Submitted to: PLoS One
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/5/2013
Publication Date: N/A
Citation: Interpretive Summary: Biofuels are slated to become an increasingly important part of the US energy production system, but might also have important implications for climate. We evaluated the greenhouse gas implications of changing pastures to energy cane (a variety of sugarcane) in Florida. Computer modeling simulations show that changing land from cattle grazed pastures to energy cane results in massive increases in plant biomass, and soil type was the strongest driver of greenhouse gas fluxes. Sandy soils became sinks for greenhouse gases, and muck soils released less greenhouse gases after conversion from pasture to cane. We conclude that on nutrient poor soils, changing land to energy cane for biofuel might result in greenhouse gas benefits.
Technical Abstract: Bioenergy related land use change will likely alter biogeochemical cycles and global greenhouse gas budgets. Energy cane (Saccharum officinarum L.) is a sugarcane variety and an emerging biofuel feedstock for cellulosic bio-ethanol production. It has a potential for high yields and can be grown on former pastures that minimize competition with grain and vegetable production. The DayCent biogeochemical model was parameterized to infer potential yields of energy cane and how changing land from grazed pasture to energy cane would affect greenhouse gas (CO2, CH4 and N2O) fluxes and soil C pools. The model was used to simulate energy cane production on sandy, nutrient poor Spodosols and organic Histosols in south-central Florida. Energy cane was productive on both soil types (46-76 Mg dry mass per hectare yield); yields were maintained through three annual cropping cycles on Histosols but declined with each harvest on Spodosols. Overall, converting pasture to energy cane created a sink for GHGs on Spodosols and reduced the size of the GHG source on Histosols. This change was driven on both soil types by eliminating CH4 emissions from cattle and by the large increase in C uptake by greater biomass production in energy cane relative to pasture. However, the change from pasture to energy cane caused Histosols to lose 4493 gCO2 eq / m2 over 15 years of energy cane production. Cultivation of energy cane on former pasture on Spodosol soils in the southeast US has the potential for high biomass yield and the mitigation of GHG emissions.