Impacts of pre-treatment technologies and co-products on greenhouse gas emissions and energy use of lignocellulosic ethanol production

Pourbafrani, Mohammad; McKechnie, Jon; Shen, Timothy; Saville, Bradley A.; MacLean, Heather L.

Abstract

Life cycle environmental performance of lignocellulosic ethanol produced through different production pathways and having different co-products has rarely been reported in the literature, with most studies focusing on a single pre-treatment and single co-product (electricity). The aim of this paper is to understand the life cycle energy use and greenhouse gas (GHG) emissions implications of alternative pre-treatment technologies (dilute acid hydrolysis, ammonia fiber expansion and autohydrolysis) and co-products (electricity, pellet, protein and xylitol) through developing a consistent life cycle framework for ethanol production from corn stover. Results show that the choices of pre-treatment technology and co-product(s) can impact ethanol yield, life cycle energy use and GHG emissions. Dilute acid pathways generally exhibit higher ethanol yields (20 to 25%) and lower net total energy use (15 to 25%) than the autohydrolysis and ammonia fiber expansion pathways. Similar GHG emissions are found for the pre-treatment technologies when producing the same co-product. Xylitol co-production diverts xylose from ethanol production and results in the lowest ethanol yield (200 litres per dry t of stover). Compared to producing only electricity as a co-product, the co-production of pellets and xylitol decreases life cycle GHG emissions associated with the ethanol, while protein production increases emissions. The life cycle GHG emissions of blended ethanol fuel (85% denatured ethanol by volume) range from -38.5 to 37.2 g CO2eq/MJ of fuel produced, reducing emissions by 61% to 141% relative to gasoline. All ethanol pathways result in major reductions of fossil and petroleum energy use relative to gasoline, at least 47% and 67%, respectively. Pathways with electricity as the sole co-product use the least fossil energy All ethanol pathways studied meet the USA Energy Information and Security Act requirement of a 60% reduction in GHG emissions compared to gasoline for classification as a cellulosic biofuel; however, greater reductions are achievable through strategic selection of co-products.

Citation

Pourbafrani, M., McKechnie, J., Shen, T., Saville, B. A., & MacLean, H. L. (2014). Impacts of pre-treatment technologies and co-products on greenhouse gas emissions and energy use of lignocellulosic ethanol production. Journal of Cleaner Production, 78, https://doi.org/10.1016/j.jclepro.2014.04.050

• Journal Article Type: Article
• Acceptance Date: Apr 20, 2014
• Online Publication Date: May 9, 2014
• Publication Date: Sep 1, 2014
• Deposit Date: May 27, 2016
• Publicly Available Date: May 27, 2016
• Journal: Journal of Cleaner Production
• Print ISSN: 0959-6526
• Electronic ISSN: 1879-1786
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 78
• DOI: https://doi.org/10.1016/j.jclepro.2014.04.050
• Keywords: Bioethanol; Corn stover; Life cycle assessment; Biorefinery; Co-products; Pre-treatment
• Public URL: https://nottingham-repository.worktribe.com/output/733385
• Publisher URL: http://dx.doi.org/10.1016/j.jclepro.2014.04.050