Economics of flash pyrolysis of short rotation willow from phytoextraction

Abstract

Valorization opportunities for short rotation willow determine the feasibility of its use for phytoextracting farmland polluted with heavy metals. Cost-benefit analysis (taking into account uncertainties via Monte Carlo analysis) has been performed from the viewpoint of both an investor in renewable energy and a farmer confronted with metal pollution. In the Campine willow production can only result in electricity plants between 1 and 15 MWe. All thermal conversion techniques are loss-making at the lowest scales, indicating the importance of the amount of phytoextracting farmers. At these lowest scales flash pyrolysis has the best economic prospects, whereas gasification is preferred at the highest scales although the maximum possible willow price then still results in income loss for the farmer. Because it is expected that only a limited number of farmers participate, pathways have been identified to turn flash pyrolysis profitable. One option is to co-pyrolyse willow with biopolymer waste, resulting in oils with less pyrolytic water. Flash co-pyrolysing willow with PHB seems very profitable, as crystals for crotonic acid are formed.