Combined Heat and Power through Biomass - An Overview

Energy generation and its use affect the surrounding environment. About sixty five percent of the energy comprises of global anthropogenic green house gas emissions which are renewable. Reduction of this emission must necessarily begin with action targeted shift of energy sources that are renewable. Out of the various sources of renewable energy biomass and specifically agro-biomass has a lot of potential as it can be utilized in the existing energy conversion systems with minor modification. Biomass can be utilized in energy conversion system by co-firing in a modern coal fired power plant with biomass content up to 10% by weight. The combustion efficiency of biomass feedstock can be about 10% lower than that for coal. Biomass can also be combusted in a dedicated power and combined-heat and power (CHP) plant that is typically smaller in size and of lower efficiency of up to 35%. In cogeneration mode the efficiency may go up to 90%. Biomass integrated gasification has yet to be commercialized. However integrated gasification combined cycle (IGCC) burning black liquor a by-product of the pulp and paper industry is presently in use. Depending on type of biomass feedstock e.g. agriculture waste, animal manure, forestry waste, industry waste, municipal waste, sewage, etc. suitable processes like direct combustion, gasification, pyrolysis, extraction, fermentation, etc. can be used to produce energy in various forms. As per estimates global electricity generation from biomass is likely to increase from its current share of 1.3% to about 4% by 2050. Among agro-biomass rice-husk can be effectively burned in an externally fired gas turbine based combined cycle power plant which has been mathematically modeled. The proposed cycle exhibits plant efficiency in the range of 35-45% depending on the cycle operating parameters.