A Review of the Key Findings from the Special Issue on “Life Cycle Sustainability Analysis of Resource Recovery from Waste Management Systems in the Context of Circular Models of the Economy and the Bioeconomy”

1. Introduction

The economy over the last century and a half has followed the take–make–use–dispose model, which, as known, leads to the unresponsible, uncontrolled extraction of resources for production and consumption, with no effective plans for waste reutilisation and economy regeneration (Wojnarowska et al. [1]).

As Wojnarowska et al. [1], have noted, this linear model of the economy has become a global concern, being responsible for several problems, mainly related to the following:

• Virgin materials being extracted beyond their replenishment capacities;
• Post-use commodities often being landfilled or treated in incineration plants, which has the consequence of valuable and scarce natural resources being extracted anew and the original resources being lost for the manufacturing of new products;
• Unsafe, unsustainable waste management practices leading to hazardous substances being emitted into the air, water and soil, and generating alarming environmental pollution conditions;
• Product manufacturing and distribution being responsible for extensive energy use and emissions of greenhouse gases and other pollutants, thus leading to climate change and heavily damaging human health, resources and ecosystem quality.

All those aspects contribute to making the linear model of the economy completely unsustainable from an integrated, holistic perspective. This emphasises the urgent need to transition to a model of the economy that maximises the circularity of resources, thus generating environmental and socioeconomic benefits that are well documented in the literature, mainly derived from resource prevention (Ingrao et al. [2]).

In this context, the circular economy (CE) is gaining increasing interest and attention from international science and policy communities, as it focuses on eco-design and the promotion of durable products that can be reused, repaired and remanufactured before being recycled. Through this, the CE helps in maintaining products, components and materials at their highest levels of utility and value.

CE implementations at all levels of society can stimulate economic growth by reducing material costs, mitigating price volatility, and improving supply chain security issues (Gaidukova et al. [3]; Ingrao et al. [2]).

The CE differs from the linear economic model, as it is essentially based upon the two complementary features of slowing and closing resource loops that are accomplished through five circular flows (i.e., share, repair, reuse, remanufacture and recycling) whilst maximising resource efficiency. In practice, through those flows, the CE minimises waste and excessive resource utilisation by transforming goods at the end of their lifespan, along with wastes from their manufacturing and usage, into zero-burden resources to produce value-added commodities (Ingrao et al. [4]; Wojnarowska et al. [1]). Therefore, from a CE perspective, integrated strategies should be implemented to prevent waste generation in both the technical and the biological cycles and to manage and recover biomass and non-biomass waste that are inevitably generated in more sustainable manners.

From this perspective, affordable, effective and sustainable waste management systems are essential for sustainable development, as they help reduce the depletion of material and energy resources driven by increased globalisation and industrialisation (Govindan [5]; Goulart Coelho and Lange [6]).

From this point of view, environmentally sustainable waste management systems that are, at the same time, affordable and effective can significantly align with sustainable development principles and goals (Ingrao et al. [2]).

Thus, EU policies are needed to establish and promote strategies optimising waste recycling, starting from effective and citizen-friendly separate municipal collection systems (Ingrao et al. [2]). Through this, decision and policy makers should keep in mind that recycling is preferred over conventional treatments, like landfilling and incineration, as they result in resource depletion, greenhouse gas (GHG) emissions and environmental pollution. In contrast, recycling produces secondary raw material that, when of equal quality, can replace virgin counterparts in the production of commodities. Through this, from a life cycle thinking perspective, recycling contributes to increasing resource and energy efficiency and improving products’ environmental profiles (Ingrao et al. [2]). To encourage this, the EU has set targets for the 27 Member States (EU-27) to increase recycling and reduce landfill waste. Specifically, 55% of municipal waste and 65% of packaging waste must be prepared for reuse or recycling by 2030 (Ingrao et al. [4]).

Energy and waste recovery systems play multiple key roles in the green transition of a significant number of sectors, including material industries, agriculture, food production and packaging, buildings and bioenergy, and promote the implementation of sustainable development paths in the urban and rural context. This underscores the need for research that identifies opportunities for innovation and improvement in CE-based systems, which is why they are receiving increasing attention and interest from researchers, producers and policy makers.

Thus far, several studies have been conducted that addressed the three dimensions of sustainability (i.e., environmental, economic and social) in the waste management sector, with the aim of supporting the development of strategies, guidelines and policies for the creation of CE business models (Ingrao et al. [2]). However, the literature has documented that CE implementations are not always as technologically feasible, economically viable and environmentally beneficial as expected, and in some cases, less so than others (Sehnem et al. [7]; Ingrao et al. [2]). This underscores the importance of carefully selecting CE scenarios to prioritise and integrate into policies and measures for climate change mitigation and environmental protection.

This is the main reason why comparative assessments of CE implementation alternatives are recommended to identify those that perform best from an environmental and socioeconomic perspective (Ingrao et al. [2]). Life Cycle Sustainability Assessment (LCSA) has been extensively documented in the literature as a valid tool for this purpose (Finkbeiner et al. [8]; Traverso et al. [9]). It has been proven to be effective for assessing the environmental, economic and social impacts of both products and services from a life cycle perspective (Lin et al. [10]). It combines three individual assessments, which are the environmental life cycle assessment (ELCA), the life cycle costing (LCC) and the social life cycle assessment (SLCA) (Ioppolo et al. [11]; Lin et al. [10]). These assessments are guided by international standards, with the aim of providing scientific and standardised results for research objects regarding their impacts on environment, finance and society (Lin et al. [10]).

