The fuel particles are transported into an externally heated silicon carbide (SiC) tube pneumatically through an insulated and water-cooled injector. Prior to the injection, the feed­ing stream, composed of air and fuel particles, has to pass through an agitation chamber for "disaggregation and filtering of pulses in the feeding." The feeding fuel is ignited by a natural gas/air burner at the reactor entrance (Jimenez and Ballester, 2006). There are three main stages that occur during biomass combustion: drying, pyrolysis and reduction, and com­bustion of volatile gases and solid char (IEA, International Energy Agency, Task 32: biomass combustion and co-firing: an overview. http://www. ieabioenergy. com/MediaItem. aspx? id=16).The combustion of volatile gases contributes to more than 70% of the overall heat generation. It takes place above the fuel bed and is generally evident by the presence of yellow flames.

Combined Heat and Power (CHP): Production of electricity and heat from one energy source at the same time is called CHP. In almost all cases, the production of electricity from biomass resources is most economical when the resulting waste heat is also captured and used as valuable thermal energy—known as CHP or cogeneration (http://www. epa. gov/chp/ documents/biomass_fs. pdf). Biomass is most economical as a fuel source when the CHP system is located at or close to the biomass feed stock. In some cases, the availability of bio­mass in a location may prompt the search for an appropriate thermal host for a CHP applica­tion. In other circumstances, a site may be driven by a need for energy savings to search for biomass fuel within a reasonable radius of the facility (http://www. epa. gov/chp/basic/ renewable. html).

Using biomass instead of fossil fuels to meet energy needs with CHP provides many poten­tial environmental and economic benefits, which can include (i) reduced greenhouse gas and other emissions, (ii) reduced energy costs, (iii) improved local economic development,

(iv) reduced waste, (v) expanded domestic fuel supply, (vi) reduced transmission and distribution losses. CHP offers distributed generation of electrical and/or mechanical power; waste heat recovery for heating, cooling, or process applications; and seamless system integration for a variety of technologies, thermal applications, and fuel types into existing building infrastructure. CHP systems typically achieve total system efficiencies of 60-80% for producing electricity and thermal energy (http://www. epa. gov/chp/documents/ biomass_fs. pdf).