CEE Oct-Dec 2012

I was plastered with a cement-mortar mixture in a ratio of 1:2. The gas holder of 2.2m diameter and 1.2 m height was fabricated with a 3.16 mm thick mild steel (MS) sheet and a gas outlet pipe was connected with the gate valve. A stirrer arrangement was made within the inlet tank for It~ 2. h.itdtul .uul d tnntnp; wa~tc mi,tng The plant was loaded after curing it with a mix of 6 tonnes each of cow dung and water to maintain the initial total solid content of 10 per cent. It was allowed to stabilize for 40 days and during this period, it was regularly fed with cow dung and water mixed in a ratio of 1:1. After stabilization, in the first week, the cow dung usage was reduced to 90 per cent and the kitchen and dining waste was added as the remaining 10 per cent. Subsequently, 10 per cent cow dung was reduced and 10 per cent of waste was increased every week. And by the tenth week, the plant was running 100 per cent on kitchen and dining waste (Table 1). Table1. Feed combination of kitchen and dining ' waste and cow dung. I .. Kitchen Quantity of Quantity of Water and food kitchen cow dung addition (I) • waste(%) and food (kg) I waste (kg) 0 0 150 150.0 10 7.5 135 142.5 20 15.0 120 135.0 30 22.5 105 127.5 40 30.0 90 120.0 50 37.5 75 112.5 60 45.0 60 105.0 70 73.5 45 118.5 80 60.0 30 90.0 90 67.5 15 82.5 100 75.0 0 75.0 proper cutting, stirring and m1x1ng of the waste (Figure 2). An inlet pipe made of polyvinyl chloride with a diameter of 30 em and length of 2.05 m, fixed at an angle of 75° to the horizontal for easy flow of the mixed waste feed , was used. I )in r n~ w.t,l< 1-.:itchut .utd d lflill~ \\,f\1< .d tt'l fllf \1111.: The average monthly biogas gas production has been observed in the range of 5.61 to 5.84 cubic metre per day and the gas production rate is observed to be constant. The biogas produced is utilized in the hostel kitchen for about 6 to 6 ~ hours per day for cooking. The rated input capacity of the plant is 70 kg/day and depending upon the availability of the feed, it varies from 50 to 80 kg/day. The net savings on fuel are estimated to be 3 to 4 LPG gas cylinders per month which means that Rs.3000 per month towards LPG cost is saved due to the installation of the biogas plant. Annual savings are estimated at around Rs.36,000. The simple payback period has been worked out to be 3 years. It is by far the best technology for the treatment of kitchen and dining waste because it not only generates energy from waste but also solves the problem of waste disposal. The authors are prof./Head, Associate prof. (Physics). and Associate Prof. , Department of Bioenergy, Agricultural Engineering College Tamil Nadu. E-mail: bioenerqv@tnau.ac.in Courtesy: Renewable Energy Akshay Urja, June 2012, Pp36-37. 32