Gaseous emission from acidified raw and co-digested solid fraction
Balsari P., Cuk D., Dinuccio E., Gioelli F., Rollè L.
Department of Agriculture, Forest and Food Sciences (DiSAFA), Università degli Studi di Torino. Largo Paolo Braccini, 2 – 10095 Grugliasco (To)
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Gaseous pollutants emissions are a major problem associated with animal slurry management and solutions to overcome this issue are required worldwide by farmers and stakeholders. A way to abate emissions from slurry (with special regards to ammonia) is to reduce its pH by adding acids or other acidifying products. This solution has been commonly used since 2010 in countries such as Denmark, and its efficiency with regard to the reduction of NH3 and greenhouse gases emissions has been documented in many studies. Nevertheless, acidification is commonly performed by using strong acids, namely concentrated sulfuric acid. Some limitations to their use, such as their hazards to human health, are important issues that need to be overcome. Furthermore at present, solutions to acidify solid manures (e.g. farmyard manure and slurry separated solid fraction) are lacking. The paper presents the results of a preliminary study performed to assess the feasibility to acidify digested and undigested separated solid fraction by using a commercial powdery sulfur-based fungicide. Raw and co-digested slurry were mechanical separated by a lab-scale screw press device. The sulfur powder (80% concentration) was added to the obtained separated solid fractions at three application rates: 0.5%, 1 % and 2% (w/w). Gaseous emissions were afterwards measured during the storage of the acidified samples and compared to those measured from untreated samples (control). Emission were measured by the dynamic chamber method. CO2, CH4, N2O and ammonia emissions were quantified by a photo-acoustic multigas analyser (1412 Multi-gas Monitor, Innova® Air Tech Instruments, Ballerup, Denmark). Gaseous losses were monitored along 30 and 60 days of storage time for raw solid fraction and digested solid fraction respectively. Results showed a significant reduction of both ammonia and greenhouse gases emission regardless to the sulfur application rate and separated solid fraction type. The highest sulfur application rate (2% w/w) led to a reduction of up to 78% of GHG emission and 65% of ammonia losses from raw separated solid fraction when compared to control. Similar results were achieved from the digested solid fraction, with emission reduction of up to 67% for ammonia and 61% for GHG. Further trials are in progress to evaluate the possibility to acidify the slurry by powdery sulfur prior to mechanical separation in order to abate emission from both the obtained solid and liquid fractions.