Bioenergy from energy crops is a source of negative emissions and carbon-neutral fuels in many 1.5/2 ∘C IPCC pathways. This may compete with other land uses. In contrast, ancillary biomass like by-products and waste is not primarily grown for energy and thus without land/food/feed competition. Here, we examine the availability and environmental impacts of ancillary bioenergy from agricultural sources under 190 circular agroecological strategies using the global food-system model SOLm for the year 2050. We find that there is a diverse option space for the future food and energy system to meet both global warming targets (1.5 ∘C) and food system sustainability (medium to highly organic) – a similar range of ancillary bioenergy global potential (55–65 EJ)from very different food systems (50%–75% organic agriculture and various levels of waste and concentrate feeding reduction). We find three trade-offs between food system sustainability and ancillary bioenergy provision. First, there is a clear trade-off between nutrient recycling and negative emissions potential. 1.4–2.6 GTCO2eq of negative emissions supplied through ancillary bioenergy with carbon capture and storage comes at the cost of nutrient deficits and resulting incompatibility with even a medium degree of organic farming. Second, reducing feed from croplands increases the ancillary bioenergy production with low shares of organic agriculture and reduces it for high shares. Third, food waste reduction reduces ancillary bioenergy provision. Hence, the sustainable transformation of the food system towards a less animal-based diet and waste reduction may conflict with a higher ancillary bioenergy provision, especially when the organic share is high as well. The policy implication of our results is that ancillary bioenergy can provide a similar range of future bioenergy as foreseen in IPCC AR6 illustrative pathways (±10% ) without additional land use or compromising food availability. However, higher ancillary bioenergy provision or additional negative emissions compete with food system sustainability; hence, we recommend policymakers consider aligning energy system planning with the compatibility of sustainable food systems simultaneously.@en

Biomass is a growing renewable energy source in Europe and is envisioned to play a role for realising carbon neutrality, predominantly using dedicated energy crops. However, dedicated biomass is controversial for reasons including its competition with food production or its land-use and emissions impacts. Here we examine the potential role of a land-free alternative: ancillary bioenergy (AB) from biomass sources not primarily grown for energy and without land/food/feed competition. We provide the first dataset of 2050 ancillary biomass potential using the agricultural system model SOLm, which encompasses untapped by-/co-products and detailed agricultural residues. Results show that there is a limited future potential for AB in Europe (2394-10 342 PJ, which is 3-6 times lower than other estimates including dedicated biomass). We design and investigate alternative scenarios where this bioenergy resource can be fully utilised, not utilised at all, or utilised optimally by the sector-coupled energy system model Euro-Calliope. We find that fully utilising ancillary biomass can help phase out controversial nuclear or land-intensive dedicated biomass, so might achieve higher societal acceptability. Using all ancillary biomass as a negative-emissions source at stationary bioenergy carbon capture and storage plants in a nuclear-free system provides additional climate benefits. It is also possible to leave the AB potential completely unused, which barely increases total system cost, but would preserve agricultural nutrients. We conclude that there are synergies and trade-offs among possible strategic uses of AB, which can provide guidelines for a more coherent European bioenergy strategy. Although the 2050 potential of AB is limited, our findings suggest that it could fill critical strategic niches for realising carbon-neutrality.@en

Bioenergy is currently a major renewable energy source in Europe but faces an unclear future because of conflicting modelling results and the lack of long-term policy. This paper identifies three challenges and potential opportunities by analysing bioenergy's historical national deployment, current policy support, and possible future roles in Europe. The first challenge is on the supply side. Calculating the supply-consumption dynamics and import dependency of EU bioenergy, we find that the security of bioenergy supply is challenging for liquid biofuels and those countries with the highest per-capita bioenergy consumption in Europe. Second, the definition of “sustainable bioenergy” in modelling studies is sometimes inconsistent with how EU policies label it. Third, on the demand side, there are unique but competing uses for bioenergy without a clear long-term strategy in Europe. We conclude with three opportunities to tackle these challenges for future research. First, utilising the untapped bioenergy potential with low environmental impacts could improve supply security. A clear and harmonised definition of “sustainable bioenergy” could better convey modelling results to policymaking. Finally, understanding where best to use limited sustainable bioenergy supply through sector-coupled energy system models can provide direction for a clearer EU bioenergy strategy towards 2050.@en

Very few developed economies have a full free trade agreement (FTA) with China. This study employs one GTAP model and builds an extended environmental multi-region input–output model to investigate a hypothetical China-UK FTA, concerning embodied industrial emissions of SO2, PM2.5, NOX, and NH3. The economic sectors are also classified based on their embodied pollution intensity and trade advantage index under various FTA scenarios. Results show that the UK’s GDP and welfare and China’s welfare will increase, along with changes in their trade structures. Overall, this FTA brings about larger net impacts on embodied emissions of SO2 than on PM2.5, NOX and NH3, and both countries are net importers of the latter three pollutants. Key sectors such as non-metallic mineral products, chemical products, and agriculture are inclined to become less competitive and less polluting under the FTA. The inclusion of agri-food sectors exhibits slight counteracting effects in general. The findings are of policy importance as they provide insights into how best to target key sectors, seeking a balance between trade development and environmental protection.@en

With the increasing demand and limited production, China has to import a large amount of soybeans. However, soybean has been chosen as one target of the recent trade war between the US and China. It is therefore critical to assess the sustainability of soybean supply in China. Under such a circumstance, this study aims to fill such a research gap by using an emergy accounting approach from both spatial and temporal perspectives and at provincial-level. The impact of trade war on soybean imports and production is simulated by one GTAP (Global Trade Analysis Project) model. The results of Emergy Sustainability Indices (ESI) show that it is urgent to improve the sustainability of soybean planting in Heilongjiang, while Yunnan is the most appropriate place for planting soybean. For the international supply, the EER (Emergy Exchange Ratio) of China has decreased by 72% and the decrease of EERs at provincial level ranged from 59% to 86% during 2000–2015. The simulation results indicate the necessity of adjusting spatial structure of soybean planting and applying reasonable economic instruments to encourage sustainable soybean production.

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Urban environmental governance is critical for responding climate change. Existing policies have been inefficient for addressing complicated socio-ecological issues. In order to further promote related studies, it is critical to have a comprehensive review so that recent research progresses can be summarized and future research directions can be identified. Under such a circumstance, this paper aims to conduct a bibliometric review on urban environmental governance, with a focus on addressing climate change. Based on 1697 articles published from 1997 to 2017 and searched from Web of Science, a systematic method combining bibliometric analysis and network analysis is applied to uncover the dynamic trends, academic collaboration and research hotspots. Results show that the overall publication quantity had been gradually improved. The key journals include Journal of Cleaner Production, Sustainability and Energy Policy. Authors from USA have the most publications and international co-authorships, followed by China and UK, while the most influential institution is the Chinese Academy of Science. Moreover, research keywords have been identified, including GHG emission, energy, water, health and transport. In terms of research methods, life cycle assessment and ecological footprint are the dominating methods. In order to further improve research in this field, it is crucial to combine different methods so that more innovative perspectives can be presented. Research findings from this study can also provide valuable policy insights to policy-makers so that appropriate urban environmental governance policies can be raised to mitigate the overall greenhouse gas emission.@en