Animal manure waste solutions

INTRODUCTION

Animal manure waste, that’s livestock and poultry manure waste mainly refers to a type of rural solid waste generated in livestock and poultry breeding, including pig manure, cow dung, sheep manure, chicken manure, duck manure, etc.

Impact of animal waste on the environment

(1) The impact of animal manure waste on the environment is mainly caused by the large amount of excreta and waste entering the environment due to improper or improper disposal of livestock and poultry.

(2) The main ways that animal wastes enter the environment and cause pollution:

First, during the storage and transportation of waste, nutrients are lost due to the washing and washing of rainwater;

Second, the volatilization of unstable substances during the storage and disposal of animal waste;

Third, the direct discharge of wastewater, waste gas or solid waste during the production and processing of livestock and poultry will affect water sources, soil and air to varying degrees.

Air pollution

The pollution of animal manure to the air is mainly the malodor, harmful gas and dust carrying pathogenic microorganisms caused by anaerobic decomposition of organic matter in the manure. Noxious and harmful gases mainly include NH3, CH4 H2S, (NH4) 2S and skatole.

Studies have shown that 20% to 30% of the nitrogen in poultry manure is ammonium nitrogen, which is volatile and lost. The volatilization of NHa raises the pH value of rainwater, so that more SO2 is dissolved in the rainwater to form (NH4) 2SO and (NH4) 2SO4 is oxidized in the soil to release HNO. And H. SO increased the amount of acid deposition by 2.5 times. Pathogenic microorganisms are mainly bacteria and viruses. A large number of pathogenic microorganisms in the air are likely to cause some epidemics, seriously affect production and economic benefits, and endanger the health of surrounding residents.

Water pollution

(1) Water pollution from animal wastes is also becoming more and more serious, mainly manifested by organic pollution, N and P pollution. Farm wastewater is mainly urine and washing wastewater. It is a high-concentration organic wastewater with large pollution load, concentrated discharge, and difficult purification treatment. The impact on the agricultural ecological environment and water environment plays a leading role in animal husbandry.

(2) Practice has shown that untreated manure contains a large amount of nutrients such as N and P and flows into rivers and ponds, which can cause eutrophication of water bodies, cause algae to multiply in water, reduce dissolved oxygen, and cause fish death. In addition, the feces of livestock and poultry also contain a large number of pathogenic microorganisms. The entry of organisms into the water body will affect the water quality, cause aquatic organisms to become diseased, and endanger human health.

Soil pollution

According to measurements, poultry manure contains 21 trace amounts of aluminum, barium, calcium, chromium, tin, copper, iron, potassium, magnesium, platinum, sodium, nickel, chlorine, phosphorus, lead, sulfur, aluminum, vanadium and zinc. element. When these substances enter the soil and exceed the environmental capacity, environmental pollution will occur.

The effects on soil physical and chemical properties are mainly the accumulation of organic matter and the increase of cation exchange capacity after livestock and poultry manure is applied to the field, which causes the accumulation of inorganic salts, and the non-removable phosphoric acid in the soil accumulates in the lower layer of the soil, causing soil compaction.

Biological pollution

Livestock and poultry manure and waste water contain a large number of pathogenic microorganisms, pathogenic bacteria, parasite eggs and so on. Practice has shown that because livestock and poultry manure is not treated in a timely manner, mosquitoes and mosquitoes are breeding in the environment, the number of pathogens is increased, the amount of bacteria is increased, the pathogens and parasites are spread, and eventually the spread and development of livestock and poultry infectious diseases and parasitic diseases .

Current situation

With the rapid development of China’s livestock and poultry breeding industry, especially in suburban, rural, industrial and mining areas, the scale of livestock farms is getting larger and larger, the degree of intensification is getting higher and higher, and the direct discharge of a large number of livestock and poultry manures has caused the deterioration of agricultural ecological environment.

The scale and output value of China’s aquaculture industry have undergone tremendous changes in recent years. Many large and medium-sized intensive farms have been established in the suburbs. The number of livestock and poultry has soared and the amount of manure has increased. The discharge of livestock and poultry manure has become one of the three major sources of water pollution alongside industrial wastewater and domestic sewage. With the further development of the aquaculture industry, the discharge of livestock and poultry manure will further increase, and the resulting environmental pollution will be more serious. Livestock, poultry and manure contain a large amount of organic matter that is not digested and absorbed by animals, and it is harmful to the atmosphere, water and soil.

The use of traditional livestock and poultry manure is the organic fertilization of livestock manure and the reuse of livestock manure. The use of livestock and poultry manure can be used as a source of energy in addition to composting and biodegradable methods to achieve feed utilization. The methods of traditional energy utilization have their own drawbacks, such as incineration and heat production, because of the high moisture content of the manure and the difficulty of drying, it takes a lot of energy to convert into fuel. If it is not fully utilized, it is easy to cause air pollution; For biogas utilization, how to improve biogas has not been solved; Power generation uses the livestock manure to be incinerated in a non-polluting manner, and then power generation, and the ash generated during the incineration can also be used as a high-quality fertilizer. The use of fecal combustion replaces non-renewable resources such as coal, oil and natural gas in many ways. It not only saves resources but also protects the environment. It has multiple prospects and has broad prospects. But how to increase the power generation rate is a key.

Animal manure waste treatment technology

Reduction and harmless technologies

Reduction is the use of certain technologies to reduce the volume or mass of the waste to facilitate transportation and disposal.

