PROCESS TECHNOLOGIES FOR PRODUCING BIOFUELS AND COPRODUCTS FROM LIGNOCELLULOSIC FEEDSTOCKS
Location: Bioenergy Research Unit
Title: Biomass to Butanol Conversion: Recent Technologies and Process Economics
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 6, 2010
Publication Date: October 6, 2010
Citation: Qureshi, N., Saha, B.C., Cotta, M.A., Singh, V. 2010. Biomass to butanol conversion: Recent technologies and process economics [abstract]. In: Proceedings of Clostridium 11 Workshop, October 3-6, 2010, San Diego, California. p. 10.
To gain independence from foreign oil, we focused our research program on biological conversion of biomass to butanol. The biomass feedstocks that we have investigated include wheat straw, barley straw, corn stover, and switchgrass with a significant degree of hydrolysis and fermentation variability. These feedstocks were pretreated with dilute sulfuric acid followed by enzymatic hydrolysis to release sugars (hexoses and pentoses); that were then fermented to acetone butanol ethanol (ABE) by Clostridium beijerinckii P260. Barley straw, corn stover, and switchgrass hydrolyzates were toxic to the culture and required removal of toxic chemicals prior to fermentation, while wheat straw hydrolyzate contained fermentation stimulators that enhanced productivity or rate of fermentation by a factor of 2.14. Improvement in productivity results in reduction in process volumes such as reactor sizes and process streams. As a result of this productivity increase, process economics were improved. For wheat straw, the process economics of butanol production was assessed with a plant capacity of 150 x 10**6 kg butanol year**-1. For this plant, a capital cost of $162.06 x 10**6 was estimated. Using batch fermentation and distillative recovery, butanol production cost was estimated to be $1.44 kg**-1. Employing alternative product recovery technologies could reduce this price to $0.81 kg**-1. Cost of hydrolytic enzymes affects the process economics significantly. Additional factors that impact the price of butanol production from wheat straw hydrolyzate include sulfuric acid, cooling/chilling water, and steam/high pressure steam. It is suggested that the cost of enzymes be reduced, and recycle of cooling/chilling water and steam/high pressure steam be investigated. Additionally, focus should be placed on recovery of co-products that would make the process of butanol production economically attractive.