Bioresources and Bioproducts

Methane is a potent greenhouse gas that requires its emissions to be mitigated. A significant source for methane emissions is in the form of the biogas that is produced from anaerobic digestion in wastewater reclamation and landfill facilities. Biogas has a high valorization potential in the form of its bioconversion into ectoines, an active ingredient in skin care products, by halotolerant alkaliphilic methanotrophs. Cultures of Methylotuvimicrobium alcaliphilum 20Z were grown in bench scale stirred-tank reactors to determine factors to improve methane uptake and removal. Tangential flow filtration was also implemented for a bio-milking method to recover ectoine from culture media. Methane uptake and reactor productivity increased, with a temperature of 28 °C compared with 21 °C. Decreasing the methane gas bubble diameter by decreasing the sparger pore size from 1 mm to 0.5 µm significantly improved methane removal and reactor productivity by increasing mass transfer. Premixing methane and air before sparging into the reactor saw a higher removal of methane, while sparging methane and air separately created an increase in reactor productivity. Maximum methane removal efficiency was observed to be 70.56% ± 0.54 which translated to a CH₄-EC of 93.82 ± 3.36 g CH₄ m⁻³ h⁻¹. Maximum ectoine yields was observed to be 0.579 mg ectoine L⁻¹ h⁻¹. Full article

Spontaneous combustion of charcoal is still not fully understood, generating uncertainties among producers, regulatory agencies, and the scientific community. This study evaluated the influence of final pyrolysis temperature (350, 450, 550, and 650 °C) on the properties of Eucalyptus spp. charcoal and its relation to ignition behavior. Gravimetric yield, proximate composition, calorific value, and ignition temperature were determined. Charcoal yield decreased by 31% between 350 °C and 650 °C. Fixed carbon content increased from ~65% to ~93%, accompanied by a reduction in volatile matter (~35% to ~6%) and a corresponding rise in calorific value. Step-heating experiments, conducted in a furnace with infrared camera monitoring, showed that ignition temperature increased from ~273 °C in charcoal produced at 350 °C to ~424 °C in charcoal produced at 650 °C. Strong correlations indicated that higher fixed carbon and lower volatile matter contents are directly associated with higher ignition temperatures. These results demonstrate that increasing the final pyrolysis temperature improves both the thermal stability and the energy quality of charcoal, although at the expense of gravimetric yield. Since the methodology was based on forced heating rather than spontaneous combustion under near-ambient conditions, complementary tests are required to evaluate spontaneous combustion propensity. Overall, the findings provide practical insights to balance yield, quality, and safety while reinforcing the importance of standardized assessment protocols to ensure safer storage and transport of charcoal. Full article

The growing challenge of managing end-of-life creosote-treated railroad ties, along with the increasing demand for effective water treatment solutions, has highlighted the potential of converting railroad tie biomass into functional biochar through pyrolysis. Pyrolysis temperatures ranging from 250 °C to 700 °C were evaluated to determine their influence on biochar yield, physicochemical properties, and adsorption performance for nitrate and phosphate. The findings revealed that increasing pyrolysis temperature enhanced biochar surface area and porosity, reaching 454.9 m²/g at 700 °C. Elemental analyses showed maximum carbonization at 550 °C, with carbon content peaking at 80%, reflecting the development of more stable aromatic structures. SEM and FTIR analyses confirmed these structural changes, including the emergence of extensive pore networks and aromatic frameworks. Biochar produced at 600 °C demonstrated high nitrate (80%) and phosphate (79%) removal efficiencies, following Freundlich isotherm models. Magnesium-modified biochar further improved nitrate adsorption, reaching 90% removal at 5 ppm. Importantly, polycyclic aromatic hydrocarbons in the biochar decreased significantly at higher temperatures, ensuring environmental safety. This work demonstrates the dual environmental benefits of converting hazardous railroad tie waste into value-added biochar for nutrient removal in water treatment applications, offering a sustainable and scalable solution for circular waste management. Full article

