Bioconversion of switchgrass: Identification of a leading pretreatment option based on yield, cost and environmental impact. (October 2017)

• Record Type: Journal Article
• Authors: Smullen, Emma; Finnan, John; Dowling, David; Mulcahy, Patricia
• Is Part Of: Renewable energy. Volume 111(2017)
• Page Start: 638
• Page End: 645
• Publication Date: 2017-10
• Subjects: Switchgrass -- Chemical pretreatment -- Simultaneous saccharification and fermentation (SSF) -- Environmental impact -- Economic value; Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.renene.2017.04.059
• Languages: English
• ISSNs: 0960-1481

Abstract

Abstract: Switchgrass (Panicum virgatum L) is considered to be one of the best feedstocks for second generation ethanol production. However, its use as a biofuel resource for the ethanol market is challenged by high investment costs and inconsistent production methodologies. This study explores the use of switchgrass as a potential feedstock for ethanol production, investigating the effects of different pretreatment chemicals – sodium hydroxide, methanol, sulphuric acid and ammonia – employed at various concentrations of 0.5, 1 and 2 mol L −1 on conversion yields, while also minimising cost and assessing potential environmental impacts. Glucose and ethanol yields showed that methanol was the most effective pretreatment chemical at 1 mol L −1, producing 230 g of glucose and 340 cm 3 of ethanol kg −1 of feedstock with a 97% conversion rate. Pretreatment employing sodium hydroxide was found to be the least effective, with cellulose to glucose conversion rates of 38% and 62% following simultaneous saccharification and fermentation (SSF). In general, SSF significantly increased cellulose conversion rates, up to 32% for some samples. At 0.55 € kg −1 glucose and 0.50 € L −1 ethanol methanol was also found to be the most cost effective pretreatment technique compared to sodium hydroxide at 1.96 € kg −1 glucose and 7.94 € L −1 ethanol. Highlights: Switchgrass ( Panicum virgatum L) is a native North American perennial grass which is considered to be one of the best feedstocks for ethanol production due to its high annual biomass yield and high carbohydrate content. Methanol was determined to be the most effective pretreatment chemical, compared to sodium hydroxide which was the least effective. Optimal pretreatment concentration was found to be 1 mol L −1, which produced higher conversion yields than those pretreated at 0.5 mol L −1 and 2 mol L −1 . Simultaneous, saccharification and fermentation (SSF) significantly increased conversion yields. Methanol pretreated switchgrass achieved conversion yields of 69% (glucose) and 97% (ethanol). Methanol was identified as the most environmentally friendly pretreatment chemical and the least costly (0.50 € L −1 ) when evaluated at the optimum concentration of 1 mol L −1 .