Potential Losses of Soil Nutrients and Energy Content on the Complete Removal of Sugarcane Leaf Material as a Biomass Feedstock

Abstract

Green cane (unburnt) harvesting of sugarcane (Saccharum sp.) deposits between 6 and 24 Mg/ha of extraneous leaf material (residue) on the surface of soil. The removed leafy material has value as biomass for use as a potential second generation biofuel or bioproduct feedstock. Negative aspects of crop residue removal, however, are well documented and include reduced subsequent crop ratoon yields, reduced soil quality, increased soil erosion, and loss of soil fertility. The objective of the study was to determine the yield and nutrient content of sugarcane leaf material harvested from three Louisiana, USA, commercial sugarcane varieties HoCP 96-540, L 99-233, and L 99-226. Leafy material was harvested five times across two growing seasons: 2009 and 2010. Data varied by year due to weather conditions, but overall HoCP 96-540, L 99-226, and L 99-233 leaf yields were 11.5, 12.4, and 8.36 Mg/ha, respectively. Energy yields for HoCP 96-540, L 99-233, and L 99-226 were 190, 134, and 205 GJ/ha, based on bomb calorimeter measurements of leaf material valued at 16.5 MJ/kg. Average nitrogen, phosphorus, and potassium leaf nutrient yields that would not be returned to the soil were 74.0, 8.6, and 83.0 kg/ha/yr, respectively. Replacing these nutrients with chemical fertilizers would increase yearly fertilizer costs significantly. Overall, yields, and nutrient and energy contents of the sugarcane leaf material were similar to other potential second generation cellulosic feedstocks for biofuels, and bioproducts. Since only the leaf material would be used as a biofeedstock, sugarcane harvest for sugar would not be affected. Thus, multiple land use criteria could be achieved.