The General Office of the State Council recently issued the Opinions on Accelerating the Resource Utilization of Livestock and Poultry Breeding Wastes, clearly stating that by 2020, the comprehensive utilization rate of livestock and poultry excrement and wastewater in China will reach 75% or above. On the basis of promoting the treatment of livestock and poultry excrement and wastewater, we have collected and sorted out seven typical models for the treatment of livestock and poultry excrement and wastewater, in order to play a demonstration role.

I. The mode of collecting all excrement and wastewater and returning them to the field

The excrement, urine and wastewater generated by the farm are collected and stored in the oxidation pond. The oxidation pond is divided into two types: an open type and a film type. The excrement and wastewater are stored in the oxidation pond for harmless treatment, and subjected to farmland utilization during the fertilization season.

Mode features: main advantages: The costs of excrement and wastewater collection, treatment and storage facility construction are low, and the treatment and utilization costs are also low; all the excrement and wastewater are collected, and the nutrient utilization rate is high.

The main shortcomings: The excrement and wastewater storage period is generally half a year or more, and sufficient land is needed to construct the storage facility of the oxidation pond; the fertilization period is relatively concentrated, and specialized mixing devices, fertilizing machines, farmland application pipe networks, etc. are needed; the long-distance transport cost of the excrement and wastewater is high, and it can only be applied within a certain range.

Scope of application: It is suitable for the process of pig farm manure cleaning by water submerging and the process of automatic excrement scraping and backwash for the dairy farm. The total solid content of the excrement and wastewater is less than 15%; and the farmland which is in line with the excrement and wastewater nutrient amount is needed.

A typical case of the large-scale farm excrement and wastewater returning to the field: taking Jiaogang Lake Farm in Anhui Province as an example, the existing cultivated land area is 6,800 mu, mainly planting rice, wheat, soybeans and melons and vegetables. Large-scale pig farms have 13,000 pigs on hand, 13,000 cubic meters of film type oxidation ponds and 40,000 cubic meters of open type oxidation ponds have been built, and the excrement and wastewater storage time exceeds 9 months, and the total investment of the facilities is about RMB 3 million. The liquid manure after the storage is used for integrated water-fertilizer application through the farmland pipe network. Through combination of planting and breeding, the cost can be reduced to increase the benefit by about RMB 900,000.

The returning of the excrement and wastewater to the field is performed by third-party service organizations. Taking Beijing Danqingnuohe Animal Husbandry Technology Co., Ltd. which operates in Shuangcheng District, Heilongjiang Province as an example, based on regional small and medium-sized farms, there are 100 public manure storage pools and 50 manure spraying machines and supporting mechanical devices. 20,000 tons of excrement and waste (the dry matter content is less than 12%) from dairy farms and pig farms in Shuangcheng District, and the collected excrement and wastewater are stored in the closed storage facilities. Before the spring sowing and after the autumn harvest, the high-efficiency devices for returning to the field are used to carry out homogeneous and precision returning to the field according to the soil testing and manure testing formula. The total investment is RMB 14.2 million, including RMB 10.2 million for service stations and transportation vehicles, RMB 4 million for farm excrement and wastewater storage pools, and annual operating costs of RMB 1.1 million. The farm service fee is RMB 200,000, and the manure farmland application fee is RMB 1.12 million, with a total annual income of RMB 1.32 million.

II. The mode of specialized energy utilization of excrement and wastewater

With the main purpose of specializing in the production of renewable energy, it relies on specialized livestock and poultry excrement and wastewater treatment enterprises to collect excrement and wastewater from surrounding farms, invest in large-scale biogas projects, conduct high-concentration anaerobic fermentation, biogas power generation or purification of biological natural gas, use biogas residue to produce organic fertilizer for farmland use, use biogas slurry for farmland use or perform advanced treatment for up-to-standard discharge.

Mode features: main advantages: The excrement and wastewater from the farms are subjected to centralized treatment, reducing investment in small-scale farm excrement and wastewater treatment facilities; professional operation is performed, and energy utilization efficiency is high.

Main shortcomings: the one-time investment is high; the energy product utilization difficulty is high; the biogas output is large and concentrated, the treatment cost is high, and it requires a supporting follow-up treatment and utilization process.

Scope of application: It is suitable for large-scale farms or intensive breeding areas. It has the conditions for biogas power generation or biological natural gas to enter the pipeline network, and it needs the local government’s supporting policies for guarantee.

