Physicochemical Characterization of Solid Residential Fuels in Northeast India

Despite global shifts toward clean energy, traditional biomass remains the primary source of household energy for millions of people in Northeast India. This study presents a comprehensive assessment of residential fuel chemistry using a large-scale, uniform grid-based survey covering 522 grids and 8,577 households, complemented by rigorous laboratory characterization. Physicochemical analyses categorized the fuels into three distinct groups: hardwoods, softwoods, and grasses.

To capture real-world fuel-use conditions, over 312 solid residential fuel samples were collected directly from households and subjected to proximate and ultimate analyses to evaluate their combustion efficiency and energy potential. The results revealed that volatile matter was the dominant component across all samples (>92%), indicating high reactivity and suitability for energy applications. Regionally, samples from Nagaland exhibited the lowest moisture (1.77%) and ash content (1.78%). Among biomass types, softwood (pine) demonstrated the most favourable characteristics, with the highest volatile matter content (96.9%), whereas bamboo (grass) showed the highest ash content (4.97%), significantly exceeding the average for hardwood (3.57%). These findings highlight the importance of considering both regional origin and biomass type when predicting combustion behaviour.

Furthermore, fourteen dominant biomass species were comprehensively analysed using Fourier Transform Infrared Spectroscopy (FTIR; non-destructive) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS; destructive) to elucidate their molecular-scale thermal degradation behaviour and correlate it with energy performance. High-acidity species such as Artocarpus heterophyllus (jackfruit) and Quercus spp. (oak) exhibited elevated acetic acid yields (up to 14.20%), indicating a high acetylated hemicellulose content and increased bio-oil corrosivity. Nitrogen-rich feedstocks, including Hevea brasiliensis (rubberwood) and Syzygium cumini (jamun), produced higher levels of nitrogenous compounds such as dimethylamine (11.05%) and ammonium salts (9.93%), suggesting enhanced NOₓ emission potential. In contrast, bamboo (Bambusoideae) was characterized by a high abundance of 4-vinylphenol (~7.39%).

These findings, supported by thermogravimetric analysis (TGA) and FTIR results, provide critical insights into the combustion and pyrolytic behaviour of regional biomass resources and will be used to develop an energy–economic model for predicting the energy potential of solid residential fuels in Northeast India.

Keywords: Solid residential fuel, Energy economic model, thermochemical properties, pyrolytic characteristics