Assessment of the biogas production potential of renewable resources with near infrared spectroscopy

Abstract

The increasing use of biomass for biogas production requires the development of appropriate analytical processes with which the potential gas yields of the plants used can be evaluated. Particularly in energy plant breeding, quick methods to determine genotypical differences in gas development potential are needed that can be applied on large sample series as close to harvest time as possible and at as low a cost as possible. The suitability of near infrared spectroscopy (NIRS) for this task was studied on silage maize, grass and grass-legume mixtures. The calibration-validation experiments were carried out on fresh and accordingly dried, ground samples, as well as on the basis of two reference data bases on methane yield, one calculated from batch tests and the other calculating potential methane yield on the basis of the fermentable organic dry matter. It is shown that the measured methane yield cannot be calibrated or vali­dated with adequate certainty. The reason for this is the inexactness in the repetitions of the batch tests in relation to the crop type specific variance of the methane production potential. With the reference data on the calculated potential methane yield, in contrast, the NIR calibration/validation can be made with adequate exactness. Here the prediction ability lies within the screening area for fresh plant material and an acceptable level of laboratory analysis for dry material is possible.