for chemical processing reduces emissions not only within the chemical industry system boundary (see Figure 7) but also at a broader national level under the geo-scenario. However, achieving the emission reduction targets requires additional measures. This is because, in the geo-scenario, the CO₂ feedstock used for producing chemical materials originates from fossil or geogenic sources, which limits the potential for deeper decarbonization.

A comparison between the geo- and bio-scenarios underscores the critical importance of selecting CO₂ feedstock sources with lower carbon footprints to achieve meaningful emission reductions at the national level. While the use of emission reduction technologies for basic chemicals, combined with fossil-based CO₂ resources, can achieve approximately a 46% reduction in emissions compared to the Ref-S, transitioning to bio-based sources for CO₂ feedstock could lead to reductions exceeding 80% at the national level, even without accounting for embedded emissions.

When embedded emissions in recycled and long-lived materials are eventually released into the atmosphere, the choice of CO₂ source used as the feedstock becomes even more significant. In the geo-scenario, although recycling plastics reduces the need for virgin material production and its associated emissions, the CO₂ emissions from incinerating recycled plastics are comparable to those from virgin plastics. This similarity arises because the carbon content remains unchanged primarily during recycling. As this carbon originates from fossil sources, their emissions contribute negatively to national-level emissions, as shown in Figure 10 under “Total Emissions”.

In contrast, in the bio-scenario, CO₂ feedstocks with biogenic origins have a positive impact on national emissions. When biogenic CO₂ remains embedded in materials, it sequesters carbon, contributing to reducing net CO₂ emissions on a national scale. Furthermore, when this biogenic CO₂ is eventually re-released into the atmosphere, it is considered carbon-neutral at the national level, as it originates from renewable sources.

In conclusion, mitigating emissions solely within the chemical industry is insufficient to meet national climate neutrality goals. A comprehensive strategy that encompasses the entire CO₂ utilization chain is crucial for achieving these targets.

6. Conclusions and Outlook

This study investigates the role of various technologies in reducing emissions across three scopes in the chemical sector: Scope 1 (direct emissions), Scope 2 (indirect emissions from electricity consumption), and Scope 3 (indirect emissions from upstream and downstream activities). The analysis focuses on basic chemicals such as ammonia (and its derivative urea), methanol, and olefins using the Austrian chemical industry as a case study.

In summary, the findings emphasize the critical role of advanced emission reduction technologies and the integration of alternative feedstocks, including hydrogen and methanol, in mitigating emissions. The use of hydrogen in ammonia and methanol production, as well as low-carbon methanol in olefin production, has the potential to reduce approximately 80% of carbon emissions (in Scope 1 and 2 emissions) in the chemical industry compared to conventional production methods. However, to fully understand the emission reduction potential, a holistic system approach is required—one that considers the entire lifecycle of chemical products and their downstream effects, particularly Scope 3 emissions.

Due to the use of CO₂ as a feedstock and the inherent carbon content of many chemical products, emissions from these products can extend beyond their production phase. For example, during their use and end-of-life stages, these products may release CO₂ in sectors such as transportation, agriculture, and energy. This underlines the interconnectedness of industrial processes and the necessity of lifecycle assessments to evaluate the overall environmental impact. Therefore, understanding the lifecycle impacts of CO₂ feedstocks, including their production and use stages, is essential to comprehensively assess emission reductions—especially Scope 3 emissions, which extend beyond the chemical industry’s system boundaries.

In addition to assessing the impact of emission reduction technologies in the chemical production process, the current work evaluates the effects of different CO₂ feedstock sources through three scenarios: the reference scenario, the geogenic scenario, and the bio-based scenario. The comparative analysis demonstrates the significance of CO₂ feedstock selection in determining overall emissions.

In the reference scenario, which relies on a conventional production process using fossil feedstocks, emissions embedded in materials and subsequently released in downstream processes remain high, limiting the potential for CO₂ reductions.

The geogenic scenario implements abatement technologies while using geogenic and fossil-based CO₂ as the feedstock, captured through carbon capture and utilization from CO₂ emissions generated by other industrial manufacturing processes, such as the cement industry. In line with industrial symbiosis and circular economy strategies, this approach achieves significant emission reductions by incorporating advanced abatement technologies. However, continued reliance on fossil carbon or fossil-based CO₂ feedstocks leads to considerable downstream emissions within Scope 3, such as those from plastic waste incineration. Overall, this scenario results in approximately a 46% reduction in national emissions compared to the reference scenario but is still insufficient to meet climate targets.

The bio-based scenario presents a more sustainable approach. In this scenario, alongside the implementation of abatement technologies, a biogenic source of CO₂ is utilized as a feedstock. This method not only reduces emissions associated with fossil-derived CO₂ but also provides additional carbon sequestration benefits when biogenic CO₂ is incorporated into long-lived materials. At the national level, biogenic CO₂ is considered carbon-neutral, contributing to a more favorable impact on net emissions. As a result, the bio-based scenario achieves around an 80% reduction in emissions compared to the reference scenario, positioning it as a crucial strategy for achieving climate neutrality.

In conclusion, this study demonstrates that while emission reductions in the chemical sector are essential, they alone are not sufficient to meet national climate targets. Despite the comprehensive analysis presented, several limitations must be acknowledged. Uncertainties related to future international climate agreements, technological market developments, energy costs, carbon taxation policies, and waste management regulations may influence the accuracy of the projections.

A further challenge lies in the lack of accurate input data for Scope 3 emissions in current emissions trading systems, particularly for end-of-life emissions from plastics. These emissions are influenced by local regulations, consumer behavior, and advancements in recycling technologies, making long-term projections inherently uncertain. Additionally, the availability of bio-resources and the efficiency of CO₂ capture, purification, and reuse technologies remain critical factors in determining their feasibility. If these technologies are not optimized, they may require additional energy inputs, potentially leading to higher indirect emissions.

Addressing these challenges will be crucial for the chemical industry to develop a more resilient and effective decarbonization strategy, which will enhance its contribution to national and global climate goals.