Tropical Bioenergy Limits

A technology designed to mitigate global warming could, paradoxically, contribute to carbon emissions if hotter temperatures lead to a shift in where bioenergy crops are grown. Bioenergy with carbon capture and storage (BECCS) involves combusting or fermenting biological materials to produce energy while capturing the carbon dioxide emitted by the process and storing it underground. BECCS could help mitigate climate change, and many models of a net-zero emissions future assume widespread use of the technology. However, first generation bioenergy production requires substantial land area to grow the crops used as feedstocks. Robert Fofrich Navarro and colleagues modeled how climate warming will affect the production of key bioenergy crops. The authors find that up to 40% of existing oil palm production, up to 13% of existing sugarcane production, and up to 10% of existing soybean production will occur in locations within the tropics that will not be suitable for these crops by 2060 under lower warming scenarios. These results raise the possibility that farmers may expand production to new, cooler areas to maintain production, potentially leading to deforestation. Deforestation would release carbon dioxide as trees are burned or felled. Reductions in ecosystem carbon from deforestation could outweigh the climate benefits of biofuel-based mitigation and threaten species in the tropics, the most biodiverse part of the world. According to the authors, bioenergy strategies must be assessed in the context of climate warming.