Physicochemical and thermal characterization of nonedible oilseed residual waste as sustainable solid biofuel

• Potential of Jatropha curcas and Pongamia pinnata oilseed waste as solid biofuel.
• Proximate analysis suggesting the minimum environmental pollution after combustion.
• XRF shows ash deposition tendencies in boilers minimizes by monitoring conditions.
• Results promote the use of residual biomasses as a substitute for coal in future.

The present study aims to investigate the potential of nonedible oilseed Jatropha (Jatropha curcas) and Karanja (Pongamia pinnata) defatted residual biomasses (whole seed, kernel, and hull), as solid biofuel. These biomasses showed good carbon contents (39.8–44.5%), whereas, fewer amounts were observed for sulfur (0.15–0.90%), chlorine (0.64–1.76%), nitrogen (0.9–7.2%) and ash contents (4.0–8.7%). Their volatile matter (60.23–81.6%) and calorific values (17.68–19.98 MJ/kg) were found to be comparable to coal. FT-IR and chemical analyses supported the presence of good amount of cellulose, hemicellulose and lower lignin. The pellets prepared without any additional binder, showed better compaction ratio, bulk density and compressive strength. XRF analysis carried out for determination of slagging–fouling indices, suggested their ash deposition tendencies in boilers, which can be overcome significantly with the optimization of the blower operations and control of ash depositions. Thus, overall various chemical, physical properties, thermal decomposition, surface morphological studies and their high biofuel reactivity indicated that residual biomasses of Jatropha and Karanja seeds have high potential to be utilized as a solid biofuel.