Harmless treatment of dead livestock and poultry turns them into sought-after organic fertilizer

Editor's Note

To advance the harmless treatment of dead animals and explore an effective mechanism for demonstrating and promoting harmless treatment equipment and technology, in 2014 the Agricultural Mechanization Technology Development and Extension Station of the Ministry of Agriculture carried out trials and demonstrations of the advancement, applicability and safety of harmless treatment equipment in 5 provinces (municipalities) including Beijing, Liaoning, Fujian, Shandong and Henan, with the aim of providing a basis for relevant departments to formulate policies and measures and for large-scale breeding farms to purchase and use machinery. As one of the pilot provinces (municipalities), how have Beijing's pilot operations fared after nearly two years of running? A reporter recently went to the suburbs of Beijing for an interview.

In an orchard in Zhangjiawan Town, Tongzhou District, Beijing, grapevines were laden with grapes turning from purple to red. "The fruit has grown especially well this year, with vivid color, sweet taste and considerably higher yield too. This organic fertilizer really works well." Liu Feng, head of the Beijing Bifu Ecological Park, pointed to a bag of powdery fertilizer and told the reporter that this fertilizer is made from processing dead pigs.

To solve the difficult problem of disposing of dead poultry and livestock, in 2014 Beijing selected three breeding enterprises to carry out experimental demonstrations of mechanical technology for the harmless treatment of dead animals. After nearly two years of use, the organic fertilizer produced by these demonstration enterprises has won farmers' recognition.

1. The whole process emits no pollutants at all

Drenched in sweat, with a stench filling the air, busy workers wearing masks dumped dead pigs into a 4-meter-deep pit dug by an excavator, sprinkled white lime at about 1.5 meters from the ground, and then backfilled it... This was the scene as workers of Beijing Taixin Fumin Pig Farming Co., Ltd. handled dead pig carcasses a few years ago. Recalling these scenes, Zhao Hongxing, deputy general manager of the company, still remembers them vividly: "Back then we used deep burial, which was really troublesome and prone to polluting the environment. Deep burial was all done on the open ground of our own pig farm, and the biggest headache at the time was the fear of not having enough land. Just think, if you dig a pit a month, where would all that open land come from?"

But today, Zhao Hongxing's worries are gone. When entering the harmless treatment workshop of the company's breeding stock nursery, the reporter saw a worker in a white epidemic-prevention suit place a whole dead pig from the cold storage into the machine's hydraulic hopper; the hydraulic hopper jerked upward and "fed" the entire dead pig into the machine. "Now it's fine. With this harmless treatment equipment, it takes only 48 hours for these dead pigs to be fully converted into dry organic fertilizer," Zhao Hongxing said happily.

Before the application of mechanical technology for the harmless treatment of dead animals, our country mainly used four methods to dispose of animal carcasses: burial, incineration, carcass decomposition wells, and rendering.

However, each of these methods has its drawbacks. Burial easily causes soil and groundwater pollution and involves complicated procedures; incineration produces thick smoke and odor, pollutes the air and has high fuel costs; carcass decomposition wells produce foul odors and bloody water, easily pollute groundwater and breed disease vectors, and take a long time to treat; the relatively environmentally friendly rendering method also deterred breeding enterprises due to problems such as high equipment investment and operating costs, complex treatment processes and large land occupation.

"Using harmless treatment equipment can effectively solve these problems." Xiong Bo, assistant to the station head of the Beijing Agricultural Machinery Testing and Extension Station, explained, "The principle of this technology is actually not complicated. It mainly uses equipment to cut, mince, ferment, sterilize and dry dead and discarded animals, and by adding special microbial bacteria, the animal carcasses are degraded and converted into harmless powdery organic fertilizer, ultimately achieving batch environmentally friendly treatment and a circular economy."

"Compared with the previous deep burial, treating dead pig carcasses this way is indeed very environmentally friendly, and also very efficient," Zhao Hongxing said. "After 48 hours of treatment, the dead pig carcasses are completely dehydrated, and the water vapor produced during dehydration naturally evaporates." According to him, the exhaust gas generated during equipment operation is discharged only after being filtered through water tank disinfection and deodorizing devices, so the whole process has no odor at all, no residual bloody water or carcasses, and the high temperature can kill harmful pathogens, emitting no pollutants whatsoever.