LCSA research in the waste sector is growing but is still limited compared to E-LCA, which, on the contrary, has been used extensively for environmental comparisons of different waste management systems [12,13]. Both LCA and LCSA have great potential for evaluating circular versus linear economic models or for identifying the best CE strategies among different alternatives, such as recycling versus reuse. This is performed by considering the trade-offs both between life cycle stages and between different sustainability dimensions (Traverso et al. [9]). However, challenges are often reported in LCAs/LCSAs of CE-relevant waste management systems, which include modelling recycling processes and the substitutability of secondary materials [14,15].

The challenges tend to increase when applying the latest methodologies (e.g., SLCA), mainly due to the lack of highly sensitive data. For waste management systems to be sustainable, it is important to compute the environmental, economic and social aspects (Ingrao et al. [2]).

Resources has an excellent track record in the area of sustainability in resource and waste management, with an impressive number of LCAs and LCSAs appearing in the journal. This SI aims to improve knowledge on this topic by broadening the scope and range of scenarios and systems analysed. It was designed to encourage researchers to explore the relevance of the assessment—and potential integration—of these dimensions for the improvement and promotion of sustainable waste management systems based on the CE.

In this context, the significant response to the previous Special Issue (SI), whose editorial was published by Ingrao et al. [2], encouraged this guest editorial team to produce another issue on this topic, aiming to further contribute to the advancement of the literature and knowledge on this important area of research.

The Guest Editors are confident that this second volume, together with the previous one (Ingrao et al. [2]), will provide a reliable and up-to-date picture of the state of the art of LCA and LCSA applications for waste management systems in the context of the circular economy and circular bioeconomy.

2. Scope of This Special Issue

This SI aims to further explore the notion that sustainable waste management from a CE perspective can contribute towards a just and sustainable post-fossil carbon society, as highlighted by Ingrao et al. [16]. The time has come for CE-based societies in which responsible and sustainable ways of dealing with waste will be implemented and pursued. A successful transition will require the planning, design, testing and implementation of waste-based products that meet the three dimensions of sustainability or the 17 UN Sustainable Development Objectives [16,17].

This SI seeks to highlight the importance of academic research for assessing and stimulating the integrated sustainability of waste recovery systems from a CE point of view. Thus, this SI serves as a platform for advancing knowledge on new methodologies, practical applications, state-of-the-art analysis and findings in this important research field.

Lastly, the purpose of this editorial is to review and build upon the work included in this SI, emphasising the main objectives, results and thus their contributions to the literature.

3. Article Collection Overview

The SI attracted considerable interest and attention from the scientific community worldwide, with a total of eleven articles published between 2023 and 2025, thus replicating, and even surpassing, the success of the first volume (Ingrao et al. [2]). The articles were the result of the collaborative efforts of fifty authors from countries on three continents, often from institutions conducting research in different but complementary fields. This further underlines Ingrao et al.’s [2] statement that research in this field is quite diverse and complex, requiring a multidisciplinary perspective.

The articles’ authors have addressed several relevant aspects related to this SI’s research topic, thus enriching the current state of the art in the field of sustainable and circular waste recovery systems for added-value commodity manufacturing.

In their articles, the authors, almost exclusively through original research articles, have explored some of the sectors where the CE can be beneficial in improving sustainability performance of both biotic and abiotic element cycles.

Most of the studies included in this SI performed a combination of technical, environmental and economic assessments of both lab- and industrial-scale production systems. A number of articles analysed the application of other evaluation tools, such as surveys, social theory, econometric modelling, data analysis (Sobaih and Elnasr; Bravo et al.) and agent-based modelling (Fontaine et al.), to explore the field of household and food waste management behaviours in urban and rural areas. However, LCSA was not conducted in any of the articles in this SI, which may either reflect the difficulty practitioners often encounter in incorporating the social dimension into their sustainability assessments or its perceived low importance.

Table 1. SI article classification based on research focus and assessment methodology. Articles were numbered based upon the alphabetical order of the first authors’ surnames.

Article Number	Authors’ Team	Research Focus	Assessment Methodology Applied
1	Bashiri et al.	Extraction of protein ingredients from fish processing residues	Combined ELCA-LCC
2	Bravo et al.	Investigating how social dynamics and digital connectivity are influencing residents’ willingness to adopt waste sorting in rural areas.	A combined social theory and econometric modelling, supported by results from participants’ surveys.
3	Brigida et al.	Technogenic reservoir resources of mine methane to support circular waste management implementations	Reconstruction of the response space for the dynamics of methane release from frontal and lateral projections.
4	Fontaine et al.	Exploring the effects of municipal strategies on household waste management behaviours and sustainability performances	Agent-based modelling
5	Ketkale and Simske	Corrugated Carbon Box (CCB) life cycle with different disposal scenarios (i.e., reusing, recycling, and landfilling).	ELCA, combined with economic tools like willingness-to-pay versus marginal cost curves and benefit–cost analysis.
6	Levickaya et al.	Recycling of phosphogypsum, derived from the synthesis of orthophosphoric acid from phosphorite rock.	Product characterisation and testing
7	Provenzano et al.	Vinification residue valorisation	Systematic literature review
8	Rebolledo-Leiva et al.	Apple pomace/vinasse integrated biorefinery for production of biofuels and bio-nutrients.	Techno-economic analysis (TEA) and ELCA
9	Sobaih and Elnasr	Tackling problems related to food waste management in Saudi Arabia, with special regard to family restaurants	Surveys for data collection and analysis
10	Vinci et al.	Plastic waste recycling through pyrolysis for oil production.	ELCA
11	Wojnarowska et al.	Exploring glass bottle recycling, with the combined accounting of cullet content and transport distance	ELCA

shows, for each individual article, the research field investigated and the methodology—or the combination of methodologies—applied.

