Environmental impacts of valorisation of crude glycerol from biodiesel production - A life cycle perspective.

Biodiesel production produces significant quantities of impure crude glycerol as a by-product. Recent increases in the global biodiesel production have led to a surplus of crude glycerol, rendering it a waste. As a result, different methods for its valorisation are currently being investigated. This paper assesses the life cycle environmental impacts of an emerging technology for purification of crude glycerol - a multi-step physico-chemical treatment - in comparison to incineration with energy recovery commonly used for its disposal. For the former, three different acids (H3PO4, H2SO4 and HCl) are considered for the acidification step in the purification process. The results suggest that the H2SO4-based treatment is the best option with 17 net-negative impacts out of the 18 categories considered; this is due to system credits for the production of purified glycerol, heat and potassium salts. In comparison to incineration with energy recovery, the H2SO4-based process has lower savings for the climate change impact (-311 versus -504 kg CO2 eq./t crude glycerol) but it performs better in ten other categories. Sensitivity analyses suggest that that the impacts of the physico-chemical treatment are highly dependent on crude glycerol composition, allocation of burdens to crude glycerol and credits for glycerol production. For example, treating crude glycerol with lower glycerol content would increase all impacts except climate change and fossil depletion due to the higher consumption of chemicals and lower production of purified glycerol. Considering crude glycerol as a useful product rather than waste and allocating to it burdens from biodiesel production would increase most impacts significantly, including climate change (22-40 %), while fossil depletion, freshwater and marine eutrophication would become net-positive. The findings of this research will be of interest to the biodiesel industry and other industrial sectors that generate crude glycerol as a by-product.

Biochar from agricultural wastes: Environmental sustainability, economic viability and the potential as a negative emissions technology in Malaysia.

Biochar used for soil amendment is considered a viable negative emissions technology as it can be produced easily from a wide range of biomass feedstocks, while offering numerous potential agricultural benefits. This research is the first to present a comprehensive sustainability assessment of large-scale biochar production and application in Malaysia. The five feedstocks considered comprise the country's most abundant agricultural wastes from palm oil (empty fruit bunches, fibres, palm fronds and shells) and rice (straw) plantations. Combined with process simulation, life cycle assessment and life cycle costing are used to assess the sustainability of biochar production via slow pyrolysis at different temperatures (300-600 °C), considering two functional units: i) production and application of 1 t of biochar; and ii) removal of 1 t of CO2from the atmosphere. The cradle-to-grave system boundary comprises all life cycle stages from biomass acquisition to biochar use for soil amendment. The positive impacts of the latter, such as carbon sequestration, fertiliser avoidance and reduction in soil N2O emissions, are also included. The global warming potential (GWP) is net-negative in all scenarios, ranging from -436 to -2,085 kg CO2 eq./t biochar and -660 to -933 kg CO2 eq./t CO2 removed. Per t of biochar, the systems with shells have the lowest GWP and those with straw the highest, all showing better performance if produced at higher pyrolysis temperatures. However, the temperature trend is opposite for all other 17 impacts considered, with fibres being the best option and fronds the worst for most categories. Per t CO2 removed, fronds have the highest impact in eight categories, including GWP, and shells the lowest in most categories. All impacts are lower for biochar production at higher temperatures. The main hotspot is the pyrolysis process, influencing the majority of impact categories and contributing 66-75 % to the life cycle costs. The costs range from US$116-197/t biochar and US$60-204/t CO2 removed. The least expensive systems per t biochar are those with straws and per t CO2 removed those with shells, while fronds are the worst option economically for both functional units. Utilising all available feedstocks could remove 6-12.4 Mt of CO2 annually, reducing the national emissions from the agricultural sector by up to 54 % and saving US$36.05 M annually on fertilisers imports. These results will be of interest to policy makers in Malaysia and other regions with abundant agricultural wastes.

Biodegradable and conventional plastic packaging: Comparison of life cycle environmental impacts of poly(mandelic acid) and polystyrene.