The typical case on relying on the large-scale farms to perform specialized energy utilization of excrement and wastewater: taking Hebei Jing’an Bio-Energy Technology Co., Ltd. as an example, the company has 200,000 pigs for slaughter per year, has signed manure and urine purchase agreements with 32 pig farms and cooperatives in the county and performs uniform collection and centralized treatment, and the government departments price the excrement and wastewater collection. The enterprise has invested RMB 96.33 million to build a 20,000 cubic meter of biogas project, and treated 800 cubic meters of livestock and poultry excrement and wastewater per day. It can produce 6.6 million cubic meters of biogas per year and has installed 2 megawatts of biogas generator sets. The on-grid price is RMB 0.75 /kWh. It generated 15.12 million kWh of electricity in 2016, and the income from power generation was RMB 11.34 million. The biogas slurry is subjected to solid-liquid separation, and the solid part is used to produce organic fertilizer for sale, the liquid part is used in the near field and made into water-soluble fertilizer. The annual sales income of organic fertilizer is RMB 13 million. The unused biogas slurry enters the urban wastewater treatment plant for advanced treatment and then is up to the standard and is discharged.

Specialized energy utilization of excrement and wastewater by relying on third-party excrement and wastewater treatment enterprises: with Kai Qi Energy Technology Co., Ltd. as an example, most the solid manure in the pig farms in Longyou County is treated by the company. It uses 16 fully enclosed fecal suction trucks to regularly collect solid manure from the farms, with an annual collection of 180,000 tons, which accounts for 72% that of the county. The company has invested RMB 80 million to build an anaerobic fermentation biogas project, forming a 2 megawatt generator set for grid-connected power generation. The annual power generation capacity is 12 million kWh, and the power generation on-grid price is RMB 1.1/kWh, and the annual power generation income is RMB 13.2 million. Biogas residue produces 16,000 tons of organic fertilizer, which is mainly distributed to farmers through centralized government procurement. The annual income is RMB 4 million; the biogas slurry is concentrated and 10-fold concentrated to produce liquid concentrated fertilizer. The annual output is about 15,000 tons, and the remaining 90% of the biogas slurry is subjected to advanced treatment and is up to the standard and discharged.

III. Solid manure composting utilization mode

It is based on solid manure of large-scale farms for breeding pigs, beef cattle, laying hens, broiler chickens and sheep, and after aerobic composting and harmless treatment, the product is used in the near farmland or used to produce organic fertilizer.

Mode features: main advantages: the aerobic fermentation temperature is high, the harmless treatment of manure is thorough, and the fermentation cycle is short; and the composting treatment increases the added value of manure.

Main disadvantages: the aerobic composting process is prone to generate a lot of odor.

Scope of application: It is suitable for large-scale broiler chicken, laying hen or sheep farms and the like where there is only solid manure and no wastewater is generated.

A typical case of production of organic fertilizer in large-scale pig farms: taking Hunan Xinguang'an Organic Fertilizer Treatment Center as an example, the company invested RMB 25 million to build an organic fertilizer production base with an area of over 10,000 square meters and an annual production capacity of 40,000 tons. The pig manure, biogas residue and rice hull powder and other ingredients collected are mixed according to a certain ratio and then are subjected to groove type fermentation or windrow composting fermentation, undergo later period composting, and then are dried and screened to produce the commercial organic fertilizer. In addition to treating about 18,000 tons of solid manure and biogas residue in its own farm, the base also collects and treats 12,000 tons or more of manure or biogas residue from surrounding small and medium-sized farms through 8-15 people. In 2016, the actual output of organic fertilizer was 13,000 tons, the cost per ton of organic fertilizer was about RMB 700, and the average profit per ton was about RMB 100.

Production of organic fertilizer in large-scale broiler chicken farms: taking Sichuan Yuguan Chicken Manure Centralized Treatment Center as an example, the “company + farmer” mode is used to raise broiler chickens, and 350,000 chickens are kept in the farm. The farmers have 30 million broiler chickens for slaughter annually, and all the manure was collected for centralized treatment to produce commercial organic fertilizer. The company invested about RMB 11 million to build a production line with an annual production capacity of 40,000 tons of granular organic fertilizer. The collected chicken manure and mushroom residue and other ingredients are mixed according to a certain proportion, composted and thoroughly decomposed to produce granular organic fertilizer, the price of organic-inorganic compound fertilizer is RMB 3,200-4,000 / ton, and the price of common organic fertilizer is RMB 1,300-1,500 / ton. The cost of chicken manure raw materials is RMB 150-250 / ton, and the transportation cost is about RMB 50 /ton.

IV. Manure litter recycling mode

Based on the features of high content of cellulose in the dairy cow manure and the soft texture, the excrement and wastewater of dairy cows are subjected to solid-liquid separation, and then the solid manure is subjected to harmless treatment by aerobic fermentation and then is recycled as a cow bed litter, and after being stored, wastewater serves as a fertilizer for farmland utilization.

