The continual generation and discharge of waste are currently considered two of the main environmental problems worldwide. There are several waste management options that can be applied, though anaerobic digestion (AD) process technology seems to be one of the best, most reliable, and feasible technological options that have attracted remarkable attention due to its benefits, including the generation of renewable energy in the form of biogas and biomethane. There is a large amount of literature available on AD; however, with the continuous, progressive, and innovative technological development and implementation, as well as the inclusion of increasingly complex systems, it is necessary to update current knowledge on AD process technologies, process variables and their role on AD performance, and the kinetic models that are most commonly used to describe the process-reaction kinetics. This paper, therefore, reviewed the AD process technologies for treating or processing organic biomass waste with regard to its classification, the mechanisms involved in the process, process variables that affect the performance, and the process kinetics. Gazing into the future, research studies on reduced MS-AD operational cost, integrated or hybrid AD-biorefinery technology, integrated or hybrid AD-thermochemical process, novel thermochemical reactor development, nutrient recovery from integrated AD-thermochemical process, and solid and liquid residual disposal techniques are more likely to receive increased attention for AD process technology of biomass wastes.

Biodiesel from waste frying oil is an effective alternative fuel for conventional diesel and can be directly used as fuel in a diesel engine without any modifications to the engine. It has many positives like high biodegradability, reduction in greenhouse gas emissions, non-sulfur emissions, non-particulate matter pollutants, low toxicity, and excellent lubricity and is obtained from renewable source like vegetable oils, animal fat, etc. The major objectives of this work were to produce and compare the biodiesel yield from Waste Frying Vegetable Oil (WFVO) and Waste Frying Palm Oil (WFPO) using transesterification process. The physicochemical characterization of the biodiesel, as well as the effects of process variables on biodiesel yield, were evaluated. Also, optimum levels of process conditions for optimum production of biodiesel were determined. The WFVO and WFPO with methanol and catalyst were heated in a hot plate-magnetic stirrer at a temperature of 60°C and operated at 300 rpm. Potassium hydroxide (KOH) was used as catalyst. The one-factor-at-a-time method was used to select the optimum levels of process variable that gives high biodiesel yield. The results showed that the physicochemical characteristics (acid value, free fatty acid, density, kinematic viscosity, pour point and flash point) of the biodiesel obtained from WFVO and WFPO were within the standard value of EN14214 and ASTMD-6751.From the results, the possible optimum conditions of the process variables for transesterification process using KOH catalyst were found to be as follows: reaction time of 90 min, methanol to oil molar ratio of 12:1 and the catalyst loading of 1.5 wt%. At these optimum conditions, the optimum yield of biodiesel obtained from transesterification of WFVO and WFPO were found to be 97% and 90%, respectively. Thus, in comparison, the transesterification of WFVO resulted in higher biodiesel yield than WFPO. Conclusively, both WFVO and WFPO has good potential to be used for bio-diesel production.

Under batch experiment conditions, this work seeks to successfully remove Diclofenac-Na (DCF-Na) from an aqueous solution utilizing a composite sorbent made of Bentonite, Kaolinite clay, and Worm casting (BKW). This study investigated the structural modification of the H₃PO₄ Modified Clay by X-ray fluorescence and the effect of selected adsorption factors – DCF-Na concentration and modified BKW composite dosage. The concentration equilibrium data was used to study six isotherm models. Freundlich isotherm model better explained the adsorption of DCF-Na onto modified BKW composite with a correlation coefficient close to 1. Kinetics models were examined, and the Elovich model gave a better fit than other kinetic models studied. Mass diffusion mechanisms and thermodynamics studies were successfully carried out. The enthalpy change values evaluated were negative, which revealed the spontaneity of DCF-Na remediation onto modified BKW, and that DCF-Na adsorption is exothermic and occurred through a physisorption process.