CN101235388A - An anaerobic fermentation process for joint treatment of manure and straw - Google Patents

Abstract

An anaerobic fermentation process for joint treatment of feces and straw. Firstly, the feces are retting, then mixed with crushed straw and adjusted to a moisture content of 60% to 70%, and then used as bait for earthworm breeding. After the earthworms eat the bait The produced vermicompost is added to the biogas digester for anaerobic fermentation to produce biogas. Through earthworm pretreatment, the present invention solves the long-term technical problems that have long restricted the use of straw as raw material for biogas fermentation, such as stratification of raw materials, floating crusts, difficulty in discharging materials, and poor gas production effect. Vermicompost, as raw material for biogas fermentation, also has the functions of increasing the gas production rate of raw materials, increasing the activity of anaerobic sludge, and enhancing the stability of anaerobic fermentation process, and the production of earthworms improves the economic output of the treatment process.

Description

An anaerobic fermentation process for joint treatment of manure and straw

technical field

The invention belongs to the field of renewable energy development and utilization and environmental protection, and in particular relates to an anaerobic fermentation process for jointly treating manure and straw.

Background technique

Wastes discharged from agricultural production and rural life have become one of the main sources of pollution causing eutrophication of water bodies in my country. According to the data provided in the "Tenth Five-Year Plan for Water Pollution Prevention and Control in Taihu Lake", the contribution rate of agricultural pollution to the main pollutant ammonia nitrogen in the Taihu Lake Basin exceeds 50%. Every year, 320,000 tons of solid waste flows into Dianchi Lake, including 240,000 tons of human and livestock waste. These wastes contain 426.6 tons of total phosphorus and 1167 tons of total nitrogen. Another example is that the pollution in Hangzhou Bay now mainly comes from the vast rural areas in the Yangtze River Basin. Among the total pollution, agricultural pollution sources account for a large proportion. Taking inorganic nitrogen as an example, livestock and poultry manure account for 35%.

At present, among the many agricultural and rural pollution sources that cause water pollution, aquaculture manure and farmland runoff contribute the most to the water pollution load, which has become an important factor that plagues the improvement of the water environment. The control of these two types of pollution sources has become an important issue in improving the quality of water environment. However, many current control measures do not take the agricultural and rural issues related to water pollution as a whole, and most of them focus on governance, ignoring the utilization of resources, so some governance facilities have to stop operating due to lack of economic support.

The development of agriculture and rural areas is inseparable from the "three materials", namely fuel, fertilizer and feed. These "three materials" are directly or indirectly related to water pollution. Farmland runoff pollution is essentially fertilizer pollution. With the continuous improvement of rural living standards, the way of fuel utilization has also undergone major changes, namely From the original burning of straw and other biomass to mainly burning of commercial energy such as coal and liquefied petroleum gas, coupled with the desalination of the feed function of straw, resulting in the waste and incineration of straw. Random stacking of straw in fields and ditches will inevitably lead to a large loss of N and P. If these wastes are developed and utilized as resources through reasonable technical means, while solving the "three materials" problem, the problem of water pollution will also be fundamentally solved.

First of all, as far as the livestock and poultry manure produced by the breeding industry is concerned, the energy contained in the more than 2.5 billion tons of livestock and poultry manure produced in my country every year can be equivalent to about 300 million tons of standard coal. Secondly, the annual production of crop straw in my country is about 700 million tons, which is equivalent to 350 million tons of standard coal. And my country's total coal consumption in 2005 was 2.1 billion tons of raw coal. Therefore, transforming and utilizing them in rural areas can produce high-quality clean energy while solving the water pollution problems caused by them. For example, the conversion of straw and livestock and poultry manure into biogas through anaerobic biological fermentation can not only solve the demand for high-quality energy products in rural areas, but the by-products produced by fermentation can also be used as organic fertilizers. That is to say, the recycling of materials is realized in this way, and the water pollution problems caused by their discharge or disposal will be solved accordingly, thus playing a natural effect.

Both feces and straw are biomass resources, and their energy development and utilization are in line with my country's current strategic demand for vigorously developing bioenergy. As an important resource that affects the future development of mankind, the development and utilization of biomass energy has received unprecedented attention in many countries, especially in Europe and the United States.