From Table 1, it can be concluded that there is significant heterogeneity in the methodological approaches and indicators that can be used to assess and improve circular business models. In addition, from the table, there is evidence that Provenzano et al.’s review is the only one to be included in this SI’s collection of articles that investigated paths for the valorisation of wine-growing residues. From their study, Provenzano et al. highlighted that the most frequently used wastes are grape marc and seeds, along with cellar waste, and that agriculture, food and energy production are the sectors where these wastes can be valorised the most. This article can guide wine-growing enterprises to best manage and valorise their waste into sustainable circular revenue streams, thereby creating additional economic income opportunities. Furthermore, this review provides an overview of the state of the art and the main strategies used to valorise wine-growing wastes. It has also helped identify new products derived from these wastes, such as bioactive compounds, biogas and compostable materials; knowledge of these materials is fundamental for further sustainability assessments. Through this, the contribution that Provenzano et al. makes is twofold: they promote improved organisation management and enhance the scientific literature currently available on the subject.

In addition to Provenzano et al., the ten original research articles that were collected in this SI were classified using a methodological approach-based criterion (

Table 2. SI article clustering, consistent with the classification shown in Table 1.

Cluster		Belonging Articles
Number	Description
1	Assessments of technical aspects, which are related to more holistic LCSAs, are included here.	Brigida et al.; Levickaya et al.
2	This cluster includes assessments that have considered one single sustainability dimension.	Vinci et al.; Wojnarowska et al.
3	Combined assessments of at least two sustainability dimensions and other related ones.	Rebolledo-Leiva et al.; Ketkale and Simske; Bashiri et al.
4	Other empirical studies (e.g., surveys, social theory, econometric modelling, data analysis and agent-based modelling) for evaluation of the sustainability-relevant issues of waste recovery systems	Sobaih and Elnasr; Bravo et al.; Fontaine et al.

) and are reviewed in the following sections in terms of their main objectives and findings.

3.1. Technical Assessments (Cluster 1 Articles)

In this section, this SI’s editorial authors reviewed the articles that addressed the technical aspects of waste recovery systems, as this knowledge is essential for any planning and assessment of sustainability strategies.

In their study, Brigida et al. explored the drainage process of technogenic methane reservoirs in dead pits or abandoned sublevels of operating mining enterprises, thereby emphasising the need for sustainable geotechnologies. Mine methane contributes an average of 12% of global methane emissions, which accounts for around 20% of the total climate-active gas emissions (Brigida et al.). The key problem lies in the fact that methane continues to be emitted for a long period after coal production has ceased and the mine has been abandoned, contributing to climate change (Kholod et al. [18]).

From this perspective, the implementation of the circular economy concept for abandoned mine methane (AMM) would be beneficial for climate change mitigation and would make AMM an economically promising target (Brigida et al.). It is necessary, however, to improve the quality and quantity of gas extraction from technogenic reservoirs along with the generation of electricity to connect with the mine’s energy system (Brigida et al.).

Developing measures to prevent energy resource loss is an urgent scientific task that should be based on regularities in the spatial-temporal variability of gas flows and the dynamics of methane concentrations (Brigida et al.). This is the research field that Brigida et al. aimed to contribute to by studying rock mass degassing during reservoir mining in the central part of the Donetsk-Makeyevsky geological and industrial district in the territory of Donetsk city. Thus, the authors reconstructed the response space for the dynamics of methane release from frontal and lateral projections, which is the innovative aspect of this study. Their research confirmed the findings regarding the evolution of the cracking density obtained from the 3D models (Chen et al. [19]). Furthermore, Brigida et al. concluded that a significant amount of methane escapes from excavated abandoned strata and is associated with conceptual problems in underground venting and total collapse management.

In another study, Levickaya et al. explored the usage of phosphogypsum to produce of gypsum-based materials, such as plasterboard, blocks and plaster, which are in high demand for building applications. Phosphogypsum (PG) is a gypsum-bearing waste that can be reprocessed into gypsum binders, thus contributing to reducing natural gypsum (NG) exploitation; aside from avoiding the related environmental impacts, this is mostly beneficial in countries where NG deposits are limited (Levickaya et al.).

Given this significant potential, Levickaya et al. comprehensively investigated the properties of PG waste from three different industrial plants to assess the relationship with the properties of the gypsum materials that they produce. To this end, they accurately analysed the relevant characteristics of PG compared to NG, including the chemical and elemental compositions, microstructure, morphology, specific surface area and pore size distribution. From their comparative assessment, Levickaya et al. demonstrated that PG can be used as an alternative raw material resource to NG in the synthesis of plaster binders. However, they showed the need for measures to reduce water demand, such as the use of grinding processes and the introduction of superplasticisers, to increase the efficiency of the use of PG as a raw material to produce PG-based materials.

3.2. Single Sustainability Dimension Assessments (Cluster 2 Articles)

This cluster contains the articles in this SI that addressed assessments of one single dimension of sustainability. This includes Vinci et al. and Wojnarowska et al., who performed an environmental LCA of plastic and glass recycling systems, respectively, according to ISO 14040 and 14044 [20,21].

