PS 24-43 - New flux dataset highlights the biogeophysical benefits of land cover change from row crops to dedicated bioenergy feedstocks.

Background/Question/Methods

Dedicated crops for renewable bioenergy production have potential to partially offset carbon release associated with extensive fossil fuel consumption. Perennial feedstocks such as switchgrass and miscanthus are promising candidates in part because they have the additional potential to favorably alter biogeophysical cycles through carbon storage and radiative cooling. Despite a growing understanding of the physiology of dedicated bioenergy feedstocks, they remain underrepresented in widely-available flux data. Here we present preliminary results from a newly-released 30+ site-year dataset of co-located bioenergy feedstocks. We find that, relative to maize, perennial feedstocks are stronger carbon sinks and sources of radiative cooling.

Results/Conclusions

The newly-released dataset includes eddy flux and meteorological data for 5 candidate bioenergy crops: maize (Zea mays), giant miscanthus (Miscanthus × giganteus), switchgrass (Panicum virgatum), native prairie (27 Illinois-native species), and energy sorghum (Sorghum bicolor). Miscanthus and switchgrass were carbon sinks even when accounting for harvest C removal, storing on average 2 tC ha^-1 y^-1 and 1.2 tC ha^-1 y^-1 respectively. Cumulatively, 15 years of Miscanthus cultivation stored 30tC ha^-1 while 15 years of maize cultivation released 20 tC ha^-1. Miscanthus and switchgrass were also radiatively cooler than maize. A theoretical conversion from maize to miscanthus or switchgrass results in a -6.9 Wm^-2 and -6.1 Wm^-2 radiative cooling respectively, while a theoretical conversion to sorghum results in 5.4 Wm^-2 radiative warming. Our findings strongly confirm the biogeophysical favorability of perennial bioenergy feedstocks relative to annual maize-soy rotation.