Amonia (NH3) emissions during drying of untreated and detwatered biogas digestate in a hybrid waste-heat/solar dryer

Publication Type

Journal contribution (peer reviewed)

Authors

Maurer, C; Müller, J

Year of publication

2012

Published in

Eng. Life Sci.

Pubisher

Wiley-VCH

Band/Volume

12/3

DOI

10.1002/elsc.201100113

Page (from - to)

321-326

Keywords

ammonium, drying

Digestate from the biogas digestion process contains high amounts of water and
nitrogen, which can lead to over-fertilization problems in regions with intensive
livestock farming due to a surplus of ammonium, which contributes to the global
warming effects. The best option to reduce thewater content aswell as to concentrate
the nitrogen is to dry digestate; however, volatile nitrogen present in the digestate
has the tendency to be emitted. Therefore, the objective of this study was to investigate
the emissions of untreated and dewatered digestate during the drying process and to
determine the nitrogen loss of the drying product by calculating the loss over time
by the emissions and compare it with initial and final ammonium content made by
chemical analysis. The drying procedure was performed in a hybrid waste-heat/solar
dryer.Ammoniaratewas measured continuously during drying by Fourier transform
infrared spectroscopy. Untreated digestate showed higher cumulative emissions of
ammonia (25.9 gNH3 kgDM
−1) than dewatered material (7.75 gNH3 kgDM
−1) due to
lower water content and shorter drying time. Emissions fromthe filtratemay still be
an issue, which should be addressed in future studies.