Recovery of energy and carbon fibre from wind turbine blades waste (carbon fibre/unsaturated polyester resin) using pyrolysis process and its life-cycle assessment

Recovery of carbon fibres and resin from wind turbine blade waste (WTB) composed of carbon fibres (CF)-reinforced unsaturated polyester resin (UPR) has been environmentally challenging due to its complex structure that is not biodegradable and that is rich in highly toxic styrene (main component of UPR). Within this framework, this paper aims to liberate CF and UPR from WTB using a pyrolysis process. The treatment was performed on commercial WTB (CF/UPR) up to 600 °C using a 250 g reactor. The UPR fraction was decomposed into liquid and gaseous phases, while CF remained as a residue. The composition of gaseous phase was monitored during the entire treatment using a digital gas analyser, while gas chromatography-mass spectrometry (GC-MS) was used to characterize the collected liquid phase. CF fraction was collected and exposed to additional oxidation process after treatment at 450 °C for purification propose, then it was analysed using FTIR and SEM-EDX. Finally, the life cycle assessment (LCA) of the CF/UPR pyrolysis was studied using SimaPro software and the results were compared with landfill disposal practices. The pyrolysis results manifested that 500 °C was sufficient for UPR decomposition into styrene-rich oil and gaseous products with yields of 15.23 wt% and 6.83 wt%, respectively, accompanied by 77.93 wt% solid residue including CF. The LCA results showed that pyrolysis with oxidation process has high environmental potential in WTB recycling with significant reduction in several impact categories compared to landfill. However, the pyrolysis scenario revealed several additional environmental burdens related to ecosystems, acidification, Ozone formation, and fine particulate matter formation that must be overcome before upscaling.

Life-cycle and economic assessments of microalgae biogas production in suspension and biofilm cultivation systems

Biogas production via anaerobic digestion is highly attractive for microalgae. The technology of microalgae cultivation has profound impacts on biogas production system as it is the most energy-consuming process. However, a comprehensive evaluation of the environmental and economic benefits of different cultivation systems has yet to be sufficiently conducted. Here, life-cycle and economic assessments of open raceway ponds, photobioreactors and biofilm systems were investigated. Results showed greenhouse gas emissions of all systems were positive because more than two-thirds of carbon in fuel gas was lost and the fixed carbon in product gas and solid fertilizer was less than the emitted carbon during energy input. Particularly, biofilm system achieved the least greenhouse gas emissions (9.3 g CO2-eq/MJ), net energy ratio (0.7) and levelized cost of energy (0.9 $/kWh), indicating the optimum cultivation system. Open raceway ponds and photobioreactors failed to achieve positive benefits because of low harvesting efficiency and biomass concentration.

Waste to energy: Trending key challenges and current technologies in waste plastic management

Due to the 'forever' degrading nature of plastic waste, plastic waste management is often complicated. The applications of plastic are ubiquitous and inevitable in many scenarios. Current global waste plastics production is ca. 3.5 MMT per year, and with the current trend, plastic waste production will reach 25,000 MMT by 2040. However, the rapid growth in plastic manufacture and the material's inherent nature resulted in the accumulation of a vast amount of plastic garbage. The current recycling rate is <10 %, while the large volumes of discarded plastic waste cause environmental and ecological problems. Recycling rates for plastic vary widely by region and type of plastic. In some developed countries, the recycling rate for plastics is around 20-30 %, while in many developing nations, it is much lower. These statistics highlight the magnitude of the plastic waste problem and the urgent need for comprehensive strategies to manage plastic waste more effectively and reduce its impact on the environment. This review critically analyses past studies on the essential and efficient techniques for turning plastic trash into treasure. Additionally, an attempt has been made to provide a comprehensive understanding of the plastic upcycling process, the 3Rs policy, and the life-cycle assessment (LCA) of plastic conversion. The review advocates pyrolysis as one of the most promising methods of turning plastic trash into valuable chemicals. In addition, plastic waste management can be severely impacted due to uncontrollable events, such as Covid 19 pandemic. Recycling and chemical upcycling can certainly bring value to the end-of-life plastic. However, the LCA analysis indicated there is still a huge scope for innovation in chemical upcycling area compared to mechanical recycling. The formulation of policies and heightened public participation could play a pivotal role in reducing the environmental repercussions of plastic waste and facilitating a shift towards a more sustainable future.

Replacing Plastics with Alternatives Is Worse for Greenhouse Gas Emissions in Most Cases

Plastics are controversial due to their production from fossil fuels, emissions during production and disposal, potential toxicity, and leakage to the environment. In light of these concerns, calls to use less plastic products and move toward nonplastic alternatives are common. However, these calls often overlook the environmental impacts of alternative materials. This article examines the greenhouse gas (GHG) emission impact of plastic products versus their alternatives. We assess 16 applications where plastics are used across five key sectors: packaging, building and construction, automotive, textiles, and consumer durables. These sectors account for about 90% of the global plastic volume. Our results show that in 15 of the 16 applications a plastic product incurs fewer GHG emissions than their alternatives. In these applications, plastic products release 10% to 90% fewer emissions across the product life cycle. Furthermore, in some applications, such as food packaging, no suitable alternatives to plastics exist. These results demonstrate that care must be taken when formulating policies or interventions to reduce plastic use so that we do not inadvertently drive a shift to nonplastic alternatives with higher GHG emissions. For most plastic products, increasing the efficiency of plastic use, extending the lifetime, boosting recycling rates, and improving waste collection would be more effective for reducing emissions.

Environmental damages, cumulative exergy demand, and economic assessment of Panus giganteus farming with the application of solar technology

The use of photovoltaic (PV) technology in agricultural production can mitigate the environmental impacts of mushroom farming. However, changes in the environmental impacts and economic benefits of the application of PV technology are still unclear. Thus, we evaluated the environmental impacts, energy flow, and economic aspects of mushroom (Panus giganteus) farming systems without solar PV (WS) technology and with PV technology from the generation of substrate materials through harvesting. In addition to a 27 % increase in terrestrial ecotoxicity, P. giganteus farming with PV technology reduced all impact categories by 4-60 %, with a 60 % reduction in CO2 emissions and a 25 % reduction in land resources. These findings highlight the importance of combining PV technology with mushroom farming in agricultural carbon reduction and the efficient use of land resources. In terms of the climate change impact, the PV system reduced CO2 emissions by 2.94 kg CO2 eq./kg of mushrooms compared with the WS system, wherein the aspects of substrate transformation, spawn running, and cultivation were reduced by 78.27-89.91 %. The cumulative exergy demand (CExD) analysis showed that P. giganteus farming combined with PV technology reduced the total CExD by 48 %. With the application of PV technology, the top contributor to the total CExD of mushroom farming shifted from electricity to transportation throughout the supply chain. The PV system reduced costs by 22.09 % and increased the total revenue by 22 % and the cost-benefit ratio by 50 %. Halving the transportation distances of substrate materials and performing localized substitution of wood chips resulted in a 3-34 % reduction in the environmental impacts category and a 23-30 % reduction in nonrenewable fossil energy consumption. These results showed that improvements helped optimize the environmental performance in terms of carbon reduction and energy mixing. Thus, combining PV technology with greenhouse mushroom farming can improve trends in energy and environmental damage.

