A hydrothermal co-liquefaction of spirulina platensis with rice husk, coconut shell and HDPE for biocrude production

A comprehensive review of sustainable valorisation of lignocellulosic biomass and plastic waste into biofuels and chemicals via co-liquefaction

Liquefaction stands out as a promising strategy within the bioeconomy, offering a pathway to convert waste into valuable fuels and products. However, bio-oil from biomass liquefaction has high oxygen content and poor calorific value, limiting its practical applications. To overcome these challenges, one promising approach is the co-liquefaction of oxygen-rich biomass with hydrogen-rich plastic, offering a sustainable means of producing high-quality oil. This review explores lignocellulosic biomass and plastic co-liquefaction, highlighting its behaviours, reaction pathways, and process parameters' effects. The co-liquefaction process offers significant advantages over lignocellulosic biomass or plastic liquefaction in improving oil quality and yield. Comprehensive studies on the effect of process parameters and reaction pathways are much needed to optimise the conditions and design an efficient and effective co-liquefaction process for lignocellulosic biomass and plastics. Life cycle assessment (LCA) and techno-economic assessment (TEA) are two viable approaches to evaluating the potential environmental impacts and economic performance, respectively. Finally, lignocellulosic biomass and plastic waste co-liquefaction is a viable approach to managing waste and producing valuable materials, which promotes significant values, including resource efficiency, waste reduction, environmental sustainability, and economic opportunities.

Use of Residual Lignocellulosic Biomass and Algal Biomass to Produce Biofuels

Efforts are intensifying to identify new biofuel sources in response to the pressing need to mitigate environmental pollutants, such as greenhouse gases, which are key contributors to global warming and various worldwide calamities. Algae and microalgae present themselves as excellent alternatives for solid-gaseous fuel production, given their renewable nature and non-polluting characteristics. However, making biomass production from these organisms economically feasible remains a challenge. This article collates various studies on the use of lignocellulosic waste, transforming it from environmental waste to valuable organic supplements for algae and microalgae cultivation. The focus is on enhancing biomass production and the metabolites derived from these biomasses.

Hydrothermal Processing of Agar Waste to Levulinic acid and Fermentation of Hydrolysate to Bioethanol

Increasing global energy consumption and depleting fossil-fuel supplies prompted the search for green-alternatives. This study focuses on conversion of waste agar using different acids/alkalis (0.5% and 1%) as catalysts under varied temperature and time towards galactose (Gal), 5-hydroxymethylfurfural (HMF) and levulinic acid (LA) production in a sequential reaction. The optimized process for agar depolymerisation was achieved using 1 % acid (H₂SO₄/HCl) catalysed conditions with a maximum of 11 g/L Gal yield (121 °C; 15 min). Increase in temperature (150 °C) and time (180 min) with 1% HCl/H₂SO₄ catalyst resulted in improved LA production along with Gal and HMF. The hydrolysis process was optimised for the selective production of LA (10 g/L) at 175 °C; 180 min. Further, galactose-rich hydrolysates were assessed for bioethanol fermentation using Saccharomyces cerevisiae and resulted 3 g/L ethanol. Thus, the study comprehensively demonstrates waste agar utilization to yield biochemicals/fuels in a circular bio-based economy approach.