Search Results (98)

Decentralized biomethane is vital for the energy transition; however, small-scale plants face significant energy penalties. This study evaluates the mass and energy balance of a TRL 6 pilot biorefinery treating pig manure, integrating anaerobic digestion with a microalgae-based photobioreactor coupled to an absorption column for biogas upgrading (>93 vol% CH₄, dry basis). A Life Cycle Inventory (LCI) was used to compared a theoretical mesophilic design (Scenario I, 35 °C) against an experimental psychrophilic baseline (Scenario II, avg. 12 °C). The results indicate that while winter mesophilic heating consumes 58% of gross energy production, the passive psychrophilic strategy eliminates this demand, ensuring a positive Net Energy Balance year-round. Both scenarios achieved competitive Specific Energy Consumption (SEC) (1.20 vs. 4.17 kWh·m⁻³ CH₄), while upgrading reached peak efficiency at a 10 min Hydraulic Residence Time. Furthermore, solar-synchronized load-shifting allowed for 100% electrical self-sufficiency. We conclude that although passive operation offers a superior Energy Return on Investment during cold periods (average EROI of 2.35 vs. 1.44 under winter mesophilic conditions), active mesophilic heating yields a 3-fold revenue increase, making it the superior economic choice despite the thermal penalty. Full article

This study examines how sustainability accounting practices are integrated into a Romanian medium-sized enterprise in the context of the Corporate Sustainability Reporting Directive (CSRD), addressing the lack of applied evidence from Central and Eastern Europe. The research uses a qualitative single-case study design based on internal documents, ESG and financial reports, carbon accounting data, and six semi-structured interviews with key organizational actors. The methodological framework includes mapping ESG data flows within accounting systems, applying an extended Return on Investment (eROI) model, and using an internal carbon price to assess the environmental benefits of energy-efficiency investments. The results show a structural transformation of the accounting function, including expanded sustainability-related roles, integration of ESG indicators into budgeting and reporting cycles, and improved transparency in evaluating investment projects. The use of analytical tools strengthened decision-making, increasing the assessed return of the investment portfolio when environmental and operational co-benefits were incorporated. The analysis also identifies key barriers—fragmented data systems, limited ESG expertise, and partial digitalization—and enabling factors such as CFO leadership and cross-functional collaboration. The study concludes that accountants play a strategic role in operationalizing CSRD requirements and demonstrates how SMEs can integrate financial, environmental, and operational metrics to support sustainability-oriented decisions. The findings provide theoretical contributions and practical guidance for organizations seeking to improve sustainability accounting in line with EU regulations. Full article

Globally, winery wastewaters (WWWs) are estimated to account for about 62.5 billion L annually (2021), with COD levels up to 300,000 mg O₂/L primarily attributed to residual ethanol, posing serious environmental concerns. Conventional treatments are effective in COD removal, but they often miss opportunities for energy recovery and resource valorization. This study investigates the aqueous phase reforming (APR) of ethanol-rich wastewater as an alternative treatment for both COD reduction and energy generation. Two scenarios were assessed: electricity and heat cogeneration (S1) and hydrogen production (S2). Process simulations in Aspen Plus^® V14, based on lab-scale APR data, provided upscaled material and energy flows for techno-economic analysis, life cycle assessment, and energy sustainability analysis of a 2.5 m³/h plant. At 75% ethanol conversion, the minimum selling price (MSP) was USD0.80/kWh with a carbon footprint of 0.08 kg CO₂-eq/kWh for S1 and USD7.00/kg with 2.57 kg CO₂-eq/kg H₂ for S2. Interestingly, S1 revealed a non-linear trade-off between APR performance and energy integration, with higher ethanol conversion leading to a higher electricity selling price because of the increased heat reactor duty. In both cases, the main contributors to global warming potential (GWP) were platinum extraction/recovery and residual COD treatment. Both scenarios achieved a positive energy balance, with an energy return on investment (EROI) of 1.57 for S1 and 2.71 for S2. This study demonstrates the potential of APR as a strategy for self-sufficient energy valorization and additional revenue generation in wine-producing regions. Full article

