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Hydrothermal carbonization of rapeseed meal for Biofuel production: Effect of the reaction temperature on fuel quality and emissions

Abstract:

A proper management of agro-industrial waste is strongly required since these residues represent an alternative energy source. In this study, it was conducted the hydrothermal carbonization (HTC) of rapeseed meal, which is a biomass waste from the rapeseed oil extraction process that shows interesting properties in terms of calorific value. The effect of the reaction temperature was evaluated on basic fuel properties, pellet quality, and emissions from a pellet stove. First, the mass yields were decreased as reaction temperature increased showing significant mass loses even at low HTC temperatures. The higher heating values were, conversely, increased with temperature reaching an improvement of more than 30% compared to raw biomass. On the other hand, the ash content was dramatically reduced at 150 °C; however, an increasing trend was observed as temperature rose. About the pellet quality, moisture uptake and compression strength tests were performed resulting in hydrochar pellets showing enhanced hydrophobicity and durability, which facilitates the storage and transportation of these novel pellets. Finally, combustion tests in a household pellet stove were carried out to assess the effect of the HTC process on the air pollution control from residential combustion. Emissions from incomplete combustion such as CO and particulates were significantly diminished when burning hydrochar pellets obtained at low HTC temperatures, whereas NOX concentrations were gradually reduced with hydrochars obtained at higher temperatures. These findings definitely represent a promising contribution from biomass conversion technologies to take advantage of rapeseed meal residues, and also, to overcome the current scarcity of commercial pellets made of woody biomass.