Carbon emissions from various natural gas end-use sectors for 31 Chinese provinces between 2017 and 2021

Natural gas (NG) is a low-carbon fuel that is becoming a crucial transitional energy in China for reducing carbon emissions. In this study, a life-cycle assessment was performed to correlate carbon emissions and NG consumption for different end uses in China. A bottom-up life-cycle assessment framework was combined with carbon emission coefficients to quantify NG consumption in 31 Chinese provinces between 2017 and 2021, as well as the carbon emissions (in carbon dioxide (CO2) equivalents, including CO2 and methane) released during NG production, transportation, and consumption. The carbon emission factors for different types of end-use consumption were considered. The assessment results indicate that both NG consumption and life-cycle carbon emissions from NG use have increased since 2017. Between 2017 and 2021, NG consumption in China increased from 260 to 370 billion cubic meters and life-cycle carbon emissions from NG increased by 39% (from 930 to 1292 Mt CO2). The carbon emissions released during NG production and transportation accounted for approximately 31% of NG life-cycle emissions. Considerable variations in NG life-cycle carbon emissions were identified across different provinces and sectors, highlighting the need for targeted efforts to reduce carbon emissions. The objective of this study was to provide useful insights into sustainability development of the NG industry in China for optimizing NG allocations to different end uses and maximizing the environmental and economic benefits of NG.

Advances in nitrogen removal and recovery technologies from reject water: Economic and environmental perspectives

This review critically assesses nitrogen removal technologies applied in the reject water treatment, across different stages of technological development, with a focus on their economic and environmental impacts. The prevalent use of biological processes raises concerns due to potential environmental impacts caused by N2O emissions. However, partial nitritation-anaerobic ammonium oxidation demonstrated economic benefits and the potential for positive environmental outcomes when properly operated and controlled. Furthermore, reject water, in many cases, provides sufficient nitrogen concentrations for nitrogen recovery processes, such as ammonia stripping, substituting production of industrial fertilizers and contributing to a circular economy. Nonetheless, their financial competitiveness is subject to various conditions, including the nitrogen concentration or reject water flow. As the environmental benefits of bioprocesses and economic benefits of nitrogen recovery processes may vary, it is crucial to further optimize both and investigate novel promising technologies such as electrochemical systems, denitrifying anaerobic methane oxidation or direct ammonia oxidation.

Recycling waste dolomite powder in cement paste: Early hydration process, microscale characteristics, and life-cycle assessment

Waste dolomite powder (WDP) is a byproduct obtained from dolomite quarries during the preparation of dolomite products. To study the re-utilisation of WDP, an eco-friendly cement-based material was prepared using WDP as a micro-aggregate. The effects of WDP on the early hydration process, microscale characteristics, and life-cycle assessment of cement paste are discussed in this study. The isothermal calorimetry results showed that the incorporating WDP in cement paste accelerated the early hydration process of cement according to the degree of reaction. In this case, the setting time of the cement pastes with WDP was shortened, and the early compressive strength was significantly improved. The results of X-ray diffraction and scanning electron microscopy analysis at early curing ages (1 and 3 d) showed changes in the peak intensity of ettringite and portlandite and a denser microstructure. Mercury intrusion porosimetry tests showed that the middle and large capillary pores were refined by the nucleation and filling effects of WDP. Based on environmental and economic evaluations, the utilisation of WDP reduced energy consumption, CO2 emissions, and economic costs. Compared to the sample without WDP, the energy consumption, CO2 emissions, and economic cost indices were 42 %, 42.69 %, and 39.4 % lower, respectively. Our results may provide valuable references for the re-utilisation of WDP in low-carbonation cement-based materials.

LEED-NC platinum-certified industrial manufacturing space projects in Bangladesh and their environmental assessment

This study aimed to investigate the Leadership in Energy and Environmental Design for New Construction (LEED-NC) version 3 (v3) platinum-certified industrial manufacturing space projects in Bangladesh via a life-cycle assessment (LCA). A total of 27 LEED-NC v3 projects were sorted by the energy and atmosphere (EA) "optimize energy performance" credit (EAc1) achievement: 12 projects with the highest EAc1 achievement were collected in Group 1, and 12 projects with the lowest EAc1 achievement were collected in Group 2. Significance tests demonstrated that Group 1 and Group 2 differed based on different achievements in EA, as well as in their materials and resources (MR) credits: namely, EAc1, EAc2 "on-site renewable energy", and MRc1.1 "building reuse-maintain existing walls, floors, and roof". Regarding LCA, MRc1.1 was used in the production (P) stage, and EAc1 and EAc2 were used in the operational energy (OE) stage. The ReCiPe2016 endpoint results show that, in the P stage, the Group 2 strategy resulted in the least environmental damage (p = 0.0030), while in the OE stage, the Group 1 strategy resulted in the least environmental damage (p = 0.0130). However, the overall P + OE score showed the same environmental damage, as based on both certification strategies (p = 0.4699). The contribution and novelty of this study lie in its design, which makes it possible to compare at least two LEED certification strategies in the same country, and therefore to select the best alternative among the green building projects in a particular country.

Optimal pathways for upgrading China's wastewater treatment plants for achieving water quality standards at least economic and environmental cost

Wastewater treatment plants (WWTPs) in China must be upgraded to meet new discharge standards, but this incurs both economic and environmental costs and benefits. To select the optimal upgrade pathway, we developed ten upgrade paths based on two common decision-making scenarios for WWTP upgrade in developing countries. Using model simulation, life-cycle assessment, life-cycle cost, and multiple-attribute decision-making, we incorporated the full costs and benefits associated with the construction and operation into the decision-making process. We used a weighting scheme of attributes for the three regions and ranked the upgrade paths using the technique for order preference by similarity to an ideal solution (TOPSIS). The results showed that constructed wetlands and sand filtration were advantageous in terms of lower economic costs and environmental impacts, while the denitrification filter pathways required less land. Optimal pathways differed by region, highlighting the importance of a detailed and integrated assessment of the costs and benefits of WWTP upgrade options over the full life cycle. Our findings can inform decision-making on upgrading China's WWTPs to meet stringent discharge standards and protect inland water and coastal environments.

Life-cycle assessment as a prospection stage for the biochemical methane potential of pretreated lignocellulosic biomass

The goal of neutrality in greenhouse gas emissions has intensified the search for renewable fuels. However, it is crucial to ensure sustainability of new technologies before proposing their implementation. This study proposes the use of life-cycle assessment (LCA) as an intermediary tool to identify critical hotspots in the exploration of hydrothermal pretreatment of lignocellulosic biomass, followed by biochemical methane potential assessment. Brewer s spent grain (BSG) was investigated, and laboratory-scale results were applied in an attributional assessment model with business-as-usual serving as the baseline. The LCA revealed that assumptions made in the lab could pose limitations. In Brazil, the two-stage co-digestion of pretreated hydrothermal BSG showed promising prospects, with a reduction to a new value of -54 kg CO2-eq Ton-1 BSG compared to 90 kg CO2-eq Ton-1 BSG in the business-as-usual scenario. Within the top ten global beer producing countries, only Brazil and Spain demonstrated potential for exploring this proposal.

Removal of toilet paper fibers from residential wastewater: a life cycle assessment

Toilet paper has been reported as one of the major insoluble pollutant components in the influent of wastewater treatment plants. Toilet paper fibers contribute to a large production of sewage sludge, resulting in a high treatment cost and high energy consumption. To find energy-efficient, cost-effective, and environment-friendly technologies for fiber removal and resource recovery from wastewater, a life-cycle assessment (LCA) was performed to analyze the wastewater treatment processes, including a sieving process for removing and recovering suspended solids before the biodegradation units. Based on the LCA results, it was estimated that the sieve screening process saved 8.57% of energy consumption. The construction phase of sieving consumed 1.31% energy cost compared with the operation phase. Environmental impact analysis showed that sieving reduced the impacts of climate change, human toxicity, fossil depletion, and particulate matter formation, which reduced the total normalized environmental impacts by 9.46%. The life-cycle analysis of the removal of toilet paper fibers from wastewater revealed the need to use more efficient methods to enhance the recovery of cellulose fibers.

