Characterisation of branch and twig mangrove bio-pellets as solid energy carriers for coastal communities

Abstract

Indonesia is characterised by a substantial opportunity to use mangroves as an energy source in coastal areas due to their abundant availability. Green chemistry emphasises sustainability, waste minimisation, and renewable resources, which aligns with using mangrove twigs and branches as bio-pellets for alternative energy. This research used only mangrove branches and twigs to make bio-pellets to preserve mangrove ecosystems and generate energy. Therefore, this research aimed to compare the physicochemical properties of mangrove-derived bio-pellets from three species, namely Rhizophora apiculata, Excoecaria agallocha, and Bruguiera sexangula. The comparison was done through various analyses such as fibre composition, ultimate analysis, calorific value, FTIR, SEM, XRD, XRF, and TGA. Hemicellulose, cellulose, and lignin composition influences Pellet fuel’s combustion and mechanical properties. Lignin enhances durability and energy density, while cellulose and hemicellulose improve combustion efficiency. Balanced biomass produces high calorific value and mechanical strength. The results showed that E. agallocha twigs (R-2) and B. sexangula twigs (R-3) contained the highest levels of hemicellulose and lignin, respectively, while B. sexangula branches (C-3) were the richest in cellulose. E. agallocha (R-2) twigs showed the highest calorific value, with element percentages for N–C-H–S-O measured at 1.33%, 47.29%, 6.98%, 0.09%, and 44.31%, respectively. XRD analysis showed that twigs-based bio-pellets generally had higher crystallinity and density, with a smoother, denser surface than branches, indicating potential as a fuel. Furthermore, XRF analysis showed that the main mineral compositions of mangrove bio-pellets were calcium, potassium, and chlorine. The chlorine content showed that E. agallocha branches’ bio-pellets had a low corrosion possibility. Based on the calorific value, both E. agallocha twigs and B. sexangula branches were considered ideal materials for fuel bio-pellets, with further improvements in preparation stages to enhance quality. This study contributes to the United Nations Sustainable Development Goals (SDG 7 and SDG 13) by promoting renewable bioenergy sources and reducing reliance on fossil fuels, thereby supporting global efforts in mitigating climate change.