Determination of Nitrogen and Sulphur Mineralization in Batch and Semi-Continuous Anaerobic Digestion Using an Artificial Fiber Bag Technique

Jacob Rosholm Mortensen, Alastair James Ward, Martin Riis Weisbjerg, Sasha Daniel Hafner and Henrik Bjarne Møller
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Jacob Rosholm Mortensen: PlanEnergi Nordjylland, Jyllandsgade 1, 9520 Skørping, Denmark
Alastair James Ward: Department of Biological and Chemical Engineering, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark
Martin Riis Weisbjerg: Department of Animal Science, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark
Sasha Daniel Hafner: Hafner Consulting LLC, Reston, VA 20191, USA
Henrik Bjarne Møller: Department of Biological and Chemical Engineering, Aarhus University, Blichers Allé 20, 8830 Tjele, Denmark

Energies, 2021, vol. 14, issue 14, 1-17

Abstract: In the biogas industry, feedstock plans are used to estimate methane production and nutrient content in the digestate, however, these predictions do not consider the mineralized nitrogen fraction of the feedstock, which is useful when determining the quality of the digestate. In this study, the artificial fiber bag technique, which is commonly used to study feedstock degradation in ruminants, was implemented in anaerobic digestion to quantify mineralization of N and S. The artificial fiber bags were used to enclose substrates but with access to inoculum because of small pores in the bags, thereby enabling digestion. The content of the bags was analyzed before and after digestion to quantify residual mass as well as N and S concentration in the substrate. The method was validated through batch anaerobic digestion of a single substrate with and without bags, where the bags showed little influence on methane production and degradation. Semi-continuous anaerobic digestion experiments showed higher substrate degradation and higher N and S release at thermophilic conditions using four different types of feedstocks and proved useful for solid feedstocks but less so for semi-solid feedstock. For N, most of the mineralization occurred during the first 15 days over a trial of 30 days.

Keywords: anaerobic digestion; artificial fiber bag technique; mineralization; nitrogen; sulphur; method validation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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