1. What is renewable energy?
Energy obtained from sources that are essentially produced at a rate higher than the rate of consumption. Renewable sources of energy include biomass, geothermal, wind, photovoltaic, and solar thermal energy.
2. What is biomass?
Biomass is any plant and plant- derived material obtained from photosynthetic reaction of carbon dioxide with water vapor. Using biomass in the context of energy source, biomass can also include woody plants, residues from agriculture or forestry, and the organic component of municipal and industrial wastes. Biomass qualifies as a renewable source of energy as long as it is used at a rate comparable to or less than the rate of production.
3. What is meant by bioenergy?
The energy derived from biomass i.e. plants and plant-derived materials is called Bio-energy.
4. Does bioenergy contribute to greenhouse gas emissions?
No. Bioenergy does not contribute to GHG as long as it is managed in a renewable manner.
5. What is "Fuel Gas" and what is it's the Btu value?
Gas that has a fuel value is a fuel gas. Natural gas is nearly only Methane and has a calorific value of. 50 MJ/nm3 and needs ten times its volume to burn up. Producer gas is the fuel gas generated through gasification process with a calorific value of 4.5 – 4.8 MJ/m3 and needs roughly equal amount of air to burn up.
6. How is biomass used to produce electric power?
Electric Power from biomass is mainly producded by,
Incineration Route, where the energy in the biomass is transferred to steam which in turn produces electric power by running the steam turbines coupled to alternator.
Gasification Route, where the solid fuel is converted to gaseous fuel called ‘Producer Gas’ and electric power is generated by supplying the gas to an internal combustion engine coupled to alternator. This route can also be termed two-stage combustion route, a scheme that offers better control over the emissions.
Biomethanation route: where the energy in the biomass is converted to gaseous fuel by anaerobic digestion and electric power is generated by supplying the gas to an internal combustion engine coupled to alternator.
7. What does "co-firing" mean?
Co-firing means usage of two different kinds of materials as a source of fuel in the boiler/furnace. Typically, it is used in the context of firing biofuels or classified municipal waste along with any fossil to gain on “renewable” quality of the use. It also provides for clean development mechanism based carbon credits.
8. What is the cost of electricity from biomass?
For normal biomass through gasification + gas engine route: The variable cost would be about Rs 2.2 per kWh, at a biomass price of around Rs. 1.4 per kg. The contribution from fixed cost for 80% PLF would be another Rs 0.6 per kWh.
9. Are there gas turbines that will operate on such low Btu gas?
Yes, California has a biomethanation facility that uses the biogas to generate electricity using a micro-turbine. ABETS-IISc has also developed the know-how for using the producer gas for gas turbine application. Gas turbines at small power levels are expensive.