Manure utilization in pig farms

Reasonable treatment and utilization of pig farm feces and sewage can not only prevent environmental pollution but also turn waste into treasure. Pig manure and sewage treatment methods are directly related to their utilization and feeding processes.

Generally, if the dry manure cleaning method is used, the sewage is relatively small and easy to handle; if the automatic manure cleaning method is used, the amount of sewage is large, and it must first be separated from solid and liquid before being processed and utilized. Pig manure and sewage are often used as fertilizer and energy (biogas), as well as for fish farming, algae farming, etc.

(1) Returning pig manure to fields as fertilizer is an important part of my country's traditional agriculture. The traditional agricultural production is "grain-pig, one fertilizer, one grain" type, that is, more pigs will make more fat, more fat will make more grain. It is a relatively typical ecological agriculture. Returning pig manure to fields plays an important role in improving soil and increasing agricultural output. The method of returning pig manure sewage to the fields is directly related to the manure cleaning process. In some countries in the world, pigs are raised with water to flush the manure. After the manure is fermented, tankers are used for sowing or special machines are used to break the soil and bury it in the cultivated land for application. This method is relatively simple, but it requires sufficient fermentation tanks or fermentation tanks. When pigs are raised using dry cleaning method, the feces can be processed through the self-purification effect of the soil. The soil obtains fertilizer and purifies the feces at the same time, saving processing costs. However, the purification capacity of the soil is limited, and excessive application can easily cause pollution. The fermentation of fresh manure in the soil produces heat and its decomposition products are detrimental to crop growth and development, so the application amount is limited. The amount of fresh manure applied per hectare of cultivated land is 7.5-9 tons. Applying fresh manure after decomposition and composting can solve the above contradiction and improve fertility. During the decomposition of pig manure, the temperature can reach 50 - 70°C, killing most of the microorganisms, parasite eggs and weed seeds in the manure. The treated fertilizer has low water content, no odor and is slow-acting. Fertilizer, safe and convenient to use. The conditions for mature compost are: maintaining an aerobic environment; the moisture content is 40-60; the carbon-nitrogen ratio of the compost material is 26-35:1, and fresh pig manure is 8-13:1. If the carbon ratio is insufficient, add wild grass, Straw supplement. The simple method of decomposing compost is: pile the mixed materials into a long strip on the cement floor or the ground covered with plastic film, or in a cement tank, 1.5-2.0 meters high, 1.5-3.0 meters wide, and 1.5-3.0 meters wide. Depends on the venue. In order to maintain an aerobic environment, a ventilation pipe or a straw handle can be inserted into the middle of the manure pile and sealed with plastic film or mud. It can be used in 15 days or 1-2 months. In economically developed countries, equipment such as compost houses, compost troughs, compost towers, and compost trays are used for composting, which greatly increases the decomposition speed, emits less odor, and enables continuous production. There are also processing methods such as processing pig manure into compound fertilizer (granular fertilizer), stirring and aerating the liquid manure in a manure storage tank, and turning it into decomposed liquid fertilizer through the action of microorganisms.

(2) Biogas production Fecal sewage can be used to produce biogas. Biogas is a mixed gas produced by anaerobic microorganisms (mainly methane bacteria) decomposing carbonaceous organic matter in the feces. Biogas is an energy source that can be used for lighting, fuel, power generation, etc. The fermented biogas residue can be used as fertilizer, and the biogas residue can be discharged into fish ponds for biological treatment. The types of biogas fermentation include: high temperature fermentation (45-55℃), medium temperature fermentation (35-40℃) and normal temperature fermentation (30-35℃). Normal temperature fermentation is commonly used in our country, and its suitable conditions are:

①) Temperature 25-35°C;

② pH 6.5-7.5, it can be used when the pH is low Limestone or plant ash adjustment;

③ Carbon-nitrogen ratio 25-30: 1

④ Sufficient organic matter, generally 1.6-1.8 kg of solid raw materials per cubic meter of biogas tank is appropriate

⑤ Appropriate volume. The volume of the fermentation tank is 0.15 cubic meters per pig. Fermentation efficiency at room temperature is low. It is only a primary treatment. The biogas slurry and biogas residue need to be further processed, otherwise it may cause secondary pollution.

If medium or high temperature fermentation is used to improve gas production efficiency and shorten fermentation time, it can also reduce the difficulty of secondary treatment and reduce secondary pollution. In the north, the application of biogas produced from pig manure is limited due to low temperatures, but it is widely used in the south.