Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Feedstock characterization for all tested energy crops

The scope of this task was to gain detailed information about the characteristics of the energy crops switchgrass, giant reed, cardoon and miscanthus by means of chemical analysis of fuel samples provided by the biomass growing partners.

The characteristics investigated are heating value, ash content, chemical composition, concentrations of main elements (C, H, N, S, Cl, Si, Ca, Mg, K, Na, P, Al), concentrations of heavy metals (Fe, Mn, Cu, Zn, Ni, Cr, Pb, Cd, Hg) and moisture content.

The main quality aspects of biomass fuels are the heating value and the ash content.

On an ash free and dry basis the heating values of the crops investigated are similar to wheat straw but lower than wood. The ash content of perennial crops is comparable with the ash content of wheat straw and significantly higher than the one of wood chips. However, there is a very strong influence of the harvesting method used and the conditions during the harvest.

Based on the analyses performed, the concentration levels of relevant elements (especially K, Na and Cl) in the perennial crops imply that generally high particulate emission levels, corrosion and deposit formation rates are to be expected during combustion of these fuels.

The chemical composition and also the morphology of the perennial crops investigated are comparable to the commonly used biomass fuel wheat straw and significantly different to wood. According to this, combustion technologies developed for straw combustion should be applicable for the combustion of perennial crops as well.

First of all, the harvest methods for the perennial crops have to be further developed and tested in order to avoid contamination of the fuel. Secondly, for large-scale applications the fuel should be stored and transported as bales and presumably also combusted as bales. For small-scale applications pelletising of the fuel prior to transportation is the best solution as the chopped material has much too low mass and energy densities for efficient transport, storage and fuel feeding.

When combusting these fuels, care has to be taken concerning emissions (especially NOx and particulates). Also operational problems such as slagging and fouling are to be expected. Especially in small-scale applications these problems are difficult to solve and thereby techniques for improving the quality of the fuel such as leaching, usage of additives or blending with other fuels should be investigated in the future work.

Reported by

VT-TUG, Institute for Resource Efficient and Sustainable Systems, Graz University of Technology
Inffeldgasse 21b
8010 Graz
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