Ammonia and methane emissions during drying of dewatered biogas digestate in a two-belt conveyor dryer

Publication Type

Journal contribution (peer reviewed)

Authors

Awiszus, S; Meissner, K; Reyer, S; Müller, J

Year of publication

2017

Published in

Bioresource Technology

Editor

Elsevier

DOI

org/10.1016/j.biortech.2017.09.099

Keywords

Ammonia scrubber, digesta, drying, Fourier transform infrared spectroscopy, greenhouse gas emission

Aim of the present study was to identify type and amount of emissions during the drying of biogas digestate in a two-belt conveyor dryer at different temperature settings and to investigate the effect on its nutrient content. Furthermore, the possibility of recovering nitrogen from the exhaust air was investigated. Emissions of CH₄, CO₂ and NH₃ were measured by Fourier transform infrared spectroscopy. Biogas is mainly composed of CH₄ and CO₂, hence gas release from the digestate during drying was expected to increase the concentration of these components. Although CO₂ concentration was elevated above the background concentration, CH₄ did not exceed the background concentration. Maximum NH₃ concentration of 183.3 mg m^-3 was detected during drying. A NH₃ concentration of 10.8 mg·m^-3 was measured in the exhaust air of the ammonia scrubber, which is equal to a NH₃ reduction rate of 94%.