Mode features: main advantages: cow manure is used as the litter instead of sand and soil, which reduces the difficulty of subsequent treatment of excrement and wastewater.

Main disadvantages: As the litter, if it is not subjected to harmless treatment thoroughly, there may be certain biosafety risks.

Scope of application: Suitable for large-scale dairy farms. Typical cases of rapid fermentation of manure to produce cow bed litter: take Tianjin Shenchi Animal Husbandry Development Co., Ltd. as an example. The company covers a total area of 370 mu and has 2,000 cows on hand. The company invested RMB 4 million to introduce a rapid drying system (BRU system) of the Austrian BAUER Group Company. All the wastewater and excrement are mixed and then enter the BRU system, the solid is conveyed to the aerobic solid state fermentation tank through solid-liquid separation to undergo aerobic high-temperature fermentation for about 20 hours, the discharged material is directly used back to the cow bed, and the wastewater can save the cost of the cow bed litter by about RMB 1.5 million throughout the year.

The manure compost is harmlessly treated and the litter is reused. Take a dairy farm in Heilongjiang Shuangcheng Nestle Co., Ltd. as an example. The company has 1,500 dairy cows on hand, including 700 cows in milk. The solid manure after the solid-liquid separation of manure has a moisture content of about 70%. After 8-9 weeks of aerobic fermentation, the bed is backfilled and the wastewater is stored in an oxidation pond with a total volume of 80,000 cubic meters for fertilization in the surrounding farmland. It can save the litter cost by RMB 0.5 per cow per day, and save RMB 270,000 per year.

V. Ectopic fermentation bed mode

On the basis of traditional fermentation bed breeding, the litter is not directly in contact with the pigs, the pig house is free of flushing, and the excrement and urine pass through the slatted floor into the lower layer of litter or transferred to the fermentation tank where the litter is placed outside, and the fermentation decomposition and harmless treatment of excrement and urine are performed, and it can be directly used as an organic fertilizer for farmland utilization after a period of time.

Mode features: main advantages: no wastewater is produced during the feeding process, and the treatment cost is low.

The main shortcomings: large-scale promotion of litter purchase is difficult; the moisture content of mixture of the excrement and urine is high, the fermentation decomposition time is long, and the use is limited in cold regions; and the construction cost of the elevated fermentation bed pig house is high.

Scope of application: It is mainly applicable to pig farms with limited surrounding farmland in the southern water network area. The fermentation bed outside the pig house is suitable for farms with an annual output of 1,000 to 2,000 pigs. The elevated fermentation bed is suitable for large-scale farms.

A typical case of extra-house fermentation beds of medium and small-scale pig farms: Take the Wen family farm mode as an example. There are 500 pigs on hand throughout the year, and there are 1,000 pigs for slaughter. The pig excrement and urine are cleared to the greenhouse outside the pig house. Fermentation beds are in the greenhouse, and wood chips, rice husks and mushroom residue are laid at the bottom. The excrement and urine are evenly spread in and turned by machines (pipes) or labor, and strains are added regularly. The investment in civil construction and equipment is RMB 43,000. Each fat pig sold on the market can increase the organic fertilizer sale income of about RMB 3 to achieve zero discharge of wastewater.

The elevated fermentation bed of a large-scale pig farm: take Guangdong Dongrui Food Group Co., Ltd. as an example. An elevated pig house with a two-layer structure is adopted, the upper layer is used for raising pigs, and the lower layer takes organic litter such as sawdust to consume excrement and urine by means of the principle of microbial aerobic fermentation, to generate organic fertilizer. The construction and equipment investment of a pig farm with 10,000 pigs is about RMB 6.2 million, and the investment in wastewater treatment facilities is reduced by about RMB 1.8 million. Compared with the traditional farming mode, the investment is increased by about 1.1 million. In terms of operating costs, the annual organic fertilizer income is RMB 540,000. Every year, it needs RMB 350,000 of litter and RMB 180,000 for labor costs, electricity costs and other expenses, and the income and expenditure are basically balanced.

VI. Wastewater fertilizer utilization mode

After the wastewater generated by the farms is subjected to anaerobic fermentation or oxidation pond treatment and storage, the harmlessly treated wastewater and irrigation water are mixed according to a certain proportion, water-fertilizer integrated application is performed, and the solid manure is subjected to composting fermentation for nearby fertilizer utilization or subjected to concentrated treatment by others.

Mode features: main advantages: after the wastewater undergoes anaerobic fermentation of the harmless treatment of the oxidation pond, the organic fertilizer water resources are provided for the farmland to solve the wastewater treatment pressure.

Main shortcomings: there must be storage facilities with a certain volume, with a certain area of farmland around; and it needs the construction of an excrement-water conveying pipe network or the purchase of excrement-water transport vehicles.

