Settling the controversy on biofuels with data A new methodology for establishing the climate and biodiversity footprints of bioenergy highlights the benefits of early and selective deployment. By quantifying the long-term ecological footprint of biofuels, the ERC-funded SIZE project provides a clear assessment of potential risks and benefits – and a roadmap for steering production accordingly. Climate Change and Environment © Naufal Image, Shutterstock The debate over biofuels has been raging for years. “Groups are extremely divided, with one side claiming that biofuels with carbon capture and storage are the only way to combat climate change, while the other categorically rejects biofuels because of their impact on biodiversity. As usual, the truth is somewhere in the middle,” says Mark Huijbregts, professor of Integrated Environmental Assessment at Radboud University and principal investigator of SIZE (Size matters: scaling principles for the prediction of the ecological footprint of biofuels). SIZE evaluated the large-scale implementation of second-generation biofuels produced from bioenergy with carbon capture and storage (BECCS). BECCS refers to the process of removing the greenhouse gases produced when burning biomass from the atmosphere and permanently storing the carbon, often underground. The project team came up with a methodology that measures the impact of this process and translates this data into concrete recommendations on when and how to deploy it for best results. Large-scale trade-offs “SIZE looked into the potential benefits of biofuels for climate mitigation, but also the related biodiversity loss due to land use change,” Huijbregts explains. “Our new framework is able to quantify the trade-offs in terms of biodiversity and climate mitigation at the global scale by combining integrated assessment modelling, biodiversity indicators and life cycle assessment data in a way that has not been done before.” Huijbregts’ team has been able to provide clear evidence on what can be physically expected from this major energy source. “Our results show that over a period of 30 years, BECCS can only play a modest role. Over the full century, however, we could theoretically reach up to 40 Gt of CO2 sequestered per year – more than the current total annual emissions.” On the other hand, full global implementation of BECCS could lead to competition with other land uses: “Think about fast-growing wood plantations all around the world, including Brazil and Indonesia,” adds Huijbregts. “Biofuel production requires vast amounts of land which could take a toll on food production and substantially threaten biodiversity.” In the most extreme scenario, up to 2.4 billion hectares of land would be required by 2100 to grow lignocellulosic crops for BECCS, which equals 16 % of the total land surface area on Earth. A roadmap for the future Factoring the interplay between these different environmental challenges into their analysis, the scientists conclude that early and limited deployment is the most promising strategy. While launching large-scale production as early as possible will help to achieve the required level of mitigation over a longer time horizon, natural land conversion should be kept to a minimum to protect species and food production. Instead, the team recommends using abandoned agricultural lands as well as residue and waste biomass, which have little effect on land use. They also highlight the need for combining BECCS with other renewables and additional technologies to reduce emissions and remove carbon dioxide, calling on policymakers to promote these in parallel. To take the results achieved in the context of the SIZE project further, Huijbregts and his team have now started to work on global-scale modelling of other renewable energy sources, including wind, solar and hydropower. Keywords SIZE, BECCS, carbon capture and storage, biofuels, climate change, biodiversity, global-scale modelling
