Gas permeable membranes (GPM) technology to capture ammonia from gaseous media

GPM technology involves passing gaseous ammonia (NH₃) through a microporous, hydrophobic membrane and concentrating it in an acidic stripping solution. The driving force behind the transfer of NH₃ is the difference in concentration between the two sides of the membrane. This process occurs at atmospheric pressure. Once in the acidic solution, the NH₃ is converted into a valuable ammonium salt fertiliser. This technology can be used to reduce the ammonia content of any gaseous medium.

GPM technology involves passing gaseous ammonia (NH₃) through a microporous, hydrophobic membrane and capturing and concentrating the ammonia in an acidic stripping solution on the other side of the membrane. The driving force behind the transfer of NH₃ is the difference in concentration between the two sides of the membrane. This process occurs at atmospheric pressure. Once in the acidic solution, the ammonia combines with free protons to form non-volatile ammonium ions (NH₄⁺), which are then converted into valuable ammonium salt fertilisers. Various inorganic or organic acids can be used to prepare the acidic solution, such as sulphuric, nitric, carbonic, hydrochloric, phosphoric, lactic and acetic acids (Soto-Herranz et al., 2022a). Additionally, water has been demonstrated to be an effective recovery solution, with slightly lower nitrogen (N) recovery values than acid-based solutions (Soto-Herranz et al., 2021a; Soto-Herranz et al., 2022a). The recovered N is conserved in the form of valuable ammonium fertiliser sources (e.g. ammonium sulphate, ammonium chloride, ammonium phosphate and ammonium lactate), which can be exported off the farm to regions where nitrogen is needed. This helps to avoid environmental pollution of soil, air and water in regions with high livestock density. This technology can be used to reduce NH₃ content in any gaseous medium and has been shown to be effective in capturing NH₃ volatilised in pig and poultry houses, as well as in aerobic composting processes (Soto-Herranz et al., 2021b; 2021c).
Environmental benefits:
The technology achieves the following environmental benefits:
Reduced consumption of energy/raw materials
Energy needs are related to the functioning of the plant to capture ammonia from gaseous media, mainly including air and liquid pumps. The energy consumption required to recover nitrogen from the air using different GPM system configurations corresponded to a range of 1.86–3.84 kWh/kg N recovered (Soto-Herranz et al., 2022b). These results are lower to those of stripping technologies employed for nitrogen recovery from slurry, which have an associated energy consumption between 3.1 and 8.65 kWh/kg N recovered.

Reduced emissions of specific pollutants to air/water/land

The GPM technology applied for ammonia reduction in the air of swine-production sheds resulted in significant improvements in human non-carcinogenic toxicity, human carcinogenic toxicity, marine ecotoxicity and terrestrial ecotoxicity. The use of the GPM system showed improvements due to the use of NH3 in the production of a valuable fertilizer by-product and the consequent reduction in the consumption of synthetic products. The impacts caused by operating the GPM system can be reduced by optimising the ammonia-capture system processes and characteristics (Murcia-Velasco et al., 2023).
When GMP GPM technology was used to treat the exhaust air of a laying hen farm, the following conclusions were drawn from the environmental impact assessment of the system (data available on request):
• Energy consumption was the only factor contributing to climate change, accounting for 75% of the damage (2,557.2 kg CO₂-eq FU-1). This impact could be offset by using renewable energy sources such as solar panels.
• Concerning freshwater eutrophication, when GPM technology was used to treat the exhaust air of a laying hen farm, the avoided production and application of synthetic fertilizers compensated freshwater eutrophication impact.
• Up to 35% of the human toxicity damage was avoided due to the use of this system (31.44 kg 1,4 diclorobenzene eq /FU).
• It is interesting to highlight the positive effect of this technology to the agricultural land occupation, that it is related to the production of a fertilizer using a by-product. More specifically, the ammonium sulphate obtained can be considered a RENURE ((Recovered Nitrogen from manURE) fertilizer, therefore acting, in terms of agronomic efficacy, comparable to inorganic mineral nitrogen fertilisers. So that this product can be applied with the same rules as inorganic nitrogen fertilisers above the threshold of 170 kg N per hectare per year for manure-derived nitrogen established by the Nitrates Directive.
• The obtention of ammonium sulphate and its application as fertilizer in substitution of a commercial fertilizer shows a better environmental performance in terms of urban land occupation and natural land transformation.

Cross-media effects

The GPM technology has no significant negative environmental impact. Its construction does not require any hazardous materials or products. Although the technology is based on the use of diluted acids, a potential spill can be avoided by using a containment tray to collect the acid. No significant residue, noise or odour has been reported (just the odour of manure).

Driving force for implementation

Two important non-environmental issues could stimulate the development of GPM technology. One issue is related to the local economy of rural areas, where livestock farming is an important industry that contributes to maintaining rural populations. Reducing ammonia emissions through this technology could enable the construction of new livestock farms in certain EU countries (such as Spain) or help preserve existing farms and maintain or increase the rural population.
Another issue relates to preserving and redistributing nutrients for agriculture. Currently, a large quantity of imported nitrogen fertilisers is used in agriculture. If the nitrogen product of ammonia trapping (ammonium sulphate) is obtained from manure and redistributed locally, fewer nitrogen fertilisers will be imported. Therefore, the economics of N fertilisation could become more localised, thereby improving the rural economy.

Production data

The GPM technology has been tested on four farms. Firstly, as part of the LIFE Ammonia Trapping project, a pilot plant was tested in two locations: Guardo and Aldealafuente. The first of these was a pig farm (Deporcyl) in San Pedro de Cansoles, Guardo, Palencia, Spain. The prototype was installed inside a building housing 912 sows in a closed cycle. The second location was a poultry farm named La Cañada, located in Aldealafuente in Soria, Spain. In this case, the prototype was located outside a farm housing 8,300 laying hens. At both locations, the prototype operated continuously for eight months. The other two farms are part of the LIFE Green Ammonia project. As part of this project, improvements were made to the design of the pilot plant. The improved pilot plant was tested for 15 months on a pig farm of 1800 animal heads (Agroporcino Manso) in Santa María La Real de Nieva, Segovia, Spain. Furthermore, the upgraded pilot plant underwent testing for 15 months at the Vale Junco poultry farm in Portugal, which houses 12,000 birds.

Associated main production process(es) and product(s): Main production processes: Pig and poultry rearing. Product: Manure/litter

Participant Companies