Bioethanol from corn stover – a review and technical assessment of alternative biotechnologies

Abstract

Reviewing the literature from the last decade regarding the bioconversion of corn stover into ethanol, 474 references were identified containing 561 datasets. We found 144 datasets which were sufficiently consistent and detailed to address the current state of the art of corn stover conversion to bioethanol, and we were able to categorise 93% of these datasets into eight different technological configurations for the production of bioethanol, based on the pretreatment approaches used. After pretreating, the corn stover is subject to hydrolysis and fermentation, but these two process steps were largely identical in all datasets, albeit a range of operating conditions was reported. The final distillation of the ethanol was very rarely included in the datasets. By parameterising the bioethanol production by 26 parameters, including corn stover compositions, solid loadings, operational conditions, conversion efficiencies and material consumption, we were able to quantify the material flows for each technological configuration and estimate the uncertainty of the flows. The eight technological configurations produced 11-22% ethanol from the dry solid content of the corn stover. Technologies using alkaline-, solvent or ammonia-based pretreatments produced the largest amount of ethanol (19-22%), while fungi-based pretreatment produced much less (11%). All technological configurations resulted in large flows of solid as well as liquid residues, typically containing 60 to 70% of the dry solid corn stover content. Based on the selected datasets, statistical description is provided for all parameters, including mode, median, average and deviation, within each technological configuration. Bivariate correlation analysis across and within all technological configurations indicates that some operational parameters usually considered crucial in laboratory studies, e.g. pretreatment severity, show from a statistical perspective very little correlation with the yields. The review reveals that a great deal of research has addressed the challenge of converting corn stover into bioethanol, but a significant part of these studies is of limited value in terms of scope and documentation when addressing overall material flows and key parameters in a technological context.

Consolidated Bioprocess for Bioethanol Production from Raw Flour of Brosimum alicastrum Seeds Using the Native Strain of Trametes hirsuta Bm-2

“…Unfortunately, with the current rate of fossil fuel consumption, it is expected that reserves will be exhausted within the next 40 to 50 years. More importantly, the burning of fossil fuels contributes to global warming due to greenhouse gas emissions, causing climate change, a rise in sea levels, loss of biodiversity, and urban pollution [1][2][3]. Among the alternative fuels options, bioethanol offers an immediate solution because it does not require to modify the current transport infrastructure.…”

Utilization of a Hydrogen Source from Renewable Lignocellulosic Biomass for Hydrogenation of Nitroarenes

“…In the case of bioethanol, most of it is produced from edible biomass by fermentation, which causes a competition with food naturally. Although bioethanol was generated from non‐edible biomass, its production is still in its infancy . Glycerol is generated as a by‐product during the manufacture of biodiesel from renewable sources .…”

“…Although bioethanol was generated from non-edible biomass, its production is still in its infancy. [12] Glycerol is generated as a by-product during the manufacture of biodiesel from renewable sources. [13] In most cases, more than stoichiometric base were required during the hydrogenation.…”

Potential Reductions in Greenhouse Gas and Fine Particulate Matter Emissions Using Corn Stover for Ethanol Production in China

“…Corn stover is a desirable raw material for producing cellulosic ethanol [5][6][7]. Corn stover for ethanol production can provide co-benefits because it can improve energy security and reduce air pollution [8][9][10][11][12][13]. Corn stover for fuel production has a great potential in China because corn made up 39.2% of all cereals in 2017 [14].…”

“…Because of different system boundaries and functional unit (FU), the results related to life-cycle GHG emission reductions, at least in their numerical forms, cannot always be compared directly with most of the reported cases. Based on some literature reviews [8][9][10]13,[26][27][28], using corn stover for ethanol production is urgent and necessary considering energy and environment profits. However, there are no studies found in the available literature to assess the potential reductions in GHG and PM 2.5 emissions from corn stover based ethanol while considering corn stover geographical distributions.In this study, the available corn stover for ethanol production and its emission reduction factors per unit corn stover were combined to assess the environmental impacts.…”