Choice of cattle manure removal system depending on manure physical properties

Abstract

Cattle manure is a mixture of solid and liquid animal excrement, bedding material, process water and feed residues. Essentially, this is a polydisperse suspension, the density and viscosity of which depend on the manure composition and the time it stays in the livestock house. Animal excrement is the most unstable manure component; its composition varies with animal diets and productivity. The study aim was to identify the optimal technical device for removing manure from the livestock house with due account for the physical properties of cattle excrement/manure. At the first stage, the mass of manure produced and its moisture content were calculated by the mass balance method, taking into account the diets, animal productivity, and the mass of moisture-absorbing material and process water, which gets into manure in the animal house. At the second stage, the optimal technical device for manure removal was identified, its parameters and technical and economic indicators were determined. Calculations were made for a cattle complex with the total stock of 1249 heads with the loose housing of animals on sawdust bedding. The estimated daily output of manure was 56 t with the integral moisture content of 90 %. After the review of different manure removal systems, the hydraulic scraper unit, with the scraper moving in steps, was found optimal for the calculated manure properties. It ensured 98 % or above manure removal, the specific energy requirement of manure transportation within 0.3-0.5 kWh·t-1, and error-free life of at least 700 hours. Under the manure canal width of 3400 mm, depth of 200 mm and length of 75 000 mm, the scraper height of 180 mm, and the moving speed of 4.3 m·min-1, the power consumption of one scraper ranged from 1.28 to 1.52 kW. Under the given moisture content of the manure removed and the cleaning interval of 4 hours, the maximum length of manure heap transferred in the canal for a distance of 50-60 m was 3.4 m. The average productivity of the scraper unit was 4.3 t·h-1