Co-pyrolysis of medical protective clothing and oil palm wastes for biofuel: Experimental, techno-economic, and environmental analyses

The ongoing global pandemic of COVID-19 has devastatingly influenced the environment, society, and economy around the world. Numerous medical resources are used to inhibit the infectious transmission of the virus, resulting in massive medical waste. This study proposes a sustainable and environment-friendly method to convert hazardous medical waste into valuable fuel products through pyrolysis. Medical protective clothing (MPC), a typical medical waste from COVID-19, was utilized for co-pyrolysis with oil palm wastes (OPWs). The utilization of MPC improved the bio-oil properties in OPWs pyrolysis. The addition of catalysts further ameliorated the bio-oil quality. HZSM-5 was more effective in producing hydrocarbons in bio-oil, and the relevant reaction pathway was proposed. Meanwhile, a project was simulated to co-produce bio-oil and electricity from the co-pyrolysis of OPWs and MPC from application perspectives. The techno-economic analysis indicated that the project was economically feasible, and the payback period was 6.30-8.75 years. Moreover, it was also environmentally benign as its global warming potential varied from -211.13 to -90.76 kg CO₂-eq/t. Therefore, converting MPC and OPWs into biofuel and electricity through co-pyrolysis is a green, economic, and sustainable method that can decrease waste, produce valuable fuel products, and achieve remarkable economic and environmental benefits.

Enhanced biomethane production with a low carbon footprint via anaerobic co-digestion of swine wastewater with rice husk

An electricity-assisted anaerobic co-digestion (EAAD) process was developed and compared with conventional anaerobic co-digestion (AD) using piggery wastewater and rice husk as feedstocks. Various methodologies, including kinetic models, microbial community analyses, life-cycle carbon footprints, and preliminary economic analysis, were integrated to comprehensively evaluate the performance of the two processes. The results demonstrated that EAAD exhibited a positive improvement of 2.6 % to 14.5 % in biogas production compared to AD. The suitable wastewater-to-husk ratio for EAAD was found to be 3:1, which corresponded to a carbon-to‑nitrogen ratio of approximately 14. This ratio demonstrated positive co-digestion effects and electrical enhancements in the process. According to the modified Gompertz kinetics, the biogas production rate in EAAD ranged from 1.87 to 5.23 mL/g-VS/d, significantly higher than the range of 1.19 to 3.74 mL/g-VS/d observed in AD. The study also investigated the contributions of acetoclastic and hydrogenotrophic methanogens to biomethane formation, revealing that acetoclastic methanogens accounted for 56.6 % ± 0.6 % of the methane production, while hydrogenotrophic methanogens contributed to 43.4 % ± 0.6 %. No significant difference in the methanogenic reaction pathways was observed between AD and EAAD, indicating that the introduction of an external electric field did not alter the predominant pathways (p > 0.05, two-sample t-test). Furthermore, retrofitting existing AD plants with EAAD units can reduce the carbon intensity of piggery wastewater treatment by 17.6 % to 21.7 %. The preliminary economic analysis indicated a benefit-cost ratio of 1.33 for EAAD, confirming the feasibility of implementing EAAD for wastewater treatment while simultaneously producing bioenergy. Overall, this study provides valuable insights into upgrading the performance of existing AD plants by introducing an external electric field. It demonstrates that EAAD can achieve higher and cost-effective biogas production with a lower life-cycle carbon footprint, thus enhancing the sustainability and efficiency of the biogas production process.

Life-cycle economic and environmental impacts of municipal solid waste reverse logistics in residential areas

The economic and environmental impacts of the reverse logistics (RL) process (including drop-off, collection and transportation [C&T]) of the waste disposal chain are becoming increasingly prominent with the increasing generation of municipal solid waste (MSW) and promotion of MSW classification. Quantitative evaluation of this process from economic and environmental perspectives is of great significance for MSW management. This study focused on the financial capital, materials, and energy consumption in the RL process in Xi an City, China. Based on field investigation, the magnitude of pollutant emissions from MSW C&T vehicles over their life cycle was predicted using the GREET software and total RL life-cycle cost and life-cycle assessment were analyzed. The results showed that the finical costs of RL were $46.35-$49.03 per ton of food waste and $62.52-$88.84 per ton of residual waste; the environmental impacts caused by the RL process accounted for 79.24%-96.00% and 20.87%-68.55% of the entire food waste and residual waste management chains, respectively. Labor costs were the biggest financial expenditure and the fuel cycle of C&T vehicles caused the majority of the environmental impacts. Source-separated waste management scenarios represented more environmental benefits but poorer economic positions. In the future, improving MSW source-separation accuracy, replacing diesel C&T vehicles with electric ones, and optimizing the RL system could reduce the environmental and economic impacts of the entire waste management system.

Using circular economy principles in the optimisation of sludge-based activated carbon production for the removal of perfluoroalkyl substances

Massive sewage sludge (SS) production from municipal wastewater treatment plants and the presence of numerous pollutant types render the process of SS treatment and disposal costly and complex. Here, resource recovery from SS was maximised via the optimisation of sludge-based activated carbon (SBAC) production for the removal of poly- and perfluoroalkyl substances (PFASs), while considering economic factors and minimising environmental impacts. SBAC production optimisation was realised under different operating conditions (different ZnCl₂ impregnation ratios and different pyrolysis activation temperatures and durations). The sorption capacity of the optimised SBAC with respect to the removal of nine commonly detected PFASs, with environmentally relevant concentrations (∽50 μg/L), from simulated wastewater was evaluated. Economic analysis and life-cycle assessment (LCA) were also performed to determine the feasibility of the process and its potential role in the circular economy. Batch adsorption tests confirmed the high efficiency of the optimised SBACs for PFAS removal (93-100 %), highlighting the possibility of converting SS to SBAC. Economically speaking, the optimised SBAC at 1.5 M ZnCl₂, 500 °C, and 0.75 h reduced total production cost by 49 %. Further, the cost could be reduced to as little as 1087 US $/metric-ton compared with that corresponding to the original conditions (2.5 M ZnCl₂, 500 °C, 2 h; 2144 US $/metric-ton). LCA results also showed that freshwater ecotoxicity, marine ecotoxicity, and human non-carcinogenic toxicity were the most affected environmental impact indicators, showing a 49 % decrease when ZnCl₂ impregnation ratio was reduced from 2.5 to 1.5 M. These findings highlighted the optimal conditions for the production of SBAC with high sorption capacity at a reduced cost and with reduced environmental impacts. Thus, they can serve as valuable tools for decision making regarding the selection of the most sustainable and economically feasible process for PFAS removal.

Life-cycle assessment of yeast-based single-cell protein production with oat processing side-stream

Production of fish meal and plant-based feed proteins continues to increase to meet the growing demand for seafood, leading to impacts on marine and terrestrial ecosystems. Microbial proteins such as single-cell proteins (SCPs) have been introduced as feed alternatives since they can replace current fish feed ingredients, e.g., soybean, which are associated with negative environmental impacts. Microbial protein production also enables utilization of grain processing side-streams as feedstock sources. This study assesses the environmental impacts of yeast-based SCP using oat side-stream as feedstock (OS-SCP). Life-cycle assessment with a cradle-to-gate approach was used to quantify global warming, freshwater eutrophication, marine eutrophication, terrestrial acidification, land use, and water consumption of OS-SCP production in Finland. Dried and wet side-streams of oat were compared with each other to identify differences in energy consumption and transportation effects. Sensitivity analysis was performed to examine the difference in impacts at various locations and fermentation times. Benchmarking was used to evaluate the environmental impacts of OS-SCP and other feed products, including both conventional and novel protein products. Results highlight the importance of energy sources in quantifying the environmental performance of OS-SCP production. OS-SCP produced with dried side-streams resulted in higher global warming (16.3 %) and water consumption (7.5 %) than OS-SCP produced from wet side-streams, reflecting the energy and water requirements for the drying process. Compared with conventional products, such as soy protein concentrates, OS-SCP resulted in 61 % less land use, while exacerbating the environmental impacts in all the other categories. OS-SCP had more impact on global warming (205-754 %), water consumption (166-1401 %), freshwater eutrophication (118-333 %), and terrestrial acidification (85-340 %) than other novel products, including yeast protein concentrate, methanotrophic bacterial SCP, and insect meal, while lowering global warming (11 %) and freshwater eutrophication (20 %) compared with dry microalgae biomass.

