Relating features and combustion behavior of biomasses from the Amazonian agroforestry chain

Abstract

The search for new alternatives to supply the overall energy demands of the Amazonia has been growing. Among the available renewable sources, the waste feedstock from the agroforestry chains stand out, but their proper characterization is an urgent need. This study proposes to assess the energy potential of five wastes from agroforestry crops of the Brazilian Amazonia by qualitative and quantitative approaches, highlighting the relation between biomass chemical composition and combustion behavior. The açai seed (AS), cocoa pod husk (CPH), coconut husk (CH), palm empty fruit bunch (PEFB), and maize cob (MC) were investigated. The high energy density (6.94 GJ m−3) and low ash content (1.4%) distinguished AS from the other biomasses. The PEFB showed the lowest ignition temperature (197 °C) combined with the highest ignition index (3.4 × 103% min−3) and net heating value (16.20 MJ kg−1). The superior amounts of hot-water-soluble extractives of PEFB (10.8%) and CPH (18.0%) anticipated the energy release in the main stage of combustion. Furthermore, increases in hot-water-soluble extractives reduced the ignition temperature, while lower H/C ratios increased the flammability. The H/C above 1.6, total lignin content up to 21.1%, and volatile matter/fixed carbon ratio above 4.4 facilitated the ignition of PEFB and MC biomasses.