Vinci et al. focussed on the chemical recycling of an agricultural plastic mix through a pyrolysis process, where the resulting bio-oil can be used downstream as a partial fossil fuel substitute. Compared to fossil diesel, Vinci et al. found that pyrolytic oil demonstrated reduced environmental impacts in almost all the impact categories considered in the assessment method. In addition, the results showed that pyrolysis provides environmental benefits in all impact categories considered and is preferable to conventional one-way treatments, such as incineration and landfill. Through this, Vinci et al. attained the proposed twofold goal of ensuring that bio-oil production and use represent a sustainable and effective solution for climate change mitigation, abiotic element preservation and energy transition while also demonstrating that chemical recycling technologies, such as pyrolysis, are effective strategies for sustainable CE implementations. However, according to the authors, it is necessary to consider limitations, such as the high energy requirements of the process; the dependence on the quality and composition of the incoming plastic waste; and the need for adequate infrastructure to scale up chemical recycling systems. This contributes to ensuring real economic competitiveness and effective environmental impact reduction (Vinci et al.).

In their study, Wojnarowska et al. explored the use of cullet-derived glass bottles for craft beer packaging and complemented their LCA by combining the two key variables of cullet content and transport distance. Consistent with Polish regulations and standard practices, the content was set to be 0%, 57% and 90%, and the travelled distance increased from 25 to 250 km within and beyond the industrial symbiosis boundaries (Wojnarowska et al.).

This study showed that increasing the cullet content could significantly reduce the environmental footprint in several categories, including climate change, resource use and land use. However, as the transport distance increases, so does the environmental impact due to road transport emissions. Provided that transport distances remain within certain limits, the use of cullet remains more environmentally friendly than virgin glass. Beyond these limits, the benefits of cullet recycling are outweighed by the environmental and energy costs of transport (Wojnarowska et al.). This study provides deeper insight into the environmental trade-offs of glass recycling systems by providing a novel integration of transport logistics and material composition into the LCA framework. This study emphasises that, where technically feasible, supply chains should be kept shorter, and recycled content should be increased to contribute to sustainable product manufacturing.

Table 3. SI article review outcomes: extracted and synthesised data related to methodological aspects and application results for cluster 2 articles.

Reference	Object of the Study	Study Area	Study Scale	Type of LCA Conducted	FU	SB	Type of Data Used	Secondary Databases	Software Used	Allocation	Substitutional Approach for Environmental Credit Accounting	IAM	MIs	Other Energy, Environmental, Economic Indicators Used	Endpoint	Main Findings from the Study
Vinci et al.	Environmental assessment of chemical plastic waste recycling (CPWR)	Italy—Spain	Laboratory	Full LCA	1 L pyrolysis oil	Cradle-to-gate (from plastic waste acquisition to oil production)	Primary data obtained through site visits and surveys, combined with secondary data	Ecoinvent v3.11	SimaPro v9.6	None	Yes, the authors used this approach to model the environmental gains coming from using pyrolytic oil as a diesel substitute	ReCiPe (I) 2016 Midpoint [22]	All those considered by the IAM	No	No	CPWR enables reducing global warming by −3849 kg CO2 eq per ton of plastic processed, ionising radiation by −22.4 kBq Co-60 eq/1000 kg, terrestrial toxicity by −58.9 kg 1.4-DCB/1000 kg, land use by −174 m2 a crop eq/1000 kg, and fossil resource consumption by −1807.5 kg oil eq/1000 kg
Wojnarowska et al.	Recycled glass bottle production complemented with the combined accounting of cullet content and transport distance	Poland	Industrial supply chain	Streamlined LCA	1 kg glass bottles	Cradle-to-gate (from glass cullet acquisition to bottle production)	Only secondary data from Polish reports and statistics and other databases were used in this study.	Ecoinvent v3.7	SimaPro v9.6	None	No	EF 3.0 [23]	All those considered by the IAM	CED	Yes. The assessment was extended to the normalisation step	Using the maximum possible cullet content (90%) results in the lowest environmental impact, even when transport distances increase up to 250 km.

FU: Functional Unit; SB: System Boundary; IAM: Impact Assessment Method; MI: Midpoint Indicato.

synthesises the main methodological aspects and application results related to the two articles reviewed in this cluster.

3.3. Combined Sustainability Dimension Assessments (Cluster 3 Articles)

This section was dedicated to reviewing the three bidimensional sustainability assessments that have been included in this article collection. Two of them, namely Bashiri et al. and Rebolledo-Leiva et al., dealt with biological cycles and focussed on fish processing residues (FPRs) and apple pomace, respectively. Ketkale and Simske were the only ones in this group to investigate the field of technical cycles, with special attention to CCB waste management.

In their article, Bashiri et al. performed a combined ELCA-LCC of fish protein hydrolysate (FPH) and oil extraction systems from Atlantic mackerel processing residues. This study finds its rationale in the increase in global fish consumption and the subsequent increase in the generation of losses and wastes. Agreeing with Bashiri et al., this emphasises the need for sustainable extraction processes that make the most of fish by-products and waste, isolating valuable components such as proteins and oils. This could make aquaculture and the seafood industry more sustainable by developing a circular economy approach, but it could also potentially put more pressure on the environment. This is because it is expected that there will be more stages in the process, which could lead to an increase in environmental impacts (Bashiri et al.). This highlights the importance of combined environmental and economic assessments to identify hotspots and areas for improvement while also considering the already published contributions in aquaculture and other closely related sectors. Integrating the environmental and economic dimensions, Bashiri et al. provided valuable insights to guide stakeholders in the aquaculture and seafood processing sectors towards more environmentally and economically sustainable practices.

