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Nutritional Components And Dewatering Methods Of Cow Dung



Biological fermentation of cow dung can increase the protein content in cow dung. And reduce the content of cellulose to increase the value of nutrients. The quality of different cow dung varies greatly, which greatly impacts the fermentation effect. At the same time, the collection method also directly affects its quality. The moisture content of cow dung, especially cow dung, is relatively high, generally around 85%. Biological fermentation requires a moisture content of 65% to 70% to meet the oxygen supply for aerobic bacteria production.

Commonly used drying methods are only suitable for summer and autumn in this region. Moreover, when cow dung is dried in the sun, the dry crust on the surface affects the evaporation of internal water. Dried cow dung forms clumps and is difficult to mix with other substances during fermentation. It often needs to be dried and then crushed. Other physical methods are either difficult to remove moisture, are time-consuming and labor-intensive, and are not easy to operate on a large scale. This screening test was conducted in order to explore a fast and easy dehydration method.

Comparison of cow dung dehydration methods

  • Collect the dung of dairy cows and beef cows (the feeding standards of the two types of cattle are the same), and measure the nutrient content of the dung feed after drying.
  • Collect fresh manure from the cow bed manure ditch in the dairy farm and fresh manure from the sports ground, dry it in the sun and measure its nutrient content.

Method comparison

  • Cloth bag extrusion method: Cow dung is wrapped in double layers of cotton cloth and squeezed by hand.
  • Centrifugation method: Put cow dung into a centrifuge tube, centrifuge at 4000r/min for 30 minutes.
  • Suspension centrifugation method: Wrap the cow dung in filter paper, hang it in a centrifuge tube with gauze, and centrifuge at 2000r/min for 30 minutes.
  • Cow dung dewatering machine: After the cow dung cloth is colored, use a jack to squeeze it.
  • Vacuum filtration method: Put the cow dung into a Buchner funnel and vacuum filtrate it.
  • Sun drying method: Cow dung was placed on the cement floor with a cloth mat and dried under direct sunlight as a control.

Determination of nutritional content of cow dung

  • Determination of moisture content in cow dung: The cow dung is dried at 60°C to constant weight and the moisture content is measured (drying method).
  • Determination of nutrient content: crude fiber (measured by acid-base method FIWE3/6 cellulose analyzer), crude protein (Kjeldahl method), true protein (Kjeldahl method) content and ash content (ignition method).

The results show that there is a big difference in nutrients, and dairy cow manure is better than beef cow manure.

TypesCollectNutrient composition
Crude proteinCrude celluloseAsh content
Cow manureInside the cowshed12.4623.4515.35
Sports ground11.7822.9532.48
Fattening beef manureInside the cowshed10.6325.6518.72
Inside the cowshed10.2226.3230.27

Effects of different dehydration methods on cow manure

  • Cloth bag extrusion method: The separation effect is poor, a small amount of water is squeezed out, and the consistency is thick. After extrusion, the moisture content still reached 82.6%, and the dry matter loss reached 15.4%.
  • Centrifugation method: The separation effect is average. The liquid in the upper layer of the centrifuge tube is thin and the lower layer is thick. The dry matter content after centrifugation was 20.8%, and the dry matter loss was 12.8%.
  • Suspension centrifugation method: good separation effect, thin liquid, no loss of dry matter. And the dehydration rate is high (the dry matter content after centrifugation reaches 29.4%, which meets the fermentation standard requirements. However, the dry matter loss rate is high, reaching 23%.
  • Cow dung drying machine: The separation effect is very good, the processing is simple, and the dry matter content after extrusion is 60.5%.
  • Vacuum filtration method: The effect is average, and a small amount of water can be separated. Dry matter content and dry matter loss were 17% and 18% respectively.
  • Natural sun drying method: This method is low-cost and simple to operate. There is no dry matter loss, but it is greatly affected by weather. This area is only suitable for summer and autumn. And it can easily cause environmental pollution after drying. In addition, when cow dung is dried, the surface becomes dry and crusty, which affects the evaporation of internal water. Dried cow dung forms clumps and often needs to be dried and then crushed during fermentation.

Analysis and Discussion

The use of high-temperature bacteria for aerobic fermentation in cow manure fermentation is a new treatment method that is suitable for large-scale production. Cow dung undergoes aerobic fermentation. The odorous and harmful substances in the raw materials are quickly degraded by biochemical oxidation into odorless and harmless substances. The quality of cow dung as a raw material for fermentation is essential. Dairy cow manure is better than beef cow manure, and it should be fresh and pollution-free when collected. The method of separating cow manure before aerobic fermentation is urgently needed to be researched and solved. It will also be directly related to industrial production methods and promotion and application. The test data shows that suspension centrifugation is the best method for dehydrating cow manure. The water separation rate is high, and nutrients are not lost at the same time.