Life cycle energy and cost analysis of small scale biogas plant and solar PV system in rural areas of Bangladesh

The work aimed in developing new design of plants and helps improving the efficiency of the plants. This study represents a complete analysis of energy and cost of selected biogas plants and solar PV systems. Data were collected from 20 small scale biogas plants and 20 solar PV systems from 3 sub-Districts of Tangail Districts and 1 sub-District of Rajshahi, Bangladesh. Often three sizes of biogas plants- small (2.4 m3), medium (3.2 m3) and large (4.8 m3) were found and five capacities of 40, 50, 65, 75 and 85 watt-peak solar PV systems were found in the sampled areas. It was found that the energy payback time of biogas plants were 2 years for 2.4m3, 1.66 years for 3.2 m3 and 2.33 years for 4.2 m3 plant. While the energy payback time for solar PV systems were found 6.53 to 7.57 years depending on system capacity. Cost payback period of biogas plants were 3.4 years for 2.4 m3, 2 years for 3.2 m3 and 2.5 years for 4.2 m3 while cost payback period for solar PV systems were found 2.55 to 4.03 years. The cost per unit biogas was found 9.8 BDT (Bangladeshi Taka) for cow dung based plants and 6.9 BDT for poultry waste based plants while the cost of per unit solar electricity was found average 8.2 BDT.