The selection and (economic) evaluation of ammonia recycling processes of manure from farms

Nitrogen emissions contribute significantly to climate change, especially in the Netherlands around Natura-2000 areas, and one of the main contributors is manure. However, not only does manure usually have high nitrogen emissions, a lot of it is in the form of ammonia, which in itself is very energy-intensive to create. Therefore MEZT developed a solution to extract ammonia from manure, reducing both nitrogen emissions and emissions from ammonia production. However, what to do with this ammonia after it is extracted was still unknown. Thus, the research question was as follows: Within the context of farms and MEZT's BPMED process, what is the best ammonia recycling process and usage, and is it financially feasible?To answer this, first, all major potential uses for ammonia were identified, after which many uses were discarded immediately due to logical and fairly obvious reasons. Then, the remaining ammonia uses, consisting of mostly fertilizers, fuel cells, and selling it as a wholesale substance, were investigated further. For this, a scoring matrix was made based on a farmer's needs, and all technologies were scored on nine criteria (maturity/feasibility, process profitability, initial costs, reliability/maintenance, ease of use, environmental impact, safety, scalability/compactness).From this scoring matrix, there were three clear top choices: selling as wholesale, ammonium sulphate, and enriched biochar. Since the stream to sell ammonia as a wholesale can be taken from either of the two other processes, a clear choice still had to be made between ammonium sulphate and biochar. After also investigating the effect of manure disposal costs, upcoming RENURE regulations, grant and subsidy differences, the legality of using both substances, and the combination of using it with other streams of the MEZT process, ammonium sulphate came out as the best solution.With this in mind, the final process was designed. Here the potassium stream was also considered and included as it was part of the ammonia stream. The final process is a flexible solution of making ammonium sulphate, potassium sulphate, their (raw) mineral concentrates and aqueous ammonia. This allows for the most flexibility depending on a farmer's needs, while having minimal additional costs and the ability to 'cut out' unwanted parts/processes.Afterwards, an economic evaluation was made. First, precise equipment and operational costs and revenues were estimated, after which it was combined with the overall MEZT solution train to form the final costing and revenues. From this it was determined that the additional parts to process ammonia was relatively cheap compared to the BPMED unit, but nonetheless the entire process was shown to be at least cost-neutral for reducing manure emissions and in many cases even lucrative for a farmer to implement. In the end, due to the new and broad nature of this topic, it was at times difficult to make very accurate estimations (especially for the costing as data is not always available), but multiple sources/methods were always checked and the final choice and financial evaluation was deemed reliable. With this, the conclusion and recommendation was given to proceed with the development of the MEZT solution train to work towards a greener and sustainable future.Mechanical Engineering | Process and Energy Technolog