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The shipping sector is seeking options to reduce its emissions of greenhouse gases (GHGs) and achieve ambitious climate change mitigation goals. Unlike short-sea shipping that can rely on electrification of coastal vessels, drop-in biofuels are among the most promising options for deep-sea shipping decarbonization. However, environmental sustainability analyses of marine biofuels are limited, and usually do not include the influence of future changes in the background energy system nor the climatic effects of near-term climate forcers (NTCFs). In our study, we assess the climate change mitigation potential of various marine biofuels produced from forest residues in Norway (a country with ambitious plans for emission reduction from shipping) using a prospective life-cycle assessment (LCA) where the projected trends in the energy and transport sectors are integrated with improvements in the biofuel value chain for the next decades (2030–2050). Relative to fossil-based alternatives, climate mitigation potentials of biofuels range from 65% to 85% with short-term (GWP20) and to 78%–87% with long-term (GTP100) climate impacts. The inclusion of NTCFs reduces the mitigation benefits of biofuels in the short term, while it slightly increases them in the long term. The explicit modeling of technology and socio-economic changes under future policy scenarios indicates a reduction in the climate impacts of biofuels by up to 54% in 2050 when compared to the current situation. The amount of residues potentially available in Norway is sufficient to meet the present demand for liquid fuels in deep-sea shipping, thus providing yearly climate mitigation of 0.9–1.1 million tons of CO 2-eq (equal to 6–7% of today's climate impacts from the entire transport sector in the country). Our analysis shows the large climate change mitigation potential of drop-in biofuels, and it provides new quantitative estimates that can help guiding a sustainability shift in the deep-sea shipping sector. [Display omitted] • Climate mitigation from biofuels can range from 65% to 87% relative to fossil fuels. • Future inventory databases can cut up to 54% of marine biofuel's climate impacts. • NO x and SO x lower the climate impacts of biofuels in the short and medium terms. • Marine biofuels can mitigate 6–7% of the Norwegian transport sector's emissions. [ABSTRACT FROM AUTHOR]

To address global food demand and sustainability challenges, aquaculture has appeared as an essential element in food systems, and an increasing number of national aquaculture policies have emerged over the past decades. However, several of these policies have failed because of an often-argued inability to anticipate their far-reaching implications on environmental and socio-economic variables. To tackle this gap, we propose a step-wise framework to assess the national environmental impacts from aquaculture industries with a prospective and systemic approach. Starting from identifying policy-based national targets, the methodology relies on economic equilibrium modeling to develop realistic future-oriented scenarios of the aquaculture sector, and couples them with life cycle assessment principles. To evidence its operability, we apply the framework to two distinct case countries: Norway and Singapore. Beyond our key findings from the analyses of the policies in both countries, we observed that feed production and usage are important drivers of impacts, hence calling for new and more environmentally-friendly feed options. Our results additionally show that the development of aquaculture following existing governmental policies may not directly reduce greenhouse gases emissions and, hence, not support climate change mitigation objectives. These findings should however be cautioned as potential shifts of diets due to the increasing seafood availability might occur, leading to indirect environmental benefits. We therefore advocate the further expansion of our framework to cover the entire food system, so it can integrate such indirect effects. Meanwhile, we recommend its interim application to support policy-making and help move towards more environmentally sustainable aquaculture systems. • A framework to assess prospective environmental impacts of aquaculture is developed. • It combines economic equilibrium modeling and life cycle assessment at national scale. • It is operationalized to assess aquaculture policies in Singapore and Norway until 2040. • Conclusions for each country are issued, and common findings are discussed. • We call for a wide application of our framework to support aquaculture sustainability. [ABSTRACT FROM AUTHOR]