Thermophilic Adaptation of Anaerobic Sludge for Electricity Production

Resumé

Anaerobic digestion of biogas inside the digester occurs in a particular temperature range. Research shows that the production can be increased by 33% by switching over from mesophilic temperature range (30­40 ° C) to thermophilic temperature range (50­60 ° C). Even then, biogas plants generally work in mesophilic range because a large amount of energy is required to maintain the high digester temperature. This huge energy input is required round the clock which makes biogas practically impossible as a permanent, continuous and cheap source of energy. At present, the digester temperature is maintained by burning the biogas produced, which increases the biogas production per unit of biomass, but it is not a cost-effective method as in totality it results in lesser production of gas.Biogas used for electricity production has CNG generator which consumes biogas and produces electricity. The generator also produces high quantity of exhaust gases due to the burning of biogas (fuel). This huge energy content is used to partially maintain the digester temperature by converting the heat content of hot exhaust gases into hot water at about 90 ° C through a heat exchanger. Solar water heaters are installed to heat water to 90 ° C which works for a specific time of the day. A hybrid system is created in which hot water is taken from the generator and the solar panels and is stored in a tank from where it is distributed as the temperature of the digester falls below 50 ° C. The temperature in the digester is maintained by pouring fresh slurry at 60 ° C and heating it in the digester by circulating hot water inside heating coils, fitted inside the digester. To regulate temperature inside the digester, a temperature control system is developed which modulates the flow of hot water. Keywords: Thermophilic, anaerobic digestion, biogas for electricity, renewal energy, biogas