|ZHU, PENG - Purdue University|
|ZHUANG, QIANLAI - Purdue University|
|JOO, EVA - University Of Illinois|
Submitted to: Global Change Biology Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2016
Publication Date: 2/17/2017
Citation: Zhu, P., Zhuang, Q., Joo, E., Bernacchi, C.J. 2017. Importance of biophysical effects on climate warming mitigation potential of biofuel crops over the conterminous United States. Global Change Biology Bioenergy. 9:577-590.
Interpretive Summary: Bioenergy feedstocks are intended to reduce the emissions of carbon into the atmosphere that stem from current fossil fuel usage. However, there is the potential for additional climate warming mitigation opportunities associated with bioenergy feedstocks, particularly with regards to evaporative cooling associated with ecosystem water use. This research uses a vegetation-climate model to investigate how different bioenergy crops and management practices can influence the climate. In general, there are small benefits to bioenergy feedstocks that result in carbon being removed from the atmosphere. But when considering the influence of evaporative cooling and other energy-related components of how ecosystems work, bioenergy feedstocks and improved management techniques results in much larger cooling effects than the removal of carbon from the atmosphere. The research shows the importance of considering both carbon and energy when assessing the impact of land use change on climate.
Technical Abstract: Current quantification of Climate Warming Mitigation Potential (CWMP) of biomass-derived energy has focused primarily on its biogeochemical effects. This study used site-level observations of carbon, water, and energy fluxes of biofuel crops to parameterize and evaluate the Community Land Model (CLM) and estimate CO2 fluxes, surface energy balance, soil carbon dynamics of corn (Zea mays), switchgrass (Panicum virgatum) and miscanthus (Miscanthus × giganteus) ecosystems across the conterminous United States considering different agricultural management practices and land-use scenarios. We find that neglecting biophysical effects underestimates the CWMP of transitioning from croplands and marginal lands to energy crops. Biogeochemical effects alone result in changes in carbon storage of -1.9, 49.1 and 69.3 g C m-2 y-1 compared to 20.5, 78.5 and 96.2 g C m-2 y-1 when considering both biophysical and biogeochemical effects for corn, switchgrass and miscanthus, respectively. The biophysical contribution to CWMP is dominated by changes in latent heat fluxes. Using the model to optimize growth conditions through fertilization and irrigation increases the CWMP further to 79.6, 98.3 and 118.8 g C m-2 y-1, respectively, representing the upper threshold for CWMP. Results also show that the CWMP over marginal lands is lower than that over croplands. This study highlights that neglecting the biophysical effects of altered surface energy and water balance underestimates the CWMP of transitioning to bioenergy crops at regional scales.