Adding gas from biomass to the gas grid - SGC

is mixed with coal in a combustor providing heat to a generator. Typical efficiency for the productionof power ranges from 25 - 42% [lit.5].Large amounts of municipal and industrial waste are combusted in special installations in order toreduce the amount of waste. Addition of biomass, either to improve the combustion properties of thewaste, or to achieve a kind of co-firing, is common practice. The efficiency of the biomass herein toelectricity conversion has efficiency between 23 and 30% [lit.6]. In some cases a part of the wasteheat is used for district heating.Anaerobic digestionAnaerobic digestion is the common denominator for a wide range of microbiological processeswhere biomass is converted to biogas. These processes are described in chapter 3 of this reportand involve biogas production from manure, landfills, sewage plants, industrial waste streams andsolid organic wastes.In some applications the biogas is converted to heat. This is mainly done for landfill gases whereabundant, low cost, biogas is used to provide heat in local industrial applications.A long existing application is the anaerobic digestion of manure, followed by the generation ofelectricity. This application provides heat and electricity in millions of Chinese and Indian housesand communities [lit.3].Also in the Western societies biogas is converted by a generator to produce electricity. Thisconversion has, due to its small scale, a modest efficiency between 20 - 35%. In some cases thatwaste heat from the generator finds a useful application. In Denmark most biogas is used forcogeneration, reaching a total heat and power efficiency between 80 and 90%.Grid applicationsBiogas can be the feedstock to produce pipeline quality gas. After cleaning the biogas can bedistributed in a medium calorific gas grid. After cleaning and treatment the biogas can be fed to anatural gas grid.Transport applicationsAll pipeline quality gases from biomass can be used as a transport fuel. Successful examples existfor cleaned biogases as well for the biogases converted to a pipeline quality gas.Thermal gasificationThermal gasification is the common denominator for all processes that thermally convert organicmaterials into a gas. The most widespread application is the gasification of coal. The gasification ofheavy residuals of oil refineries is becoming more and more important. Also thermal processes canreadily gasify biomass. In all these processes biomass is mixed with water, air (or oxygen) and putpage: 8