Cattle manure, human excreta and agriculture residues are used in anaerobic bioreactors in many parts of the world to produce methane gas, which is used for the purpose of cooking and lighting. Since such waste materials are readily available in farms, rural people of many developing countries have been benefited from this technology. Besides, this technology is cheaper and simpler, thus gaining popularity throughout the world. Nepal is one of the least developed countries with the vast majority of people involved in subsistence agriculture. The use of biogas technology in Nepal has benefited the country in improving health, environment, economy and energy conservation. In this paper, we present the state of the biogas sector in Nepal.

Synthetic polymeric foams have pervaded every aspect of modern life. Although foams provide numerous benefits, they also cause a significant environmental litter problem because of their recalcitrant and xenobiotic nature. Biodegradation may provide solution to the problem, but not enough is known about the biodegradation process of synthetic plastic and plasticbased foams. This review has been written to provide an overview of the current state of plastic foam biodegradation. Several biodegradation pathways of a few select synthetic polymers are also presented along with a discussion on some of the physico-chemical factors that can influence the biodegradation of plastic foams.

Candida rugosa lipase (EC 3.1.1.3) was used to degrade commercially-available solid poly(ester)urethane (Impranil) in an aqueous medium under different temperature, pH, enzyme and substrate concentrations. A mathematical model was developed and applied to represent the degradation kinetics of the solid polyurethane. Reaction optima were found to be pH 7 and 35 degrees C. Diethylene glycol, a degradation byproduct, generation rate was measured to be 0.12 mg/l min and the activation energy was calculated as 9.121 kcal/gmol K. This information will be useful in developing bioreactors for practical applications to manage polyurethane wastes using lipase.

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