An air treatment system that reduces ammonia emissions and produces ammonium sulfate

The Gas Loop Operational Group, thanks to the experiences and results achieved by Ammonia Washing Machine (https://ammonia.crpa.it/), has implemented and brought the prototype system from the technological level it was at (TRL 6) to a TRL level 8-9, a real system, complete and ready for applicability. Gas Loop promotes a virtuous cycle (Loop) of nitrogen which, starting from the capture of ammonia, cascades into an increase in the environmental sustainability of pig farming: the recovered ammonium sulphate allows the reduction of industrial fertilizer inputs, thus avoiding greenhouse gas emissions generated by their production; the greater animal welfare and health, due to the lower presence of ammonia in the rooms, increases pigs performance by reducing the carbon footprint of the kg of meat produced. The results achieved by Gas Loop have demonstrated the benefits of the pigsty air treatment system with ammonia capture and recovery. Among the 4 operating methods tested previously, Gas Loop developed and brought to maturity the one that had proven to be the most promising and specifically the treatment of the air sucked from the under-slatted-floor through holes drilled in the side wall of the building lower level than the walking surface. In this way, the ammonia emissions developed by the slurry present in the cracked area are captured and prevented from spreading into the environment above which hosts the animals. The treatment is based on the chemical absorption of ammonia by backwashing with an acid reagent in a tower with packing bodies. Sulfuric acid (H2SO4) reacts with ammonia (NH3) to form a stable suspension of ammonium sulphate ((NH4)2SO4) which accumulates in a tank at the base of the washing tower. The treatment system was implemented with sensors and logic for continuous operation. The recovered nitrogen, resulting in compliance with EU Regulation 2019/1009, can be valorised as a mineral nitrogen fertilizer on the same farm or marketed (Nutrient Recovery and Reuse), thus avoiding greenhouse gases (66 t CO2eq/t p.v. per year) deriving from the production of equal quantities of industrial nitrogen fertilizer. Gas Loop, by limiting ammonia emissions, is effective in reducing the acidification impact and the formation of particulate matter compared to the control, by 21% and 17% respectively. The suction of air from under the slatted floor allows significant emission reduction to be achieved with reduced treatment flow rates (14 m3/h per item). The treatment improved indoor air quality, reducing the average concentration of ammonia in the treated room by 62% and emissions by 54%.