Aiming for More Sustainable Cross-Coupling Chemistry by Employing Single-Atom Catalysis on Scale

Scaling up syntheses from mg to kg quantities is a complex endeavor. Besides adapting laboratory protocols to industrial processes and equipment and thorough safety assessments, much attention is paid to the reduction of the process' environmental impact. For processes including transition metal catalyzed steps, e.g. cross-coupling chemistry, this impact strongly depends on the identity of the metal used. As such, a key approach is the replacement of single-use with reusable heterogeneous catalysts. Transition metal single-atom heterogeneous catalysts (SAC), a novel class of catalytic materials, might exhibit all the necessary properties to step up to this task. This article shall discuss current applications of SAC in cross-coupling chemistry from the point of a process chemist and shed light on the NCCR Catalysis contribution to the field. Investigations of the stability-activity-selectivity relationship of SACs in combination with early-stage life-cycle assessments (LCA) of potential processes lay the foundation for large-scale application tailored catalyst synthesis. Ultimately, prevailing challenges are highlighted, which need to be addressed in future research.

Hydration mechanism and environmental impacts of blended cements containing co-combustion ash of sewage sludge and rice husk: Compared with blended cements containing sewage sludge ash

In this study, the hydration mechanism and environmental impacts of blended cements with the co-combustion ash of rice husk and sewage sludge (CCA) were investigated and compared to those of blended cements with sewage sludge ash (SSA). CCA possesses lower phosphate contents than SSA, leading to lower inhibition effects on early hydration of cement clinker. Moreover, the pozzolanic activity of CCA is higher than that of SSA. Thus, more hydration products from the pozzolanic reaction of CCA are generated in CCA-based blended cements. Compared to the matrix of SSA-based blended cements, that of their CCA-based counterpart is filled with more hydration products, which promotes porosity refinement and strength development of CCA-based blended cements at later ages. CCA-based blended cements exhibit greater environmental benefits than SSA-based blended cements because fossil consumption and toxic substance emissions during the co-combustion of rice husk and sewage sludge is lower than that during the mono-combustion of sewage sludge.

A comparative life-cycle assessment and cost analysis of biofilters amended with sludge-based activated carbon and commercial activated carbon for stormwater treatment

Environmental and economic issues resulting from the unsustainable management of sewage sludge from wastewater have necessitated the development of eco-friendly sewage sludge disposal methods, whereas stormwater effluent contains tremendous amounts of pollutants. This study compares the feasibility and environmental impacts associated with incorporating biofilters with sludge-based activated carbon (SBAC) versus commercial activated carbon (CAC) for stormwater treatment. The results demonstrate that the construction and disposal life-cycle stages are the dominant contributors to several environmental impact categories, including resource scarcity, carcinogenic toxicity, terrestrial ecotoxicity, and ozone formation indicators. Across multiple impact categories, the incorporation of biofilters with SBAC can reduce the negative environmental impacts associated with biofilter construction and disposal by 40% over a 50-year analysis period. In contrast, the most significant improvement is on construction-dominant indicators, where the decreased need for biofilter reconstruction results in a higher reduction in environmental impacts. Economically, amending the biofilter with SBAC can increase profits by up to 66% due to extending its lifespan. This study shows that SBAC has similar performance as CAC for lowering the negative environmental impacts resulting from biofilter construction, while increasing the overall net profits of the system. However, converting sewage sludge to an effective sorbent (SBAC) and incorporating SBAC into a biofilter to capture pollutants from stormwater is an economically and environmentally sustainable solution available to practitioners to manage sewage sludge and stormwater effluent. This solution protects the environment in a cost efficient, sustainable manner.

Systematizing Microbial Bioplastic Production for Developing Sustainable Bioeconomy: Metabolic Nexus Modeling, Economic and Environmental Technologies Assessment

The excessive usage of non-renewable resources to produce plastic commodities has incongruously influenced the environment's health. Especially in the times of COVID-19, the need for plastic-based health products has increased predominantly. Given the rise in global warming and greenhouse gas emissions, the lifecycle of plastic has been established to contribute to it significantly. Bioplastics such as polyhydroxy alkanoates, polylactic acid, etc. derived from renewable energy origin have been a magnificent alternative to conventional plastics and reconnoitered exclusively for combating the environmental footprint of petrochemical plastic. However, the economically reasonable and environmentally friendly procedure of microbial bioplastic production has been a hard nut to crack due to less scouted and inefficient process optimization and downstream processing methodologies. Thereby, meticulous employment of computational tools such as genome-scale metabolic modeling and flux balance analysis has been practiced in recent times to understand the effect of genomic and environmental perturbations on the phenotype of the microorganism. In-silico results not only aid us in determining the biorefinery abilities of the model microorganism but also curb our reliance on equipment, raw materials, and capital investment for optimizing the best conditions. Additionally, to accomplish sustainable large-scale production of microbial bioplastic in a circular bioeconomy, extraction, and refinement of bioplastic needs to be investigated extensively by practicing techno-economic analysis and life cycle assessment. This review put forth state-of-the-art know-how on the proficiency of these computational techniques in laying the foundation of an efficient bioplastic manufacturing blueprint, chiefly focusing on microbial polyhydroxy alkanoates (PHA) production and its efficacy in outplacing fossil based plastic products.

Parametrized regionalization of paper recycling life-cycle assessment

Recycling is a commonly acknowledged strategy to reduce the environmental impacts linked to primary resource exploitation. Large regional variations can be observed in recycling processes' parameters, like efficiency, energy mix and treatment of rejects. Life-cycle assessment (LCA) is widely used to evaluate the environmental impacts of recycling processes, but existing studies are neither harmonized nor sufficient to provide a comprehensive geographical and technological coverage of recycling processes. The purpose of this research is to develop an efficient and iterative approach for the parametrized generation of semi-automated regionalized life-cycle inventories that take into account technological and geographical variabilities in the recycling sector. The regionalization framework is then applied to create a parametrized paper recycling regionalization tool. This tool is used in the results section to compare the national climate change impacts of recycling three paper grades. Results show a significant global warming impact variability between countries for recycled graphic paper (0.36 to 2.25 kg CO₂-Eq/kg wastepaper recycled), newsprint (0.27 to 1.84 kg CO₂-Eq/kg wastepaper recycled) and corrugated cardboard (0.28 to 1.68 kg CO₂-Eq/kg wastepaper recycled) productions. A regionalized LCA of the international recycling of the mixed wastepaper exported from Quebec's (Canada) sorting centers is also performed with the tool and compared to the non-regionalized mixed wastepaper recycling process available in the ecoinvent database. Only nine midpoint ReCiPe impact categories remain environmentally advantageous compared to virgin paper production when applying the regionalization methodology, compared to sixteen when using the ecoinvent process, illustrating how regionalization can substantially influence LCA results.

Machine learning for surrogate process models of bioproduction pathways

Technoeconomic analysis and life-cycle assessment are critical to guiding and prioritizing bench-scale experiments and to evaluating economic and environmental performance of biofuel or biochemical production processes at scale. Traditionally, commercial process simulation tools have been used to develop detailed models for these purposes. However, developing and running such models can be costly and computationally intensive, which limits the degree to which they can be shared and reproduced in the broader research community. This study evaluates the potential of an automated machine learning approach to develop surrogate models based on conventional process simulation models. The analysis focuses on several high-value biofuels and bioproducts for which pathways of production from biomass feedstocks have been well-established. The results demonstrate that surrogate models can be an accurate and effective tool for approximating the cost, mass and energy balance outputs of more complex process simulations at a fraction of the computational expense.

