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• Biogas upgrading is environmentally and energetically favourable over combustion. • Storage or utilisation of the captured CO 2 has larger savings than biogas upgrading. • Upgrading, CO 2 storage or utilisation perform well in all impact categories. • The energy system has a substantial impact on the environmental performance. • Methanation provides large climate change savings only in renewable energy systems. Biogas from anaerobic digestion is an important renewable energy source. Combining its utilisation with carbon capture and storage (CCS) or carbon capture and utilisation (CCU) may improve climate change performance. This study uses life cycle assessment to evaluate the environmental impacts of 17 biogas management technology configurations (TCs). The technologies include biogas combustion, upgrading to natural gas quality, CCS, direct utilisation of CO 2 and methanation. The focus is mainly on energy balances and climate change impacts, and the results are subjected to sensitivity-, uncertainty-, and energy system analysis. The TCs with CCS and CCU provide the largest climate change savings (-1400 to - 2100 kg CO 2 -eq/1000 Nm3 biogas). Specifically, the methanation TCs provide the highest savings, but they also depend strongly on the energy sources. When combustion and upgrading TCs are amended with CCS, the resulting climate change savings are robust across the energy systems. The biogas upgrading TCs exhibit substantial climate change savings, mainly due to the natural gas substitution. Combustion TCs without CCS have the lowest climate change savings and the highest quantified uncertainties. The biogas upgrading TCs with storage or direct utilisation of CO 2 provide a good compromise between climate change savings and energy recovery. In the remaining impact categories, the CCU TCs generally perform best, followed by the upgrading TCs and finally, the combustion TCs. The CCS TCs consistently perform worse than their counterparts without CCS, opposite to the climate change results. Overall, amending biogas utilisation with CCS or CCU can contribute to climate change mitigation. [ABSTRACT FROM AUTHOR]

This research aims to explore the current evidence on the sustainability of Bioenergy with Carbon Capture and Storage under a life cycle approach and to understand how research on this topic has evolved in the last decade. A systematic literature review was performed, and the main focus was identifying methodological shortcomings and analysing Global Warming Potential results. Forty-seven studies were selected for in-depth revision. Results show that the number of Life Cycle Assessment (LCA) studies on BECCS has increased in the last couple of years and that most of these studies report near-carbon neutral or carbon-negative results for electricity, biofuel energy, and other products. However, in many cases, some aspects have been omitted from the discussion, such as proper accounting of land use impacts, impact allocation procedure, accounting of leakage from storage sites, and impacts related to carbon utilisation. Despite this methodological variability, Global Warming Potential results are mostly carbon-negative and carbon-neutral for both power BECCS and industrial BECCS systems. Consequently, current scientific evidence suggests climate change mitigation benefits from BECCS despite methodological variability. However, it is still insufficient to reach a consensus on the sustainability of this technology as a solution for a global energy transition. It is recommended that further LCA research deals carefully with methodological and product systems variability, which may affect environmental impact results. Moreover, carbon capture approaches with high potential benefits should be further analysed, and the most optimal BECCS typologies should be identified. Finally, additional life cycle impact categories should be reported, along with the assessment of the economic and social dimensions of BECCS. [Display omitted] • Life Cycle Assessment (LCA) of Bioenergy with Carbon Capture and Storage (BECCS) was reviewed. • LCA methodology choices were discussed. • Global Warming Potential ranges between −3.873 and 0.366 kg CO 2 eq per MJ. • Current evidence is insufficient to confirm that BECCS is a sustainable solution for climate change mitigation. [ABSTRACT FROM AUTHOR]

Existing assessments of climate mitigation technologies, like carbon capture utilisation and storage (CCUS), often rely on life cycle assessments (LCA), which are helpful for quantification but may not always be the most complete tools for decision-making. The novel contribution of this study is to provide the first application of a consequential carbon accounting approach, presented as a time-series analysis, to measure the system-wide change in emissions from CCUS linked to CO 2 -enhanced oil recovery. This method includes emissions from marginal oil production, a variable typically excluded in other LCA methods. The method was applied to a hypothetical CCUS project in Mexico to understand critical factors determining whether such an intervention can effectively contribute to emissions reduction in alignment with net-zero goals. Four intervention scenarios were assessed, comparing two distinct CO 2 injection strategies in oil reservoirs (water alternating gas and continuous gas injection) and two energy policy scenarios (current and sustainability). The findings suggest that the energy grid's role in overall emissions is relatively minor, with only a ∼2% difference between the compared scenarios, in contrast, the injection strategy has a significant impact on emissions. Scenarios 1 and 3 report a total change in emissions of −28.39 and −29.87MtCO 2 e, and scenarios 2 and 4 account for −19.63 and −21.22MtCO 2 e, respectively. The results highlight the importance of conducting system-wide analysis and comparing different scenarios to identify the critical components that drive changes in emissions and, therefore, support decision-making and project planning. • Consequential carbon accounting quantifies the system-wide change caused by CCUS. • A time-series provides decision-relevant information on climate change mitigation. • Market-mediated effects are highly relevant for CCUS projects. • CCUS is not consistent with net zero due to as remaining emissions. [ABSTRACT FROM AUTHOR]

