There are increasing demands for syngas production. Fossil‐based fuels are expensive and environmentally unfriendly. Affordable, sustainable, and environmentally healthy alternatives and sustainable fuel sources are needed. This study focused on producing tor‐chars from two different tropical biomasses (from Nigeria, West Africa), which were torrefied and characterized to improve their properties for potential use as sustainable feedstocks in an entrained flow gasifier for syngas production. Torrefaction temperatures of 230, 240, 250, and 270 °C and residence times of 30 and 60 min were used to torrefy sundried sorghum straw (SS) and millet straw (MS) at particle size ≤5 mm. The properties of torrefied MS and SS improved significantly due to torrefaction. The optimum conditions for pretreatment of sundried MS and SS were 240 °C and 60 min, at which increased energy density significantly compensated for the severe mass loss and significant degradation of hemicellulose and cellulose. Under these conditions, the respective mass and energy yields were 53 wt% and 75% for millet straw and 49 wt% and 75% for sorghum straw. The O:C atomic ratio decreased to 0.3 in MS tor‐chars and 0.2 in SS tor‐chars resulting in higher heating values of 25 MJ kg⁻¹ and 27 MJ kg⁻¹, respectively. Under optimum conditions, the ash content increased by 107% to be approximately 7 wt% in MS tor‐char, and by 118% to about 7 wt% in SS tor‐char. These properties are promising for potential feedstocks in co‐firing plants or gasification systems. © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

Corncob pyrochar activated with steam (CCA) and nonactivated corncob pyrochar (NCC) were produced and characterized. The performance of the best material was tested in a dual‐chambered microbial fuel cell (MFC) as an electrode for bioelectricity generation using wet torrefaction wastewater as substrate. Pyrolysis of 80.3 g of dried corncobs was carried out at 600°C under a constant N₂ flow of 3 L min⁻¹ for 30 min and the resulting pyrochar was activated using steam also at 600°C. Voltage and current outputs from the MFC were recorded daily for 18 days. The proximate and Brunauer–Emmett–Teller (BET) surface area analyses revealed that CCA had the highest fixed carbon content of 71.9 % and higher surface area of 104.0 m² g⁻¹ respectively. A larger pore diameter of 1.9 × 10⁻³ µm was also recorded with the CCA than 1.2 × 10⁻³ µm for NCC. The MFC produced a maximum power output of 21.5 mW. The physicochemical analyses of the wastewater effluent revealed an increased electrical conductivity from 1724 to 3460 µS cm⁻¹ with a significant decrease by 91.9% in the total organic carbon (TOC) from 3700 to 298 mg L⁻¹. Steam activation increases the surface area, porosity, stability and redox reversibility of the corncob pyrochar. Therefore, steam‐activated corncob pyrochar performed well in MFCs due to the high power output observed.

The increasing global demand for sustainable alternative sources of energy has driven the need for studies in renewable energy. Biogas may serve to satisfy energy demands as a viable substitute to fossil fuel, thereby reducing indiscriminate deforestation. The large volume of waste generated in the form of food and other solids in urban areas could serve as suitable organic substrates in the production of biogas thus, providing a cheap and eco-friendly method of managing wastes. In this study, municipal solid waste was co-digested with Food Waste (FW) and Municipal Solid Waste (MSW) at different ratios to optimize the production of biogas. The anaerobic digestion process was conducted at ambient (room) temperature for three weeks for a hydraulic retention time. The performances of the wastes were assessed based on the volume and quality of the biogas produced. The highest amount of biogas produced (765 cm3) was from the co-digestion of food waste and MSW in the ratio of 1.5:1.5. Methanogenic archaea isolated from the biogas digestate belonged to the following genera: Methanobacterium, Methanococcus, Methanosarcina, and Methanoplanus. In this study, the biogas produced from the co-digestion of food waste and municipal solid waste was better in terms of quality and quantity compared to that produced from the co-digestion of MSW with sludge. Thus, the findings of this study suggest that food waste has great potential as a substrate during the anaerobic digestion of municipal solid waste. Keywords: sludge, food waste, municipal solid waste, methanogens, biogas

Many different biomass of agricultural origin holds remarkable potential for conversion into valuable products thereby presenting a double sharp edge importance of sustainable resource supply and environmental protection. Glutamic acid was produced from rice husk using a novel strain of Corynebacterium glutamicum and effects of parameters optimization such as substrate concentration, temperature, pH and inoculum size were determined during the fermentation process. The wild-type (Novel) strain was inoculated into 13 g/L of the pre-treated rice husk previously added to basal medium (pH 7.2), after which fermentation began. Fermentation broth from each flask was taken aseptically after 96 h and was assayed qualitatively and quantitatively. The acid-treated and alkali-treated rice husk gave the best glutamic acid yield of 10.40g/L and 9.08g/L respectively with the wild-type strain under predetermined optimum fermentation conditions. Out of the four parameters optimized, only substrate concentration was not found to be significant on the performance of the wild-type strain in glutamate production (p > 0.05). Acid-treated rice husk hydrolysate was found to be a better substrate for L-glutamate production by the wild-type strain of C. glutamicum under the optimum fermentation conditions determined.

Microbial fuel cell (MFC) is an evolving technology for anaerobic bioenergy generation using electrodes and organic wastewater as a feedstock for catabolic activities of electrogenic bacteria and subsequent electricity generation. The search for suitable inexpensive electrode materials remains the leading interest of researchers in this field. The work here focused on comparative bioelectricity generation from HTC process water (pH = 5.99) and treated–biogas digestate (pH = 7.97) using locally developed corncob pyrochar electrodes and graphite in dual-chambered microbial fuel cells (MFC). The electrodes used in this study were graphite rod (non-porous and very low surface area), KOH–activated corncob pyrochar (KAC) of BET surface area, 1626 m2 g-1 and steam activated corncob pyrochar (SAC) with 485.8 m2 g-1. The highest power outputs achieved were 323.8 µW and 316.8 µW from HTC process water with SAC and KAC electrodes respectively at an external load of 47 Ω. The initial COD (48780 mg L-1), DOC (4000 mg L-1), and TNb (5600 mg L-1) of the biogas digestate decreased significantly to 36405, 3610 and 4300 mg L-1 respectively in the MFC with KOH-activated corncob pyrochar electrodes. The MFC operated with KAC electrode and treated biogas digestate was the most efficient having Coulombic efficiency of 75 % in a comparatively shorter residence time of MFC operation than the MFC with SAC electrode which had a lower Coulombic efficiency of 64 %.