Most of plastic packaging waste does not degrade over time, which can lead to harmful effects on aquatic life and humans, highlighting the need for packaging materials that are easily degradable. Poly(mandelic acid) (PMA) is a biodegradable polymer that has been proposed as an alternative to polystyrene for use in packaging. However, its potential to replace the existing packaging materials also depends, among other factors, on the environmental sustainability of its production. This study aims to estimate and compare the life cycle environmental impacts of the production of PMA via polymerisation of 5-phenyl-1,3-dioxolane-4-one (Ph-DOX) and o-carboxyanhydride (OCA) monomers. For each route, the impacts are evaluated for 18 ReCiPe categories for reported laboratory scales and potential scaled-up commercial production. The results suggest that most of the impacts of PMA production via the Ph-DOX route are significantly lower (≥20%) than that of the OCA route for both the laboratory and large scales. However, compared to polystyrene, the impacts of large-scale PMA production via the (better of the two) Ph-DOX route are more than five times higher. This is largely due to the use of benzaldehyde, enzymes, hydrocyanic acid and sodium phosphate in the production of mandelic acid and the solvents utilised in monomer synthesis. A sensitivity analysis shows that the bio-transformation of bio-glycerol to produce mandelic acid would reduce 16 out of 18 life cycle impacts of PMA by 6-77%. The impacts are also sensitive to the assumptions used in the scaling-up of laboratory data for solvents. However, the results indicate clearly that, despite all the uncertainties in the scaling-up method, the proposed production routes for PMA would still have several times higher environmental impacts than polystyrene. Therefore, further research would be needed to improve significantly the production process for (bio-)mandelic acid, synthesis of monomers and their polymerisation before PMA can be considered an environmentally sustainable option for packaging applications.

Environmental assessment of a novel ionic-liquid based method for recycling of PVC in composite materials.

Waste PVC is scarcely recycled due to its high chlorine content and its use in composite materials, which reduces the applicability of conventional waste treatment methods, including thermal, mechanical and chemical recycling. For this reason, alternative treatment options are being developed to increase the recyclability of waste PVC. This paper focuses on one such option which utilises ionic liquids (ILs) for material separation and dehydrochlorination of PVC contained in composite materials. Taking blisterpacks used as a packaging for medicines as an example of a composite material, the paper presents for the first time the life cycle environmental impacts of this novel PVC recycling method, in comparison with thermal treatment (low-temperature pyrolytic degradation of PVC). Three ILs were considered for the PVC recycling process: trihexyl(tetradecyl)phosphonium chloride, bromide and hexanoate. The results suggested that the impacts of the process using the first two ILs were comparable, while the system with hexanoate-based IL had 7-229 % higher impacts. Compared to the thermal treatment of waste blisterpacks, the IL assisted process had significantly higher impacts (22-819 %) in all 18 categories considered due to the greater heat requirements and the IL losses. Reducing the latter would lower most impacts by 8-41 %, while optimising the energy requirements would reduce the impacts by 10-58 %. Moreover, recovering HCl would increase significantly the environmental sustainability of the process, resulting in net-negative impacts (savings) in most categories. Overall, these improvements would lead to lower or comparable impacts to those of the thermal treatment. The findings of this study will be of interest to the polymer, recycling and related industries, as well as to process developers.

Energy from forest residues in Turkey: An environmental and economic life cycle assessment of different technologies.

Forest residues, as cheap and abundant feedstock, can replace current fossil-energy sources, helping to reduce greenhouse gas (GHG) emissions and improve energy security. Given 27 % of total lands covered with forests, Turkey has a remarkable potential of forest residues from harvesting and industrial activities. This paper thus focuses on evaluating the life cycle environmental and economic sustainability of heat and electricity generation utilising forest residues in Turkey. Two types of forest residues (wood chips and wood pellets) and three energy conversion options are considered: direct combustion (heat only, electricity only and cogenerated heat and power (CHP)), gasification (for CHP) and co-firing with lignite. Results suggest that direct combustion of wood chips for cogeneration of heat and power has the lowest environmental impacts and levelised costs for both functional units (per MWh heat and per MWh electricity generation) considered. Compared to fossil-fuel sources, energy from forest residues has a potential to reduce the climate change impact as well as fossil-fuel, water and ozone depletion by >80 %. However, it also causes an increase in some other impacts, such as terrestrial ecotoxicity. The bioenergy plants have also lower levelised costs than electricity from the grid (except those using wood pellets and gasification regardless of the feedstock) and heat from natural gas. Electricity-only plants using wood chips achieve the lowest LCC, generating net profits. All biomass plants, except the pellet boiler, pay back in their lifetime; however, the economic feasibility of electricity-only and CHP plants is highly sensitive to subsidies for bioelectricity and efficient use of heat. Utilising the currently available forest residues in Turkey (5.7 Mt/yr) for energy provision could potentially reduce the national GHG emissions by 7.3 Mt/yr (1.5 %) and save $0.5 bn/yr (5 %) in avoided fossil-fuel import costs.