• Substitution factors for forest products for the Canadian context were developed. • Substitution factors ranging from 0.51 to 0.91 tC/tC were found. • They will lead to more accurate assessments of the forest GHG mitigation potential. • These factors will help governments to manage forest and fight climate change. Evaluating the climate change mitigation potential of the forest sector requires a holistic approach based on forest carbon (C) sequestration, C storage in harvested wood products (HWP) and substitution on markets. High uncertainty is associated with substitution factors, that express avoided fossil greenhouse gas (GHG) emissions from the use of forest-based products in replacement of GHG-intensive materials and fossil fuels. Few studies have focused on the development of substitution factors in Canada, resulting in the use of unrepresentative generic data. Here, we provide a framework to reduce uncertainties related to substitution factors for primary wood products in a Canadian context. A life cycle assessment framework is used to quantify fossil GHG emissions for a baseline and a wood-intensive scenario. For solid product substitution, we focused on the construction sector and analyzed a range of innovative wood buildings with steel and reinforced concrete as alternative materials. We found non-weighted averages of 0.80 tC/tC for sawnwood and 0.81 tC/tC for panels. For energy substitution, we analyzed cases with different specifications on biomass product, facility type and alternative fossil fuel source in non-residential heat production and biofuel transportation sectors. We found a non-weighted average of 0.80 tC/tC for non-residential heat production and 0.51 tC/tC for biofuel transportation, that can be interpreted as 0.91 tC/tC for heavy fuel oil, 0.69 tC/tC for light fuel oil and 0.68 tC/tC for natural gas substitution. These results provide a benchmark for substitution factors in Canada, to help guide forest management strategies for climate change mitigation. [ABSTRACT FROM AUTHOR]

Bioenergy with carbon capture and storage (BECCS) is regarded as a crucial negative emission technology (NET) in many prospective climate change mitigation scenarios that limit global warming below 2 °C. However, there is still insufficient understanding of the overall life cycle environmental performance of different BECCS configurations. Despite the fact that BECCS entails many technological combinations, the technology is still regarded as a single "black box" technology in most climate scenarios. This study presents a critical review of life cycle assessment (LCA) on a wide range of BECCS options: biomass direct-fired power generation, biomass gasification power generation, bio-hydrogen production, biomass application in industry sectors and other biomass conversion processes, such as pyrolysis and fermentation. It is evident from the review that the biomass direct-fired and gasification power plant with a 100% biomass firing ratio and the gasification-based bio-hydrogen processes have a strong potential to achieve negative emissions. However, the net negative life cycle emissions range widely among studies for each configuration due to variations in technology, LCA methodology and assumptions. Additionally, there is an insufficient assessment of comprehensive environmental impacts for BECCS systems other than GWP, making it still unclear about the trade-offs between the benefit from climate change mitigation and potential negative impacts. Main recommendations for improving LCA on BECCS include developing a generalized guideline and standardization for BECCS LCA, conducting LCAs with comprehensive impact categories, focusing on BECCS configurations being overlooked, considering the impact of land use change and the global warming potential of biomass, and extending LCA in both temporal and spatial dimension. [Display omitted] • Systematically review of life cycle assessment on BECCS systems. • Detailed review on various biomass conversion technologies. • Net negative life cycle emissions range widely among studies. • Insufficient studies of some biomass conversion pathways. • Insufficient studies on multi-environmental environment impact categories. [ABSTRACT FROM AUTHOR]

