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.

Keywords:

• Vertical columns
• lactic acid
• kinetics
• airtight bags

Acknowledgements

The authors thank the Petroleum Technology Development Fund (PTDF), Nigeria, and the German Academic Exchange Service (DAAD) for supporting the PhD programme of Jerome Undiandeye. They also thank Peter Fischer from DBFZ for performing the BMP experiments, Mathias Stur for providing Figure 2, and Bärbel Haase and Martin Apelt for their technical support.

Author contributions

Study and experiment conceptualisation, WS; methodology, JU; software, DG; validation, WS, JU and HS; formal analysis, DG; investigation, JA; resources, WS; data curation, JU; writing – original draft preparation, JU; writing – review and editing, HS, WS, DG, MN, and JU; visualisation, JU; supervision, HS, MN, and WS; project administration, WS; funding acquisition, WS. All authors have read and agreed to the published version of the manuscript.

Conflicts of interest

The authors declare no conflict of interest.

Additional information

Funding

This research was funded by the German Federal Ministry of Education and Research [grant number 031B0578A].