First experiences of fertilization in the farm with plasma treated digestate.
In 2018 the first experimental plasma reactor to treat digestate and slurry was installed in a big Northern Ireland farm with a biogas plant and a 750-cow stable.The treatment splits the N2 and O2 molecules, naturally present in the air, and fixes the nitrogen obtained to the free ammonia of the slurry and digestate, to form ammonium nitrate. The process improves the agronomic and environmental characteristics of the matrices, because it reduces ammonia emissions, enriches the fertilizing power and makes nitrogen available for immediate absorption (to read more about this technology: http://coseateam.it/news/closing-the-nitrogen-cycle-nuove-prospettive-per-un-modello-aziendale-virtuoso-di-economia-circolare).
The thesis was assessed by field tests carried out by the Agri-Food and Biosciences Institute (AFBI) and the first results are now published. The tests compared the effects of ordinary digestate and the effects of treated digestate on 72 grass field. Each parcel received one of the treatments with 3 plasma digestate application rates and 3 untreated digestate application rates, equivalent to 100, 200 and 300 Kg N / ha / year. The results demonstrated a significant increase in the dry matter/ ha produced using the treated digestate. The tests with the dose of 200 Kg N/ha of treated digestate produces the same dry matter/ha as the dose of 300 Kg N/ha of untreated digestate; that means a loss of ammonia of 33% in the untreated matrix. Using the quantity of 300 Kg N/ha the absorption of N (Kg N/ha) was 38% higher than the use of the same quantity of untreated digestate. Furthermore, the tests that received plasma-treated digestate gave higher yields than those that received inorganic fertilizer.
Of course, this test has a purely indicative value, since it was carried out in a specific pedoclimatic context. New tests are planned in different environmental situations (Irland, Scotland, other European countries and South Africa) in order to obtain data to make economic evaluation.