Fluidized-bed gasification of dairy manure by Box-Behnken design

Application of excessive animal manure to the land may cause some environmental problems such as eutrophication of surface waters, degradation of ground water quality, and threats to human health. This paper reports an experimental study on the technology of biomass gasification to treat animal waste by analysing the effects of key operating parameters on gasification. In this research, dairy manure from the University of Nebraska dairy farm was first collected and dried, and then gasified in a fluidized-bed, laboratory-scale gasifier to generate syngas. The effects of three parameters, namely temperature, steam to biomass ratio (SBR) and the equivalence ratio (ER), on the gasification were described by a Box-Behnken design (BBD). Results showed that increasing the temperature favoured the formation of all three combustible gases, but the composition of each gas behaved differently according to the changing parameters. The lower heating value of the syngas varied from 2.0 to 4.7 MJ m(-3), indicating gasification could be used as a waste management option to produce bioenergy, and potentially reduce problems associated with the disposal of animal waste.