Life cycle sustainability assessment of advanced treatment techniques for urban wastewater reuse and sewage sludge resource recovery.

Wastewater treatment plants can become a source of valuable resources, such as clean water, energy, fuels and nutrients and thus contribute to the sustainable development goals and a transition to a circular economy. This can be achieved by adopting advanced wastewater and sludge treatment techniques. However, these have to be evaluated on their sustainability to avoid any unintentional consequences. Therefore, this paper presents a life cycle sustainability assessment of advanced wastewater and sludge treatment techniques by integrating the environmental, economic and social aspects. The options considered for advanced wastewater treatment are: i) granular activated carbon; ii) nanofiltration; iii) solar photo-Fenton; and iv) ozonation. The technologies for advanced sludge treatment are: i) agricultural application of anaerobically digested sludge; ii) agricultural application of composted sludge; iii) incineration; iv) pyrolysis; and v) wet air oxidation. The results for the advanced wastewater treatment techniques demonstrate that nanofiltration is the most sustainable option if all the sustainability aspects are considered equally important. If, however, a higher preference is given to the economic aspect, ozonation and granular activated carbon would both be comparable to nanofiltration; if the social aspect is considered more important, only activated carbon would be comparable to nanofiltration. Among the sludge treatment methods, agricultural application of sludge is the most sustainable technique for mean-to-high resource recovery. If the recovery rate is lower, this option is comparable with incineration and pyrolysis with high recovery of their respective products. This work helps to identify the most sustainable techniques that could be combined with conventional wastewater treatments for promoting wastewater reuse and resource recovery across a wide range of operating parameters and products outputs. The findings also support the notion that more sustainable wastewater treatment could be achieved by a circular use of water, energy and nutrients contained in urban wastewaters.

Fracking wastewater treatment: Catalytic performance and life cycle environmental impacts of cerium-based mixed oxide catalysts for catalytic wet oxidation of organic compounds.

Water scarcity and the consequent increase of freshwater prices are a cause for concern in regions where shale gas is being extracted via hydraulic fracturing. Wastewater treatment methods aimed at reuse/recycle of fracking wastewater can help reduce water stress of the fracking process. Accordingly, this study assessed the catalytic performance and life cycle environmental impacts of cerium-based mixed oxide catalysts for catalytic wet oxidation (CWO) of organic contaminants, in order to investigate their potential as catalysts for fracking wastewater treatment. For these purposes, MnCeOx and CuCeOx were tested for phenol removal in the presence of concentrated NaCl (200 g L-1), which represented a synthetic fracking wastewater. Removal of phenol in pure ("phenolic") water without NaCl was also considered for comparison. Complete (100 %) phenol and a 94 % total organic carbon (TOC) removal were achieved in both the phenolic and fracking wastewaters by utilising MnCeOx (5 g L-1) and insignificant metal leaching was observed. However, a much lower activity was observed when the same amount of CuCeOx was utilised: 23.3 % and 20.5 % for phenol and TOC removals, respectively, in the phenolic, and 69.1 % and 63 % in the fracking wastewater. Furthermore, severe copper leaching from CuCeOx was observed during stability tests conducted in the fracking wastewater. A life cycle assessment (LCA) study carried out as part of this work showed that the production of MnCeOx had 12-98 % lower impacts than CuCeOx due to the higher impacts of copper than manganese precursors. Furthermore, the environmental impacts of CWO were found to be 94-99 % lower than those of ozonation due to lower energy and material requirements. Overall, the results of this study suggest that the adoption of catalytic treatment would improve both the efficiency and the environmental sustainability of both the fracking wastewater treatment and the fracking process as a whole.

