Ensiling parameters in vertical columns and multiple kinetic models evaluation of biomethane potential of ensiled sugar beet leaves

Abstract

The quality of silages could deteriorate during feed-out to biogas reactors. Using airtight silos where silages in pulp form can be pumped directly into a reactor may mitigate this problem. In this study, sugar beet leaves were ensiled in vertical columns and in airtight bags at ambient temperature for 370 days. Homofermentative lactic acid bacteria were added to some of the samples in the airtight bags to test the effect on silage quality and biomethane potential (BMP). Quality of ensiling and BMP were studied across the height of the columns. With the exception of the silages at the top of the columns, lactic acid represented over 55% of the concentration of total fermentation products in the silages. The silages at the bottom of the columns had a 20.9% higher BMP than the silages at the top, indicating that the BMP increases with the column depth. The BMP of the silage with additive in the airtight bags was 8% higher than that of the silage without additive. Four kinetic models were used to fit the experimental BMP, out of which the one-step two-fraction kinetic model described the experimental BMP better than other models.