Microalgae-mediated wastewater treatment for biofuels production: A comprehensive review.

The growing world population, rapid industrialization, and intensive agriculture have increased environmental impacts such as wastewater discharge and global warming. These threats coupled the deficiency of fossil fuel and the rise in crude oil prices globally cause serious social, environmental and economic problems. Microalgae strains can withstand the harsh environments of modern industrial and municipal wastes. The shift toward a circular bio-economy that relies on resource diversification has also prompted the reorganization of traditional wastewater treatment (WWT) processes into a low-carbon, integrated biorefinery model that can accommodate multiple waste streams. Therefore, microalgae-based WWT is now a serious competitor to conventional WWT since the major bottlenecks of nutrient assimilation and high microalgae population have been partially mitigated. This review paper aims to collate advances and new knowledge emerged in recent years for microalgae-based WWT and related biofuel technologies.

Enhanced anaerobic digestion performance by two artificially constructed microbial consortia capable of woody biomass degradation and chlorophenols detoxification.

Catalpa sawdust (CSW) is a promising biomass-based biofuel. However, the complex lignocellulosic structure limits its efficient utilization in biorefinery applications. It is even more so when chlorophenols (CPs), highly toxic organic substances widely used as wood preservatives, are present. Hence, it is crucial to develop effective and eco-friendly approaches to attain deconstruction of lignocellulose and chlorophenols simultaneously as well as to improve methane (CH4) production efficiently. This study might be the first to explore the performance of the novel constructed microbial consortia CS-5 and BC-4 on woody biomass degradation and CPs detoxification simultaneously with CH4 production. After the degradation of CSW and CPs for 15 days by C5-5 or BC-4, significant reduction in lignocellulosic components and CPs mixture was realized with a total weight loss of 69.2 and 56.3 % and CPs degradation of 89 and 95 %, respectively. The toxicity of individual or mixed CPs after 15 days of degradation was reduced by approximately 90 %. The synergistic action of CS-5 and BC-4 enhanced biogas and CH4 yields over 76 and 64 % respectively, higher than control. Furthermore, CH4 production increased by 113.7 % at the peak phase of AD process. Methanosataceae represented 45.1 % of the methanogenic Archaea in digester G-III.

Construction of novel microbial consortia CS-5 and BC-4 valued for the degradation of catalpa sawdust and chlorophenols simultaneously with enhancing methane production.

This study might be the first to explore the novel constructed microbial consortia CS-5 and BC-4 for enhancing methane (CH4) production during anaerobic digestion (AD) with simultaneous degradation of catalpa sawdust and chlorophenols (CPs). Significant reduction in cellulose, hemicellulose and lignin contents was achieved after the biodegradation of catalpa sawdust for 15 days by CS-5 and BC-4, with a total weight loss of 69.2 and 56.3%, respectively. The synergistic microbial consortia enhanced cumulative biogas and CH4 yields by 76.3 and 64.3%, respectively higher than the corresponding control at the end of AD. More than 90% of CH4 was produced within 18 days of AD as a result of microbial pretreatment of catalpa sawdust. These consortia resulted in remarkably higher energy conversion efficiency of 44.3% (218.1 LN CH4/kg TS) over the control. CS-5 and BC-4 removed more than 69 and 77% of the total amount of CPs tested after 15 days.

Spent coffee enhanced biomethane potential via an integrated hydrothermal carbonization-anaerobic digestion process.

This study reports the implications of using spent coffee hydrochar as substrate for anaerobic digestion (AD) processes. Three different spent coffee hydrochars produced at 180, 220 and 250 °C, 1 h residence time, were investigated for their biomethane potential in AD process inoculated with cow manure. Spent coffee hydrochars were characterized in terms of ultimate, proximate and higher heating value (HHV), and their theoretical bio-methane yield evaluated using Boyle-Buswell equation and compared to the experimental values. The results were then analyzed using the modified Gompertz equation to determine the main AD evolution parameters. Different hydrochar properties were related to AD process performances. AD of spent coffee hydrochars produced at 180 °C showed the highest biomethane production rate (46 mL CH4/gVS.d), a biomethane potential of 491 mL/gVS (AD lasting 25 days), and a biomethane gas daily composition of about 70%.