Bashiri et al.’s article demonstrated that the use of enzymatic hydrolysis to extract FPH and fish oil from Atlantic mackerel processing residues is generally viable, despite potential disadvantages, such as the cost of enzymes.

The authors’ contribution is relevant to the macro-research field of organic waste, which has become a major global waste fraction due to increased unsustainable food consumption patterns (Rebolledo-Leiva et al.). From this perspective, sustainable circular biorefinery systems would be effective in valorising organic waste and other biomass waste streams into biofuels, bioactive compounds, biopolymers and several other value-added commodities (Rebolledo-Leiva et al.).

This is the research area explored by Rebolledo-Leiva et al., with the aim of conducting a design data-based assessment of the techno-economic and environmental aspects that are relevant to the production of apple pomace-derived bioethanol in a cascade biorefinery facility. The authors extended the assessment to the eco-efficiency performance of converting vinasses into biogas to produce steam for the distillation process, compared to non-energy strategies like composting or lagooning.

Through their study, the authors documented that, in line with previous studies in the literature, different sections of the biorefinery have different environmental impacts.

The techno-economic analysis showed that vinasse treatment was the main contributor to both investment and operating costs, making the minimum selling price of bioethanol commercially uncompetitive in the current market.

The authors concluded that lower bioethanol prices could potentially be achieved via lagooning and composting, although both have limitations due to their higher environmental impact. Therefore, the co-production of bioethanol and biogas was found to be the most eco-efficient scenario, although economic barriers and the low sugar content of apple pomace were found to be the main challenges for the implementation of this biorefinery configuration.

Rebolledo-Leiva et al. concluded that additional research is needed to demonstrate the extent to which additional co-products could improve the economic viability of apple pomace.

Finally, in the field of technical cycles, Ketkale and Simske performed a combined environmental and economic assessment of different CCB life cycles with reuse, recycling and landfilling as the alternative end-of-life scenarios. The authors limited the environmental assessment to overall fossil-derived carbon emissions and the economic assessment of the relevant issues related to the cost/benefit and willingness-to-pay.

The development of this study was motivated by the fact that a large part of the CCB supply chain is dedicated to raw material extraction, including the cutting and processing of hardwood and softwood trees. Extraction also plays a role in the recycling phase, where recycled fibres are extracted from old CCBs (Ketkale and Simske). Thus, although recycling produces secondary raw materials with environmental benefits that can replace virgin materials, it also generates environmental impacts due to the consumption of energy and auxiliary materials and the generation of emissions and waste. In addition, the current literature has documented that overall low recycling rates are due to low levels of public motivation, which in turn is due to the lack of economic incentive policies.

Through their study, the authors demonstrated that reuse is the preferred method compared to recycling and landfilling, both from an environmental and economic perspective.

As shown in Table 3, for this second cluster of articles, the review was complemented by

Table 4. SI article review outcomes: extracted and synthesised data related to methodological aspects and application results for cluster 3 articles.

