(760b) Bioethanol Production with Carbon, Capture and Storage: Potential As a Carbon-Negative Biofuel and Environmental Implications

Authors: 
Galán-Martín, Á., ETH Zürich
Bello, S., Department of Chemical Engineering, CRETUS Institute, Universidade de Santiago de Compostela
Feijoo, G., Department of Chemical Engineering, CRETUS Institute. Universidade de Santiago de Compostela
Moreira, M. T., Department of Chemical Engineering, CRETUS Institute. Universidade de Santiago de Compostela
Guillén-Gosálbez, G., Imperial College London
Bioenergy with carbon capture and storage (BECCS) technologies are receiving increasing attention as they are crucial to delivering the carbon dioxide removal required to achieving the climate goals sought. So far, the biomass conversion to heat and power has attracted the bulk of the attention while the BECCS concept applied to biorefineries producing biofuels remains largely unexplored. Considering the dependence of the road transport sector on fossil fuels and, therefore, its large associated emissions contributing to global warming, tacking the decarbonization of the transport sector is particularly important to stop climate change. Hence, producing carbon-negative biofuels provides a promising alternative to replace conventional fossil fuels and moving towards a carbon-neutral mobility or even achieving negative emissions.

In this study, we perform a Life Cycle Assessment (LCA) of a biorefinery coupled with a CCS technology for bioethanol production using residual lignocellulosic woodchips as feedstock. The goal of the analysis is to investigate the potential of different scenarios to produce carbon-negative biofuels as well as to assess their broader environmental implications in other relevant areas of protection. The system was modelled with Aspen Plus® and analyzed following a cradle-to-wheel approach, i.e., including the biomass feedstock procurement, transportation, process conversion, the end-use of the biofuel in vehicles as well as the whole CO2 supply chain (i.e., capture, compression, transportation and storage in geological sites). We define different scenarios varying the bioethanol-gasoline blends (10-85% bioethanol) as well as the heating sources (i.e., natural gas or sugar cane bagasse). A functional unit of 1 km of distance travelled in an internal combustion engine vehicle is used throughout the study, which allows comparison with the conventional gasoline representing the business as usual scenario

Our results show that achieving a net negative emissions balance would require bioethanol-gasoline blends above 85% (i.e., E85). Moreover, our results show that the carbon-intensity of the electricity and heat used in the processes play a key role in the final carbon balance. For example, with an E85 blend and assuming the average electricity mix for Europe, the system would provide a net-negative emissions balance of -2.7 kg CO2 eq per 100 km travelled, whereas considering electricity provided from hydropower, the carbon footprint would be further reduced up to -5.1 kg CO2 eq./100 km. However, despite the potential benefits of moving towards the use of carbon-negative biofuels, it would also lead to burden-shifting to other environmental impacts increasing the pressure on water consumption, toxicity or acidification, among others categories. Overall, this work demonstrates the potential of BECCS concept applied to biorefineries to promote carbon-negative mobility while calls for widening the scope of the future policies beyond climate change to avoid collateral damage to other environmental areas.

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