Life-cycle assessment of flue gas CO2 fixation from coal-fired power plant and coal chemical plant by microalgae

The technology of flue gas CO₂ fixation by microalgae is highly attractive in the era of CO₂ neutrality. However, CO₂ emission along the whole process has yet to be sufficiently evaluated. Here, a life-cycle assessment was performed to evaluate the energy conversion characteristics and environmental impacts of flue gas CO₂ fixation from coal-fired power plant (Case 1) and coal chemical plant (Case 2) by microalgae. The results show that total energy consumption and CO₂ gas emissions for Case 1 are 27.5-38.0 MJ/kg microalgae power (MP) and 5.7-7.7 kg CO₂ equiv/kg MP, respectively, which are lower than that for Case 2 (122.5-181.3 MJ/kg MP and 32.7-48.6 kg CO₂ equiv/kg MP). The CO₂ gas aeration rate and microalgae growth rate are the two most sensitive parameters for the energy conversion and net CO₂ emission. Therefore, increasing the CO₂ aeration efficiency and microalgae growth rate are key to advance the technology of flue gas CO₂ fixation by microalgae which will contribute to carbon naturality.

Process development, techno-economic analysis and life-cycle assessment for laccase catalyzed synthesis of lignin hydrogel

In this study, an effort has been undertaken to study process design, techno-economic analysis, and life-cycle assessment (LCA) of lignin hydrogel (LH) which has potential applications in environmental remediation. Minimum selling price (MSP) of LHs has been estimated to be 2,141 US$/ton and it lies within the range of market price (1,420-2,280 US$/ton) for commercial coagulants. Further, sensitivity analysis has been conducted and it was observed that "% efficiency of lignin hydrogel production" and "lignin price" were the most influential parameters. Uncertainty analysis has also been conducted to study the influence of volatility in the market price of lignin and total capital investment on MSP of LH. From LCA study, it was estimated that the proposed process will emit 2.8 kg CO2 eq. and 1.1 kg Oil eq./kg lignin hydrogel. The developed process can be utilized for lignin upgradation in biorefineries to develop economically feasible and sustainable processes.

Development of an economically competitive Trichoderma-based platform for enzyme production: Bioprocess optimization, pilot plant scale-up, techno-economic analysis and life cycle assessment

Despite decades of research and industrial applications of Trichoderma reesei, the development of industrially relevant strains for enzyme production including a low-cost and scalable bioprocess remains elusive. Herein, bioprocess optimization, pilot plant scale-up, techno-economic analysis and life-cycle assessment for enzyme production by an engineered T. reesei strain are reported. The developed bioprocess increased in ∼ 2-fold protein productivity (0.39 g.L-1.h-1) and 1.6-fold FPase activity (196 FPU.L-1.h-1), reducing the fermentation in 4 days. Cultivation in a 65-L pilot plant bioreactor resulted in 54 g.L-1 protein in 7 days, highlighting the robustness and scalability of this bioprocess. Techno-economic analysis indicates an enzyme cost of ∼ 3.2 USD.kg-1, which is below to the target proposed (4.24 USD.kg-1) in the NREL/TP-5100-47764 report, while life-cycle assessment shows a carbon footprint reduction of approximately 50% compared to a typical commercial enzyme. This study provides the fundamental knowledge for the design of economically competitive Trichoderma technologies for industrial use.

Life-cycle assessment approach for municipal solid waste management system of Delhi city

The life-cycle assessment (LCA) approach with route optimization technique was adopted in the present study to evaluate environmental and economic aspects associated with the prevalent waste management system in Delhi city. With an objective of cost minimization and abating environmental hazards from waste transportation systems, ArcGIS was used to identify the most appropriate route for waste transportation. The study was conducted considering four landfills located at Bawana, Bhalswa, Ghazipur and Okhla present in Delhi city. Landfilling, composting, anaerobic digestion, and recycling methods were analyzed for global warming potential (GWP), eutrophication potential (EP), acidification potential, abiotic resource depletion potential and photochemical oxidation potential parameters using LCA software GaBiPro. The results from the LCA studies for the municipal solid waste management system of Delhi city revealed that transportation emissions and landfilling negatively impact the environment. The effect of recycling rate on the landfilling, composting, anaerobic digestion was also studied using sensitivity analysis. Results of sensitivity analysis depicted that recycling of waste is inversely related to the impact categories. Overall, the results exhibited a detrimental effect of landfilling on the environment in terms of GWP and EP. Further, considering the geospatial analysis, two waste recycling stations are proposed in the vicinity of existing waste management plants to reduce the time and cost of waste transport from the landfills to the waste management plants.

The Development Scenarios and Environmental Impacts of China's Aluminum Industry: Implications of Import and Export Transition

Aluminum is widely used in buildings, transportation, and home appliances. However, primary aluminum production is a resource, energy, and emission-intensive industrial process. As the world's largest aluminum producer, the aluminum industry (ALD) in China faces tremendous pressure on environmental protection. This study combines material flow analysis and scenario analysis to investigate the potential of resource conservation, energy saving, and emission reduction for China's ALD under the import and export trade transition. The results show China's per capita aluminum stock will follow a logistic curve to reach 415 kg/capita by 2030. However, unlike the continued build-up of stocks, domestic demand for aluminum will peak at 44 million tons (MT) in 2025 and fall to 36 MT in 2030. The scenario analysis reveals that China's primary aluminum output could peak in 2025 at around 52 MT if the restrictions are not implemented (Scenario A). Compared to Scenario A, demand for primary aluminum is effectively limited in Scenarios B and C where exports of aluminum products are reduced. Correspondingly, both scenarios also have obvious benefits in reducing the environmental load of China's ALD. Besides, if hydropower used in aluminum electrolysis increases to 25% by 2030, the total GHG emissions in 2030 will be reduced by 12%. Therefore, promoting import/export and energy mix transformation can become an essential means for the sustainable development of China's ALD.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40831-022-00582-0.

Agro-industrial wastewater-grown microalgae: A techno-environmental assessment of open and closed systems

Microalgae-based treatment can be applied to the bioremediation of agro-industrial wastewater, aiming at a circular economy approach. The present work compared the technical-environmental feasibility of operating a bubble column photobioreactor (PBR) and a high rate pond (HRP) for microalgae biomass production and wastewater treatment of a meat processing facility. The comparison was made regarding biomass productivity, phytoplankton composition, treatment efficiency, life cycle assessment, and energy balance. The daily yields of total biomass and the maximum specific growth rates were 483.33 mg L^-1 d^-1 and 0.23 d^-1 for PBR and 95.00 mg L^-1·d^-1 and 0.193 d^-1 for HRP, respectively, with a predominance of the species Scenedesmus acutus. The treatment efficiency of COD (~50%) and phosphorus (100%) were similar in the two reactors. However, the PBR showed greater assimilation of ammoniacal nitrogen (100% removal) due to the higher microalgal biomass productivity. Environmental impacts were assessed through the ReCiPe methodology for midpoint and endpoint levels. Results revealed that CO₂ supply was the most impactful process for both systems (>60%), but HRP reached lower environmental burdens (-105.90 mPt) than PBR (60.74 mPt). Energy balance through the Net Energy Ratio also resulted in the HPR advantage over the PBR (NER = 14.23 and 1.09, respectively). Still, both reactors present advantages when applied to different valorization routes. At the same time, both present room for improvement in the light of bioeconomy and biorefineries, aiming at sustainable wastewater treatment plants.