The global population surge and continuously rising energy demand have led to the rapid depletion of fossil fuel reserves. Over-exploitation of non-renewable fuels is responsible for the emission of greenhouse gases, air pollution, and global warming, which causes serious health issues and ecological imbalance. The present study focuses on the potential of algae-based biofuel as an alternative energy source for fossil fuels. Algal biofuels are more environmentally friendly and economically reasonable to produce on a pilot scale compared to lignocellulosic-derived biofuels. Algae can be cultivated in closed, open, and hybrid photobioreactors. Notably, high-rate raceway ponds with the ability to recycle nutrients can reduce freshwater consumption by 60% compared to closed systems. The algal strain along with various factors such as light, temperature, nutrients, carbon dioxide, and pH is responsible for the growth of biomass and biofuel production. Algal biomass conversion through hydrothermal liquefaction (HTL) can achieve higher energy return on investments (EROI) than conventional techniques, making it a promising Technology Readiness Level (TRL) 5–6 pathway toward circular biorefineries. Therefore, algal-based biofuel production offers numerous benefits in terms of socio-economic growth. This review highlights the basic cultivation, dewatering, and processing of algae to produce biofuels using various methods. A simplified multicriteria evaluation strategy was used to compare various catalytic processes based on multiple performance indicators. We also conferred various advantages of an integrated biorefinery system and current technological advancements for algal biofuel production. In addition to this, policies and market regulations are discussed briefly. At the end, critical challenges and future perspectives of algal biorefineries are reviewed. Algal biofuels are environmentally friendly as well as economically sustainable and usually offer more benefits compared to fossil fuels. Full article

This study analyzes the feasibility of energy mixes composed of different shares of various types of power generation units, including photovoltaic (PV) and wind farms, hydropower, fossil fuel-based plants, and nuclear power. The analysis uses the concept of Energy Return on Investment (EROI), which is considered the most reliable indicator for comparing different technologies as it measures the energy required rather than monetary costs needed to build and operate each technology. Literature-based EROI values for individual generation technologies were used, along with the minimum EROI thresholds for the entire energy mix that are necessary to sustain developed societies and a high quality of life. The results show that, depending on the assumed minimum EROI value, which ranges from 10 to 30, the maximum share of intermittent renewable energy sources (IRESs), such as PV and wind farms, in the system cannot exceed 90% or 60%, respectively. It is important to emphasize that this EROI-based analysis does not account for power grid stability, which currently can only be maintained by the inertia of large synchronous generators. Therefore, the scenario with a 90% IRES share should be regarded as purely theoretical. Full article

Achieving the Paris Agreement’s 1.5 °C target requires a global-scale energy transition, reaching net-zero emissions by 2050. This transition demands not only a rapid expansion of renewable energy but also significant upfront energy investment, presenting potential trade-offs between near-term energy security and long-term sustainability. Assuming we cannot rely on as yet unproven negative emissions technology, reductions must be achieved directly, requiring fossil fuel phase-out, accelerated electrification, and substantial renewable infrastructure development. This study presents a detailed, transparent methodology for the creation of a simplified global energy system model designed to rapidly evaluate trade-offs between energy and climate policy, integrating energy investment, depletion, and saturation dynamics into energy transition scenarios. The model simulates energy supply and demand across major sectors, accounting for the upfront energy costs of deploying new renewable infrastructure and the dynamics of electrification in different demand sectors. Its transparent, user-controllable framework allows for rapid scenario adjustments based on variables such as population growth, per capita energy demand, rate and extent of electrification, and strength of climate policy. The primary purpose of this paper is to present the system modelling framework. However, we also present preliminary results from scenario analysis that point to two emergent risks: (1) prioritising energy security increases the likelihood of exceeding carbon budgets, while (2) stringent emissions reductions heighten the risk of energy shortages. Even under non-existent climate policy, fossil fuel depletion makes both the renewable transition and electrification of demand inevitable, though delayed transition leads to more severe emissions overshoot. These findings underscore the urgent need for demand reduction strategies and a more nuanced understanding of the energy investment required for decarbonisation. By offering a flexible scenario tool, this study contributes to informed public discourse and policy decisions on balancing energy security, emissions reduction, and climate resilience. Full article

The paper presents the process of electricity and thermal energy production in a cogeneration plant and the process of wood pellet production. The aim of this study was to analyze the energy gain—EROI for energy products that are created as a product contained in electrical and thermal energy and the energy contained in wood pellets. According to the obtained results, the production of only electrical energy from wood biomass in a cogeneration plant was not sustainable from an energy point of view, since the obtained electrical energy was only 1.46 times greater than the input wood energy (EROI_el = 1.46), while the obtained energy of the produced wood pellets was 4.82 (EROI_pel = 4.82). According to the results of equivalent carbon emission, positive net value was achieved only with cogeneration plant and pellet plant working in synergy. Wood is a renewable source of energy, and its economic use can create a significant energy gain. However, due to the trend of using renewable energy sources and the increasing need for electricity, such a process of obtaining electricity is financially profitable, although it is not justified from the energy profitability and environmental sustainability point of view. Full article

