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

Abstraction: There are about 3.8 billion tons of livestock and poultry manure produced every year in China. How to reusingthese wastes has becoming an important issue. In recent years, Ministry of agriculture and rural affairs of China attaches greatimportance to the treatment and utilization of livestock and poultry manure, and insists that livestock and poultry manureshould be mainly used for rural energy and organic fertilizer. At present, slurry manure can be collected by three means inChina, called dry-dung cleaning manure, water flushing manure and deep-pit slurry manure. According to the statistics dataabout the utilization of livestock and poultry manure from the third-party in 2018, the proportion of farms adopting thetechnology of dry-dung cleaning manure is 88.45%, the proportion of water flushing manure and deep-pit slurry manure is9.80%, and the proportion of other methods is 1.75%. It is noticeable that dry-dung cleaning is still the main method of manurecleaning in China's farms. Dry-dung cleaning process usually includes 3 steps such as solid-liquid separation, manurecomposting and waste water treatment, but all the products still need to be returned to the farmland finally. The treatment ofsolid and liquid wastes separately causes excessive nutrient loss and higher running cost, which is apparently a waste ofresources. Compared with dry-dung cleaning manure and water flushing manure, deep-pit slurry manure do not need flushingwater and reduced the total amount of slurry manure. Deep-pit slurry manure collected excrement through slatted floor andstored in manure storage pit has some characteristics such as easily collection of feces and urine, low operating cost and highefficiency of nutrient utilization which has been widely used in developed countries such as Europe and the United States. It isa low cost technology for slurry manure treatment and suitable for applying in North China, Northwest China and other regionswith sufficient land. In this paper, the collection amount of swine manure, the storage process parameters of slurry manure, thedesign of storage construction and the cost of investment and operation were studied, which would provide support for thepopularization and application of the technology. The results showed that the collection amount of slurry manure in the wholefeeding period of each pig is 0.70 m 3 , 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 manurecollection and storage facilities are divided into two types: under-floor pit inside the breeding house and outside below orabove ground storage tank. There are three methods for slurry manure storage: under floor deep-pit storages, outside belowground concrete storages or above ground tank storages, or a combination of both. Take a scaled farm with 5 000 pigs as anexample, the required volume of under-floor pit is 6 600 m 3 and the investment need 6.6 million yuan, the required volume ofoutdoor tank is 4 118 m 3 and the investment need 2.06 million yuan, the required volume of under-floor pit combined outdoortank is 8 214 m 3 and the investment need 6.51 million yuan. The cost of manure treatment is 38.3 thousand yuan per year, thecost of manure spreading is 108 thousand yuan per year. All the manure can be returned to 133 hm 2 farmland and save cost ofchemical fertilizer for about 60 thousand yuan per year.