Biocarbon is a promising fuel which can have several applications, for example: to provide peak load in bioenergy plants, as substitute fuel for oil boilers, as quality fuel for high efficiency and low emission small-scale heating appliances, and as a way to optimize fuel mixtures by blending.
Researchers at the University of Perugia, Italy and SINTEF, Norway have recently conducted studies on an innovative type of pellets made from a combination of biocarbon and sawdust. The material used in the production of these pellets is the result of several experimental mixtures, resulting in a combination of 52% biocarbon, 26% sawdust and 22% water. The idea behind this research was to create a pellet which would be both economically convenient and compatible with existing stoves, so as to maximise savings. Their durability (about 98%) and thermal efficiency show that this material holds real potential. The energy content of the pellet obtained by blending biocarbon and sawdust are similar to those of torrefied pellets (having a heating value of 26.1 MJ/kg).
The biocarbon pellets were tested in a 20 kWt boiler, (changing air and fuel mass flow) to measure efficiency and emissions. The thermal efficiency reached was around 87%, while emissions of particulate matter proved to be in the range of those of commercial wood pellets. Thermal performance and emissions data generated from the experimental campaign is being used to assess the overall feasibility of the value chain and the performance of biocarbon pellet combustion in small scale boilers, from the point of view of cost-efficiency, thermal efficiency, and environmental performance.
In terms of costs, a techno-economic assessment has indicated that production costs for the biopellets equate to about 27€/MWh, while the specific heat production costs can range from 36 to 67€/MWh, according to sensitivity analysis. However, it is estimated that biopellets prepared at slow pyrolysis conditions can be economically competitive with traditional wood pellets. While future research on biocarbon pellets is undoubtedly necessary to optimise this process, these results show that they represent a new competitive solution, which promises to expand the market of sustainable energy.
This post by Elisa Moioli is based on the paper “Technical and economic feasibility of combusting biocarbon in small scale pellet boilers” by P. Bartoccia, R. S. Kempegowdab, F. Libertic, G. Bidinia, Ø. Skreibergb and F. Fantozzia presented at the 25th European Biomass Conference and Exhibition.
