Pilot-Scale On-Farm Pretreatment of Perennial Grasses with Dilute Acid and Alkali for Fuel Ethanol Production

Abstract

Switchgrass (Panicum virgatum L.) and reed canarygrass (Phalaris arundinacea L.) were pretreated during anaerobic wet storage by adding sulfuric acid or calcium hydroxide (50 g kg-1 DM). Experiments were conducted at both laboratory scale (250 g DM) and pilot scale (250 kg DM) for either 60 or 180 days. Pretreated and untreated samples were fermented to ethanol by Saccharomyces cerevisiae in the presence of a commercially available cellulase (Celluclast 1.5L) and -glucosidase (Novozyme 188). With acid pretreatment, conversion of cellulose to ethanol was 35 and 12 percentage units higher than for untreated controls for reed canarygrass and switchgrass, respectively. Similarly, lime-pretreated reed canarygrass and switchgrass out-yielded controls by 3 and 13 percentage units, respectively. Cellulose and lignin contents were largely unaffected by pretreatment and anaerobic storage, but hemicelluloses were lower for both pretreatments.