Next‐generation biofuels and platform biochemicals from lignocellulosic biomass

Abstract

Rapid industrialization, increasing fuel prices, exhausting fossil fuel resources and greenhouse gas emissions are some of the factors instilling the search for alternative sources of energy and chemicals. Lignocellulose biomass-derived biofuels and biochemicals have emerged as clean products to complement fossil-based resources and reduce environmental impacts. Lignocellulosic biomasses are renewable, inexpensive and abundantly available resources to produce a wide variety of liquid, gaseous and solid biofuels and industrially relevant biochemicals. Different biological (e.g., fermentation and anaerobic digestion), thermochemical (e.g., liquefaction, gasification and pyrolysis) and catalytic (e.g., transesterification) conversion technologies can be used to produce fuel and chemical products from lignocellulosic biomass. This article makes a comprehensive review of different biofuels (e.g., biodiesel, bio-oil, bioethanol, biobutanol, biogas, hydrogen, syngas and jetfuel) and value-added biochemicals (e.g., propylene, ethylene, benzene, 5-hydroxymethylfurfural, levulinic acid, succinic acid, maleic acid, fumaric acid, phenols and other aromatic compounds) from lignocellulosic biomass. Additionally, the current status, challenges and future perspectives for the production and utilization of biofuels and biochemicals are systematically discussed.

Anaerobic Digestion of Lignocellulosic Waste Materials

“…In parallel, biogas is also used for industrial and urban applications to produce in combination heat and power [13]. AD is a mature technology, which has high potential to offer new strength to the agricultural economy by generating employment opportunities for the rural population and income from waste management and valorization [9].…”

“…The efficiency of the anaerobic digestion process is dependent also on temperature, hydraulic retention time, blending, C/N ratio, surface area, feedstock loading rate, the content of total solids and volatile solids, theoretical methane yield, biochemical methane potential, organic loading rate, shear stress and inhibitors (NH 3 , furfural, etc.) [9,13]. Some of these parameters could be adjusted during the biomethanation to ensure a beneficial AD process and biogas yield [23].…”

“…The concentration of C and N provides an image of the nutrients level of the AD substrate. More specifically, very high or low C/N ratio could affect the total ammoniacal nitrogen (NH 3 -N) and fatty acid production that may also affect the biogas production yield and rate [9]. In general terms, a C/N ratio of 20-30 is considered as a friendly environmentally that could balance C and N nutrients necessary for microbial growth.…”

“…Minimum 3 weeks are required for the AD microorganisms to be familiar with the new feedstock/substrate and conditions (temperature, pH, etc.). As evidenced, the retention time should be between 10 and 15 days [9]. The operating temperature in the digester constitutes a crucial factor for the effectiveness of AD process and a tool for control of the whole process [13,23].…”

“…), thermochemical (pyrolysis, etc.) and catalytic (transesterification) conversion processes [9]. Anaerobic digestion (AD) constitutes an attractive and effective method of waste treatment and conversion into biogas, in which both pollution mitigation and energy recovery can be achieved.…”