Global predictions of primary soil salinization under changing climate in the 21st century.

Soil salinization has become one of the major environmental and socioeconomic issues globally and this is expected to be exacerbated further with projected climatic change. Determining how climate change influences the dynamics of naturally-occurring soil salinization has scarcely been addressed due to highly complex processes influencing salinization. This paper sets out to address this long-standing challenge by developing data-driven models capable of predicting primary (naturally-occurring) soil salinity and its variations in the world's drylands up to the year 2100 under changing climate. Analysis of the future predictions made here identifies the dryland areas of South America, southern and western Australia, Mexico, southwest United States, and South Africa as the salinization hotspots. Conversely, we project a decrease in the soil salinity of the drylands in the northwest United States, the Horn of Africa, Eastern Europe, Turkmenistan, and west Kazakhstan in response to climate change over the same period.

Life cycle environmental impacts of chemical recycling via pyrolysis of mixed plastic waste in comparison with mechanical recycling and energy recovery.

A large portion of plastic produced each year is used to make single-use packaging and other short-lived consumer products that are discarded quickly, creating significant amounts of waste. It is important that such waste be managed appropriately in line with circular-economy principles. One option for managing plastic waste is chemical recycling via pyrolysis, which can convert it back into chemical feedstock that can then be used to manufacture virgin-quality polymers. However, given that this is an emerging technology not yet used widely in practice, it is not clear if pyrolysis of waste plastics is sustainable on a life cycle basis and how it compares to other plastics waste management options as well as to the production of virgin plastics. Therefore, this study uses life cycle assessment (LCA) to compare the environmental impacts of chemical recycling of mixed plastic waste (MPW) via pyrolysis with the established waste management alternatives: mechanical recycling and energy recovery. Three LCA studies have been carried out under three perspectives: waste, product and a combination of the two. To ensure robust comparisons, the impacts have been estimated using two impact assessment methods: Environmental footprint and ReCiPe. The results suggest that chemical recycling via pyrolysis has a 50% lower climate change impact and life cycle energy use than the energy recovery option. The climate change impact and energy use of pyrolysis and mechanical recycling of MPW are similar if the quality of the recyclate is taken into account. Furthermore, MPW recycled by pyrolysis has a significantly lower climate change impact (-0.45 vs 1.89 t CO2 eq./t plastic) than the equivalent made from virgin fossil resources. However, pyrolysis has significantly higher other impacts than mechanical recycling, energy recovery and production of virgin plastics. Sensitivity analyses show that some assumptions have notable effects on the results, including the assumed geographical region and its energy mix, carbon conversion efficiency of pyrolysis and recyclate quality. These results will be of interest to the chemical, plastics and waste industries, as well as to policy makers.

Predicting long-term dynamics of soil salinity and sodicity on a global scale.

Knowledge of spatiotemporal distribution and likelihood of (re)occurrence of salt-affected soils is crucial to our understanding of land degradation and for planning effective remediation strategies in face of future climatic uncertainties. However, conventional methods used for tracking the variability of soil salinity/sodicity are extensively localized, making predictions on a global scale difficult. Here, we employ machine-learning techniques and a comprehensive set of climatic, topographic, soil, and remote sensing data to develop models capable of making predictions of soil salinity (expressed as electrical conductivity of saturated soil extract) and sodicity (measured as soil exchangeable sodium percentage) at different longitudes, latitudes, soil depths, and time periods. Using these predictive models, we provide a global-scale quantitative and gridded dataset characterizing different spatiotemporal facets of soil salinity and sodicity variability over the past four decades at a ∼1-km resolution. Analysis of this dataset reveals that a soil area of 11.73 Mkm2 located in nonfrigid zones has been salt-affected with a frequency of reoccurrence in at least three-fourths of the years between 1980 and 2018, with 0.16 Mkm2 of this area being croplands. Although the net changes in soil salinity/sodicity and the total area of salt-affected soils have been geographically highly variable, the continents with the highest salt-affected areas are Asia (particularly China, Kazakhstan, and Iran), Africa, and Australia. The proposed method can also be applied for quantifying the spatiotemporal variability of other dynamic soil properties, such as soil nutrients, organic carbon content, and pH.

