Demonstrating the Suitability of Tamarind Residues to Bioenergy Exploitation Via Combustion Through Physicochemical Properties, Performance Indexes, and Emission Characteristics

Abstract

Clean thermochemical conversion of lignocellulosic residues is particularly interesting for both bioenergy production and environmental protection. For this reason, the novelty of this study is to present tamarind residues (husks and seeds) from the tamarind fruit processing industry as new prospective feedstocks for bioenergy production considering their physicochemical properties, combustion performance indexes, and emission patterns. Characterization results confirmed the suitability of tamarind residues as raw materials for combustion with considerable energy contents (~ 17.5 MJ kg−1), ash contents below 2.9 wt.%, and negligible sulfur (< 0.01 wt.%). High bulk (552.7–635.8 kg m−3) and bioenergy (9.1–10.4 GJ m−3) densities were found, indicating that the distribution and utilization of tamarind residues are significantly favored. Acceptable CO2, CO, and SO2 emissions were found during the combustion of both residues. Elevated nitrogen concentrations (2.5–3.0 wt.%) were reported, implying higher NOX emissions (8.8–10.5 g kg−1), which require rigid control. The combustion performance indices suggest that tamarind residues have better properties for combustion than feedstocks commonly used as bioenergy sources. Tamarind residues thus appear to be promising renewable feedstocks for bioenergy because of their attractive properties, better combustion performance, and acceptable emission characteristics. This study conclusively indicates that tamarind residues are promising feedstocks for bioenergy and provides valuable insights to their future applications in commercial biomass boilers with controlled emissions.