Novel ethanol production using biomass preprocessing to increase ethanol yield and reduce overall costs

Abstract

Background Ethanol biorefineries need to lower their overall production costs to become economically feasible. Two strategies to achieve this are to reduce costs using cheaper feedstocks or to increase the ethanol production yield. Low-cost feedstocks usually have high non-structural components (NSC) content; therefore, a new process is necessary to accommodate these feedstocks and overcome the negative effects of NSC. This study developed a novel ethanol biorefinery process including a biomass preprocessing step that enabled the use of lower-cost feedstocks while improving ethanol production without detoxification (overliming). Two types of poplar feedstocks were used, low-quality whole-tree chips (WTC) and high-quality clean pulp chips (CPC), to determine if the proposed process is effective while using feedstocks with different NSC contents. Results Technical assessment showed that acidic preprocessing increased the monomeric sugar recovery of WTC from 73.2% (untreated) to 87.5% due to reduced buffering capacity of poplar, improved sugar solubilization during pretreatment, and better enzymatic hydrolysis conversion. Preprocessing alone significantly improved the fermentability of the liquid fraction from 1–2% to 49–56% for both feedstocks while overliming improved it to 45%. Consequently, it was proposed that preprocessing can substitute for the detoxification step. The economic assessment revealed that using poplar WTC via the new process increased annual ethanol production of 10.5 million liters when compared to using CPC via overliming (base case scenario). Also, savings in total operating costs were about $10 million per year when using cheaper poplar WTC instead of CPC, and using recycled water for preprocessing lowered its total operating costs by 45-fold. Conclusions The novel process developed in this study was successful in increasing ethanol production while decreasing overall costs, thus facilitating the feasibility of lignocellulosic ethanol biorefineries. Key factors to achieving this outcome included substituting overliming by preprocessing, enabling the use of lower-quality feedstock, increasing monomeric sugar recovery and ethanol fermentation yield, and using recycled water for preprocessing. In addition, preprocessing enabled the implementation of an evaporator-combustor downstream design, resulting in a low-loading waste stream that can be treated in a wastewater treatment plant with a simple configuration.

Recent advances in the routes and catalysts for ethanol synthesis from syngas

“…These processes can be divided into three categories: lignocellulose hydrolysis fermentation, syngas-fermentation, and syngassynthesis. 15 The lignocellulose fermentation route, as a biochemical conversion option, faces several challenges, such as a complex pre-treatment process, high enzyme costs and low fermentability of the mixed sugar stream, and presents a lower efficiency than sugar fermentation. 15 Syngas (H 2 /CO), an important platform for carbon-containing resource transformation, can be obtained from non-petroleum carbon resources, such as coal, biomass, organic waste, carbon dioxide, etc.…”

“…15 The lignocellulose fermentation route, as a biochemical conversion option, faces several challenges, such as a complex pre-treatment process, high enzyme costs and low fermentability of the mixed sugar stream, and presents a lower efficiency than sugar fermentation. 15 Syngas (H 2 /CO), an important platform for carbon-containing resource transformation, can be obtained from non-petroleum carbon resources, such as coal, biomass, organic waste, carbon dioxide, etc. [24][25][26] Compared to fermentation of biomass and petroleum refining, conversion of syngas to ethanol (STE) provides a more environmentally friendly and economical approach.…”

“…These processes can be divided into three categories: lignocellulose hydrolysis fermentation, syngas-fermentation, and syngas-synthesis. 15 The lignocellulose fermentation route, as a biochemical conversion option, faces several challenges, such as a complex pre-treatment process, high enzyme costs and low fermentability of the mixed sugar stream, and presents a lower efficiency than sugar fermentation. 15…”

“…15 The lignocellulose fermentation route, as a biochemical conversion option, faces several challenges, such as a complex pre-treatment process, high enzyme costs and low fermentability of the mixed sugar stream, and presents a lower efficiency than sugar fermentation. 15…”

Toward Renewable Amines: Recent Advances in the Catalytic Amination of Biomass-Derived Oxygenates

“…On the contrary, the synthesis of oxygen functionalized molecules from biomass is relatively facile due to the inherent presence of oxygen-containing groups. For example, biomass conversion to ethanol by fermentation is one of the oldest and best-established methods . However, in recent years various chemocatalytic processes have been developed for the large-scale production of biomass-derived oxygenates including alcohols and aldehydes .…”