Can bioenergy carbon capture and storage aggravate global water crisis?

Bioenergy carbon capture and storage (BECCS) is an effective option for mitigation of greenhouse gas (GHG) emissions. Nevertheless, there is barely serious debate about whether its implementation can possibly jeopardize the global water resources security. Here, we provided an assessment of biomass-based Substitute Natural Gas (BioSNG) production combined with CCS, a promising BECCS technology, in terms of global water resources security, with a focus on the growth of two typical second-generation bioenergy crops: switchgrass and miscanthus. A bottom-up analysis approach was applied in this paper to calculating water consumption for BECCS and estimating water quality deterioration caused by increasing fertilizer and pesticide application. The results indicated that water usage of BECCS was equal to adding 12.86%-16.64% (switchgrass) and 17.59%-26.06% (miscanthus) additional water stress on global available water resources at 2100. Additional N fertilizer application in 2100 would be equal to over 84%, 55% and 42% for both switchgrass and miscanthus under three CCS capture efficiency scenarios, respectively, comparing to such global scale in 2012. Additional phosphate fertilizer adding to global annual available water at 2100 were 0.004-0.008 mg L^-1 (switchgrass) and 0.003-0.006 mg L^-1 (miscanthus), respectively. The secondary environmental hazards, such as N₂O emission, would offset GHG emission mitigation by BECCS. Meanwhile, the enrichment and leaching of pesticide residues increased the risk of groundwater contamination. This study revealed water consumption and contamination issues caused by BECCS cannot be neglected. Thus, additional studies of accurate land-use models in global scale and advanced technology for biofuel extraction are needed in the future.