The United States has put forward the ambitious goal of making bioenergy account for 25% of its total energy consumption by 2020, reducing carbon emissions by 100 million tons per year and increasing farmers' income by 20 billion US dollars. The European Union also attaches great importance to the development of renewable energy. In 1997, it released the "EU Strategy and Action White Paper", which proposed that by 2010, the consumption of renewable energy in the European Union should increase from about 6% in 1997 to 12%. The utilization amount should reach 200 million tons of standard coal. The announcement of the French Ministry of Agriculture shows that by 2010, France will be able to achieve a 50% increase in renewable energy consumption and 21% of the electricity produced by renewable energy. The British government is recruiting and increasing investment to stimulate the development and utilization of bio-energy, in order to achieve the goal of 10% of energy consumption provided by renewable energy by 2010.

With the continuous and rapid development of my country's national economy, some energy-consuming industries have shown a rapid development momentum, resulting in a significant increase in total energy demand and rising prices, and the frequency of tight energy supply is increasing in some economically developed regions. As an important measure to alleviate the contradiction between energy supply and demand in my country, comprehensively promoting the development of renewable energy such as biomass energy has been highly valued by the state. According to the "Medium and Long-term Development Plan for Renewable Energy" issued by the National Development and Reform Commission in 2006, by 2010 China's renewable energy will account for 10% of the total energy consumption, and the annual utilization of biogas will reach 19 billion m ³ ; Renewable energy will account for 16% of total energy consumption, and the annual utilization of biogas will reach 44.3 billion m ³ . The "Plan" also proposes to take the development and utilization of rural biomass energy as an important measure to develop modern agriculture and build a new socialist countryside.

With the support of national policies, household biogas technology has developed rapidly in my country, but as far as the current development situation is concerned, one of the main problems is that the raw materials used are too single, that is, livestock and poultry manure is mainly used as fermentation raw materials . Straw raw materials are considered unsuitable as fermentation raw materials for household biogas digesters due to problems such as stratification of raw materials, crusting and difficulty in discharging materials during anaerobic fermentation. However, in many rural areas with relatively developed economies in our country, due to the traditional breeding mode, that is, the way of raising livestock in a family has been basically eliminated, which limits the application of this technology in these areas to a large extent. On the other hand, Due to the increasing demand for clean fuels, the pressure on commodity energy supply in these areas is also increasing, and the rising commodity energy prices have also increased the burden on farmers in this regard. At the same time, a large amount of straw resources are discarded in these areas every year, which not only pollutes the environment, but also causes a great waste of resources.

Contents of the invention

The object of the present invention is to provide a process for producing biogas by using earthworms to jointly process straw and manure, and the vermicompost produced as fermentation raw materials.

The purpose of the present invention can be achieved through the following measures:

An anaerobic fermentation process for the combined treatment of feces and straw. Firstly, the feces are retting, then mixed with crushed straw, added water and adjusted to a moisture content of 60% to 70%, and then used as bait for earthworm breeding. The vermicompost produced after the bait is added to the biogas digester for anaerobic fermentation to produce biogas.

The straw is selected from one or more of corn stalks, rice straw, wheat straw, sorghum straw and rice grass. The manure is selected from one or more of pig manure, cow manure, chicken manure, sheep manure, and rabbit manure. When the straw and feces are mixed, the mass of the straw is 30%-50%, and the C/N ratio of the raw material after mixing is 15-25.

The biogas digester is selected from any one of cylindrical biogas digesters, meandering cloth biogas digesters, point-covered trough biogas digesters, separated floating cover biogas digesters, and commercial household biogas digesters.