Recently, electric fuels (E-fuel), which are the chemicals produced from the conversion of renewable-based hydrogen (H 2), are actively being developed as a sustainable energy carrier. Renewable methane is particularly a promising alternative to fossil-based natural gas, which can be produced from CO 2 or syngas methanation. In this work, techno-economic assessment (TEA) and life-cycle assessment (LCA) for renewable methane production are performed through syngas methanation, where CO 2 is collected using direct air capture (DAC) and syngas is produced by solid oxide electrolysis (SOE) with renewable-based electricity. This research considers the different technical, economic, and environmental performances of the systems for renewable methane production. A favorable reduction in a maximum of 23.3% of CH 4 production cost is observed by the scale-up effects of SOE system from 1 MW to 10 MW. TEA draws the conclusion that economic infeasibility is proved at the current level, but additional research and improvement of SOE system and a plunge in renewable electricity prices can lead to the economic equivalent of conventional natural gas. Furthermore, given that certain energy resources with low energy intensity (0.0394 kg CO 2 -eq MJ−1) are integrated with SOE system for methane production, the LCA results that renewable methane production at a large scale has a potential to access negative CO 2 emissions and accelerate climate change mitigation. Consequently, it is concluded that syngas methanation with renewable-based energy systems and DAC can make a considerable opportunity for climate change mitigation under the assumption that SOE system and renewable energy are significantly improved. [Display omitted] • Feasibility of renewable methane production from syngas methanation is investigated • Solid oxide electrolysis for syngas production with renewable energy is covered • Direct air capture as CO 2 capture technology is considered for renewable methane • Possibility of negative CO 2 emission is confirmed by utilizing direct air capture • Mitigating climate change is proved by renewable methane with direct air capture [ABSTRACT FROM AUTHOR]

The Intergovernmental panel on climate change raised awareness on the urgent need for action to limit climate change. Answers include bioenergy with carbon capture and storage (BECCS), which could theoretically generate negative emissions. The life cycle assessment (LCA) method needs to be applied to BECCS systems to assess their negative emission potential and prevent transfers from one environmental impact category to another. To allow for informed decision-making, the quality of LCA results should be evaluated. The quality of results is related to the quality of the data used. The purpose of this article is thus to review the life cycle inventory data that are used for BECCS LCA. To this end, 35 recent BECCS LCA were selected and the inventory data they used was collected. Synthesis inventory tables were then compiled, including the observed range of variability for each data item. These tables cover biomass harvesting, pre-treatment, combustion, gasification, and carbon dioxide capture with a monoethanolamine (MEA) based solvent. Data quality is also reviewed, through the representativeness, reproducibility and completeness of the life cycle inventories highlighted in the selected articles. Only a third of the articles (13/35) provide life cycle inventory tables. Only half of the articles assess the impact on climate change leading to inventory cut-offs. BECCS systems including combustion followed by MEA-based capture have been most referenced (12/35 articles). More transparency on data quality is recommended. Certain promising BECCS systems should also be further studied. This applies, for instance, to BECCS systems that involve second-generation solvents. • A review of the data quality used in life cycle assessment (LCA) of BECCS is assessed. • Only a third of the studied articles provide their life cycle inventory tables. • Inventory data currently used in LCA of BECCS is compiled into synthesis tables. • BECCS systems including MEA-based capture are most frequently referenced. • BECCS systems that should be further assessed with LCA are identified. [ABSTRACT FROM AUTHOR]

Wood and other bio-based building materials are often perceived as a good choice from a climate mitigation perspective. This article compares the life cycle assessment of the same multi-residential building from the perspective of 16 countries participating in the international project Annex 72 of the International Energy Agency to determine the effects of different datasets and methods of accounting for biogenic carbon in wood construction. Three assessment methods are herein considered: two recognized in the standards (the so-called 0/0 method and −1/+1 method) and a variation of the latter (−1/+1* method) used in Australia, Canada, France, and New Zealand. The 0/0 method considers neither fixation in the production stage nor releases of biogenic carbon at the end of a wood product's life. In contrast, the −1/+1 method accounts for the fixation of biogenic carbon in the production stage and its release in the end-of-life stage, irrespective of the disposal scenario (recycling, incineration or landfill). The −1/+1 method assumes that landfills offer only a temporary sequestration of carbon. In the −1/+1* variation, landfills and recycling are considered a partly permanent sequestration of biogenic carbon and thus fewer emissions are accounted for in the end-of-life stage. We examine the variability of the calculated life cycle-based greenhouse gas emissions calculated for a case study building by each participating country, within the same assessment method and across the methods. The results vary substantially. The main reasons for deviations are whether or not landfills and recycling are considered a partly permanent sequestration of biogenic carbon and a mismatch in the biogenic carbon balance. Our findings support the need for further research and to develop practical guidelines to harmonize life cycle assessment methods of buildings with bio-based materials. [Display omitted] • Life cycle assessments of the same multi-residential building were carried out by experts from 16 countries. • Effects of methods and datasets of biogenic carbon accounting in wood construction were identified. • Different end-of-life scenarios (incineration, landfill, recycling) cause variations in the results. • Different interpretations of the permanence of storing biogenic carbon in landfills also cause variations in the results. • The input and output flows of biogenic carbon must be balanced to correctly assess its climate change impacts. [ABSTRACT FROM AUTHOR]

