Sustainable syngas and H2 from a zootechnical waste: an investigation on fluidized bed gasification of cattle manure

Abstract

Cattle manure (CM) is a zootechnical waste no longer desired for direct land application. Therefore, alternative methods of disposal must be developed, especially in countries with high production of dairy products and meat. Fluidized bed gasification allows for the safe utilization of manure together with the recovery of energy in the form of syngas. In the presented research, CM was subjected to fluidized bed gasification in CO₂ and O₂ atmospheres at T = 850 °C. Different CO₂ levels (Y_CO2 = 0.10, 0.20, and 0.30) or equivalence ratios for O₂ (χ = 0.3, 0.4, and 0.5) were used during gasification tests at laboratory scale. For the CO₂ atmosphere, the gas yields of H₂, CH₄, and CO were the highest at Y_CO2 = 0.30 with a conversion degree of 73.7 % and maximum cold gas efficiency of 83.1 %. For O₂ atmosphere, the conversion degree of 86.4 % and maximum cold gas efficiency of 60.0 % were achieved at lowest equivalence ratio (χ = 0.3). An exploratory test confirmed the advantage of using a catalytic bed material (dolomite) compared to an inert one (quartzite). The presence of dolomite led to increased levels of H₂ and CH₄. Tar yield and characteristics for CM and reference beech wood (BW) were similar, although a slightly larger amount was appreciated for CM.