Filtrate from dewatering anaerobically digested biosolids is a side-stream of wastewater treatment that contains high concentrations of nitrogen and phosphorus compounds that can serve as nutrients for cultivating microalgae biomass as biofilms for bioproduct production at Water Resource Recovery Facilities (WRRFs). One system used to cultivate attached microalgae biofilms is the rotating algal biofilm reactor (RABR). A pilot RABR with 72 m² growth surface area, 11.5 m² footprint area, and a liquid volume of 11,500 L was operated in an outdoor environment at the largest WRRF in Utah, U.S.A, the Central Valley Water Reclamation Facility (CVWRF). The configuration of the RABR was altered from the previous configuration with regard to temperature and duty cycle with the goal to maximize biomass productivity. Results included an increase in dry biomass productivity on a footprint basis from 8.8 g/m²/day to 26.8 g/m²/day (205%) while power requirements changed from 28.3 W to 91 W. The increase in biomass productivity has direct benefits for bioproducts including bioplastic, biofertilizer, and the extraction of lipids for conversion to biofuels. Full article

Due to the ever-increasing energy demand, Algeria’s sustainable energy crisis is a significant problem. Plant and crop residues can be a solution to this problem if they are used for bioethanol production, a viable alternative to fossil fuels. This study explores the potential of existing agricultural crop residues to overcome the sustainable energy crisis in Algeria. Agricultural residues such as cereals, roots and tubers, pulses, oil crops, vegetables, and fruits have great potential to solve the problem. The agricultural residues that are normally wasted can be utilized to produce bioethanol, which provides sustainable energy and also help to obtain a clean environment. It has been found that 1.65 million tons of bioethanol can be produced from Algeria’s available residues, which is equivalent to 44.10 petajoule of energy. Cereal and fruit residues contribute to most bioethanol generation, about 47.22% and 23.38%, respectively. In addition, bioethanol generated from residue can be used in Algeria’s transportation sector. Considering Algeria’s current energy condition, gasoline blended with ethanol such as E10 and E5 can be used in Algerian vehicles since no modification of vehicles is needed for utilizing these fuels. Research indicates that lignocellulosic biomass sources in Algeria, such as Alfa, olive pomace, and cereal straw, could provide up to 0.67 million tons of oil equivalent (Mtoe), representing approximately 4.37% of the energy consumption of the transport sector in Algeria. Algeria has the potential to produce up to 73.5 Mtoe and 57.9 Mtoe of renewable energy utilizing the energy crops. This study will also encourage relevant policymakers to develop sustainable energy policies that will enhance the renewable energy share in Algerian energy dynamics. Full article

Heavy metals (HMs) including cadmium (Cd), lead (Pb), arsenic (As), zinc (Zn), copper (Cu), chromium (Cr), and nickel (Ni) pose significant challenges to bioenergy crop production due to their persistence, toxicity, and bioaccumulation in soils and plants. This study not only summarizes the mechanisms of HM absorption, translocation, and accumulation in bioenergy crops, but also critically assesses their impact on crop development, biomass quality, and biorefinery processes. Heavy metals disrupt key physiological processes and modify lignocellulosic composition, which is important for biofuel and biogas production. Global soil contamination from sources like industrial emissions, mining, and agricultural activities exacerbates these problems, posing a threat to both energy security and environmental sustainability. Sustainable management strategies, including phytoremediation, microbial bioremediation, soil amendments, and genetic engineering, are explored to mitigate HM effects while enhancing crop resilience. This review emphasizes the importance of integrating techniques to balance bioenergy production with environmental and human health and safety, including the use of HM-tolerant crop varieties, enhanced biorefinery processes, and robust policy frameworks. Future research should focus on developing scalable remediation technologies and interdisciplinary solutions that align with the United Nations’ Sustainable Development Goals and meet global bioenergy needs. Full article