More than H2S removal - The monetization of ammonia in anaerobic digestate.
If you have read my posts before in discussing biogas, then you are probably familiar with anaerobic digesters and the ammonia and H2S that they contain. H2S removal is obviously important, but many of the customers that I have talked to are skeptical on removing the ammonia from their digestate. To many, it seems simpler to simply land apply the digestate on their fields. However, there is a lot of ammonia that is being lost to land applications. Approximately, 35-60% of the ammonia in the anaerobic digestate is lost to volatilization, meaning that it evaporates from the liquid digestate and goes off into the atmosphere [1].
As more anaerobic digesters are built worldwide, this means that these ammonia emissions that once seemed small will become very significant. The American Biogas Council estimates that there is currently a potential for 17,000 sites for new anaerobic digesters, compared to the 2,500 existing facilities [2]. An anerobic digester with 100,000 gallons/day [378,540 L/day] with 2,000 mg/L of ammonia in the digestate would produce approximately 1,575 lb/day [714 kg/day] of ammonia. Building just 1,000 of these would produce 787 tons/day of ammonia which would be similar to that of a large commercial ammonia plant. Emitting this much ammonia can be a health hazard to the surrounding communities and contribute to acid rain. But fortunately, there are also more efficient ways to use that ammonia that can maximize the amount of revenue for your anaerobic digester facility and help lower ammonia emissions.
One way that this ammonia could be utilized is by using the BioSWAATS process to create ammonium thiosulfate. The ammonia from the digestate can be stripped out in a variety of methods, such as a sour water stripper. That ammonia then will react with sulfur dioxide and H2S to produce ammonium thiosulfate.
With the BioSWAATS process, the fertilizer that is produced is a commercial grade fertilizer with a well-established and in-demand market. I have discussed this quite a bit in previous articles, but there is a current market of 1.8 million tons in the United States. The market demand is increasing globally as well, particularly in the Americas, Europe, parts of Asia, and Australia. This means that most anaerobic digester projects should have no difficulty finding a home for the fertilizer that they produce.
Ultimately, the BioSWAATS process is a great way to produce low-carbon ammonia fertilizers and boost revenue for your anaerobic digester facility.
Do you have an anaerobic digester or other operation that you would like the remove ammonia and/or H2S from and make a marketable fertilizer produce? Contact me at michael.j.ray@thiosolv.com. I can take a look at your stream values and provide a basic revenue model to determine what revenue you could get from producing ammonium thiosulfate.
Also, for more articles like these discussing technology, fertilizer, and updates on ThioSolv and the industry in general, make sure to subscribe to this SubStack to keep up to date with the latest happenings.
[1] E.D. Vance, P.C. Brookes, D.S. Jenkinson; “An extraction method for measuring soil microbial biomass’ C; Soil Biology and Biochemistry; Volume 19, Issue 6, 1987; Pages 703-707,
[2] https://americanbiogascouncil.org/biogas-market-snapshot/