In the 2012-2013 harvesting season, Brazil produced nearly 164 million tons of sugarcane bagasse (wet basis). Although partially utilized for co-generation and bioelectricity, a great deal of this agro-industrial residue is still available for conversion to cellulosic ethanol. In this work, cane bagasse was subjected to steam explosion in the absence (autohydrolysis) and presence of acid catalysis such as dilute phosphoric and sulfuric acids. Phosphoric acid performed better than sulfuric acid but autohydrolysis seemed to be enough to improve the accessibility of steam-treated substrates at high yields. In addition, pretreatment of cane bagasse was carried out before and after extraction with ethanol to remove more than 80% of its solvent-extractable low molecular mass compounds and, by doing so, no effect was observed in the susceptibility of water-washed pretreated materials to simultaneous hydrolysis and fermentation. Additional experiments were also carried out using four commercial cellulase preparations, Celluclast 1.5L, Celluclast 1.5L plus Novozym 188, Cellic CTec2 and Cellic CTec 3 (Novozymes), with the last showing the best performance in substrate saccharification. However, Cellic CTec2 was already an efficient catalyst for hydrolysis of phosphoric acid-catalysed steam-exploded cane bagasse at high total solids and relatively low enzyme loadings, regardless of its high lignin content. The highest conversion of cellulose to glucose was obtained at the highest level of the factorial design, in which 77 g.L-1 were produced. The C6 fermentation of this hydrolysate produced nearly theoretical yields of ethanol (around 39 g.L-1), which corresponded to 248 L of ethanol per ton of bagasse dry matter. Considering that one autonomous distillery produces 80 L of ethanol and 125 kg of cane bagasse (dry basis) per ton of sugar cane, this value represents a net increase of 39% in the ethanol production from the same sugar cane tonnage without considering the C5 sugars arisen from pretreatment.

Technical assessment for the production of cellulosic ethanol from sugarcane bagasse at high total solids and low enzyme loadings

248th National Meeting (2014)

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