PNNL

Abstract

The maximum projected biofuel expansion potential by 2100, in scenarios limiting warming to 2°C, is equivalent to half of present-day croplands. The impacts of such large-scale biofuel expansion, and how the impacts differ from a predominantly re/afforestation scenario, is not well understood as studies examining them are either at coarse resolution or ignore crucial carbon-water-nitrogen interactions. We provide unified estimates of biofuel expansion impacts using a multisector and multi-cale human-natural system modeling framework with explicit representation of high-yield perennial bioenergy crops. We find that the net carbon accumulation of bioenergy deployment largely depends upon the type of fossil-fuel emission displacement, ranging from 12.2 to 46.3 PgC over the conterminous U.S. by 2100. These net carbon accumulation benefits are inclusive of a 10 PgC carbon release due to land-use conversions and a 2.4 PgC loss of additional carbon sink capacity associated with the biofuel-driven deforestation. Moreover, we find that nearly one-fifth of the U.S. land areas will suffer severe water stress by 2100 either due to reduced availability or deteriorated quality. These broader impacts of biofuel expansion should be weighed against the costs and benefits of re/afforestation-based strategies.