Measure the weight of the waste put into a bio gas digester. Use a scale to weigh the waste. Once a weight of waste is put in the digester, the anaerobic bacteria digest the waste, producing energy in the form of heat.
Use a reference table on bio gas volume produced in a day to find the volume produced during a day by the waste weight amount in the digestion plant. Look up the kind of waste. Write down the bio gas volume produced in a day by the waste per unit of weight. The Clean Development Mechanism, which is part of the U.N. Framework Convention on Climate Change, provides estimates for commonly used dung in liters per kilogram per day: 15 to 32 for cow dung, 15 to 32 for buffalo dung, 40 to 60 for pig dung, 50 to 60 for poultry dung and 60 to 70 for human dung. Multiply the reference volume by the weight in kilograms of the waste in the digestion plant. Now you have a day's bio gas production.
Use cubic meters for gas volumes. If the reference provides different volume units, convert the units. For example, 1 liter = 1/1,000 cubic meters. Use math conversions to convert any meter-based volume measures to cubic meters.
Calculate the daily calorific value range by using a formula used by the Clean Development Mechanism. The CDM gives the range of calorific value for 1 cubic meter of bio gas at 4,500 to 6,000 kilocalories, or roughly 19 to 25 megajoules. Write down the daily production value for the base value on a calculation sheet. You can use this value for any energy burns using the same waste for fuel in the bio gas digester.
For any period of more than one day, use the daily production value to calculate the energy produced in the entire period. Multiply the number of days in the period by the base daily value.