Production of Biogas from Waste Tea Leaves: A Case of Integrated Waste Management at DL Koisagat Tea Factory, Nandi Hills

Abstract

Waste tea leaves from tea factories are used as manure and the rest discarded on the surface. Decomposition of these dumped wastes produce methane into the environment and affect the quality of ground water through coloration. Considering environmental degradation caused by tea factories, it prompted the need for waste management and alternative sources of energy other than wood in the tea factory. Waste tea leaves are anaerobically digested in a batch reactor to produce methane which is a clean source of energy and also reduce and reuse of waste from the factory. This study aimed at determining the quantity of waste tea produced daily in the factory. It also sought to determine the optimum conditions of retention time, pH, and temperature required in generation of methane gas. The factory waste tea quantity was determined by measuring the weight of daily sweepings using industrial crane scale (KERN HFB). Waste tea leaves from the factory was mixed homogeneously with cow dung (inoculum)in the ratio of 1:2 and fed into the digester. The digestion process took place under varying conditions of retention time, pH and temperature. The gas collected was pumped into gas samplers using vacuum pump for analyzing in the Gas chromatograph (FID) within 48 hours for methane quality determination. It was found that the optimum conditions for biogas production from waste tea were pH of 7, temperature of 37oC and retention time of 20 days. Though the highest yield of methane was obtained at pH of 5, temperature of 50oC and retention time of 20 days, these conditions also promote production of high quantities of carbon dioxide gas. This impurity limits the quality of methane by hindering its combustion. Based on the results of the study, it was concluded that waste tea leaves produced biogas with 19% methane. The optimum conditions of pH, temperature and retention time have the potential to generate biogas from waste tea. Methane produced contained impurities of carbon dioxide, ammonia and hydrogen sulphide gases. Purification process of methane increased the cost of production. It was recommended that tea factories should use waste tea leaves for production of energy to run the factory instead of wood and for further research to enable the factory generate clean energy at lower cost.