Environmental sustainability of biofuels: a review.

Biofuels are being promoted as a low-carbon alternative to fossil fuels as they could help to reduce greenhouse gas (GHG) emissions and the related climate change impact from transport. However, there are also concerns that their wider deployment could lead to unintended environmental consequences. Numerous life cycle assessment (LCA) studies have considered the climate change and other environmental impacts of biofuels. However, their findings are often conflicting, with a wide variation in the estimates. Thus, the aim of this paper is to review and analyse the latest available evidence to provide a greater clarity and understanding of the environmental impacts of different liquid biofuels. It is evident from the review that the outcomes of LCA studies are highly situational and dependent on many factors, including the type of feedstock, production routes, data variations and methodological choices. Despite this, the existing evidence suggests that, if no land-use change (LUC) is involved, first-generation biofuels can-on average-have lower GHG emissions than fossil fuels, but the reductions for most feedstocks are insufficient to meet the GHG savings required by the EU Renewable Energy Directive (RED). However, second-generation biofuels have, in general, a greater potential to reduce the emissions, provided there is no LUC. Third-generation biofuels do not represent a feasible option at present state of development as their GHG emissions are higher than those from fossil fuels. As also discussed in the paper, several studies show that reductions in GHG emissions from biofuels are achieved at the expense of other impacts, such as acidification, eutrophication, water footprint and biodiversity loss. The paper also investigates the key methodological aspects and sources of uncertainty in the LCA of biofuels and provides recommendations to address these issues.

Assessing the environmental sustainability of an emerging energy technology: Solar thermal calcination for cement production.

Cement production is a highly energy-intensive process, contributing 7% to global CO2 emissions. Over 80% of the energy used in cement production is consumed by the calcination process. This paper considers a novel solar thermal technology for calcination, to investigate if it could help mitigate the climate change and other environmental impacts from cement production on a life cycle basis. The following three solar options are compared to conventional fossil-fuel calcination via life cycle assessment: a full solar system, which provides all the required thermal energy, and two hybrid systems, where the solar system provides 14% and 33% of the thermal energy, respectively. The results show that all three solar options have lower impacts than conventional calcination in 14 out of 17 categories. The full solar system is the best alternative, with major reductions in climate change (48%), fossil depletion (75%), photochemical ozone formation (92%) and terrestrial ecotoxicity (79%). Based on insolation levels in different parts of the world, the solar systems could be applied to 26% of current global cement production. This would reduce the climate change impact by 15-40%, as well as most other impacts by 14-87%, depending on the fuel mix. However, a limiting factor might be two times greater land occupation than by the conventional process. Furthermore, the solar system has higher human toxicity-cancer (102%) and metals and minerals depletion (6%) due to the construction of solar facilities. Coupling conventional calcination with carbon capture and storage (CCS) is more efficient in reducing the climate change impact (63%) than the solar system (48%) relative to conventional calcination without CCS. However, adding CCS to the solar calciner would still be a better option, decreasing the impact by 81% relative to conventional calcination without CCS. These findings will be of interest to the solar and cement industries as well as other industrial sectors using high-temperature processes.

Environmental sustainability in the food-energy-water-health nexus: A new methodology and an application to food waste in a circular economy.

Current studies on the food-energy-water nexus do not capture effects on human health. This study presents a new methodology for assessing the environmental sustainability in the food-energy-water-health nexus on a life cycle basis. The environmental impacts, estimated through life cycle assessment, are used to determine a total impact on the nexus by assigning each life cycle impact to one of the four nexus aspects. These are then normalised, weighted and aggregated to rank the options for each aspect and determine an overall nexus impact. The outputs of the assessment are visualised in a "nexus quadrilateral" to enable structured and transparent interpretation of results. The methodology is illustrated by considering resource recovery from household food waste within the context of a circular economy. The impact on the nexus of four treatment options is quantified: anaerobic digestion, in-vessel composting, incineration and landfilling. Anaerobic digestion is environmentally the most sustainable option with the lowest overall impact on the nexus. Incineration is the second best option but has a greater impact on the health aspect than landfilling. Landfilling has the greatest influence on the water aspect and the second highest overall impact on the nexus. In-vessel composting is the worst option overall, despite being favoured over incineration and landfilling in circular-economy waste hierarchies. This demonstrates that "circular" does not necessarily mean "environmentally sustainable." The proposed methodology can be used to guide businesses and policy makers in interpreting a wide range of environmental impacts of products, technologies and human activities within the food-energy-water-health nexus.

