A Critical Review on Water Overconsumption in Lignocellulosic Biomass Pretreatment for Ethanol Production through Enzymic Hydrolysis and Fermentation

Zhao, Jikai; Wang, Donghai

doi:10.1021/acs.energyfuels.3c00015

Cited by 11 publications

(5 citation statements)

References 144 publications

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“…Yet another significant challenge arises from the substantial volume of water required for rinsing the residues after the pretreatment process. This water, which contains chemical residues, is frequently discarded [89]. In this regard, biological methods are more sustainable as they break down the complex polysaccharides into simple fermentable sugars without much environmental impact [86,[90][91][92].…”

Section: Pretreatment Methodsmentioning

confidence: 99%

Perspectives and Progress in Bioethanol Processing and Social Economic Impacts

Yaverino-Gutiérrez,

Wong,

Ibarra-Muñoz

et al. 2024

Sustainability

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The liquid biofuel bioethanol is widely produced worldwide via fermenting sugars extracted from a variety of raw materials, including lignocellulose biomass, one of the world’s most abundant renewable resources. Due to its recalcitrant character, lignocellulose is usually pretreated by mechanical, chemical, and biological methods to maximize sugar recovery. Pretreated lignocellulose biomass undergoes a fermentation process performed sequentially or simultaneously to saccharification. The different fermentation strategies (e.g., separate or simultaneous hydrolysis and fermentation or co-fermentation) and conditions (e.g., inoculum type load, agitation, temperature, and pH) affect ethanol yield. Genetic modification of the inoculum has been focused recently to improve ethanol tolerance and as well as to use different sugars to enhance the performance of the microorganisms involved in fermentation. Nonetheless, these improvements result in a substantial increase in costs and have certain environmental costs. This review offers an overview of advancements in bioethanol production, with a primary focus on lignocellulosic feedstock, while also considering other feedstocks. Furthermore, it provides insights into the economic, social, and environmental impacts associated with bioethanol production.

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Section: Pretreatment Methodsmentioning

confidence: 99%

Perspectives and Progress in Bioethanol Processing and Social Economic Impacts

Yaverino-Gutiérrez,

Wong,

Ibarra-Muñoz

et al. 2024

Sustainability

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show abstract

“…Combined with the challenges in commercial realization, such as the massive collection of raw biomass and high production costs, coupled with excessive wastewater generation from pretreatment. These factors raise concern about the economic viability and sustainability of bioethanol production from LCB, particularly in regions with limited water resources [140][141][142]. Therefore, minimizing water consumption of 2G ethanol production especially in the pretreatment stage is necessary to ensure sustainability.…”

Section: Water Consumption Of the Pretreatment Processmentioning

confidence: 99%

“…While increasing the solid loading in biomass pretreatment can reduce water usage, it has some drawbacks. These include less effective pretreatment, increased generation of byproducts, and higher viscosity, all of which can impact the overall efficiency of the biofuel conversion process [142]. It has been found that while increasing the volume of water for washing pretreated biomass raises production costs, an optimal balance was achieved using 5.5 g of water per g of ionic liquid.…”

Section: Water Consumption Of the Pretreatment Processmentioning

confidence: 99%

“…Besides increasing biomass loading to enhance water efficiency in LCB pretreatment, several strategies have been proposed. These include adopting alternative methods such as alkali pretreatment to reduce the formation of inhibitory compounds, recycling the liquid fraction post-pretreatment, employing physicochemical detoxification, omitting waterwashing post solid-liquid separation, and using calcium oxide (CaO) in pretreatment with subsequent acid neutralization [142,144]. Additionally, seawater has emerged as a viable solution for water conservation during pretreatment processes in lignocellulose biorefineries.…”

Section: Water Consumption Of the Pretreatment Processmentioning

confidence: 99%

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Comparative Analysis of Acidic and Alkaline Pretreatment Techniques for Bioethanol Production from Perennial Grasses

Johannes,

Xuan

2024

Energies

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This review paper examines acid and alkaline pretreatments on perennial grasses for second-generation (2G) bioethanol production, a relatively unexplored area in this field. It compares the efficiency of these pretreatments in producing fermentable sugar and bioethanol yield. This study finds that alkaline pretreatment is more effective than acidic pretreatment in removing lignin and increasing sugar yield, leading to higher ethanol yields. However, it is costlier and requires longer reaction times than acidic pretreatment, while acidic pretreatment often leads to the formation of inhibitory compounds at higher temperatures, which is undesirable. The economic and environmental impacts of lignocellulosic biomass (LCB) are also assessed. It is revealed that LCB has a lower carbon but higher water footprint and significant costs due to pretreatment compared to first-generation biofuels. This review further explores artificial intelligence (AI) and advanced technologies in optimizing bioethanol production and identified the gap in literature regarding their application to pretreatment of perennial grasses. This review concludes that although perennial grasses hold promise for 2G bioethanol, the high costs and environmental challenges associated with LCB necessitate further research. This research should focus on integrating AI to optimize the pretreatment of LCB, thereby improving efficiency and sustainability in 2G biofuel production.

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“…However, these methods require high energy consumption and can be expensive [6]. Chemical methods, such as acid and alkaline pretreatment, have also been used to reduce the concentration of inhibitors in the hydrolysate [7]. However, these methods have limitations in terms of cost, environmental impact, and efficiency [8].…”

Section: Introductionmentioning

confidence: 99%

Minimization of Inhibitor Generation in Rice Straw Hydrolysate Using RSM Optimization Technique

et al. 2023

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Ethanol production from lignocellulosic biomass comprises pretreatment, hydrolysis, and fermentation. However, several inhibitors are generated during rice straw chemical hydrolysis, including furfural, 5-hydroxymethylfurfural (HMF), and phenolics. These inhibitors, i.e., furfural and HMF, are toxic to yeast cells, can negatively impact yeast growth and metabolism, and reduce the process efficiency and production yield. Total phenolics are also reported to inhibit yeast growth and metabolism and act as a source of reactive oxygen species (ROS), which can damage yeast cells. Therefore, minimizing the generation of these inhibitors during rice straw hydrolysis is essential to improve the efficiency and yield of ethanol fermentation. Optimization of process variables can help reduce inhibitor generation and increase the efficiency of used detoxification methods such as adsorption, ion exchange, and biological methods. This study aimed to minimize inhibitor generation during the chemical hydrolysis of rice straw biomass. Minitab 17 software was employed and response surface curve regression analysis was used to develop a quadratic equation of an optimized process for minimized release of inhibitors molecules. The main inhibitors in pretreated rice straw hydrolysate identified were furfural (48.60%/100 g solid biomass), HMF (2.32%/100 g solid biomass), and total phenolics (1.65%/100 g solid biomass). The optimal pretreatment conditions were a biomass solid loading rate of 15% w/v, an H2SO4concentration of 12% v/v, a pretreatment reaction time of 30 min, and a temperature of 100 °C. Optimization of these process variables reduced the inhibitor generation by up to one and a half fold.

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A Critical Review on Water Overconsumption in Lignocellulosic Biomass Pretreatment for Ethanol Production through Enzymic Hydrolysis and Fermentation

Cited by 11 publications

References 144 publications

Perspectives and Progress in Bioethanol Processing and Social Economic Impacts

Perspectives and Progress in Bioethanol Processing and Social Economic Impacts

Comparative Analysis of Acidic and Alkaline Pretreatment Techniques for Bioethanol Production from Perennial Grasses

Minimization of Inhibitor Generation in Rice Straw Hydrolysate Using RSM Optimization Technique

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