Biomass pyrolysis and gasification processes have been sufficiently developed to play a signifi­cant role in our sustainable energy future, especially as part of a biorefinery. While these processes can yield a number of gaseous and liquid fuels, this chapter provides a review of studies on the combustion and emission characteristics of syngas and biogas. There are notable differences between the combustion behavior of these two fuels and that of hydrocarbon fuels. While the syngas composition can vary widely, it generally has lower heating value, higher flame speeds, wider flammability limits, lower density, and higher mass diffusivity. Similarly biogas has lower heating value compared to natural gas, and significant variation in its composition. Such differ­ences imply different optimum operating conditions for combustion devices using these fuels, and thus significant opportunities for fundamental and applied research on both the production and utilization of such fuels. Fundamental combustion aspects requiring further research include

Flame structures in temperature, velocity, and species profiles for methane-air and biogas-air partially premixed flames at Ф = 1.4, pressure = 1 atm, and strain rate = 200 s-1.

cellular instabilities, flame stabilization and blowout behavior, turbulent flames, and emission characteristics. Such efforts would lead to the development of optimized systems for producing these fuels, and provide general guidelines for optimizing their composition for a given set of operating conditions.