Environmental assessment of domestic water supply options for remote communities.

Access to clean water is one of the targets in the UN Sustainable Development Goals. However, millions of people are still without basic water services, predominantly in rural areas in developing nations. Previous studies have investigated the environmental impacts of water provision, but they mostly focused on large-scale urban systems. This paper considers for the first time the life cycle environmental impacts of different water supply options applicable to remote communities in developing countries. Focusing on the Southeast Asia-Pacific (SEAP) context, a cradle-to-grave approach is followed to estimate the impacts of locally-sourced groundwater, surface water and desalinated seawater as well as externally-sourced bottled water. The results reveal that surface water is environmentally the most sustainable alternative. Locally desalinated water, powered by diesel electricity, has two orders of magnitude higher impacts than surface water. However, externally-sourced water in plastic bottles is the worst option with 4-155 times higher impacts than desalinated water and up to three orders of magnitude higher impacts than surface water. This is largely due to the impacts related to the production of bottles. Doubling their recycling would reduce the impacts by 7-23% but bottled water would still be environmentally the least sustainable option. Although water in single-use bottles currently provides only 3% of the water supply of a representative remote community in the SEAP region considered in this study, it accounts on average for more than 50% of the total impacts from water consumption. By 2030, population increase could lead to greater reliance of remote communities on bottled water and 60-73% higher impacts of water consumption per household. Relying solely on local surface, ground and water desalinated using solar power and avoiding bottled water would reduce the impacts by 33-99% relative to the current situation. This would also improve considerably water availability and security in remote communities. The findings of this study will be of interest to national and local governments developing future policies aimed at increasing access of remote communities to clean water.

Life cycle environmental impacts of sewage sludge treatment methods for resource recovery considering ecotoxicity of heavy metals and pharmaceutical and personal care products.

Sewage sludge handling is becoming a concern in Europe due to its increasing amount and the presence of contaminants, such as heavy metals and pharmaceutical and personal care products (PPCPs). Currently, over 70% of sludge in Europe is treated thermally by incineration or used as fertilizer in agriculture. New thermochemical methods are under development and are expected to be implemented in the near future. This paper considers the life cycle environmental impacts of the following five alternatives for sludge handling, taking into account the presence of heavy metals and PPCPs: i) agricultural application of anaerobically digested sludge; ii) agricultural application of composted sludge; iii) incineration; iv) pyrolysis; and v) wet air oxidation. The results suggest that anaerobic digestion with recovery of nutrients and electricity has the lowest environmental impacts in 11 out of 18 categories considered. For the mean to maximum resource recovery, composting is the worst alternative, followed by pyrolysis with lower recovery rates. Agricultural application of anaerobically digested sludge has the highest freshwater ecotoxicity due to heavy metals, unless their concentration is in the lowest range, as found in some European sewage sludge applied on land. Therefore, stricter control of heavy metals in the sludge is needed for this option to limit freshwater ecotoxicity to the levels comparable with the thermal processes. The results also indicate that PPCPs have a negligible contribution to freshwater ecotoxicity when compared to heavy metals in the anaerobically digested sludge. Since thermal processes are currently drawing attention due to their potential benefits, the findings of this work suggest that their adoption is environmentally beneficial only if high resource recovery rates can be achieved.

Environmental sustainability of cooking fuels in remote communities: Life cycle and local impacts.