Prospective Life Cycle Assessment (pLCA) is useful to evaluate the environmental performance of current and emerging technologies in the future. Yet, as energy systems and industries are rapidly shifting towards cleaner means of production, pLCA requires an inventory database that encapsulates the expected changes in technologies and the environment at a given point in time, following specific socio-techno-economic pathways. To this end, this study introduces premise , a tool to streamline the generation of prospective inventory databases for pLCA by integrating scenarios generated by Integrated Assessment Models (IAM). More precisely, premise applies a number of transformations on energy-intensive activities found in the inventory database ecoinvent according to projections provided by the IAM. Unsurprisingly, the study shows that, within a given socio-economic narrative, the climate change mitigation target chosen affects the performance of nearly all activities in the database. This is illustrated by focusing on the effects observed on a few activities, such as systems for direct air capture of CO 2 , lithium-ion batteries, electricity and clinker production as well as freight transport by road, in relation to the applied sector-based transformation and the chosen climate change mitigation target. This work also discusses the limitations and challenges faced when coupling IAM and LCA databases and what improvements are to be brought in to further facilitate the development of pLCA. [Display omitted] • Prospective LCA can benefit from projections of models such as IAM. • Premise streamlines the production of LCA databases based on prospective scenarios. • Emissions and energy efficiencies of major industries are aligned with IAM scenarios. • Stricter greenhouse gas targets result in larger transformations in the LCA database. • However, such targets result in increased LCA impacts other than global warming. [ABSTRACT FROM AUTHOR]

Globally, governments have increased their commitment to mitigate greenhouse gas (GHG) emissions. At the same time, the compostable bioplastic market is growing rapidly as many single-use petrochemical plastics are being banned internationally. A prospective consequential life cycle assessment approach was conducted to quantify the environmental envelopes of compostable bioplastic production for the bioplastic value chains to operate within the bounds of climate neutrality. Four indicative feedstocks of (i) lignocellulosic biomass from forestry, (ii) maize biomass, (iii) food waste digestate, and (iv) food waste were evaluated for potential bioplastic production. Upstream and end-of-life emissions for these feedstocks equated to GHG balances of -16.3 to +23.5, 0.3 to 1.0, 1.0 to 4.8, and -0.1 to +0.4 kg CO 2 eq. per kg bioplastic, respectively. The scenarios demonstrated that indirect land-use change could have a considerable negative impact on the environmental performance of maize-based plastic, but a positive impact, via terrestrial carbon sequestration, for lignocellulosic-derived plastic (unless increased feedstock demand drives deforestation). Appropriate use of residues and sidestreams is critical to the environmental performance of bioplastics. Efficient utilisation of residues may require decentralisation of bioplastic production and implementation of biorefinery and circular economy concepts. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) is at the interface of biowaste management, energy generation, food production and land-based carbon dioxide removal. Strategic deployment of AD requires careful scoping of interactions with prospective alternative biowaste management, energy generation technologies and land uses to ensure effective delivery of climate neutrality and circularity. There remains a need to assess the greenhouse gas (GHG) mitigation efficacy of AD in the context of future alternative (counterfactual) processes associated with differential rates of decarbonisation across energy, waste management and land (including agriculture) sectors. To address this gap, prospective life cycle assessment (LCA) is applied to AD deployment scenarios across three decarbonisation contexts, using the UK as an example. Food waste prevention and diversion to animal feed always achieve more GHG mitigation than AD, even with sustainable intensification of food and feed production. Compared with maize- or grass-biomethane transport fuel, solar electricity generation can avoid 16 times more fossil energy and afforestation can mitigate six times more GHG per hectare of land occupied. Transport biomethane is currently the most effective biogas use for GHG mitigation, but large-scale combustion of biogas for electricity or industrial heat generation is the most effective long-term option as transport is electrified and bioenergy carbon capture & storage (BECCS) is deployed. Prioritising waste prevention and diversion to animal feed (including via insect meal) instead of maximising AD deployment could simultaneously: offset an additional 10–15% of national GHG emissions; meet an additional 2–4% of national energy demand; free enough arable land to provide 20–21% of national recommended protein and kcal intake. However, AD is likely to remain the best option to manage substantial volumes of residual food wastes and manures that will remain available even if ambitious projections on waste prevention and diet change are realised. [Display omitted] • Consequential LCA of anaerobic digestion (AD) in future decarbonisation contexts • GHG mitigation efficacy of AD declines as energy & transport systems decarbonise • AD-crop cultivation is a highly inefficient land use for energy generation and GHG mitigation • Carbon capture & storage could maintain effective mitigation from large-scale biogas use • Sustainable niche for waste-AD alongside waste prevention & diversion to animal feed [ABSTRACT FROM AUTHOR]