Non-oxidative thermal decomposition and thermo-kinetics study of mangrove biomass for bioenergy production

Abstract

Mangroves are well-known for their tremendous capacity to fix CO₂ and energy potential. In this study, the thermal characteristics of 3 mangrove biomass (leaf, stem, and roots) of natural and replanted gray mangrove (species: Avicenna marina) reserves have been investigated in an inert medium and compared to assess their fuel production potential. The chemical composition, physiochemical properties, and thermal behavior by proximate and ultimate analyses and thermogravimetric analysis (TGA) were investigated for this. Transplanted stem biomass showed the least ash content, with higher volatile contents when compared to other biomass samples. The higher heating value (HHV) in natural mangrove stems was 16.29 MJ/kg, with a calorific value (CV) of 16.58 MJ/kg, whereas the HHV in replanted mangrove stems was higher at 17.50 MJ/kg, with a CV of 22.41 MJ/kg. The apparent kinetic parameters, including activation energy and frequency factor, were estimated by fitting the experimental data to the n^th-order rate model. The apparent activation energies ranged from 73.2 to 78.5 kJ/mol for leaves, 96.0 to 97.3 kJ/mol for the stem, and 71.5 to 94.5 kJ/mol for roots, which are less than other mangrove species, indicating gray mangrove biomass was more reactive. Statistical analysis (e.g., Pearson correlation, t-test) indicated strong similarities and negligible differences between the experimental and simulation results. Several environmental factors (e.g., pH and salinity of soil) at study locations were investigated, suggesting higher HHV and carbon content of replanted mangrove stem biomass was noticeable due to higher salinity. Overall, this article promotes the UN's sustainable development goals by highlighting the potential of mangrove biomass as a catalyst for the sustainable development of energy, precious materials, and climate change.