Optimizing peracetic acid pretreatment conditions for improved simultaneous saccharification and co-fermentation (SSCF) of sugar cane bagasse to ethanol fuel

• Published in: Renewable energy 1999, Vol.16 (1), p.1070-1073
• Main Authors: Teixeira, Lincoln C., Linden, James C., Schroeder, Herbert A.
• Format: Article
• Language: English
• Subjects: Alcohols: methanol, ethanol, etc; Alternative fuels. Production and utilization; Applied sciences; Biomass; Energy; enzymatic hydrolysis; ethanol; Exact sciences and technology; fuel; Fuels; peracetic acid; pretreatment; SSCF; sugar cane bagasse
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/S0960-1481(98)00373-5

The use of several lignocellulosic materials for ethanol fuel production has been studied exhaustively in the U.S.A.. Strong environmental legislation has been driving efforts by enterprises, state agencies, and universities to make ethanol from biomass economically viable. Production costs for ethanol from biomass have been decreasing year by year as a consequence of this massive effort. Pretreatment, enzyme recovery, and development of efficient microorganisms are some promising areas of study for reducing process costs. Sugar cane bagasse constitutes the most important lignocellulosic material to be considered in Brazil as new technology such as the production of ethanol fuel. At present, most bagasse is burned, and because of its moisture content, has a low value fuel. Ethanol production would result in a value-added product. The bagasse is available at the sugar mill site at no additional cost because harvesting, transportation and storage costs are borne by the sugar production. The present paper presents an alternative pretreatment with low energy input where biomass is treated in a silo type system without need for expensive capitalization. Experimentally, ground sugar cane bagasse is placed in plastic bags and a peracetic acid solution is added to the biomass at concentrations of 0, 6, 9, 15, 21, 30, and 60% w/w of peracetic acid based on oven dried biomass. The ratio of solution to wood is 6:1; a seven day storage period had been used. Tests using hydrolyzing enzymes as an indicator for SSCF have been performed to evaluate the pretreatment efficiency. As an auxiliary method, a series of pre-pretreatments using stoichiometric amounts of sodium hydroxide and ammonium hydroxide based on 4-methyl-glucuronic acid and acetate content in the sugar cane bagasse have been performed before addition of peracetic acid. The alkaline solutions are added to the raw bagasse in a ratio of 17:1 solution to biomass and mixed for 24 hours at room temperature. Biomass is filtered and washed to a neutral pH before the peracetic acid addition. According to enzymatic hydrolysis results, peracetic acid is a powerful chemical for improving enzymatic digestibility in sugar cane bagasse with no need for using high temperatures. Basic pre-pretreatments are helpful in reducing peracetic acid requirements in the pretreatment.