Background In Europe, the farming and livestock sectors contributed 94% of the total ammonia (NH3) emissions in 2011 (EEA, 2014). Although this figure showed a reduction of 26% from 1990 to 2011, more effort is required to reduce these emissions. In some countries, such as Spain, they have actually increased. Ammonia emitted to the air, soil and water causes environmental problems, such as eutrophication and acidification. The Directive on National Emission Ceilings (NEC) for certain atmospheric pollutants established ammonia as a priority concern. According to various investigations, it has been estimated that a 50% decrease in ammonia emissions, by means of range of technologies, could greatly benefit human health. Objectives The LIFE AMMONIA TRAPPING project will develop an innovative and sustainable solution for reducing ammonia emissions from animal husbandry excretions. In particular, the project will implement an anaerobic digestion and composting process, using devices that capture ammonia, to produce nitrogen fertiliser. The process will also decrease the energy necessary to ventilate the installations. The technology, which has a high potential for replication, will be demonstrated on farms by treating pig slurry (raw and digestate) and hen excretions. The project contributes to the implementation of the Nitrates Directive, the Water Framework Directive, the NEC Directive and the Directive on ambient air quality and cleaner air for Europe under which ammonia is considered a particulate matter precursor. Specific project objectives are to: Design and construct two mobile prototypes that absorb ammonia using gas-permeable membranes, a pioneering technology developed and tested at laboratory scale by the Universidad de Valladolid (UVA) and the Instituto Tecnológico Agrario de Castilla y León (ITACYL); Determine the environmental, technical and economic viability of the prototypes; Characterise the concentrations of purified streams (gas and liquid), to check that air quality and effluents have improved; Evaluate the economic and commercial viability of the added-value fertiliser produced; Develop an action plan to transfer the results to other European countries with intensive livestock industries; Monitor the prototypes from the environmental, social, technical and economic point of view; and Develop tools for boosting the transferability of the technology. Expected results: A sustainable excretion-management solution for the livestock sector by reducing ammonia and particulate emissions, reducing eutrophication potential in rural areas, and by exporting nitrogen surpluses from areas with high livestock density to areas with high demand for nitrogen fertilisers; Defined installation protocols and operation manuals for the prototypes to facilitate further installations; 60-80% reduction in the concentration of ammonia in liquid manure (with potential reductions in the emissions of ammonia), catching between more than 150 mg NH4+/litres per day, for a concentration in the liquid manure between 1 000 and 300 mg NH4+/l; Reduction of more than 70% in ammonia content of anaerobically co-digested liquid manure; More than 70% concentration of gases (porcine and poultry installations, and composting process), with rates of ammonia trapping of 1.3 gm-2/day; and Fertiliser production: 214.3 l from swine manure, 571 l from digestate, 20.8 l from poultry litter and 20.8 l from composting (785.3 l in total from the liquid manure and 62.4 l from the gas).