Reference	Object of the Study	Study Area	Study Scale	Type of LCA Conducted	FU	SB	Type of Data Used	Secondary Database	Software Used	Allocation	Substitutional Approach for Environmental Credit Accounting	IAM	MIs	Other energy, Environmental, Economic Indicators Used	Endpoint	Main Findings from the Study
Bashiri et al.	Economic/environmental sustainability assessment of enzymatic hydrolysis for extraction of protein compounds and oils from Atlantic fish processing residues	Norway	Laboratory	Combined LCC-ELCA	1 g FPH	Cradle-to-gate (fish residue acquisition and preparation to the combined production of FPH and fish oils through enzymatic hydrolysis)	Primary data from laboratory experiments, combined with secondary data	Ecoinvent v3.8	OpenLCA	Economic allocation between FPH and fish oil	No	Recipe (H) Midpoint	All those considered by the IAM	Breakdown of economic costs	No	ELCA results - For all Mis residue preparation and hydrolysis are the system hotspots; - The former most largely contributes to ozone depletion, particulate matter formation, fossil depletion, photochemical oxidant formation, and terrestrial acidification; - The latter is mostly responsible for climate change, freshwater eutrophication, and water depletion; - Freshwater ecotoxicity is equally contributed by both phases. - Electricity and ready-to-use fish residues are the major environmental impact drivers. LCC results Labour and electricity are mostly responsible for cost of producing 1 g of FPH.
Rebolledo-Leiva et al.	Techno-economic and environmental assessment of apple pomace biorefinery. A scenario analysis was performed on the vinasse comparing their valorisation into biogas (for recirculation within the biorefinery for energy purposes) with composting and lagooning	Chile	Biorefinery plant design	Technical analysis combined with a discounted cash flow analysis and an ELCA	A multifunctional approach was used in this study for bioethanol: - 1 kg; - 1 L (based on a 789 kg/m3 density); - 1 MJ (considering a 23.21 MJ/kg heating value)	Cradle-to-gate (apple pomace generation from cultivated apple processing, bioethanol production, and vinasse treatment)	Process design data, combined with background data from previously published literature and databases	Ecoinvent v3.8	Superpro designer v11 SimaPro v9.4	Economic allocation performed in the upstream part of the system, between apple juice and pomace. In the core part, all burdens were allocated to bioethanol	No	ReCiPe 2016 (H) [22]	All those considered by the IAM	Optimum Plant Capacity (OPC), Minimum Feedstock Requirements (MFR), Cumulative Energy Demand, Discounted Payback Period (DPP)	No	Different biorefinery phases contribute differently to the environmental impact of the whole system: - Pre-treatment is mostly responsible for marine eutrophication; - Purification is the major contributor to land use, water consumption, terrestrial ecotoxicity and ozone formation issues - Fermentation most largely contributes to global warming, particulate matter formation, terrestrial acidification, freshwater eutrophication, and human carcinogen-related toxicity. - Human non-carcinogen-related toxicity and marine and freshwater toxicity are mostly caused by steam generation. Vinasse treatment was the main contributor to investment and operational costs. The carbon footprint was 1.13 kg CO2 eq∙kg−1 when biogas production was integrated to reduce the energy demand of the biorefinery. If the vinasse management strategy is lagoon and compost, the footprint increases to about four. Overall, the eco-efficiency analysis showed that the scenario of co-production of bioethanol and biogas was the best alternative, although the economic dimension was a significant limitation due to high investment costs.
Ketkale and Simske	ELCA and economic cost analysis applied to CCB life cycle. The assessment was extended to testing different end-of-life (EoL) scenarios for post-use CCBs	United States of America	Industrial supply chain	Carbon-focussed and economic analysis	1 kg of a typical CCB	Cradle-to-grave (CCB manufacturing, use, and end-of-life)	Only background data were used from previously published reports and statistics combined with databases.	Ecoinvent v3.7 Environmental footprint v2.0 ELCD v3.2 Exiobase v3.4 and others	OpenLCA v2.1.3	No	No	AR5—IPCC (2013) [24]	GWP100	- Cost–benefit ratio - Marginal Cost–Willingness-to-Pay	No	Carbon footprint assessment The reuse of the CCB would also result in a saving of 1.54 kgCO2-eq for the second use since the effort to produce a new CCB would be saved. Economic analysis The general conclusion from the cost–benefit analysis is that, assuming 100,000 uses, the 50,000 CCBs that would be reused would generate USD 83,103 in net profit, with a 1.44 cost–benefit ratio. Businesses can break even at no profit by reducing new crate costs to USD 1.17, selling return crates at USD 3.66, and increasing motivational costs to USD 3.46. Exceeding these limits will have a negative impact on the profitability of the reuse cycle. The marginal cost curve shows the difference between the marginal value and the cost of motivating the population.

FU: Functional Unit; SB: System Boundary; IAM: Impact Assessment Method; MI: Midpoint Indicator.

to synthesise their main methodological aspects and application results.

3.4. Other Empirical Studies (Cluster 4 Articles)

Population growth and increased consumption are exacerbating the challenges of waste collection and treatment, requiring a rethinking of approaches to maintain ecological balance (Fontaine et al.). Local authorities aim to create sustainable urban environments through the promotion of green practices and investment in modern waste management infrastructure. From this perspective, a household engagement strategy could shift individual behaviour towards sustainability by focusing on reducing and separating waste at the source and participating in collection efforts. This strategy would facilitate efficient recycling of materials by encouraging citizens to separate their waste and make the best use of different collection methods (Fontaine et al.). Effective implementation of source separation is challenging: its success is strictly dependent on a set of factors, including design, infrastructure and incentives affecting citizens’ behaviours (Fontaine et al.).

Given the recognised importance of effective and participated separate collection for sustainable circular waste management systems, Fontaine et al. explored this research area. Proper waste source separation can contribute to minimising waste, optimising resource use and reducing environmental loads of waste management systems, as stated by Bravo et al. in the article they contributed to this SI.

In this context, by examining how strategic decisions made by local authorities affect citizens’ behaviour, Fontaine et al. identified best practices. To achieve this, they used key performance indicators (KPIs), such as sorting quality and durability metrics (e.g., greenhouse gas emissions, labour costs and energy expenses). They used an agent-based model that, though based in Canada, was calibrated for several urban contexts and considered several parameters to provide a realistic overview of the impacts that municipal decisions have on citizens’ behaviour and the environmental performance of the municipality. From the analysis, they highlighted that reducing collection frequency increased participation rates, reaching 78.2 ± 5.1% for collections every two weeks and 96.5 ± 8.3% for collections every five weeks. An additional finding from Fontaine et al.’s article worth nothing is that, while frequency reduction optimises bin filling levels, it also decreases recyclable materials up to 19.5%, which undermines the success of the recycling programme. There is an important interplay identified by the authors between collection frequency, citizen participation behaviour, waste stream quality and overall environmental performance.

From this perspective, reducing the frequency of waste collection and ensuring that citizens have access to appropriately sized bins would improve the environmental performance of municipalities. This would result in less stopping for collection vehicles and reduced carbon-related emissions and operational costs. Therefore, in addition to less frequent collection, cities should consider the introduction of larger capacity bins to optimise the environmental performance of their waste management operations (Fontaine et al.).

