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 exceeds certain limits.
There are several ways to solve this problem:
1. Dilution with water or sewage
According to the well-known playful proverb among scientists “Solution for pollution is dilution”. Addition of water leads to decrease in ammonium concentration. Dilution of dung with water is also a solution for removal of mineral sediments before input to the reactors. On the other hand, this leads to an increase in reactor volumes.
The second disadvantage of this method is the presence of effluent that need to be discharged onto filtration fields or in sewage treatment plants. If the problem with effluent is solved, this processing method is preferable as it is the most inexpensive.
2. Adding carbon-rich organics liek maize silage or fat pulp
Adding carbon-rich organics has two effects: First, the addition of carbon changes the ratio of nitrogen to carbon in the mixture to non-inhibition levels and second, water in the additional substrate reduces ammonia concentration.
Such methods are very common in Europe, the maize zone, and where the environmental legislation does not allow dilution with water. The disadvantage of the method is the significant increase in the project scale and a doubling of the price.
3. ANA-strip reactors and reagent - technical gypsum
In fact, this method is very similar to the first method described above. 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.