Harmlessness is the elimination or removal of harmful substances, such as sterilization and deodorization, through certain technologies.

(1) Incineration method

Because animal waste contains organic matter, similar waste incineration treatment technology is used to ash it to achieve the purpose of reducing and killing harmful pathogens. However, harmful gas is generated during the process, and many nutrients are lost. At the same time, it consumes a lot of energy and has a large investment, so it is not easy to promote.

(2) Drying method

The drying method uses heat energy, solar energy, wind energy and other energy to treat livestock and poultry manure, so that animal waste can remove most of the water in a certain period of time. The purpose of drying is not only to reduce the moisture in the feces, but also to achieve the effects of deodorization and sterilization. Therefore, dried animal and poultry manure greatly reduces environmental pollution. In addition, dried animal manure can be processed into granular fertilizer or used as feed for livestock and poultry, which has multiple uses.

According to different heat sources and heating methods, the drying methods are divided into natural drying, high-temperature rapid drying, and mechanical drying.

Chickens have a short digestive tract and poor absorption capacity. Most of the nutrients in the feed (about 70%) are not digested and are excreted in the form of feces. Therefore, chicken manure is often processed at home and abroad. Although the drying method has many advantages, it can only focus on solving a certain aspect of the problem, and cannot consider the problem from the perspective of the entire ecological environment system, so it is difficult to fundamentally solve the problem of environmental pollution.

(3) Deodorization method

At present, the odorous gases generated from livestock manure are mainly attributed to sulfur compounds, nitrogen compounds, volatile fatty acids and ketones. It is generally believed that ammonia, carbon dioxide, methane and hydrogen sulfide are the main causes of air pollution and odor.

Formalin, ethylene, sodium bicarbonate, methyl bromide and other agents were added to the livestock and poultry manure to kill the germs and reduce the volatilization of ammonia. The processed products were used to feed ruminant livestock. However, the large one-time investment in chemical treatment technology and high product costs make it difficult to obtain good economic benefits and cannot be accepted by the market smoothly.

Comprehensive technology

Generally speaking, technologies such as drying and deodorization have only achieved the purpose of waste reduction and harmlessness, while comprehensive technologies can not only reduce waste and reduce harmlessness, but also use the resources in it. Oxygen compost, fermentation, etc.

(1) Composting method

Composting is one of the effective methods for treating various organic wastes. It is to stack solid organic wastes such as animal manure in a certain proportion, adjust the C / N ratio of the compost materials, control the appropriate moisture, temperature, oxygen and pH. Biochemical reactions under the action cause natural decomposition, and as the temperature of the compost increases, the pathogens, eggs and pupae are killed. The treated material is used as a high-quality organic fertilizer.

(2) Fermentation

Biological treatment technology is a technical method that uses microorganisms to decompose organic matter in livestock and poultry manure so as to achieve harmlessness and resource utilization. It is an effective and economical technology method for treating livestock and poultry manure. Utilizing microorganisms widely existing in the natural world and controlling appropriate conditions will not only enable the organic matter in livestock and poultry manure to be fermented and rotted to produce organic fertilizer, but also to obtain biogas. According to the different requirements of the microorganisms acting on oxygen in the treatment process, biological treatment can be divided into anaerobic biological treatment and aerobic biological treatment.

(3) Anaerobic biological treatment method

The anaerobic biological treatment method refers to a biological treatment method that mainly decomposes and stabilizes the organic matter in livestock and poultry manure by anaerobic microorganisms without providing free oxygen, that is, anaerobic fermentation method. Anaerobic treatment is currently an important environmental technology for the treatment of livestock and poultry manure.

Its advantage lies in the fact that it can obtain available energy and materials while eliminating the environmental pollution of livestock and poultry manure. It has the common point with aerobic treatment that it can be completed with the participation of microorganisms.

The use of natural or inoculated microorganisms converts organic matter to carbon dioxide and biogas under hypoxic conditions. The advantage is that the malodor of the final product is reduced, and the biogas produced can be used as an energy source. The disadvantage is that the ammonia volatilization loss is large, and the volume of the treatment tank is large.

(4) Aerobic biological treatment method

The aerobic biological treatment method refers to a biological treatment method that mainly decomposes and stabilizes the organic matter in livestock and poultry manure under the condition of providing free oxygen, mainly aerobic microorganisms. For example, artificial wetland, solar greenhouse fermentation, dynamic aerobic fermentation, etc. High temperature aerobic composting method is one of the most promising, widely used and most promising methods for the treatment of livestock and poultry manure. It is an effective method for the harmless and safe treatment of livestock and poultry manure.

The advantage of using high-temperature aerobic composting method to treat livestock and poultry manure is that aerobic high-temperature fermentation has the characteristics of fast decomposition of organic matter, complete degradation and uniform fermentation. The fermentation temperature is generally 55 ~ 65 ℃, the dehydration speed is fast, the fermentation period is short, and the organic matter is completely decomposed. The moisture content can be reduced to 40% to 50% at about 15 days, and the killing effect of pathogenic bacteria, parasite eggs and weed seeds is also good. The final product treated has less odor and is drier, which is easier to package and fertilize. However, the appropriate moisture content of the initial fermentation should be 55% to 65%. Ventilation or stacking is required. At the same time, the volatilization of ammonia during the fermentation will produce odors, reduce fertilizer efficiency, and require large compost sites.