The issue of waste sorting behaviours was also explored by Bravo et al., but unlike Fontaine et al., the assessment focussed on the rural dimension of communities in China. The main aim of Bravo et al.’s investigation was to explore the complex interplay between interacting with the community, accessing the internet and environmental behaviours. To achieve this, the authors used a novel mixed-method approach based on data from the China Labour-Force Dynamic Survey (CLDS) conducted by Sun Yat-sen University. This approach integrates quantitative analysis with the Manski social interaction framework and a recursive bivariate probit model. This study is distinguished by its unique combination of social theory and econometric modelling to address a pressing environmental problem (Bravo et al.).

Bravo et al.’s findings highlighted the significant impact of mobile internet use and social interactions within communities on increasing willingness to sort waste, building upon previous research by Fontaine et al. Digital networking has emerged as an important enabler of environmental engagement, mediating social impacts and promoting collective approaches to waste management.

Given these findings, the authors proposed targeted policy interventions that combine digital strategies with traditional community engagement activities. To support community-centred environmental governance, they recommended digital literacy programmes and the use of social media. These strategies will increase the effectiveness of waste classification initiatives in rural China while providing scalable models for sustainable development (Bravo et al.).

Finally, Sobaih and Elnasr addressed food waste from family restaurants in the Kingdom of Saudi Arabia by performing a combined semi-structured survey of the owners and managers of these restaurants. They first performed an in-depth overview of the key factors based on their analysis, including restaurant classification; food waste drivers and types; and regional strategies and policies for preventing food waste sustainably managing what, for various reasons, could not be prevented.

The results from this study showed that the most common types of food waste in family restaurants were starchy foods, especially bread and rice, with over 50% of these items going to waste. In addition, the average rate of food waste in the sampled restaurants was at least 20% of the food served per customer. Sobaih and Elnasr found that one main reason for that was consumers’ behaviour, which was in line with Fontaine et al. and Bravo et al. In particular, the survey revealed consumers’ positive attitude towards food waste and a lack of awareness of the importance of prevention. Other reasons involved external factors, including a lack of regulations, the portion of food served and the way food waste is collected and managed, thereby involving both restaurants and local administrations.

Sobaih and Elnasr revealed that 70% of the Saudi restaurants surveyed did not have strategies to handle leftover food and reduce food waste. Thus, their study calls for a national policy and programme to favour sustainable and circular management patterns of food waste in Saudi Arabia.

4. Final Remarks from the LCA-Article Review

Eleven articles were collected in this Special Issue, which, aside from Provenzano et al., were all original research articles. Half of these were environmental LCAs, sometimes applied in combination with economic analyses, while the second half consisted of technical assessments and other empirical studies. All LCAs were conducted according to ISO 14040 and 14044 [20,21], and Wojnarowska et al. combined them with specific product category rules. In this SI, like the previous one (Ingrao et al. [2]), there were no LCSAs in the reviewed articles, which further confirms what was stated in the introductory section of this editorial. The reason for this lies in the complex integration of the three sustainability dimensions, with the social one always excluded due to the difficulty of collecting sensitive data.

Regarding the objective and scope, in all LCAs, the objectives were clearly defined and were motivated by specific research needs, often derived from gaps in the literature. All articles were characterised by a clear discussion of the main features and contributions of the research, which went beyond theoretical discussions and focussed on practical applications. This enhanced the contribution of these articles to the advancement of knowledge on the topic and confirmed LCA as a valid tool for assessing and improving sustainable and circular waste recovery, whether as a standalone production system or as the final phase within a product’s life cycle.

The functional unit and the system boundaries were set in a way that was consistent with the study’s objectives and best represents the use of the analysed system. In most cases, the system was set to focus on recovering a given waste stream to produce fuel (Vinci et al.; Rebolledo-Leiva et al.), a value-added compound (Bashiri et al.) or a commodity (Wojnarowska et al.). For all LCAs, the reference for system modelling and assessment was not the waste to be treated but the produced derived from it; the related functional unit was set accordingly, as shown in Table 3 and Table 4. Ketkale and Simske were the only authors who examined the whole life cycle of the product and found recycling vs. alternative disposal scenarios. As shown in Table 4, the study focus was represented by 1 kg of CCBs produced. Consistent with this, Ketkale and Simske performed a cradle-to-grave assessment, whereas all other authors used a cradle-to-gate approach.

Authors such as Vinci et al., Bashiri et al., and Rebolledo-Leiva et al. collected primary data for their assessments from system design or laboratory experiments and, as a standard practice in LCAs, combined them with background data from published reliable literature sources and databases. However, Ketkale and Simske and Wojnarowska et al., in line with the aim and scope of their studies, used statistical data combined with secondary data. Ecoinvent was shown to be a reliable data source that is well suited to model the background part of such recovery systems and has been used effectively by all authors in this SI; Simapro and OpenLCA were the two software packages used.

Substitution and allocation were confirmed to be two delicate modelling issues: The former were used only by Vinci et al., whereas economic allocation was used by Bashiri et al. and Rebolledo-Leiva et al. In all three studies, the choice of both approaches was coherent with the objectives set and the function of the system investigated.

The midpoint approach was preferred over the endpoint approach by almost all authors, reflecting the controversy around this approach because it is mainly based on sociopolitical considerations and generally lacks scientific rigour and accuracy for holistic evaluations of products’ life cycle profiles (Ingrao et al. [25]). This is why, despite its undoubted importance both for system-level decision and larger-scale planning activities, there is still limited interest in and consideration of the weighing stage within the field of LCA (Ingrao et al. [25]). This SI further emphasises the need for efforts to aggregate midpoint results into holistic evaluation classes using accurate, scientific approaches, such as the multicriteria decision analysis, which was performed by Ingrao et al. [25]. This would help make life cycle environmental information easier to understand and use without the need for arbitrary simplifications, while strengthening the endpoint approach to become a part of the product category rules to implement the Environmental Product Declaration (Ingrao et al. [25]).

