Diverse lignocellulosic feedstocks can achieve high field‐scale ethanol yields while providing flexibility for the biorefinery and landscape‐level environmental benefits

Abstract

Increasing the diversity of lignocellulosic feedstocks accepted by a regional biorefinery has the potential to improve the environmental footprint of the facility; harvest, storage, and transportation logistics; and biorefinery economics. However, feedstocks can vary widely in terms of their biomass yields and quality characteristics (chemical composition, moisture content, etc.). To investigate how the diversity of potential biofuel cropping systems and feedstock supply might affect process and field‐scale ethanol yields, we processed and experimentally quantified ethanol production from five different herbaceous feedstocks: two annuals (corn stover and energy sorghum) and three perennials (switchgrass, miscanthus, and mixed prairie). The feedstocks were pretreated using ammonia fiber expansion (AFEX), hydrolyzed at high solid loading (~17%–20% solids, depending on the feedstock), and fermented separately using microbes engineered to utilize xylose: yeast (Saccharomyces cerevisiaeY128) or bacteria (Zymomonas mobilis8b). The field‐scale ethanol yield from each feedstock was dependent on biomass quality and cropping system productivity; however, biomass yield had a greater influence on the ethanol yield for low‐productivity crops, while biomass quality was the main driver for ethanol yields from high‐yielding crops. The process ethanol yield showed similar variability across years and feedstocks. A low process yield for corn stover was determined to result from inhibition of xylose utilization by unusually elevated levels of hydroxycinnamates (p‐coumaric and ferulic acids) in the untreated biomass and their acid and amide derivatives in the resulting hydrolyzate. This finding highlights the need to better understand factors that influence process ethanol yield and biomass quality. Ultimately we provide evidence that most feedstocks fall within a similar range of process ethanol yield, particularly for the more resistant strain Z. mobilis8b. This supports the claim that the refinery can successfully diversify its feedstock supply, enabling many social and environmental benefits that can accrue due to landscape diversification.

Biorefinery of the Olive Tree—Production of Sugars from Enzymatic Hydrolysis of Olive Stone Pretreated by Alkaline Extrusion

“…Furthermore, EOP and OL have also been evaluated as valuable sources of antioxidants, biofuels and bioenergy in a process strategy that would be applied as a multi-feedstock biorefinery built around the olive oil sector [8,9]. One of the main advantages of using these materials within this concept of advanced biorefinery is that they are all generated in a very specific area, which may facilitate the transport and logistic operations by providing a constant and sufficient feedstock supply according to its availability in a given moment [10].…”

Multiomic Fermentation Using Chemically Defined Synthetic Hydrolyzates Revealed Multiple Effects of Lignocellulose-Derived Inhibitors on Cell Physiology and Xylose Utilization in Zymomonas mobilis

“…Two xylose-utilizing strains of Z. mobilis , named Z. mobilis 2032 and Z. mobilis 8b, have been engineered by integration of E. coli talB-tktA and xylA-xylB genes into the chromosome or plasmids of wild-type Z. mobilis ZM4 (Zhang et al, 1995, 2007; Yang et al, 2018). Although both Z. mobilis 2032 and 8b can readily ferment xylose in rich medium (Zhang et al, 1995, 2007; Franden et al, 2013), xylose utilization remains slow, inefficient, and often incomplete in lignocellulosic hydrolyzates (Serate et al, 2015; Yang et al, 2018; Zhang et al, 2018). Several studies demonstrate that the high osmolarity of hydrolyzates, presence of lignocellulose-derived inhibitors (LDIs), and end-product toxicity can negatively affect microbial conversion of sugars in lignocellulosic hydrolyzates, especially xylose (Schwalbach et al, 2012; Keating et al, 2014; Tang et al, 2015; Zhang et al, 2018).…”

“…Although both Z. mobilis 2032 and 8b can readily ferment xylose in rich medium (Zhang et al, 1995, 2007; Franden et al, 2013), xylose utilization remains slow, inefficient, and often incomplete in lignocellulosic hydrolyzates (Serate et al, 2015; Yang et al, 2018; Zhang et al, 2018). Several studies demonstrate that the high osmolarity of hydrolyzates, presence of lignocellulose-derived inhibitors (LDIs), and end-product toxicity can negatively affect microbial conversion of sugars in lignocellulosic hydrolyzates, especially xylose (Schwalbach et al, 2012; Keating et al, 2014; Tang et al, 2015; Zhang et al, 2018). Recently, we investigated the impacts of biomass feedstock variability on microbial conversion using both S. cerevisiae and Z. mobilis as model ethanologens (Ong et al, 2016; Zhang et al, 2018).…”

Future prospects of delignification pretreatments for the lignocellulosic materials to produce second generation bioethanol

“…The design of biorefineries is considered to have three main objectives: (1) to ensure energy security where a large volume of biomass is produced, (2) to reduce environmental impacts associated with the production of chemical products, ie, less waste generation and less greenhouse gases emissions, and (3) to develop rural areas. To design a biorefinery, the most widely used approaches are superstructures, conceptual design, and optimization . The new trends are to install biorefineries for optimal biofuel and biomaterial production.…”

“…To design a biorefinery, the most widely used approaches are superstructures, conceptual design, and optimization. [152][153][154] The new trends are to install biorefineries for optimal biofuel and biomaterial production.…”