Spanish biofuels heating value estimation based on structural analysis

Abstract

The importance of waste biomass as an energy source is likely to increase during the coming years as a result of European energy policy objectives, and because of the wide range of possibilities that it offers: it is a cheap fuel, widespread, and available in large quantities. In addition to crops and forestry operations, the Spanish fruit, olive and wine industries generate large amounts of currently undervalued solid wastes such as stones, branches, pulps or pomaces. The use of these by-products offers environmental benefits like removing waste and preventing fires at the same time as providing an energy yield. A proper energy valorization will require a complete physicochemical characterization. In this article, a structural and thermal characterization is developed from twenty samples from the olive and wine industries, as well as from forest and agro wastes. In addition, predictive equations are proposed to determine higher heating value (HHV) from chemical composition. For this purpose, the chemical extraction method (also called the ‘classic’ method) was used, and results were obtained in accordance with the data shown in the bibliography. Two predictive equations were developed: one based on lignin and hemicellulose content, and the other based on lignin quantity. Both present an absolute average error (AAE) of 0.87% and 1.13%, respectively.