Systems analysis of digestate primary processing techniques

In this paper, we performed technology assessment and systems analysis of primary digestate processing techniques to provide a comprehensive analysis of their environmental and cost performance. We compiled more than 100 observations from large-scale biogas plants and considered digestate based on manure, crops and agro-wastes, and food waste under the geographical contexts of Sweden and Belgium. Centrifuge, screw press, and rotary drum were identified as suitable primary processing techniques. We analyzed the climate impact, energy use, and operational cost of digestate management under these scenarios: no processing, partial processing (solid-liquid separation) and full processing (solid-liquid separation followed by ammonia stripping). As expected, the suitable digestate processing varied with the context, transport was often the most critical cost factor, and emissions from storage reduced the climate savings from the use of biofertilizers. However, treating liquid fraction became a main contributor to cost and climate impact under the Belgian conditions. Consequently, the possibility for local application of liquid fraction as biofertilizer could prevent costs and impacts associated with its further treatment. The main novelty of this work is in its integrative and comprehensive approach toward the choices and impacts of primary processing of digestate. We tried to bridge many individual case studies, drew from experiences of biogas plants in different geographical contexts, assessed suitable processing techniques for different digestate types, and analyzed the environmental impacts and cost of digestate management from a life cycle perspective. We believe that such integrated approaches would help decision-making for increased sustainability of the biogas sector.

Multicriteria analysis on environmental impacts of accelerated vehicle retirement program from a life-cycle perspective: A case study of Beijing

The environmental benefits of accelerated vehicle retirement programs (AVRPs), which have been extensively adopted in many countries, are highlighted by the proponents. However, the methods for evaluating their environmental effects are lacking of considering material and water criteria as well as continuous improvement in vehicle fuel efficiency and emission control. Additionally, the studies on Chinese case only considered air pollutants during vehicle usage and assumed a fixed remaining lifetime of old vehicles. This study therefore proposed a multicriteria life-cycle analysis model, which embeds not only vehicle lifetime distribution but also dynamics of vehicle fuel efficiency and emission factors, to examine the environmental effects of AVRP more comprehensively in terms of material, water, and energy consumption as well as emission of greenhouse gas, air pollutants and water pollutants. The assessment of the AVRP in Beijing, China, shows that short-term environmental benefits can be hardly gained from a life-cycle perspective, and energy consumption, greenhouse gases and other pollutants (except for volatile organic compound) decrease only when the users keep their new vehicles for 3 years or more. In the medium term, the AVRP would slightly increase material, energy and water consumption, sulfur-oxide, greenhouse gas and water pollutants, but significantly or moderately reduce other air pollutants. Moreover, the results reveal that merely considering the phase of vehicle usage may also lead underestimating some environmental benefits of AVRP by ignoring the phase of fuel production, whilst promoting vehicle fuel efficiency standards and the environmental regulations on vehicle and fuel supply chains may minimize the environmental benefits of AVRP or even have adverse effects.

A negative-carbon footprint process with mixed biomass feedstock maximizes conversion efficiency, product value and CO2 mitigation

The great variety of biomass species offers unique features for synergistic optimization of process outcomes. In this work, spent mushroom substrate and bagasse with optimize ratio were processed to produce value-added products of activated carbon and biofuel yet achieve negative CO₂ emission. By integrating experimental characterization, this work uses process simulation, techno-economic analysis and life-cycle assessment to evaluate the techno-economic viability and CO₂ footprint of processes with single or dual-/mixed-biomass feedstocks. The combination of biomass species provides unique match of the production of flue gas and primary carbon that is critical for the optimization of mass and energy flow. Such combination has been demonstrated effective to improve product yield and energy efficiency. Results show that mixed biomass feedstock offers favourable figures such as high carbon efficiency of 66.74%, short payback period of 3.16 years, considerable net present value of 80.48 million dollars, and low GWP of -2.37 kg CO₂-eq.

Integrated cost and environmental impact assessment of management options for dredged sediment

Large quantities of sediment must be dredged regularly to enable marine transport and trade. The sediments are often polluted, with e.g. metals, which limits the management options. The aim of this study has been to assess costs and environmental impacts (impact on climate, marine organisms, etc.) of different management options for polluted dredged sediment, by combining life-cycle assessment (LCA) of the climate impact, scoring of other environmental aspects and a cost evaluation. This approach has been used to study both traditional and new management alternatives for a real port case. The studied options include landfilling, deep-sea disposal, construction of a port area using a stabilization and solidification (S/S) method, and a combination of the aforementioned methods with the innovative option of metal recovery through sediment electrolysis. The LCA showed that deep-sea disposal had the lowest climate impact. The assessment of the other environmental impacts showed that the result varied depending on the pollution level and the time perspective used (short or long-term). Using sediment for construction had the highest climate impact, although other environmental impacts were comparably low. Electrolysis was found to be suitable for highly polluted sediments, as it left the sediment cleaner and enabled recovery of precious metals, however the costs were high. The results highlight the complexity of comparing different environmental impacts and the benefits of using integrated assessments to provide clarity, and to evaluate both the synergetic and counteracting effects associated with the investigated scenarios and may aid early-stage decision making.

Global Shipping Emissions from a Well-to-Wake Perspective: The MariTEAM Model

Improving the robustness of maritime emission inventories is important to ensure we fully understand the point of embarkment for transformation pathways of the sector toward the 1.5 and 2°C targets. A bottom-up assessment of emissions of greenhouse gases and aerosols from the maritime sector is presented, accounting for the emissions from fuel production and processing, resulting in a complete "well-to-wake" geospatial inventory. This high-resolution inventory is developed through the use of the state-of-the-art data-driven MariTEAM model, which combines ship technical specifications, ship location data, and historical weather data. The CO₂ emissions for 2017 amount to 943 million tonnes, which is 11% lower than the fourth International Maritime Organization's greenhouse gas study for the same year, while larger discrepancies have been found across ship segments. If fuel production is accounted for when developing shipping inventories, total CO₂ emissions reported could increase by 11%. In addition to fuel production, effects of weather and heavy traffic regions were found to significantly impact emissions at global and regional levels. The global annual efficiency for different fuels and ship segments in approximated operational conditions were also investigated, indicating the need for more holistic metrics than current ones when seeking appropriate solutions aiming at reducing emissions.

Biofuels and biorefineries: Development, application and future perspectives emphasizing the environmental and economic aspects

The fossil fuel utilization adversely affected the environmental health due to the rising emission levels of greenhouse gases. Consequently, the challenges of climate change loaded great stress on renewable energy sources. It is noted that extreme consumption of fossil fuels increased the earth temperature by 1.9 °C that adversely influenced the life and biodiversity. Biorefinery is the sustainable process for the production of biofuels and other bio-products from biomass feedstock using different conversion technologies. Biofuel is an important component of renewable energy sources contributing to overall carbon-neutral energy system. Studies reported that on global scale, over 90% of petroleum goods could be produced from renewable resources by 2023, whereas, 33% chemicals, and 50% of the pharmaceutical market share is also expected to be bio-based. This study details the brief review of operation, development, application, limitations, future perspectives, circular bioeconomy, and life cycle assessment of biorefinery. The economic and environmental aspects of biofuels and biorefineries are briefly discussed. Lastly, considering the present challenges, the future perspectives of biofuels and biorefineries are highlighted.

Non-sterile examination gloves and sterile surgical gloves: which are more sustainable?

BACKGROUND

Healthcare professionals should consider environmental sustainability when using personal protective equipment (PPE). One of the most frequently used items of PPE in medical settings are gloves.

AIM

This study aims to quantify the environmental impact of sterile versus non-sterile gloves using the life cycle assessment (LCA) methodology.

METHODS

This study used three glove types: non-sterile gloves and sterile gloves (latex and latex-free). Sixteen different environmental impact categories were used to demonstrate the impact of each glove type.

FINDINGS

Non-sterile gloves had the least environmental impact in all categories. The two types of sterile gloves, non-latex (synthetic rubber) and latex (natural rubber), performed similarly, although the non-latex gloves had a greater impact on ozone depletion, mineral use and ionizing radiation. For climate change impact, sterile latex gloves were 11.6 times higher than non-sterile gloves. This study found that for both sterile type gloves (latex and non-latex), the manufacture of the gloves contributes to the most considerable environmental impact, with an average of 64.37% for sterile latex gloves and 60.48% for non-latex sterile gloves.

