Energetica India Magazine January 2024

CASE STUDY Comparison of Flexi Biogas Plant with KVIC & Deenbandhu Biogas Plant In hilly places, like Sikkim, where high transportation cost of construction material adds significantly to their expenses, conventional biogas plants are not feasible. Furthermore, con- ventional underground digesters are not suitable for use along India’s coastlines. Flexible balloon-style digesters made of neo- prene-rubber can operate effectively in mountainous and coastal areas. Flexi biogas plants can be easily and affordably installed at any time above the ground and are readily transportable to remote locations. Technology of Flexi Biogas Plant Flexi biogas plant is a prefabricated air cushion type (flexi) household biogas digester with a high-density polyethylene gas container. The flexi biogas digester and gas holder are made from fabric that has been PVC coated. The gas holder of the flexi di - gester is above ground in an earthen pit. The biogas digester re- quires minimal maintenance and is simple to build without the need for civil construction. Installation of a 1m3, 2m3, or 3m3 flexi biogas plant requires no civil work, whereas 5m3 and bigger flexi biogas plants require just minimal civil work. The biogas digester for a 2m3 flexi biogas plant is made up of a 6-inch feed - ing funnel, a 0.5-inch gas opening and shutting valve, a 3-inch inlet PVC pipe, and a 3-inch elbow on the 3-inch outlet PVC pipe. Cattle dung and water are mixed before feeding in a mixing tank (a plastic drum) using a hand-operated agitator. To supply pressurised biogas to the cooking stove, a 20 watt (200 V, 50 Hz) biogas booster pump should be installed in the kitchen (Fig. 1). When the plant is being fed, the biogas outlet valve is closed. Due to pressure from the biogas that accumulates in the gas holder, the digested slurry flows out of the outlet pipe into the slurry drying pit. Flexi biogas models provide the most advanced tech- nology while continuing to be the most affordable in the market. Fig 1. Flexi Biogas Model KVIC (Floating Drum) & Deenbandhu (Fixed Dome) Biogas Plant Flexi Biogas Plant • Required high initial capital investment for both KVIC and Deenbandhu biogas plant • Required to replace drum of KVIC plant after 5 years, which cost around 40% of initial investment • Civil construction work is needed • Required Skilled Labor for construction • 30 to 45 days HRT (Hydraulic retention time) is required • Maintenance is required to operate KVIC and Deenbandhu plant • Less Initial Investment • No civil construction work • Installation can be done within 1 day • No skilled labor is required • HRT= 25-40 days • Temperature is easily maintained in winter season by providing straw insulation • Material is easily available in nearby market • Can be installed easily in hilly and remote areas • No additional maintenance is required • Easy Operation Substrates for 2 m3 Biogas Production • Farm manure up to 50 kg/day– poultry, cattle, pig, horse, poultry (when mixed with other) manure. • Plant wastes up to 55 kg/day – leaves, twigs, little branches(shredded) waste. • Food waste up to 18 kg/day raw and 40kg/ day cooked; from restaurants, cafeterias, groceries – food wastes like leftover food, fruit and vegetable peelings, over-ripped or spoiled fruits and vegetables, date expired food (shredded) waste. energetica INDIA- Jan_2024 45