2. Ecological organic fertilizer is safe, environmentally friendly and highly effective

"Made from these dead pigs, this ecological organic fertilizer can be called the cleanest fertilizer: pollution-free, odorless, does not attract insects, and its fertilizer efficiency is higher than pig manure fertilizer and chemical fertilizer." As a loyal customer of Zhao Hongxing's company's organic fertilizer, Liu Feng, who grows 200 mu of grapes and 100 mu of cherries, commented, "After nearly two years of use, the effect is quite obvious. The fruit grown with this fertilizer has more vivid color and higher sweetness, and the overall yield of grapes and cherries has increased by over a hundred jin per mu."

According to Liu Feng, pig manure fertilizer still needs to be piled and composted for a period after purchase, which takes up space and gives off odor, whereas organic fertilizer made from dead pigs can be applied directly. In terms of application amount, one mu of land generally needs 14 to 15 cubic meters of pig manure fertilizer, while this organic fertilizer usually takes effect with only about 7 cubic meters. "So overall, I think the organic fertilizer made from dead pigs is more cost-effective."

Xiong Bo told the reporter that Beijing has conducted scientific testing on the organic fertilizer produced at the pig farm and chicken farm demonstration sites, and all met the harmless treatment standards. Its organic matter content is about 72%, higher than the national standard of 45%, and it can effectively increase the chlorophyll content in plant leaves and promote photosynthesis.

Of course, organic fertilizer made from dead poultry and livestock currently also faces the problems of low output and difficulty in building a brand during processing and sales. "Our customers for ecological organic fertilizer are mainly repeat customers around us who grow fruit and other cash crops. Because the quantity is too small and demand often exceeds supply, we can only sell to our regular customers," Zhao Hongxing predicted. "If this technology can be promoted on a large scale in the future, I think the market prospects for brand organic fertilizer made through centralized production will be very considerable."

So can the operation of this equipment achieve good economic benefits? On this, Zhao Hongxing did some economic calculations: if auxiliary material costs, electricity costs, labor costs, equipment depreciation and so on are all included, the cost of one full-load harmless treatment run of the 1.4-ton equipment is about 1168.5 yuan, producing 600 kg of organic fertilizer. Calculated at 1 yuan per kg of organic fertilizer, the revenue is 600 yuan. Added to this is the national subsidy of 80 yuan per dead pig for harmless treatment, which is about 800 yuan for roughly 10 pigs per ton, so the comprehensive revenue is 231.5 yuan.

3. It can be promoted at large-scale breeding farms

The equipment looks quite high-tech, but it is very simple to operate. "All kinds of operating data are displayed on the screen, clear at a glance. We only need to set the program in advance, and the whole process runs automatically without anyone watching over it," said Wang Weizhong, deputy general manager of the Doudian Agriculture, Animal Husbandry, Industry and Commerce General Company in Fangshan District, Beijing. "After the machine starts and loading is completed, all we have to do is wait 6 hours and then collect a batch of organic fertilizer degraded from dead chickens."

Zhao Hongxing feels the same way. "Look at that hydraulic hopper; it automatically rises and lowers to load materials, so manual feeding is no longer needed, and after the process is completed it automatically discharges materials in a spiral manner, making bagging convenient and greatly reducing workers' labor intensity. If a fault occurs, the equipment automatically alarms, so after startup no manual supervision is needed. Here, for example, it is the repairman who handles dead pigs on a part-time basis."

"The equipment occupies little space and has low power consumption, greatly reducing investment and operating costs." Xiong Bo told the reporter that the material trough inside the machine uses a double-layer structure, with a heat-conducting liquid filled in the interlayer, so that the materials in the trough are heated evenly and electricity is saved by about 50%.

From the cold storage to the equipment, it is an almost enclosed assembly line, and wireless remote-control operation can also be adopted to physically isolate dead poultry and livestock, which can minimize direct contact between people and dead animal carcasses and produce a good epidemic-prevention effect. Moreover, using cold storage to first store carcasses and then treating them uniformly once enough has accumulated for one batch improves the efficiency of handling dead poultry and livestock. "Now that breeding industry technology is advanced, the mortality rate of dead pigs has been greatly reduced, and most of the dead are piglets, so storing them in cold storage first and then treating them in a centralized way better suits current realities," Zhao Hongxing told the reporter. "The rated batch processing capacity of this equipment is 1400 kg, and we generally start it only once a week."

Adding auxiliary materials such as rice husk powder and corncob is an indispensable part of the organic fertilizer production process. According to Zhao Hongxing's calculations, 1 ton of dead pigs requires about 300 kg of rice husk powder, and the pigs will lose water accounting for 60% of their own weight, finally producing about 600 kg of organic fertilizer.

"After nearly two years of demonstration trials, we believe this technology can be promoted at large-scale breeding farms," Xiong Bo said.