Suitalbility and Cost Effectiveness of Biochars Produced from Different Agricultural Residues with Different Methods for Briquette Making as a Renewable Biofuel

Abstract

Four feedstocks, corncob, coconut shell, coconut husk, and rice straw, were selected to produce biochar using a 200L oil drum kiln and a pyrolysis reactor with gasification at 500 o C in Thailand. Coconut shell, coconut husk and rice straw also sent to the United Kingdom for biochar production by pyrolysis under well-controlled temperature conditions of 550 o C and 750 o C. From the results of proximate analysis, it was found that the production of biochar with pyrolysis reactors gave higher fixed carbon and lower volatile matter content than biochar produced with the 200L oil drum kiln. The relationship between O/C and H/C ratios showed that biochar from coconut shell produced by the pyrolysis at 750 o C in the United Kingdom had the highest stability and would decompose slowly. It achieved the limit on both ratios of O/C (<0.4) and H/C (<0.7) required by European Biochar Certificate. Biochar made from coconut husk produced by the 200L oil drum kiln had high heating value. Thus, it was suitable for briquette making by using a manual compactor. We calculated the net present value (NPV), the internal rate of return (IRR) and the payback period (PB) from cash flow projections of biochar and briquette production from coconut husks with the oil drum kiln method. The scenario passed criteria for all three indicators. Therefore, this scenario presents a worthwhile investment for waste valorization and renewable energy production in the rural economy.