The multi-indicator approach was proven to be effective in contributing to more holistic integrated assessments of a product’s environmental profile. This approach was utilized by all authors except Ketkale and Simske who performed a carbon footprint assessment. For all other assessments, Recipe was the most used method, thereby aligning with the general trend in LCA applications (Vinci et al.). Global warming potential, ozone layer depletion, photochemical oxidation, eutrophication and acidification, ecotoxicity and water depletion and abiotic depletion were considered to be sufficiently representative of the environmental profile of waste recovery systems.

Finally, all LCAs were conducted in a way that their findings could be generalised, projected to the future and used as the starting point for research advancement and long-term best practice development.

5. Conclusions

The SI gathered relevant studies to address sustainability issues related to resource recovery from waste management in the CE. From this perspective, according to the Guest Editors, this SI further contributed to the awareness that waste can be valorised as a zero-burden resource and sustainably transformed into value-added material and energy commodities.

In addition, this SI allowed to understand that CE principles can be applied to a wide range of sectors and issues and that there are several scientifically based methodologies, such as LCA and other related methods.

In the articles in this SI, these methodologies were confirmed to be quite effective in scientifically assessing the impacts that CE measures can have on the systems to which they are applied.

All articles documented that circular efficient recovery systems can be effective in the transition to sustainable waste management systems. Based on the findings of this review of the articles in this SI, there is still room for improvement, mainly in terms of biomass feedstock availability and conversion yields. From this point of view, the plant configuration and the availability of innovative technologies have been documented as key determinants. In addition, including local communities in the decision- and policy-making process and promoting responsible behaviours amongst citizens are essential for the success of sustainable and circular waste management implementations.

Finally, it is particularly encouraging to see that the academic community is continuing to undertake relevant research in such an important area, as evidenced by the strong response to this SI.

6. List of the Contributions to This SI

This editorial was intended to serve as an introduction to the SI, reviewing and building upon the key objectives and findings of the eleven valuable collected articles to draw observations and conclusions.

For a more in-depth study, the reader is encouraged to refer to the collection of articles available at “https://www.mdpi.com/journal/resources/special_issues/W04V6PGW59 (accessed on 20 February 2025)”.

For the reader’s convenience, the eleven articles mentioned in this review, with all bibliographical details, are listed below:

• Bashiri, B., Cropotova, J., Kvangarsnes, K., Gavrilova, O., Vilu, R., 2024. Environmental and Economic Life Cycle Assessment of Enzymatic Hydrolysis-Based Fish Protein and Oil Extraction. Resources 13(5), 61.
• Bravo, L.M.R., Cosio Borda, R.F., Quispe, L.A.M., Rodríguez, J.A.P., Ober, J., Khan, N.A., 2024. The Role of Internet and Social Interactions in Advancing Waste Sorting Behaviors in Rural Communities. Resources 13(4), 57.
• Brigida, V., Golik, V.I., Voitovich, E.V., Kukartsev, V.V., Gozbenko, V.E., Konyukhov, V.Y., Oparina, T.A., 2024. Technogenic Reservoirs Resources of Mine Methane When Implementing the Circular Waste Management Concept. Resources 13(2), 33.
• Fontaine, L., Legros, R., Frayret, J.-M., 2024. Sustainability and Environmental Performance in Selective Collection of Residual Materials: Impact of Modulating Citizen Participation Through Policy and Incentive Implementation. Resources 13(11), 151.
• Ketkale, H., Simske, S., 2023. A LifeCycle Analysis and Economic Cost Analysis of Corrugated Cardboard Box Reuse and Recycling in the United States. Resources 12(2), 22.
• Levickaya, K., Alfimova, N., Nikulin, I., Kozhukhova, N., Buryanov, A., 2024. The Use of Phosphogypsum as a Source of Raw Materials for Gypsum-Based Materials. Resources 13(5), 69.
• Provenzano, M., Pacchera, F., Silvestri, C., Ruggieri, A., 2024. From Vineyard to Value: A Circular Economy Approach to Viticulture Waste. Resources 13(12), 172.
• Rebolledo-Leiva, R., Estévez, S., Hernández, D., Feijoo, G., Moreira, M.T., González-García, S., 2024. Apple Pomace Integrated Biorefinery for Biofuels Production: A Techno-Economic and Environmental Sustainability Analysis. Resources 13(11), 156.
• Sobaih, A.E.E., Elnasr, A.E.A., 2024. From Your Plate to Our Bin: Tackling Food Waste in Saudi Family Restaurants. Resources 13(10), 134.
• Vinci, G., Gobbi, L., Porcaro, D., Pinzi, S., Carmona-Cabello, M., Ruggeri, M., 2024. Environmental Evaluation of Chemical Plastic Waste Recycling: A Life Cycle Assessment Approach. Resources 13(12), 176.
• Wojnarowska, M., Muradin, M., Paiano, A., Ingrao, C., 2025. Recycled Glass Bottles for Craft-Beer Packaging: How to Make Them Sustainable? An Environmental Impact Assessment from the Combined Accounting of Cullet Content and Transport Distance. Resources 14(2), 23.