Slurry manure collection and design of storage system on scaled pig farms

There are about 3.8 billion tons of livestock and poultry manure produced every year in China. How to reusing these wastes has becoming an important issue. In recent years, Ministry of agriculture and rural affairs of China attaches great importance to the treatment and utilization of livestock and poultry manure, and insists that livestock and poultry manure should be mainly used for rural energy and organic fertilizer. At present, slurry manure can be collected by three means in China, called dry-dung cleaning manure, water flushing manure and deep-pit slurry manure. According to the statistics data about the utilization of livestock and poultry manure from the third-party in 2018, the proportion of farms adopting the technology of dry-dung cleaning manure is 88.45%, the proportion of water flushing manure and deep-pit slurry manure is 9.80%, and the proportion of other methods is 1.75%. It is noticeable that dry-dung cleaning is still the main method of manure cleaning in China's farms. Dry-dung cleaning process usually includes 3 steps such as solid-liquid separation, manure composting and waste water treatment, but all the products still need to be returned to the farmland finally. The treatment of solid and liquid wastes separately causes excessive nutrient loss and higher running cost, which is apparently a waste of resources. Compared with dry-dung cleaning manure and water flushing manure, deep-pit slurry manure do not need flushing water and reduced the total amount of slurry manure. Deep-pit slurry manure collected excrement through slatted floor and stored in manure storage pit has some characteristics such as easily collection of feces and urine, low operating cost and high efficiency of nutrient utilization which has been widely used in developed countries such as Europe and the United States. It is a low cost technology for slurry manure treatment and suitable for applying in North China, Northwest China and other regions with sufficient land. In this paper, the collection amount of swine manure, the storage process parameters of slurry manure, the design of storage construction and the cost of investment and operation were studied, which would provide support for the popularization and application of the technology. The results showed that the collection amount of slurry manure in the whole feeding period of each pig is 0.70 m3, and 6 months storage time was needed before the manure was returned to the farmland. When the pH value of slurry manure is acidified to 5.5-6.5, ammonia emission can be reduced by up to 80%. Slurry manure collection and storage facilities are divided into two types: under-floor pit inside the breeding house and outside below or above ground storage tank. There are three methods for slurry manure storage: under floor deep-pit storages, outside below ground concrete storages or above ground tank storages, or a combination of both. Take a scaled farm with 5 000 pigs as an example, the required volume of under-floor pit is 6 600 m3 and the investment need 6.6 million yuan, the required volume of outdoor tank is 4 118 m3 and the investment need 2.06 million yuan, the required volume of under-floor pit combined outdoor tank is 8 214 m3 and the investment need 6.51 million yuan. The cost of manure treatment is 38.3 thousand yuan per year, the cost of manure spreading is 108 thousand yuan per year. All the manure can be returned to 133 hm2 farmland and save cost of chemical fertilizer for about 60 thousand yuan per year. © 2020, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.