Lignocellulosic-based biomass
Unlike starch, lignocellulosic biomass is a plant-based material composed of lignin, cellulose, and hemicellulose. This class of biomass includes wood and fibrous materials from organic sources, agricultural wastes, organic municipal wastes, and organic industrial wastes [18]. Agricultural wastes contribute as the major lignocellulosic resources investigated for biofuel production. Among them are oil palm biomass [19,20], corn stalk [21], rice straw [22], wheat straw [23–25], and sugarcane baggase [26]. Other lignocellulosic biomass such as king grass [27], switch grass [28,29], and phragmites [29] known as dedicated energy crops have been also tested for butanol production. On average, this lignocellulosic biomass …show more content…
This process requires pretreatment process to remove the lignin and/or alter the compositional structure and/or reduce the particle size for efficient enzymatic degradation. The pretreatment process could be performed in a single step or multiple steps such as physical, biological, and chemical processes. The pretreatment has been considered as the most expensive process to utilize lignocellulosic biomass as the substrate. The pretreatment process accounts for >50% of the total operating cost for converting lignocellulosic biomass into sugar, not yet accounting for the fermentation process into biofuel [35]. Besides, the hydrolysis of lignocellulosic biomass by cellulase is usually complex, requiring a complete cellulase mixture of endo- and exo-glucanase as well as β-glucosidase in a suitable ratio [36]. These cellulase components act synergistically to hydrolyse cellulose and hemicellulose into a mixture of pentose and hexose sugars and could afford ∼90% of sugar recovery yield depending on the type of substrate and pretreatment process [37]. The enzyme has limitation too, as it being inhibited by glucose produced from the hydrolysis, reducing its efficiency on degrading lignocellulosic biomass. The saccharification process of lignocellulosic biomass usually takes >72 h [36,38–40], producing some amount of phenolic compounds, acids, and furfural that inhibit the cells …show more content…
The remaining biomass (algal residues) primarily made of protein and carbohydrate was subjected to anaerobic digestion, producing biogas for power generation. However, recent conceptual approach is considering the energetic yield form algal biomass for the co-production of other fermented products (e.g., sugar to ethanol, butanol or other biofuels), as it could improve the economics and sustainability of the whole utilization of algae as a feedstock [45]. Economic considerations and principles of green design recommended that biofuels must be produced simultaneously with value-added co-products for algae-to-fuel technology to be successful [46]. In comparison to other types of biomass, microalgae has superfluous benefits as it is a fast growing microorganism with simple requirement for growth, efficient carbon dioxide fixation, not competing for arable lands and potable water, and hoarding high amounts of lipids and carbohydrates
Unlike starch, lignocellulosic biomass is a plant-based material composed of lignin, cellulose, and hemicellulose. This class of biomass includes wood and fibrous materials from organic sources, agricultural wastes, organic municipal wastes, and organic industrial wastes [18]. Agricultural wastes contribute as the major lignocellulosic resources investigated for biofuel production. Among them are oil palm biomass [19,20], corn stalk [21], rice straw [22], wheat straw [23–25], and sugarcane baggase [26]. Other lignocellulosic biomass such as king grass [27], switch grass [28,29], and phragmites [29] known as dedicated energy crops have been also tested for butanol production. On average, this lignocellulosic biomass …show more content…
This process requires pretreatment process to remove the lignin and/or alter the compositional structure and/or reduce the particle size for efficient enzymatic degradation. The pretreatment process could be performed in a single step or multiple steps such as physical, biological, and chemical processes. The pretreatment has been considered as the most expensive process to utilize lignocellulosic biomass as the substrate. The pretreatment process accounts for >50% of the total operating cost for converting lignocellulosic biomass into sugar, not yet accounting for the fermentation process into biofuel [35]. Besides, the hydrolysis of lignocellulosic biomass by cellulase is usually complex, requiring a complete cellulase mixture of endo- and exo-glucanase as well as β-glucosidase in a suitable ratio [36]. These cellulase components act synergistically to hydrolyse cellulose and hemicellulose into a mixture of pentose and hexose sugars and could afford ∼90% of sugar recovery yield depending on the type of substrate and pretreatment process [37]. The enzyme has limitation too, as it being inhibited by glucose produced from the hydrolysis, reducing its efficiency on degrading lignocellulosic biomass. The saccharification process of lignocellulosic biomass usually takes >72 h [36,38–40], producing some amount of phenolic compounds, acids, and furfural that inhibit the cells …show more content…
The remaining biomass (algal residues) primarily made of protein and carbohydrate was subjected to anaerobic digestion, producing biogas for power generation. However, recent conceptual approach is considering the energetic yield form algal biomass for the co-production of other fermented products (e.g., sugar to ethanol, butanol or other biofuels), as it could improve the economics and sustainability of the whole utilization of algae as a feedstock [45]. Economic considerations and principles of green design recommended that biofuels must be produced simultaneously with value-added co-products for algae-to-fuel technology to be successful [46]. In comparison to other types of biomass, microalgae has superfluous benefits as it is a fast growing microorganism with simple requirement for growth, efficient carbon dioxide fixation, not competing for arable lands and potable water, and hoarding high amounts of lipids and carbohydrates