Chemical products yielded from different pyrolysis processes of rice waste residues: a comprehensive review
Saad A. El‐Sayed
Abstract
Abstract Researchers are conducting extensive research on renewable energy sources to offset the decline in petroleum-based products. It is becoming more and more important to use biomass as a source of energy and renewable fuels. The most promising method for converting biomass into alternative energy in the forms of biochar, biooil, combustible gases, and other important compounds is pyrolysis. To produce such important alternative fuels in an efficient and cost-effective manner, biomass is thermochemically broken down without the presence of oxygen. The vast amount of biomass that comprises rice waste, including husk, bran, and straw, makes it the perfect feedstock for biomass conversion. First, rice waste is synthesized and used for the production of bio-char and biofuels, which are alternatives to fossil fuels. The conversion of rice waste into platform chemicals is then emphasized as a way to use the current industrial facilities to produce sustainable chemical production using renewable carbon feedstocks. Additional uses for rice waste bio-char include the production of bio-diesel, bio-methane, biohydrogen, sugars (xylose and glucose), furan derviatives, organic acids, and aromatic hydrocarbons (benzene, toluene, etc.). This review examines the outcomes of rice pyrolysis, equipment and operating parameters, the composition of bio-oil, the chemical composition of rice wastes, and their heating value from the perspective of research on biomass pyrolysis. The review demonstrates that the primary operating parameters that impact the quantity and quality of yields are the pyrolysis temperature, inert gas sweeping rate, residence durations, heating rate, particle size, catalysts, pre-washing, and equipment employed, among others. An empirical formula for HHV based on the elemental analysis of rice residue with reasonably high accuracy is presented. Also, comparisons between the different yield types from different pyrolyzed reactors are introduced and discussed. Future research on rice waste valorization for the sustainable production of chemicals and fuels will be guided by the issues and opportunities that are outlined here.