Electricity generation is a key contributor to global emissions of greenhouse gases (GHG), NO x and SO 2 and their related environmental impact. A critical review of 167 case studies involving the life cycle assessment (LCA) of electricity generation based on hard coal, lignite, natural gas, oil, nuclear, biomass, hydroelectric, solar photovoltaic (PV) and wind was carried out to identify ranges of emission data for GHG, NO x and SO 2 related to individual technologies. It was shown that GHG emissions could not be used as a single indicator to represent the environmental performance of a system or technology. Emission data were evaluated with respect to three life cycle phases (fuel provision, plant operation, and infrastructure). Direct emissions from plant operation represented the majority of the life cycle emissions for fossil fuel technologies, whereas fuel provision represented the largest contribution for biomass technologies (71% for GHG, 54% for NO x and 61% for SO 2 ) and nuclear power (60% for GHG, 82% for NO x and 92% for SO 2 ); infrastructures provided the highest impact for renewables. These data indicated that all three phases should be included for completeness and to avoid problem shifting. The most critical methodological aspects in relation to LCA studies were identified as follows: definition of the functional unit, the LCA method employed (e.g., IOA, PCA and hybrid), the emission allocation principle and/or system boundary expansion. The most important technological aspects were identified as follows: the energy recovery efficiency and the flue gas cleaning system for fossil fuel technologies; the electricity mix used during both the manufacturing and the construction phases for nuclear and renewable technologies; and the type, quality and origin of feedstock, as well as the amount and type of co-products, for biomass-based systems. This review demonstrates that the variability of existing LCA results for electricity generation can give rise to conflicting decisions regarding the environmental consequences of implementing new technologies.

Greenhouse gas (GHG) emissions related to composting of organic waste and use of compost was assessed from a waste management perspective. The GHG accounting for composting includes use of electricity and fuels, emissions of methane and nitrous oxide from the composting process, and savings obtained by the use of the compost. The GHG account depends on waste type and composition (kitchen organics, garden waste), technology type (open systems, closed systems, home composting), the efficiency of off-gas cleaning at enclosed composting systems, and the use of the compost. The latter is an important issue and is related to the long term binding of carbon in the soil, to related effects in terms of soil improvement and to what the compost substitutes; this could be fertilizer and peat for soil improvement or for growth media production. The overall Global Warming Factor (GWF) for composting therefore varies between significant savings (-900 kg CO 2 -equivalents tonne -1 wet waste (ww)) and a net load (300 kg CO 2 -equivalents tonne -1 ww). The major savings are obtained by use of compost as a substitute for peat in the production of growth media. However, it may be difficult for a specific composting plant to document how the compost is used and what it actually substitutes for. Two cases representing various technologies were assessed showing how GHGs accounting can be done when specific information and data are available.

Anaerobic digestion (AD) of source separated municipal solid waste (MSW) and use of the digestate is presented from a global warming (GW) point of view by providing ranges of greenhouse gas (GHG) emissions useful for calculation of global warming factors (GWFs), i.e. the contribution to GW measured in CO 2 -equivalents tonne -1 wet waste. The GHG accounting was done distinguishing between direct contributions at the AD plant and indirect upstream or downstream contributions. GHG accounting for a generic AD plant with either biogas utilization at the plant or upgrading of the gas for vehicle fuel -in both cases the digestate was used for fertilizer substitution -resulted in a GWF from -375 (a saving) to 111 (a load) kg CO 2 -eq. tonne -1 wet waste. This large range was a result of the variation found for a number of parameters. In descending order of importance these were: energy substitution by biogas, N 2 O-emission from digestate in soil, fugitive emission of methane, unburned methane, carbon bound in soil and fertilizer substitution. GWF for a specific AD plant was in the range -95 to 28 kg CO 2 -eq. tonne -1 of wet waste. The ranges of uncertainty, especially of fugitive losses of methane and carbon sequestration highly influenced this result. Compared to the few published GWFs for AD, the range of our data was much larger demonstrating the need to use a consistent and robust approach to GHG accounting and simultaneously accept that some key parameters are highly uncertain.