CONCLUSION

Using the LCA methodology, this study quantitatively demonstrated the environmental impact of sterile versus non-sterile gloves.

Study of seashell waste recycling in fireproofing material: Technical, environmental, and economic assessment

The productive sector must incorporate waste into traditional materials in order to grow sustainably. In Galicia (Spain) alone, the canning industry produces over 150,000 metric tons of seashell waste per year. Most of this waste is still disposed of in landfills or open fields due to the lack of a technically feasible, environmentally sustainable, and economically profitable recycling alternative. This paper aims to study the feasibility of a new recycling alternative for seashell waste from industrial canning, based on the production of fireproof material suitable for construction use. The waste was pre-treated in order to remove salts and remaining organic matter and reduce particle size. According to international standards, physical, mechanical, and insulating properties were assessed for four compositions: 0, 40, 60 and 80% of gypsum substituted with pre-treated seashell waste. Results showed that substitution of up 60% gypsum was technically feasible. A Life-Cycle Assessment and a preliminary production cost analysis were performed by analysing a recycling case in Galicia. The case study found that 40-60% gypsum substitution obtained an environmental impact reduction of 0.4%-59% for 13 of the 18 impact categories considered compared with 0% substitution. Increases in the other 5 categories were analysed due to aquatic emissions released in the waste pre-treatment washing process. The locations of the fireproof material production facility and the waste source were a key factor. Production costs could be reduced by 20-31% by using 40-60% gypsum substituted with seashell wastes.

Evaluation of the eco-efficiency of waste treatment facilities in Korea

As waste treatment facilities become old, their operation and maintenance costs could increase, which translates to higher treatment costs and environmental burden. This study applies the concept of eco-efficiency to evaluate waste treatment facilities considering the various conditions of waste treatment operations based on the case of Korea. In Korea, waste treatment methods were largely divided into five categories, and facilities for each treatment method were chosen based on their size, location, and waste properties for data collection. The method for evaluating the facilities' eco-efficiencies were developed using the concepts of environmental and economic performances. The results of the eco-efficiency evaluation showed that landfills were most environmentally efficient, followed by the organic waste biogasification facilities, food waste recycling facilities, incineration facilities, and, lastly, combustible waste-to-fuel facilities. The results of the eco-efficiency evaluation were further reviewed in terms of three factors which assess the status of existing facilities as well as to identify the environmental and economic indicators which significantly affect the eco-efficiency of waste treatment facilities by treatment method and propose strategic policies for promoting better waste treatment operations.

Sustainability and Pet Food: Is There a Role for Veterinarians?

Sustainability has become a watchword for a wide array of resource-intensive goods and services. This is promulgated by an increasing global population and concerns that natural resources and a hospitable climate will not be preserved for future generations. Life-cycle analysis is a tool that provides a framework to determine the magnitude products contribute to carbon emissions and depletion of natural resources. In this review, published research has been summarized to provide an overview of the impacts that pet food production and pet ownership have on the environment and the prospective role of veterinary practitioners in advocating for sustainability.

Study of biorefineries based on experimental data: production of bioethanol, biogas, syngas, and electricity using coffee-cut stems as raw material

Energy-driven biorefineries can be designed considering biotechnological and thermochemical conversion pathways. Nevertheless, energy and environmental comparisons are necessary to establish the best way to upgrade lignocellulosic biomass and set the requirements of these processes in different scenarios. This paper aims to evaluate experimentally a biorefinery producing energy vectors using coffee-cut stems (CCS) as feedstock. The obtained yields were the basis for energy and environmental analysis, in two different biorefinery scenarios: (i) production of bioethanol and biogas and (ii) production of syngas and electricity. The energy results indicated that the overall energy efficiency calculated in the first scenario was only 9.15%. Meanwhile, the second biorefinery configuration based on thermochemical routes presented an energy efficiency value of 70.89%. This difference was attributed to the higher consumption of utilities in the biorefinery based on biotechnological routes. The environmental results showed that the impact category of climate change for the first biorefinery (i.e., 0.0193 kg CO₂ eq./MJ) had a lower value than that of the second process (i.e., 0.2377 kg CO₂ eq./MJ). Thus, the biorefinery based on the biotechnological route presented a better environmental performance. Additionally, the results for both biorefineries allowed concluding that the inclusion of by-products and co-products in the calculation of the environmental analysis can dramatically affect the results.

Techno-economic evaluation and life-cycle assessment of poly(3-hydroxybutyrate) production within a biorefinery concept using sunflower-based biodiesel industry by-products

This study presents techno-economic evaluation of a biorefinery concept using biodiesel industry by-products (sunflower meal and crude glycerol) to produce poly(3-hydroxybutyrate) (PHB), crude phenolic extracts (CPE) and protein isolate (PI). The PHB production cost at two annual production capacities ($12.5/kg for 2,500 t PHB/year and $7.8/kg for 25,000 t PHB/year) was not cost-competitive to current PHB production processes when the revenues derived from co-products were not considered. Sensitivity analysis projected the economic viability of a biorefinery concept that could achieve a minimum selling price of $1.1/kg PHB similar to polypropylene. The annual PHB production capacity and the identification of marketable end-uses with respective market prices for the co-products CPE and PI were crucial in attaining process profitability. Greenhouse gas emissions (ca. 0.64 kg CO_2-eq/kg PHB) and abiotic depletion potential (61.7 MJ/kg PHB) were lower than polypropylene. Biorefining of sunflower meal and crude glycerol could lead to sustainable PHB production.

Life-cycle assessment of sewage sludge-based large-scale biogas plant

The aim of this work was to study the life-cycle assessment (LCA) and impact of a biogas plant based on the municipal sewage sludge (6000 m³ capacity biogas plant at Wastewater Treatment Plant (WWTP), Delawas, Jaipur - Rajasthan, India), analyzing the environmental effects instigated due to basic systems of biogas production and also to examine the impact of using biogas as an alternate fuel using ReCiPe and midpoint methods. The results indicatedthat the construction of plant was insignificant to the whole life cycle impacts. Biogas plant showed negative GHG emissions (-0.2385 kg CO₂ eq/m³) compared to coal-based electricity plants and digestate produced could be a good option to replace chemical fertilizer. Biogas production and agricultural spreading contributed -3.059E-08 kg CFC-11 eq/m³ towards beneficial effects which may be attributed to the avoidance of electricity and artificial fertilizers. The results indicated that sewage sludge-based biogas plant showed beneficial impact on the environment.

Smart vs conventional motorways: Environmental impact assessment under realistic traffic conditions

This research aims at assessing the environmental impacts exerted by a smart motorway compared to those of a traditional motorway. The study has global policy implications: it takes into account the impacts due to the construction and maintenance of the infrastructure and the environmental effects produced by the traffic emissions, taking into account smart technologies and truck platooning regulation. Through a classical LCA approach, 1 km-long smart motorway with 2 m-high embankment was assumed as the functional unit for the analysis. A realistic traffic condition has been considered. A comparison between environmental effects produced by the use of virgin material and by Reclaimed Asphalt Pavement was made by assuming two maintenance plans. Thanks to C-ITS systems the greater safety featured by smart motorways has a significant effect on the environmental impact, compared to conventional motorways. The impact produced by safety barriers during the life cycle was also estimated. For smart motorways the impact categories GWP, POCP, AP and EP are observed to be considerably reduced in the maintenance phase of zinc-coated steel safety barriers and in those associated to traffic emissions. It must be noted that in smart motorways vehicle emissions are markedly influenced by the percentage of heavy vehicles travelling in Truck Platooning mode. The results show that concomitant use of lime stabilization and RAP leads to a significant reduction in energy consumption (up to 35%) and pollutant emissions (up to 34% of CO₂) than in case of exclusive use of virgin material. The accidents reduction produce a 30% decrease of GWP, POCP, AP and EP related to safety barriers maintenance phase than the corresponding values of traditional motorway. Truck platooning mode generates GWP reduction close to 4%. The environmental advantages of a smart motorway increase progressively with the increase of AADT, platooning truck percentage and heavy vehicles percentage.

