Combustion Behavior of Animal-Manure-Based Hydrochar and Pyrochar

Abstract

The sustainability of energy production can be increased by combusting waste-derived solid fuels, alone or as blends with coal. This paper investigated whether two thermochemical processes (hydrothermal carbonization and pyrolysis) can be used in sustainable manure management systems to convert surplus manure waste streams into renewable fuels. Hydrochars and pyrochars derived from swine manure and poultry litter at various process conditions were characterized. Their combustion behavior was studied by thermogravimetric analysis, individually and simulated as a blend with fossil coal. The hydrochars underwent two combustion stages, active and char combustion, while the pyrochars and four fossil coals showed only one stage. The substantial differences in characteristic combustion temperatures, kinetic parameters, and ash content between animal-manure-derived chars and coal suggest that fossil coals should not be replaced entirely with char, but used preferably as a blend. Simulation of blends with coal showed combustion characteristics similar to coal alone with amounts up to 10% (hydrochar) and 80% (pyrochar). Although more scale-up and ash characterization study is needed before implementation, the results suggest high potential of cocombusting small percentages of animal-manure based hydrochar and pyrochar with coal in existing coal power generation facilities.