Access to clean cooking fuels and technologies is essential for achieving the Sustainable Development Goals, particularly in developing countries, to minimise human health and environmental impacts. This paper assesses for the first time the environmental sustainability of household cooking, focusing on remote communities in developing countries in the Southeast Asia-Pacific (SEAP) region and considering both life cycle and local impacts. To guide rural development policies, the impacts of the following cooking fuels are considered: liquefied petroleum gas, kerosene, wood, charcoal, crop residues, biogas and electricity. Both the present situation and three future (2030) scenarios are evaluated on 18 life cycle impacts, as well as on local environmental and health impacts caused by cooking. The results show that electricity is the worst option in 13 out of 18 life cycle categories since it is generated from diesel in off-grid communities. Biogas from manure is the best fuel with 16 lowest life cycle impacts. Biomass fuels can have lower life cycle impacts than fossil fuels but they have high combustion emissions which lead to higher local environmental and health impacts. Future scenarios with higher biomass utilisation have up to 47 times lower life cycle impacts than at present, but 4-23% higher local impacts. Health impacts related to fuel combustion are higher in Vietnam, the Philippines, Cambodia, Laos and Myanmar compared to the other SEAP countries due to regional background pollutant concentrations and health trends. A fuel mix with liquefied petroleum gas, biogas and renewable electricity offers considerable reductions in 13 life cycle impacts compared to the present situation, while also reducing local health impacts by 78-97%. A self-sufficient fuel mix with local biomass and renewable electricity would reduce 17 out of 18 life cycle impacts, but all local impacts, including on health, would be 11-28% higher than at present. The results from this study can be used by policy makers and other stakeholders to develop policies for clean cooking in remote communities and reduce both environmental and human health impacts.

Assessing the economic and environmental sustainability of household food waste management in the UK: Current situation and future scenarios.

The value embedded in food waste is increasingly being recognised, with the UN targeting a 50% reduction in consumer food waste and the EU recycling of 60% of all household waste, both by 2030. Aiming to provide guidance on the most sustainable food waste utilisation routes, this study evaluates the life cycle environmental and economic sustainability of five plausible scenarios for the year 2030. Focusing on the UK for context, these are compared to the current treatment of food waste as well as to its potential future prevention. The scenarios consider a differing share of four widely-used treatment methods: anaerobic digestion, in-vessel composting, incineration and landfilling. The scenario with the highest anaerobic digestion share that recovers both heat and electricity is the best option for seven out of 19 environmental impacts and the second best for life cycle costs. Upgrading anaerobic digestion biogas to biomethane achieves the lowest global warming potential and life cycle costs. Net-negative global warming potential (savings) can be achieved if the heat from anaerobic digestion and incineration or biomethane are utilised to displace natural gas. Displacing a future electricity mix does not lead to significant global warming potential savings due to the expected grid decarbonisation. However, savings are still achieved for metal depletion and human and terrestrial toxicities as they are higher for decarbonised grid electricity due to the increased share of renewables. A greater share of in-vessel composting leads to higher impacts because of the high electricity consumption. Landfill reduction has an economic advantage for all the scenarios, except for the business-as-usual, with life cycle costs 11-75% lower than for the current situation. While future scenarios improve the overall sustainability compared to the current situation, halving food waste by 2030 can save 15 times more greenhouse gas emissions than the best treatment scenario without waste reduction. Therefore, any commitments to improve the sustainability of food waste treatment must be accompanied by an effective waste prevention strategy. The outcomes of this work can help waste treatment operators and policy makers towards more sustainable food waste management. Although the focus is on UK situation, the overall conclusions and recommendations are applicable to other regions.

Desiccation crisis of saline lakes: A new decision-support framework for building resilience to climate change.

