Manure processing offers opportunities for dairy farmers

Livestock farmers will already have a surplus of fertilizer in 2024 and this will only increase until 2026. Innovations in manure processing are happening quickly. According to FarmConsult, part of ForFarmers, there are many options for dairy farmers.

At a meeting at the Voet family dairy farm in Schaijk, North Brabant, organized by ForFarmers, the possibilities for manure evaluation were discussed in mid-October. The topic is clearly alive and well among dairy farmers; more than 75 interested entrepreneurs listened attentively to the speakers.

The biggest challenges in dairy farming were explained by team leader Larson Arendsen Raedt from FarmConsult’s fertilizer legislation and circular agriculture knowledge center. According to him, the evaluation of fertilizers provides opportunities to make the sector more sustainable.

Better use of fertilizers plays an important role in circular agriculture and reducing emissions. For example, Arendsen Raedt mentions the production of energy substitutes and fertilizers. By producing manure from animal manure, approximately 25 cubic meters less manure needs to be removed per hectare. This means saving on costs both for the sale of equipment and the purchase of fertiliser.

“The legislation and regulations determine the framework, but the chain determines the speed with financial incentives,” said Arendsen Raedt. ‘For example, because of the steady flow of milk which benefits the price of milk.’

If you want to compost, it is important that you use fresh compost, continues the FarmConsult team leader. As a result, the combustion engine produces 30 percent more gas per cubic meter of engine. In addition to liquid manure, a small amount of solid material can also be added, such as straw manure from calf pens.

Biogas applications

Depending on the size of the digger, the compost is there for 35 to 45 days. There it is heated to about 39 degrees and mixed. The methane released during this process becomes biogas and can be used in a number of ways. It can be converted into green gas, which can be supplied to the grid. It is also possible to convert it into electricity or heat with a cogeneration unit.

On the Voet family dairy farm, the heat is used, among other things, for the nitrogen stripper. In the fertilizer separator, which is placed after the barrier, the thick and thin fractions are separated.

The thick fraction is used by Brabant livestock farmers as bedding for the stalls. The thin fraction goes through the stripper, where the liquid is heated to more than 70 degrees. This releases nitrogen in gaseous form. This gas is washed with sulfuric or nitric acid, forming ammonium sulphate. This clear liquid is a fertilizer, or regenerative, and can be used by the livestock farmer.

Fertilizer processing revenue model

The revenue model behind different tool processing techniques varies greatly between companies. With a manure digester, the income model depends, among other things, on the investment, the number of cows, the modernization of the machine, the portion and the way you treat the gas. A cow produces around 30 cubic meters of manure per year. The fermentation process produces 900 cubic meters of biogas per cow. If the option is converted to natural gas, that is 600 cubic meters.

It is necessary to convert biogas into natural gas if the entrepreneur wants to put it on the gas network. For most dairy farmers this is only profitable if the farm is of sufficient size. This can be profitable for dairy farmers with smaller farms if they participate in a biogas hub.

A biogas plant is a collaboration between several companies, where the gas is converted into natural gas at one of these companies. On average, between 1,000 and 1,500 euros are earned per cow per year from gas, depending on the size of the company, the price of gas and the sales method.

Nitrogen stripper efficiency

The return on investment of a nitrogen agitator depends on the following factors: investment location, subsidy, removal of fertilizers, energy and acid costs, letting rent and capacity utilization.

To illustrate, calculations were made at the meeting in Schaijk based on an example farm with two hundred dairy cows, one hundred young cows, 80 hectares and manure disposal costs of 25 euros per cubic meter. The difference in machine accounting is then just over 2,000 tons of liquid manure that no longer needs to be removed.

Cost savings

If Renure can be used as a composting plant, the company will save for example more than 80,000 euros in the costs of disposal of manure and compost. In addition, organic matter and minerals such as potassium and phosphate are retained on the farm. This means that more than 14,000 euros are saved in addition to the costs of manure disposal.

A nitrogen stripper can be interesting, especially for companies with a big difference in when they need to release based on phosphate compared to nitrogen. Nitrogen is converted by stripper, but phosphate is not. A nitrogen stripper also requires additional labor and the investment is significant. Therefore it must be determined according to each company whether a nitrogen stripper fits the entrepreneurs, environment and financial space.

In this way, dairy farmers can make good use of recovered manure flow

If manure processing is used on a dairy farm, it is important that the manure streams are used in the composting plan in the best possible way. Then it is good to know how much nutrients are in the fertilizer. For this it is necessary to take samples before the start of the breeding season.

Measure the ratio of organically bound nitrogen to mineral nitrogen and the amount of nitrogen (N), phosphate (P) and potassium (K) in the plant. It is important to know the NPK ratio, it is very different after processing the manure compared to liquid fertiliser. If this ratio is not included in the production plan, there is a risk of a shortage or surplus of important minerals in the soil.

The ratio of organic and mineral nitrogen changes significantly during the manure processing process. After fermentation, an average of 20 percent organic nitrogen is converted to mineral nitrogen. The action of mineral nitrogen is much faster than the action of organically bound nitrogen. If the proportion of organically bound nitrogen in the fertilizer is high, it is important to apply it early in the season because of the residual effect.

If the fertilizer has been through a nitrogen stripper, you will get ammonium sulphate or nitrate. It contains no organically bound nitrogen, but on average three to seven times more than mineral nitrogen. This affects the efficiency coefficient and the method of administration. FarmConsult’s advice is to apply this mineral nitrogen in summer. Due to the residual effect of organically bound nitrogen that was applied to the land before, you use more efficient fertilizer flows.