摘要：Limiting mean global warming to well below 2 °C will probably require substantial negative emissions
(NEs)within the 21st century. To achieve these, bioenergy plantations with subsequent carbon
capture and storage (BECCS) may have to be implemented at a large scale. Irrigation of these
plantations might be necessary to increase the yield, which is likely to put further pressure on already
stressed freshwater systems. Conversely, the potential of bioenergy plantations(BPs) dedicated to
achieving NEs through CO2 assimilation may be limited in regions with low freshwater availability.
This paper provides a first-order quantification of the biophysical potentials of BECCS as a negative
emission technology contribution to reaching the 1.5 °C warming target, as constrained by associated
water availabilities and requirements. Using a global biosphere model, we analyze the availability of
freshwater for irrigation of BPs designed to meet the projected NEs to fulfill the 1.5 °C target, spatially
explicitly on areas not reserved for ecosystem conservation or agriculture. We take account of the
simultaneous water demands for agriculture, industries, and households and also account for
environmental flow requirements(EFRs) needed to safeguard aquatic ecosystems. Furthermore, we
assess to what extent different forms of improved water management on the suggested BPs and on
cropland may help to reduce the freshwater abstractions. Results indicate that global water
withdrawals for irrigation of BPs range between∼400 and∼3000 km3 yr−1
, depending on the scenario
and the conversion efficiency of the carbon capture and storage process. Consideration of EFRs
reduces the NE potential significantly, but can partly be compensated for by improved on-field water
management.