Evaluating the cost and carbon footprint of second-life electric vehicle batteries in residential and utility-level applications

The volume of end-of-life automotive batteries is increasing rapidly as a result of growing electric vehicle adoption. Most automotive lithium-ion batteries (LIBs) are recycled but could be repurposed as second-life batteries (SLBs) since they have 70-80% residual capacity, which can be adequate for stationary applications. SLBs have been proposed as potential, inexpensive, low-carbon energy storage for residential and utility-level applications, with or without photovoltaics (PV). However, it is unknown whether SLBs will be better than new batteries and whether SLBs will provide similar cost and carbon emission reduction for the different stationary applications in all locations. This work compared the levelized cost of electricity and life-cycle carbon emissions associated with using SLBs and new LIBs in the US for three energy storage applications: (1) residential energy storage with rooftop PV, (2) utility-level PV firming, and (3) utility-level peak-shaving, leading to a total of 41 scenarios. SLBs reduced the levelized cost of electricity by 12-57% and carbon emissions by 7-31% compared to new LIBs in the considered applications, with higher reductions for utility-level applications. SLBs still provided benefits at the residential level when compared to rooftop PV alone by reducing the levelized cost by 15-25% and carbon emissions by 22-51%, making SLBs attractive to residential consumers as well. SLBs offer an opportunity to utilize an end-of-life product for energy storage applications, provided the uncertainty in SLB quality and availability is addressed.

The environmental impact of rock support for road tunnels: The experience of Norway

Despite the high levels of investment in the construction of underground space, there has been relatively little research so far on the environmental impact of tunnelling and rock support. In an attempt to fill this gap, this paper explores and compares the environmental impact of rock support on road-tunnel design in Norway for different rock-mass classes and tunnel sizes. Norwegian rock-support practices in road-tunnelling over the last twenty years are used to estimate figures for the consumption of material, equipment and energy. The background data are drawn from various Ecoinvent databases and environmental product declarations for major materials. The results indicate: 1) that the global warming potential (GWP) varies from 1 ton to 3.6 t per meter of rock support for different tunnel sizes and rock masses; 2) that all the environmental impacts of the shotcreting (or concrete-spraying) process are significantly greater than of all other processes; 3) that when a tunnel becomes larger or the rock mass becomes poorer, the relative contribution of the bolting process will increase; 4) that all environmental impacts are more sensitive to rock-class than to cross-section parameters; and 5) that potential improvements include reducing rebound, better designs of shotcrete admixtures and binders, improving durability and mechanical properties, and implementing the GWP or other environmental indicators during the design and tendering stages.

Comparative environmental assessment of end-of-life carbonaceous water treatment adsorbents

This study evaluates and compares the environmental impacts arising from the disposal of different carbonaceous sorbents used for wastewater treatment. Three different adsorption materials were considered, i.e. activated carbon, biochar and hydrochar, and three end-of-life management approaches, i.e. incineration, regeneration and landfilling. The highest overall environmental impact was of Carcinogenic effects and Freshwater Ecotoxicity due to emissions of heavy metals during production of all types of sorbents. The use of materials with higher adsorption capacities and regeneration of carbonaceous materials were considered and shown to be an efficient way for reducing the overall environmental impacts of the different adsorbents. The compensation of fossil fuel incineration by using recovered heat led to negative impacts in all categories. Recirculation of HTC process water reduced the impact on Freshwater Ecotoxicity and Eutrophication.

Biorefineries in circular bioeconomy: A comprehensive review

Biorefinery is a sustainable means of generating multiple bioenergy products from various biomass feedstocks through the incorporation of relevant conversion technologies. With the increased attention of circular economy in the past half-decade with the emphasis of holistically addressing economic, environmental, and social aspects of the industrial-sector, biorefinery acts as a strategic mechanism for the realization of a circular bioeconomy. This study presents a comprehensive review of different biorefinery models used for various biomass feedstocks such as lignocelluloses, algae, and numerous waste-types. The review focuses on how biorefinery is instrumental in the transition of various biomass-based industries in a circular bioeconomy. The results reveal that the social-economic aspect of the industrial sector has a major influence on the full adoption of biorefineries in circular bioeconomy. Biomass wastes have played a major role in the implementation of biorefinery in circular bioeconomy. The current challenges are also presented along with future perspectives.

Prediction of greenhouse gas emissions from Ontario's solid waste landfills using fuzzy logic based model

In this study, multi-criteria assessment technique is used to predict the methane generation from large municipal solid waste landfills in Ontario, Canada. Although a number of properties determine the gas generation from landfills, these parameters are linked with empirical relationships making it difficult to generate precise information concerning gas production. Moreover, available landfill data involve sources of uncertainty and are mostly insufficient. To fully characterize the chemistry of reaction and predict gas generation volumes from landfills, a fuzzy-based model is proposed having seven input parameters. Parameters were identified in a linguistic form and linked by 19 IF-THEN statements. When compared to measured values, results of the fuzzy based model showed good prediction of landfill gas generation rates. Also, when compared to other first order decay and second order decay models like LandGEM, the fuzzy based model showed better results. When plotting the LandGEM and Fuzzy model values to the actual measured data, the fuzzy model resulted in a better fit to actual data than the LandGEM model with a coefficient of determination R² of 0.951 for fuzzy model versus 0.804 for LandGEM model. The results show how multi-criteria assessment technique can be used in modelling of complicated processes that take place within the landfills and somehow accurately predicting the landfill gas generation rate under different operating conditions.

Aligning sustainability assessment with responsible research and innovation: Towards a framework for Constructive Sustainability Assessment

Emerging technologies are increasingly promoted on the promise of tackling the grand challenge of sustainability. A range of assessment and governance approaches seek to evaluate these claims, but these tend to be applied disparately and lack widespread operationalisation. They also face specific challenges, such as high levels of uncertainty, when it comes to emerging technologies. Building and reflecting on both theory and practice, this article develops a framework for Constructive Sustainability Assessment (CSA) that enables the application of sustainability assessments to emerging technologies as part of a broader deliberative approach. In order to achieve this, we discuss and critique current approaches to analytical sustainability assessment and review deliberative social science governance frameworks. We then develop the conceptual basis of CSA - blending life-cycle thinking with principles of responsible research and innovation. This results in four design principles - transdisciplinarity, opening-up, exploring uncertainty and anticipation - that can be followed when applying sustainability assessments to emerging technologies. Finally, we discuss the practical implementation of the framework through a three-step process to (a) formulate the sustainability assessment in collaboration with stakeholders, (b) evaluate potential sustainability implications using methods such as anticipatory life-cycle assessment and (c) interpret and explore the results as part of a deliberative process. Through this, CSA facilitates a much-needed transdisciplinary response to enable the governance of emerging technologies towards sustainability. The framework will be of interest to scientists, engineers, and policy-makers working with emerging technologies that have sustainability as an explicit or implicit motivator.

Evaluation of the environmental impact of plastic cap production, packaging, and disposal

This study analysed the impact of the production of high-density polyethylene (HDPE) caps on the environment. To determine the environmental impact of injection moulding production, a life-cycle assessment was performed. The life-cycle assessment results showed that, in the injection moulding tool manufacturing process, the largest amount of environmental loading is attributable to electricity and steel consumption. Additionally, the HDPE cap production phase had the largest environmental impact associated with electricity consumption. However, scenario analysis showed that the environmental impact from electricity consumption can be reduced by up to ten times if cleaner sources of electricity are used. Large differences related to electricity sourcing should help developing countries to better understand the need to increase the use of cleaner sources of electricity.