Feature: Ammonium formation
The main feature of dung is its high protein content. During the decomposition of protein in biogas plants ammonium is released. It inhibits the process of methane formation. Ammonium itself is needed to build bacteria cells. Inhibition occurs when the ratio of carbon to nitrogen less 30:1
There are several ways to solve this problem:
1. Water scrubbing of biogas and returning of sulphuric acid back to the reactor
Protein in the poultry dung gives ammonium and also hydrogen sulphide. Biogas goes through a water scrubber column. The scrubber not only cleans the biogas from sulphur. It's also enreaches the water with the acid.
A small amount of FeCl3 is used as a reagent. The effluent from the water scrubber with pH 3 is returned back into the anaerobic reactor. The acidic effluent helps to fight the ammonia in the reactor.
The described method is the cheapest and the most effective. Water scrubber is 2 in 1 solution.
2. Adding carbon-rich organics like maize silage, fat pulp or cow manure
Adding carbon-rich organics has an effect: the addition of carbon changes the ratio of nitrogen to carbon in the mixture to non-inhibition levels
3. ANA-strip reactors and reagent - technical gypsum
An additional module for wastewater treatment is added to a conventional biogas plant. The effluent is cleaned, and water is recycled. Such an additional module adds a half to the cost to a biogas plant.
However, the plant provides additional benefits in the form of a mineral fertilizer - ammonium sulfate. The ANA-strip reactor is a standard product and produced in large quantities.
There is a direct proportion between the number of birds, dung quantity, and the capacity of the biogas plant.
For example, the Kurma poultry farm (Kazakhstan) has 1 million laying hens, and accordingly, a biogas plant with a capacity of 1 MW was built there.
To get a quotation for a biogas plant, please fill out the questionnaire for egg poultry farms.