Energy densification of animal waste lignocellulose biomass and raw biomass

Abstract

The need to reduce carbon emissions has encouraged more research into use of biomass energy in place of coal. Biomass is carbon neutral; its use can therefore lower net emissions. Biomass can be upgraded to a fuel similar to coal by torrefaction. Different biomass have been torrefied but there is limited research in possible use of lignocellulose biomass from animal waste. This study aims to compare extent of energy densification of torrefied cow dung, corn cob and pine wood. They were dried, ground and sieved. Proximate and ultimate analysis was conducted. The samples were then torrefied at 200, 250 and 300 °C at 10 °C/min for 40 min. The resulting biochar were characterized using mass yield, higher heating value, energy yield and density. Biochar obtained at 250 °C were analyzed for elemental composition. Results were compared to Anglo bituminous coal and other torrefied biomass in literature. Corn cob and pine wood reached a maximum of 25.98 MJ/kg and 20.90 MJ/kg in heating value respectively whilst cow dung only increased to a maximum of 18.60 MJ/kg. Increase in heating value for corn cob was attributed to reduction in oxygen due to release of volatiles as well as water. This lowered the O/C ratio thereby densifying the fuel. The O/C and H/C ratio for corncob and wood moved towards that of bituminous coal unlike that of cow dung. Cow dung had a high inorganic composition so its heating value could not be upgraded as much as the other 2 biomass. Its use as a torrefaction raw material was therefore discouraged.