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INVESTIGATOR: O`Halloran, T.

PERFORMING INSTITUTION:
CLEMSON UNIVERSITY
CLEMSON, SOUTH CAROLINA 29634

EVALUATING THE NET CLIMATE BENEFITS OF SWITCHGRASS VERSUS PINE PLANTATIONS IN THE SOUTHEAST: A SEED GRANT TO SUPPORT DATA COLLECTION AND MODEL DEVELOPMENT

NON-TECHNICAL SUMMARY: Developing resilient agricultural systems that can supply climate mitigation services is key to improving the sustainability of U.S. agriculture. It is imperative to determine whether land use changes driven by agricultural needs could have counterproductive effects on climate through biogeochemical or biogeophysical mechanisms. Producing biomass for energy, for instance, will only be successful if managed plantations accumulate large amounts of carbon uninterruptedly. Therefore, bioenergy production is sensitive to external forces that reduce the productivity of these crops; the bioenergy-agriculture-climate system is thus highly interdependent. In the southeast, switchgrass and loblolly pine have been identified as potentially attractive biomass feedstocks. Herein we propose to leverage two existing eddy flux towers to directly measure the carbon sequestration and biophysical climate impacts of their production. Measuring important variables that drive productivity will determine the sensitivity of production to short term climate variability. Field measurements, and conversions of albedo radiative forcing to determine carbon fluxes and stocks will be used along with parameters from the full production chain to develop a life cycle greenhouse gas emission assessment. This analysis will evaluate and compare the total CO2e emission mitigation potential of using the two feedstocks to generate electricity by co-firing in a coal power plant. Integrating measured field data with modeling more fully represents the net climate effects of land use and identifies points of climate-vulnerability along the production chain. A larger future proposal can increase the scope of this seed grant by expanding to include a full LCA, and more sites and feedstocks.

OBJECTIVES: The overarching objective of this proposal is to define the net climate benefits, in terms of greenhouse gas emissions and biophysical feedbacks, as well as the climate sensitivity, of switchgrass and loblolly pine plantations, to inform decision makers on the climate mitigation potential of these land use types.Specific objectives are:• Quantify the net CO2 fluxes and aboveground and belowground carbon stocks of switchgrass and loblolly pine plantations using eddy covariance towers and biometry• Define the sensitivity of switchgrass and loblolly productivity to environmental drivers and short-term climate variability• Quantify the biophysical feedback from albedo to climate from these two land use types• Perform life cycle greenhouse gas emission assessment (GHG-LCA) of the full production chain for switchgrass and pine in the southeast to evaluate emission mitigation potential of 1 kWh of electricity generated by co-firing biomass in a coal power plant vs. a conventional coal power plant.