Agricultural Wastes as Feedstock for Thermo-Chemical Conversion: Products Distribution and Characterization

Pyrolysis is one of the most promising thermal conversion technologies for biomass conversion. In pyrolysis, biomass is decomposed into solid char, bio-oil, and gas, that satisfies different forms of energy requirement. Further, Pyrolysis also offers the unique advantage of utilizing diverse lingo-cellulosic biomasses including agricultural wastes as feedstocks. Globally, India is the second largest sesame seed producing country. So, a vast amount of sesame stalk is generated as an agricultural waste in India. In this work, slow pyrolysis of sesame stalk was done at four different temperatures in the range of 350–650 °C at a heating rate of 40 °C/min in a laboratory-scale fixed bed reactor. The variation of pyrolysis products yield with temperature was observed, and all the products were quantified. The liquid and solid products of pyrolysis i.e. bio-oil and biochar respectively, were characterized by elemental analyser (CHN analyser), GC-MS, SEM and FTIR. From the study it was observed that pyrolysis temperature had significantly affected the yield of pyrolysis products. Biochar yield decreased while volatile gas yield increased with increase in temperature. The bio-oil yield was maximum at 550 °C and it was found that the higher heating value (HHV) of the oil was 26.89 MJ/kg. The carbon content of the biochar also increased with the temperature and hence the HHV. The pH of the biochar increased with the temperature and basic in nature which is suitable for soil amendment in north-eastern region. The study established that the sesame stalk was a suitable raw-material for pyrolytic valorization.