Drying characteristics and nitrogen loss of biogas digestate during drying process
- Publication Type
- Contribution to conference
- Authors
- Maurer C; Müller J
- Year of publication
- 2010
- Published in
- Proceedings of the XVIIth World Congress of the International Commission of Agricultural Engineering (CIGR)
- Page (from - to)
- 1-8
- Conference name
- XVIIth World Congress of the International Commission of Agricultural Engineering (CIGR) - Section IV: Rural Electricity and Alternative Energy Sources
- Conference location
- Quebec City (Canada)
- Conference date
- 13-17 June 2010
Digestate occurring during the fermentation of biomass in biogas plants contains high content of major plant nutrients like phosphorus, potassium and nitrogen. Due to the high water content of biogas digestate (90 – 97%) it is not economically justified to transport the digestate over longer distances. Reducing water content of biogas digestate by drying is an option to reduce volume and therefore alleviate transportation costs. However, during drying the digestate emits volatile compounds due to decomposition which are not yet sufficiently known in quality and quantity. Therefore, the objective of this study was to investigate the drying behavior and the change of digestate composition.
Drying was performed in a hybrid solar/waste-heat dryer, which uses solar energy besides waste heat of a combined heat and power unit (CHP) and the exhaust air of a micro turbine. In this experiments 60 t of liquid digestate were applied. Climatic data were measured inside and outside the drying hall. Dry matter (DM) and organic dry matter (ODM) were measured on a daily basis. Furthermore, energy consumption of waste and solar heat were recorded and related to the quantity of dried feedstock. Chemical analysis of total nitrogen, ammonium, phosphate, potassium oxide, magnesium oxide and calcium oxide was undertaken before and after the drying process and losses of nitrogen were calculated. Specific energy consumption dependent on the climatic conditions and most of the energy consumption was covered by the waste heat of the CHP. During the drying process a significant loss of nitrogen was observed.