In Brazil, sugarcane ethanol competes directly with gasoline as a fuel for motor vehicles, emerging as a challenging biofuel to traditional fossil fuels. The problem this article solves and presents is the Return on Energy Investment (EROI) for the production cycle of first-generation ethanol derived from sugarcane in the central-southern region of Brazil, with the main objective to compare this EROI with the gasoline marketed in Brazil, as documented in the scientific literature. The methodology for the energy analysis of the ethanol production cycle is the ratio between the energy present in a quantity of sugarcane delivered for processing and the energy consumption required for the entire process. This analysis occurs from the agricultural phase through the distribution phase of ethanol for consumption, enabling the calculation of the EROI of sugarcane ethanol and a comparative assessment with the EROI values of the gasoline marketed in Brazil. The results for EROI of sugarcane ethanol fluctuate between 8.20 and 6.52. Therefore, for each unit of energy utilized in processing ethanol, 6.52 to 8.20 units of energy are available for end use. In contrast, the EROI values for gasoline range between 2.34 and 5.50, underscoring the competitive advantage of ethanol in this context. Full article

This study aimed to assess the energy performance of three different charcoal production systems: “encosta” kiln, “rectangular” kiln, and “fornalha” kiln. Data collection involved measuring carbonization product yields and essential process variables, enabling determination of material and energy flows, and evaluation of two main energy indicators: the EROI and the energy balance. The study found that all evaluated systems had a negative energy balance, indicating inefficiency. The encosta kiln system displayed the best energy performance with the highest EROI (0.90 ± 0.45) and the greatest energy intensity (264.50 MJ t⁻¹ ± 132.25), despite having faced technological, operational, and mechanization limitations that explained its limited use on a global scale. Research that evaluates the sustainable production of charcoal has grown in recent years, however, and it is necessary to invest in studies that evaluate the existing energy flow. Thus, the energy performance indicators presented in this study offer valuable insights for decision-making in charcoal production, potentially maximizing efficiency of the systems. Optimizing carbonization system energy performance can be achieved by implementing operational parameters focused on reducing avoidable energy losses, such as improving thermal insulation and introducing systems for heat recovery or combustion gas utilization. Full article

The energy sector is responsible for a large share of climate-damaging emissions. Regarding the decarbonization of the energy sector, deep geothermal energy is considered to have high potential, particularly in the area of heat supply. In order to gauge the extent to which heat use from deep geothermal energy can make a positive contribution to climate protection, deep geothermal systems should be appraised using an environmental sustainability assessment. Although electricity generation from deep geothermal power plants has been evaluated in many ways in the literature with respect to its sustainability, no such sustainability evaluations of pure geothermal heat plants have been conducted so far. In order to close this research gap, this study presents a systematic approach that makes it possible to apply suitable sustainability criteria across the individual life stages of deep geothermal heat plants based on life-cycle assessment (LCA) guidelines. To demonstrate the effectiveness of the systematic approach presented here, a planned geothermal heat plant in the Upper Rhine Valley, Germany, serves as an example. Based on the estimated plant parameters and the predicted total heat yield, it was possible to determine, for example, the “energy returned on energy invested” (EROI) of the plant, which was approximately 34, and the specific CO₂ emissions, which were approximately 5.6 g/kWh_th. Full article

It is often claimed that marine renewable energy alone could meet the electricity demand of current and future human societies. However, such claims are based on highly uncertain estimations of the global potentials of marine renewable energy sources (including tidal, ocean currents, wave, offshore wind and salinity and thermal gradients), and do not take into account the embedded energy of current technologies. To better understand the effective potential of marine energy, we conducted a literature review of its gross, technical, economic and sustainable potentials, as well as the energy return on investment (EROI), and estimated the net energy potential. We found that all marine technologies could provide a maximum energy surplus of 57,000 $\mathrm{TWh}$/$\mathrm{yr}$. This figure goes down to $\sim 5000\mathrm{TWh}/\mathrm{yr}$ when excluding offshore wind. The previous figures do not include the contribution from ocean currents, for which no reliable estimates of global potentials and EROIs could be obtained. Due to its high upfront costs and environmental impacts and low social acceptance, no additional tidal range capacity expansion is envisioned. Similarly, the combination of a low sustainable potential and the low EROI makes the large-scale exploitation of salinity gradients unlikely with current technologies. Including all technologies, the average EROI of marine energy is $\sim 20$, but excluding offshore wind reduces the average EROI to $\sim 8$. While we did consider sustainability constraints for some marine energy sources, our estimation of marine net energy potential primarily relied on technical factors and did not account for economic and legal constraints. Therefore, the results presented here should be interpreted as an upper bound for the actual net energy contribution of marine energy sources to the global energy mix. Full article

