Print PageThe Renewable Fuel Standard calls for the production of 136 billion liters of ethanol in the United States by 2022. Most ethanol is currently fermented from corn, but there is increasing interest in employing ligno-cellulosic technology for ethanol production. Crops like energy cane, a cold tolerant, low-sugar, high fiber (~20%) variety of sugar cane that is highly productive (>30 Mg dry mass yield · ha-1), could be employed to this end. Energy cane could be widely deployed in regions of the Southeastern United States, as land prices there are relatively inexpensive, there are large areas of fallow land not used for food production, and there is sufficient rainfall to meet crop water demands.
The expansive production of ligno-cellulosic biofuels will require large amounts of land with potentially extensive effects on biogeochemical processes. How will carbon and nitrogen cycling be impacted? Will these plantations become a source or sink for greenhouse gases? To address these questions we employed the DayCENT biogeochemical model to predict changes in greenhouse gas emissions and element cycling changes resulting from conversion of degraded pasture in central Florida to energy cane.
Results/Conclusions
We parameterized the DayCENT model using soil data from a pasture site in Highlands County, Florida, that is currently undergoing conversion to a ~8,000 ha energy cane plantation. Our preliminary model simulations suggest that above ground carbon pool (per annum) in energy cane would be more than an order of magnitude larger than in existing pasture. Our model results also suggest a significant reduction in reactive N leaching under energy cane, and that converting pasture on these soils to energy cane could result in a 50% decline in N2O efflux.
These results suggest that tangible greenhouse gas benefits could be realized by changing marginal pasture to energy cane production. Furthermore, mandates are in place that ensure the growth of the ethanol industry, so it is requisite to promote feedstocks that do not interfere with food production and have positive or neutral climate impacts.
