EMISSIONS OF NH3, CH4 AND N2O DURING STORAGE AND AFTER APPLICATION OF UNTREATED AND ANAEROBICALLY DIGESTED SLURRY

Abstract

The paper presents the investigations results of the effect of anaerobic digestion on emissions of NH3, N2O and CH4 during storage and after application of slurry. Dairy cattle and pig slurry was stored in concrete tanks (12 m3) over a period of 100 days. Gaseous emissions were collected continuously by a large open dynamic chamber. Gas concentrations (NH3, N2O and CH4) were analysed by high resolution FTIR-spectrometry. After storage, the slurries were surface applied on permanent grassland. NH3 emissions were followed for two days by a large open-dynamic-chamber. N2O and CH4 emissions were quantified with closed chambers until day 20 after application. 65 – 95 % of net total NH3 emissions were lost after slurry application. NH3 abatement will therefore be effective, if low emission application techniques are used. This is especially important when anaerobically digested slurry is applied. More than 90 % of net total CH4 emissions from untreated slurry were lost during slurry storage. Anaerobically digested slurry still emitted methane during storage. These emissions can be totally avoided if the secondary fermentation tank and the slurry store are connected with the gas bearing system of the biogas plant. Then, CH4 produced in these tanks is collected and used as renewable energy source. In conclusion it can be assumed that biogas plants will play a major role in the reduction of greenhouse gas emissions as they generate renewable energy and reduce CH4 emissions during manure storage. Furthermore, anaerobic digestion improves the fertiliser value of animal manures.