Comparison of carbon budget, evapotranspiration, and albedo effect between the biofuel crops switchgrass and corn

Interest in biofuels produced from perennial crops like switchgrass (Panicum virgatum L.) has increased over the past decades. It has been suggested that perennial biofuel crops have additional climate benefits compared to annual crops, such as carbon sequestration and albedo increase, but these effects have not been quantified in field studies. We compared carbon dioxide and water exchange results from eddy covariance measurements and surface albedo over a switchgrass and a corn field in Southwestern Ontario, Canada, for the year 2014. Results for the carbon budget showed more carbon uptake for switchgrass compared to corn (annual net ecosystem exchange NEE of −336 ± 40 vs +64 ± 41 g C m−2). Switchgrass was a small sink of carbon with a net ecosystem carbon balance (NECB) of −66 ± 59 g C m−2 but corn was a source for a scenario where corn grain only is harvested (NECB 393 ± 44 g C m−2) and a 1.5 times larger source if both corn grain and stover are harvested (NECB 699 ± 47 g C m−2). Switchgrass had, however, a lower yield 568 ± 93 g m−2 than either corn scenario (751 ± 40 g m−2 for grain only and 1439 ± 52 g m−2 for grain plus stover). Results from the albedo measurements showed a negative radiative forcing on an annual basis for the switchgrass field compared to corn. Differences in albedo were especially pronounced during spring and fall when radiative forcing values of −10.2 and −5.5 W m−2 were observed, respectively. Qualitative analysis of the carbon budget, evapotranspiration, and albedo results from this study suggests that biofuel produced from switchgrass can have more climate benefits than biofuel produced from continuous corn cropping systems.