International audienceAs compost use in agriculture increases, there is an urgent need to evaluate the specific environmental benefits and impacts as compared with other types of fertilizers and soil amendments. While the environmental impacts associated with compost production have been successfully assessed in previous studies, the assessment of the benefits of compost on plant and soil has been only partially included in few published works. In the present study, we reviewed the recent progresses made in the quantification of the positive effects associated to biowaste compost use on land by using life cycle assessment (LCA). A total of nine environmental benefits were identified in an extensive literature review and quantitative figures for each benefit were drawn and classified into short-, mid-, and long-term. The major findings are the following: (1) for nutrient supply and carbon sequestration, the review showed that both quantification and impact assessment could be performed, meaning that these two benefits should be regularly included in LCA studies. (2) For pest and disease suppression, soil workability, biodiversity, crop nutritional quality, and crop yield, although the benefits were proved, quantitative figures could not be provided, either because of lack of data or because the benefits were highly variable and dependent on specific local conditions. (3) The benefits on soil erosion and soil moisture could be quantitatively addressed, but suitable impact assessment methodologies were not available. (4) Weed suppression was not proved. Different research efforts are required for a full assessment of the benefits, apart from nutrient supply and carbon sequestration; additional impact categories—dealing with phosphorus resources, biodiversity, soil losses, and water depletion—may be needed for a comprehensive assessment of compost application. Several of the natural mechanisms identified and the LCA procedures discussed in the paper could be extensible to other organic fertilizers and compost from other feedstocks

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It remains unclear which kinds of nanoproducts are available on the European market, although this information is a prerequisite for any kind of exposure and risk assessment.

23Life cycle assessment (LCA) has been used extensively within the recent decade to 24 evaluate the environmental performance of thermal Waste-to-Energy (WtE) 25 technologies: incineration, co-combustion, pyrolysis and gasification. A critical review 26 was carried out involving 250 individual case-studies published in 136 peer-reviewed 27 journal articles within 1995 and 2013. The studies were evaluated with respect to 28 critical aspects such as: i) goal and scope definitions (e.g. functional units, system 29 boundaries, temporal and geographic scopes), ii) detailed technology parameters (e.g. 30 related to waste composition, technology, gas cleaning, energy recovery, residue 31 management, and inventory data), and iii) modeling principles (e.g. energy/mass 32 calculation principles, energy substitution, inclusion of capital goods and uncertainty 33 evaluation). Very few of the published studies provided full and transparent descriptions 34 of all these aspects, in many cases preventing an evaluation of the validity of results, 35 and limiting applicability of data and results in other contexts. The review clearly 36suggests that the quality of LCA studies of WtE technologies and systems including 37 energy recovery can be significantly improved. Based on the review, a detailed 38 overview of assumptions and modeling choices in existing literature is provided in 39 conjunction with practical recommendations for state-of-the-art LCA of waste-to-40 energy. 41 42

Summary Plastic recycling is promoted in the transition toward a circular economy and a closed plastic loop, typically using mass‐based recycling targets. Plastic from household waste (HHW) is contaminated and heterogeneous, and recycled plastic from HHW often has a limited application range, due to reduced quality. To correctly assess the ability to close plastic loops via recycling, both plastic quantities and qualities need to be evaluated. This study defines a circularity potential representing the ability of a recovery system to close material loops assuming steady‐state market conditions. Based on an average plastic waste composition including impurities, 84 recovery scenarios representing a wide range of sorting schemes, source‐separation efficiencies, and material recovery facility (MRF) configurations and performances were assessed. The qualities of the recovered fractions were assessed based on contamination and the circularity potential calculated for each scenario in a European context. Across all scenarios, 17% to 100% of the generated plastic mass could be recovered, with higher source‐separation and MRF efficiencies leading to higher recovery. Including quality, however, at best 55% of the generated plastic was suitable for recycling due to contamination. Source‐separation, a high number of target fractions, and efficient MRF recovery were found to be critical. The circularity potential illustrated that less than 42% of the plastic loop can be closed with current technology and raw material demands. Hence, Europe is still far from able to close the plastic loop. When transitioning toward a circular economy, the focus should be on limiting impurities and losses through product design, technology improvement, and more targeted plastic waste management.