Biogas production from vegetable foliage as supplement to cattle dung
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Date
2013
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CCSHAU
Abstract
The basic problem we face today is that the earth's natural resources of energy are being depleted at a
most alarming rate but our conventional energy resources are limited and already have been over exploited.
Motivated by the need to meet the ever-increasing energy demand and sustainability consciousness, many
Governments have promoted renewable energy technologies such as biogas. Biogas (a mixture of approximately
60% methane and 40% carbon dioxide) is a well-established fuel that can supplement as an energy source for
cooking and lighting in developing countries. Most of the biogas plants in India are being operated with diluted
cattle dung slurry at 7-8% total solid concentration. Due to constraints in these conventional biogas systems, solid
state fermentation system operated at about 15% total solid concentration using cattle dung as substrate has come
into existence. Availability of animal waste is one of the major problem for successful operation of biogas
digesters. So researchers are looking towards other alternative substrates. Raw vegetables wastes are used to
produce biogas by anaerobic digestion process from a long time because in principle, it has high energy potential
and enormous quantity of vegetable wastes are dumped daily in municipal and urban areas which needs to be
processed to minimize environmental pollution. Anaerobic digestion of vegetable foliage alone is inefficient
because the nutrients and minerals required for bacterial growth are not present at sufficient level. To reduce
environmental pollution and to supply sufficient biogas production necessitated this study, with the ultimate goal
of assessing the effect of co-digestion of cattle dung and vegetable foliage on biogas production. Vegetable foliage
was mixed with cattle dung @ 5, 10, 15 and 20 % on wet weight basis and digested in batch as well as semi
continuous mode for seven weeks. The maximum biogas production (34.1 l/kg) and TS degradation (21.9%) was
obtained on supplementation of 20% vegetable foliage to cattle dung in batch digestion. The N, P and K content of
effluent were1.78, 0.56 and 1.52%, respectively. Under semi-continuous mode with digestion period of seven
weeks, the maximum biogas production (45.2 l/kg) was found at 20% supplementation level of vegetable foliage to
cattle dung. This indicates that 20% vegetable foliage can be supplemented safely to cattle dung for higher biogas
production. However, under semi-continuous conditions, increase in biogas production was found upto four weeks
only and it decreased after wards. The solid conversion efficiency of TS (0.304 l/g) and VS (0.357 l/g) was also
highest in digester-5 as compared to digesters 1, 2, 3, and 4, respectively during four weeks and decreased in
subsequent weeks. This suggest that for higher biogas production, the supplementation of vegetable foliage can be
made upto four weeks only in semi-continuous digestion and after four weeks, fresh vegetable foliage has to be
added to get higher amount of biogas production. Further, it can be interprated that the supplementation of
vegetable foliage more than 20 % may increase the biogas production further but it needs to be tested.
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Keywords
Costs, Mangoes, orchards, Markets, Productivity, Planting, Area, Manpower, Fruits, Crops