Anthony Lau
University of British Columbia, BC, Canada
Title: Improving the Quality of Waste Biomass by Reducing the Ash Content and the Inorganic Constituents
Biography
Biography: Anthony Lau
Abstract
Fuel pellets can be produced from forest residues and agricultural crop residues. This study aims at improving the quality of crop residues (canola straw, wheat straw and corn stover) by reducing the ash content and the inorganic constituents using mechanical size fractionation and water leaching in sequence as the pretreatment techniques. It is desirable to minimize the need for leaching, as the subsequent drying of the biomass for further processing into fuel pellets can be energy intensive thus increasing the production cost. Experimental treatments involve water temperature (25, 45°C), leaching time (3, 12, 24 h) and water-to-sample mass ratio (30:1) after preliminary tests were conducted to identify the appropriate levels for these parameters. Results indicated that the finest fraction of ground crop residues (particle size < 0.25 mm) had much higher ash contents than the coarser fractions up to 3.15 mm. Hence, size fractionation can effectively reduce the need for leaching to remove ash and it is most effective for corn stover. Subsequently, leaching test was performed on the finest fraction of crop residues. Canola straw was found to have the best leaching performance compared to wheat straw and corn stover, as it had the highest ash removal efficiency and element removal efficiency (greater than 90% and 50% for K2O and SiO2 respectively). Leaching time of 3 h or 12 h at 25 o C temperature was sufficient for effective ash removal for canola straw, yet longer leaching time of 24 h would improve the ash removal efficiency for corn stover and wheat straw. Leaching temperature had negligible effect on K2O removal efficiency, but significant effect on SiO2 removal efficiency. A preliminary cost analysis indicates that pretreatment by mechanical size fraction followed by water leaching would lead to a 30% increase in the total production cost (TPC) of agro-pellets, whereas the TPC would increase by 66% if the pretreatment is done by water leaching only.