Bioethanol Production from Lignocellulosic Biomass—Challenges and Solutions

Abstract

Regarding the limited resources for fossil fuels and increasing global energy demands, greenhouse gas emissions, and climate change, there is a need to find alternative energy sources that are sustainable, environmentally friendly, renewable, and economically viable. In the last several decades, interest in second-generation bioethanol production from non-food lignocellulosic biomass in the form of organic residues rapidly increased because of its abundance, renewability, and low cost. Bioethanol production fits into the strategy of a circular economy and zero waste plans, and using ethanol as an alternative fuel gives the world economy a chance to become independent of the petrochemical industry, providing energy security and environmental safety. However, the conversion of biomass into ethanol is a challenging and multi-stage process because of the variation in the biochemical composition of biomass and the recalcitrance of lignin, the aromatic component of lignocellulose. Therefore, the commercial production of cellulosic ethanol has not yet become well-received commercially, being hampered by high research and production costs, and substantial effort is needed to make it more widespread and profitable. This review summarises the state of the art in bioethanol production from lignocellulosic biomass, highlights the most challenging steps of the process, including pretreatment stages required to fragment biomass components and further enzymatic hydrolysis and fermentation, presents the most recent technological advances to overcome the challenges and high costs, and discusses future perspectives of second-generation biorefineries.

Lignocellulosic residues from bioethanol production: a novel source of biopolymers for laccase immobilization

“…To address this challenge, signicant efforts have been made to develop processes and products that utilize all or most of the components of lignocellulosic biomass in an efficient manner. 3,4 Pretreatment of the lignocellulosic biomass deconstructs the lignocellulosic matrix, with the aim of making the cellulose available for the next step in the production of bioethanol. Steam explosion pretreatment is one of the options to achieve this objective.…”

“…4 factorial design with four central points matrix and their observed responses for laccase activity…”

Thermoanaerobacter Species: The Promising Candidates for Lig-nocellulosic Biofuel Production

“…The usage of biofuels such as bioethanol can reduce fossil fuel consumption, cut down the emission of SO2 and NOX, and consequently do good to the environment [3]. Lignocellulose is seen as an abundant, sustainable and low-cost resource on the earth for biofuels production, which can not only avoid the conflict between food and fuels, but also help to deal with the globally abundant agricultural residues to protect the local environment [4,5]. Lignocelluloses such as wheat straw, rice straw and sugarcane bagasse were adopted for biofuels production [6][7][8], suggesting bio-processing of biomass is widely accepted due to the good perspective [9].…”

Mitigating biomass recalcitrance for plant‐based bioenergy production

“…The lignocellulosic barrier is estimated to impede biomass conversion by 20% or more; therefore, the corresponding production cost increases by nearly 20%-30%. 12 To resolve this issue, pretreatment is a key step in the bioconversion process that provides access to lignocellulose walls for carbohydrate hydrolysis. 13,14 During pretreatment, the hard lignocellulose barrier of the cell wall is disrupted, followed by enzymatic saccharification.…”

“…Notwithstanding the availability and potential of lignocellulosic materials for bioenergy and other industrial applications, their composition and network structure in SCW impede digestibility through chemical or enzymatic methods. The lignocellulosic barrier is estimated to impede biomass conversion by 20% or more; therefore, the corresponding production cost increases by nearly 20%–30% 12 . To resolve this issue, pretreatment is a key step in the bio‐conversion process that provides access to lignocellulose walls for carbohydrate hydrolysis 13,14 .…”