River flow reductions as a result of agricultural withdrawals and climate change are rapidly desiccating endorheic lakes, increasing their salinity and affecting the bio-diversity and human wellbeing in the surrounding areas. Here we present a new framework to guide eco-hydrological restoration of saline lakes and build their resilience to climate change by optimizing agricultural land use and related water withdrawals. The framework involves four steps: 1. selection of global circulation models for the basin under study; 2. establishment of a hydrological balance over the lake's area to estimate the amount of water required for its restoration; 3. water allocation modeling to determine the water available for restoration and allocation of the remaining water across different users in the lake's basin; and 4. basin-scale optimization of land use and cropping patterns subject to water availability. We illustrated the general applicability of the framework through the case of the second largest (by volume) hyper-saline lake globally, Lake Urmia, which lost 96% of its volume in only 20 years, primarily as a result of upstream water withdrawals. Through the application of the framework, we estimated the amount of water needed to restore the lake, either fully or partially, and proposed a sustainable land-use strategy, while protect farmers' income in the basin. Considering future climate change projections under two representative concentration pathways (RCP) 4.5 and 8.5, we found that an average annual surface inflow of 3,648 Mm3 (∼70% increase in RCP 4.5) and 3,692 Mm3 (∼73% increase in RCP 8.5) would be required to restore the lake by 2050, respectively. This would require the respective conversion of 95,600 ha and 133,687 ha of irrigated land to rain-fed cropland or grassland across the basin by 2050. The proposed framework can be used for building resilience to climate change and mitigating human-induced threats to other declining saline lakes.

Environmental impacts of copper­indium­gallium-selenide (CIGS) photovoltaics and the elimination of cadmium through atomic layer deposition.

Thin-film technologies have been part of the rapidly-expanding solar photovoltaics (PV) market for many years, led by cadmium-telluride (CdTe) and copper­indium­gallium-selenide (CIGS). However, their environmental impacts remain largely unknown, particularly considering state-of-the-art CIGS manufacturing techniques. This study estimates the life cycle environmental impacts of CIGS PV installations in the UK and Spain, including balance-of-system components, using real manufacturing data. It also analyses newly-developed CIGS, replacing the cadmium sulphide (CdS) buffer layer with zinc oxysulphide (Zn(O,S)) via atomic layer deposition (ALD). The results show that UK installations have 72% higher impacts than those in Spain, including climate change (25.1 vs 14.6 g CO2 eq./kWh). The inverter and electrical components are the main contributors (46% on average), followed by the PV modules (41%). In comparison to CdTe, mono-Si and multi-Si PV, CIGS has 6%-90% lower impacts in 16 out of 18 categories, including climate change (16%-50% lower). However, metal depletion is five times higher, and land use 12%-31% greater. The replacement of CdS has a small but positive effect, demonstrating that cadmium can be eliminated from the CIGS life cycle without environmental penalties. These results will be of interest to PV manufacturers and policy makers, indicating improvement opportunities and areas for policy intervention.

Environmental and economic implications of recovering resources from food waste in a circular economy.

Around a third of food is wasted globally, requiring significant resources for its treatment and disposal, in addition to wasting valuable resources. Following the circular economy principles, this waste should ideally be avoided, and if not possible, treated to recover resources. This paper considers the life cycle environmental and economic implications of recovering energy and material resources from food waste, focusing on the UK situation. Four treatment methods are considered: anaerobic digestion, in-vessel composting, incineration and landfilling. The results show that per tonne of waste treated, anaerobic digestion has the lowest environmental impacts in 13 out of the 19 categories considered in the study, including net-negative global warming potential. In-vessel composting is the least sustainable option environmentally, in contrast to being preferred over incineration according to the circular economy principles. Incineration has the lowest life cycle costs (£71/t), while landfilling is the costliest option (£123/t). Managing the 4.9 Mt of food waste collected annually from UK households via the four methods generates 340,000 t CO2 eq. and costs £452 m, in addition to causing a number of other environmental impacts. However, it also saves 1.9 PJ of primary energy, primarily due to electricity generation through incineration. If all of this food waste was incinerated, £103 m and 360,000 t CO2 eq./year could be saved compared to current waste management, rendering incineration a carbon-negative technology. This would also result in savings in 14 other impacts, but would increase summer smog by 30% and metal depletion by 56%. The environmental benefits of incineration would be exceeded only if all food waste was treated by anaerobic digestion, which would save 490,000 t CO2 eq./year and produce 50% more electricity per tonne of waste than incineration. Anaerobic digestion would also lead to savings in 14 other impacts compared to the present situation, but would result in a four times higher acidification and three times greater emissions of particulate matter. In addition, it would save £251 m/year compared to the current costs. Nevertheless, prevention of avoidable food waste would realise far greater environmental and economic savings, estimated here at 14 Mt CO2 eq. and £10.7 bn annually.