Scope of application: It is suitable for large-scale pig farms or dairy farms with a certain area of farmland around. In the south, harmless treatment such as anaerobic fermentation for producing biogas should be used in the north. In the north, the oxidation pond should be used directly for storage, and water and fertilizer integrated application is performed during the farmland crop irrigation and fertilization.

A typical case of “orchard-biogas-livestock” water-fertilizer integrated utilization: take the water-fertilizer integrated project of the 1000-mu ecological orchard in the Liangjia River Basin in Yan'an, Shaanxi Province as an example. The project is implemented in accordance with the idea of “fixing the biogas with the orchard, fixing the livestock with the biogas, and promoting the orchard with the livestock”. The total investment of the project is RMB 2.2 million. According to the technical standard of "one kilogram of fertilizer for one kilogram of fruits", a 200-cubic meter biogas project and a 1000-mu water and fertilizer integrated demonstration project in the Liangjia River Mountain Apple Orchard have been built. It can handle 1,800 tons of excrement and wastewater in the Liangjia River Basin livestock and poultry farm, and can produce 1600 tons of biogas slurry per year. It can meet the application of organic fertilizer in 1000 mu of apple orchard in Liangjia River Basin. Through the implementation of the “orchard-biogas-livestock” mode, the livestock and poultry excrement and wastewater in the Liangjia River Basin have been utilized, and the total consumption in the region has been achieved. The organic fertilizer (biogas residue and biogas slurry) has replaced 60% of the fertilizer.

Wastewater undergoes anaerobic fermentation, is subjected to concentrated collection and returns to the field for utilization. Taking Ruotang Village of Longyou County as an example, there are 6 large-scale pig farms in the village, nearly 15,000 pigs. The wastewater is harmlessly treated by anaerobic fermentation, and the biogas slurry matches the 3800 mu planting base in the village. It returns to the field for utilization through concentrated distribution. 18,000 cubic meters of biogas tanks have been built in total, and nearly 18 kilometers of irrigation pipe networks have been laid. About 60,000 tons of biogas slurry is consumed per year, and the fertilizer used is reduced by about 300 tons. Calculated on the basis of saving RMB 150 of fertilizer per mu, the annular cost can be reduced by RMB 500,000 or more, and the farmers have received benefits.

VII. Wastewater up-to-standard discharge mode

The wastewater produced by the farm is subjected to anaerobic fermentation + aerobic treatment and other combined processes for advanced treatment, and the wastewater reaches the Discharge Standard of Pollutants For Livestock And Poultry Breeding (GB18596-2001, in which the concentration of COD is lower than 400mg/L, the concentration of NH3-N is lower than 80mg/L, and the concentration of TP is less than 8mg/L) or local standards and then is directly discharged, the solid manure is subjected to composting fermentation for nearby fertilizer utilization or centralized treatment by others.

Mode features: main advantages: after the advanced treatment of wastewater, the discharge up to standard is achieved; there is no need to build a large wastewater storage tank, which can reduce the land for the excrement and wastewater storage facilities.

The main shortcomings: the wastewater treatment cost is high, and it is difficult for most of farms to bear it.

Scope of application: Applicable to large-scale pig farms or dairy farms with no supporting farmland around the farm.

The advanced treatment and up-to-standard discharge of wastewater in large-scale pig farms: take Zhejiang Meibaolong Boar Breeding Co., Ltd. as an example. The company has 2000 sows on hand, and the high-efficiency solid-liquid separation system, the high-efficiency UASB anaerobic fermentation system, and the four-stage biochemical combined treatment technology and other processes are adopted. The total investment of wastewater treatment center is RMB 8 million. It daily treats 240 tons of wastewater, and the total wastewater treatment cost is about RMB 6.2 per ton. After treatment, the water is up to the standard and is discharged. Part of the water discharged circulates to be used for seedling irrigation, aquatic vegetable cultivation and aquaculture and the like.

Advanced treatment and recycling of wastewater of large-scale pig farms: take Netease Weiyang Anji pig farm as an example. At present, there are about 6,000 pigs in the pig farm. The excrement and urine are collected by “pig toilet”. The toilet is flushed regularly. The collected excrement and wastewater are first subjected to solid-liquid separation, and the separated wastewater is treated by using a "Bio-efficient nitrogen and phosphorus removal (A/O)" + "membrane bioreactor (MBR)" combination process. The total investment of wastewater treatment facilities is about RMB 2 million, the current daily wastewater treatment capacity is about 50 tons, the operating cost per ton of wastewater is about RMB 8.7. The treated effluent can reach COD≤150mg/L and ammonia nitrogen content≤10mg/L, and the final water is recycled as the flushing water for “pig toilet”, which not only achieves “zero emission” but also saves consumption of fresh water.