Techno-economic assessment of fast pyrolysis for the valorisation of short rotation coppice cultivated for phytoremediation in the Campine

Abstract

The Belgian Campine has long been the subject of multidisciplinary research into phytoremediation of a vast area of farmland that has been moderately polluted with heavy metals such as cadmium. On an experimental field in the municipality of Lommel biologists have been investigating the metal extraction potential of energy maize, rapeseed and short rotation coppice amongst others. Especially willow demonstrated some phytoextracting capacity whereas the metal extraction potential of energy maize appeared to be rather limited. From an economic point of view however, energy maize is a feasible option for generating an alternative income for the affected farmers whereas the economic potential of willow has been open for further investigation. Because willow mainly consists of lignin, cellulosis and hemicellulosis, thermochemical technologies are better suited than biological ones for the conversion of willow into valuable products. Fast pyrolysis appears to be more promising than combustion and gasification both from an ecological and an economical point of view. Due to the lower process temperature of fast pyrolysis most of the metals do not volatilize and remain in the residual char. For the small scale of operation expected in the Belgian Campine, fast pyrolysis is also preferred above combustion and gasification in terms of return on investment. However, economic risk analysis showed that even with fast pyrolysis there is a high chance of economic loss. Therefore risk reduction strategies have been identified: combined production of heat and power, fast co-pyrolysis of willow with biopolymers, and activation of the residual char show promising results.