Agricultural residues are still being burned in the open field despite the current sufficient availability of agricultural biomass as a renewable energy source because they are a major source of greenhouse gas emissions and ambient air pollution. Although numerous studies have been reported on biomass briquetting, the available literature is very disjointed, and there is lack of synthesis between feedstock characteristics, processing modalities, and thermochemical characteristics and fuel characteristics. This is a critical review of the process of converting agricultural waste into briquettes, as it is an issue on how choice of raw materials, densification and compositional properties affect the quality of briquettes produced. Proximate and ultimate analyses are methodically investigated in order to determine important determinants of calorific value, durability, and combustion efficiency. Further, the data of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) are relatively evaluated to explain the process of thermal degradation and reaction pattern- an aspect that has been largely ignored by previous reviews. The results were that the high ash content always has a notable limitation of the energy performance, but the moisture loss and thermal stability is mostly controlled by lignin, cellulose, and intrinsic moisture content. This novelty of this review lies within its incorporation of compositional evaluation with thermal characterization to outline more concrete performance indicators of agricultural briquettes. The findings highlight the possibility of locally available agricultural residues as a cheap and sustainable solid fuel, and place briquetting as a successful approach to reducing the burning of residues and promoting the development of a circular bioenergy system in rural areas.
Velusamy et al. (Sun,) studied this question.