Biomass is the term attributed to any renewable resource derived from organic matter that can be used in energy production. Agricultural production generates residues that are of great importance for their energy use, of which sugar cane, eucalyptus, and rice. Various residues are generated from rice cultivation, among which the rice husk and rice straw are the most important. Several thermal conversion technologies have been developed for the use of biomass in industry. Pyrolysis has been notable for its ability to produce biofuels at different stages of aggregation. The slow pyrolysis of biomass has been proposed as a pretreatment method to improve the physical-chemical characteristics of rice straw. In this process is produced, mainly, a solid called biochar, which has a higher energy content when compared to the biomass of origin. This study investigated the slow pyrolysis of rice straw at 300 - 700°C for the purpose of obtaining biochar, bio-oil, and gases for energy purposes. The experimental results show that pyrolysis temperature has important roles in yield product. The highest biochar yield was observed at a temperature of 300°C with 49.91 wt%. This represents 47% more when compared to yield at 700°C (33.87 wt.%). This behavior is linked to the proximate analysis results for fixed carbon 26.01 wt.% at 300°C. The high pH of the biochar was attributed to the presence of alkali metals, according to XRF. Thermal decomposition of the biomass resulting in a gradual increase of bio-oil (16.81 - 34.70 wt.%) and gas (6.53 - 18.05 wt.%) on a wet basis. Thus, in the dry base parameter, the bio-oil increases from 19.22 - 30.6 wt.% and the gases at 9.42-20.19 wt.%. Drying of the raw material showed, by the results, a significant increase in the co-products formed. As a consequence, we have a more efficient energy process.
Effect of pretreatment and biomass blending on bio-oil and biochar quality from two-step slow pyrolysis of rice straw