Global bioenergy with carbon capture and storage potential is largely constrained by sustainable irrigation

Capturing the carbon from energy crops-bioenergy with carbon capture and storage (BECCS)-requires water to grow the crops. This study finds that although unlimited irrigation could increase BECCS potential by 60-71% by 2100, doing so sustainably would increase it by only 5-6%. Bioenergy with carbon capture and storage (BECCS) is crucial in many stringent climate scenarios. Although irrigation can enhance BECCS potential, where and to what extent it can enhance global BECCS potential are unknown when constrained by preventing additional water stress and suppressing withdrawal of nonrenewable water resources. With a spatially explicit representation of bioenergy crop plantations and water cycle in an internally consistent model framework, we identified the irrigable bioenergy cropland on the basis of the water resources reserve. Irrigation of such cropland enhanced BECCS potential by only 5-6% (<60-71% for unconstrained irrigation) above the rain-fed potential (0.82-1.99 Gt C yr(-1)) by the end of this century. Nonetheless, it limited additional water withdrawal (166-298 km(3) yr(-1)), especially from nonrenewable water sources (16-20%), compared with unconstrained irrigation (1,392-3,929 km(3) yr(-1) and 73-78%). Our findings highlight the importance of irrigation constraints in global BECCS potential.