The paper presents the results of research aimed at evaluating the possibility of using selected biomass wastes to produce solid biofuels. In this work, the thermochemical properties of two lignocellulosic biomasses, namely, miscantshus (Miscanthus × Giganteus) and hops (Humulus lupulus), and non-lignocellulosic biomass, namely, municipal solid waste, and their mixtures (micanthus + municipal solid waste and hops + municipal solid waste) were studied using the torrefaction process as the main method for investigation. The effects of various torrefaction temperatures (250, 300, and 350 °C) and times (30 and 60 min) were evaluated. Proximate and ultimate analyses were performed on the torrefied samples. The following can be stated: as the torrefaction temperature and time increased, mass and energy yields decreased while the higher heating values (HHVs) and fuel ratios (FRs) increased, together with carbon contents (C). In addition, energy on return investment (EROI) was studied; the maximum EROI of 28 was achieved for MSW biochar at 250 °C for 30 min. The results of studying greenhouse gas emissions (GHGs) showed a reduction of around 88% when using torrefied biochar as a substitute for coal. In sum, this study shows that torrefaction pre-treatment can improve the physicochemical properties of raw biomasses to a level comparable with coal, and could be helpful in better understanding the conversion of those biomasses into a valuable, solid biofuel. Full article

We use a system dynamics model to analyse the cycle of production of a nonrenewable natural resource, with a specific interest in crude oil. This subject has been empirically studied for a long time. However, modelling studies able to correlate the peaking with the parameters of the system have been very rare, and only recently proposed. In the present paper, we examine the timing of the peaking mainly as a function of the energy return for energy invested (EROI). The model provides approximate formulas for evaluating the peak time and “rules of thumb” that are useful for understanding the peaking phenomenon in the exploitation of natural resources. It shows that the peaking of the production curve occurs at a time that is inversely proportional to the EROI of the process at the start of the cycle. Full article

A number of technical solutions have been proposed for tackling global climate change. However, global climate change is not the only serious global environmental challenge we face demanding an urgent response, even though atmospheric CO₂ ppm have risen from 354 in 1990 to 416 in 2020. The rise of multiple global environmental challenges makes the search for solutions more difficult, because all technological solutions give rise to some unwanted environmental effects. Further, not only must these various problems be solved in the same short time frame, but they will need to be tackled in a time of rising international tensions, and steady global population increase. This review looks particularly at how all these environmental problems impact the future prospects for renewable energy (RE), given that RE growth must not exacerbate the other equally urgent problems, and must make a major difference in a decade or so. The key finding is that, while the world must shift to RE in the longer run, in the short term what is more important is to improve Earth’s ecological sustainability by the most effective means possible. It is shown that reducing both the global transport task and agricultural production (while still providing an adequate diet for all) can be far more effective than converting the energy used in these sectors to RE. Full article

A priori knowledge of the shelf life of energetic materials (EMs) is relevant due to its direct association with safety and functionality. This paper proposes a quick and reliable approach to predicting the shelf life of EMs whose thermal decomposition is an autocatalytic process once their failure threshold has been defined as a function of the limiting extent of conversion. This approach is based on the assumption of a kinetic law consistent with the autocatalytic behavior and on the subsequent extraction, via a suitable procedure of parameter identification, of the kinetics of thermal decomposition from differential scanning calorimetry (DSC) data gathered under dynamic conditions at three different heating rates. Its reliability is proven for picric acid (PA) through the comparison of kinetic predictions with evaluations of conversion obtained by using high performance liquid chromatography (HPLC) analysis for samples subjected to isothermal and non-isothermal accelerated aging tests, as well as for a sample of naturally aged material, i.e., PA, stored at room temperature for more than 10 years. Full article