In the present invention, fresh feces are firstly subjected to stack retting treatment, and the stack retting time can be controlled within 20 to 30 days according to different types of feces. Crush the straw into 1-2cm particles, then mix the composted feces and straw evenly (the mass of straw is 30%-50%, and the C/N ratio of the raw material after mixing is 15-25) and adjust After the water content reaches the range of 60% to 70%, put it into the earthworm breeding bed for treatment. The earthworm breeding bed can be selected to be built in the greenhouse or outside the shed, can be built on the ground, or can be built into a semi-underground. The temperature of the earthworm breeding bed is preferably 15°C to 25°C. In winter, the bed surface can be covered with a film to prevent wind, and covered with straw mats and other materials for heat preservation. Remove the plastic film in summer, cover the bait with 10-15cm of wet grass, and set up a simple pergola for shade and rain. The vermicompost produced after the treatment of earthworms is collected and added to the biogas digester for anaerobic fermentation to produce biogas. Add vermicompost to the biogas tank after adding the inoculation sludge, and then add water to the biogas tank. After adding water, the volume of the fermentation feed liquid should not exceed 85% of the volume of the biogas tank. The process of adding vermicompost should be based on seasonal changes Control the concentration of the fermentation broth, preferably 10% to 15% TS in winter, and 6% to 8% TS in summer. After adding water, cover the movable cover and make a good seal. During the normal operation of the biogas digester, the input and output of the biogas digester adopts an intermittent method, that is, the material is output every 3 to 5 days, and then vermicompost is added again, and the amount of input and output should be equal. The biogas produced by anaerobic fermentation is used as cooking or lighting fuel after desulfurization treatment. The resulting slag liquid can be directly applied to farmland as organic fertilizer.

The anaerobic fermentation process for joint treatment of feces and straw involved in the present invention adopts a low-cost, pollution-free, and easy-to-operate full biological treatment method, that is, the method of earthworm treatment solves the key technical problem that has plagued the utilization of straw anaerobic fermentation for a long time Compared with directly using straw or manure as raw material for biogas fermentation, it has the following four characteristics:

① Vermicompost has good settling properties, so this process solves the long-term constraints of straw as raw material for biogas fermentation, such as stratification of raw materials, floating crusts, difficulty in discharging materials, and poor gas production effect. The raw material problem.

②Using livestock and poultry manure directly as raw material for biogas fermentation may sometimes cause acidification of the fermentation liquid. The pH value of vermicompost is neutral and slightly alkaline, which can effectively avoid such phenomena and make the anaerobic fermentation process more stable. Therefore, it is used as raw material The concentration of the fermentation feed liquid can be increased, thereby increasing the gas production rate of the tank capacity.

③ Vermicompost is a porous particle with a large specific surface area, and has a good ability to absorb and maintain nutrients. It is easy to form a microenvironment suitable for the survival of anaerobic bacteria. Therefore, vermicompost can significantly improve the growth rate of anaerobic microorganisms. Activity, thus laying a good foundation for improving biogas yield.

④ The earthworms produced in the treatment process can be sold as Chinese medicinal materials, fishing bait, etc., which improves the economic output of the treatment process.

Description of drawings

Fig. 1 is the flow chart of the anaerobic fermentation process for joint treatment of manure and stalks of the present invention.

Detailed ways

The following detailed description is only to illustrate the general principles of the present invention, and is not restrictive. Reasonable adjustments and modifications can be made according to the different properties and processing requirements of the raw materials to be processed in the actual application process.

Example 1

The fresh pig manure is firstly retting, and the retting time is controlled at about 25 days. Crush the straw into 1-2cm particles, then mix the retting pig manure and straw according to the ratio of manure: straw = 7:3 (TS) and adjust the water content of the mixed raw materials after adjusting the C/N to 20 rate to around 65%.

Put the proportioned raw materials into the earthworm breeding bed for processing. The earthworm breeding bed adopts the method of building in the greenhouse, the accumulation height of raw materials is 15-20cm, and the temperature in the greenhouse is maintained at 20°C-25°C. Sprinkle water on the raw materials regularly every 1 to 2 days to maintain the moisture content of the raw materials. The species of earthworms is Eisenia chinensis, and the number of earthworms planted is about 8,000 per square meter of worm beds. Collect vermicompost every 15 days, and add new raw materials to the breeding bed at the same time. The collected vermicompost is added to the cylindrical hydraulic biogas digester for anaerobic fermentation to produce biogas. Add vermicompost at a concentration of about 12% TS, and record the biogas production for 7 days continuously when the ambient temperature changes within the range of 25-30°C. After calculation, the average gas production rate of the biogas digester reaches 0.29m ³ /m ³ · d.

Example 2

The fresh chicken manure is firstly subjected to stack retting treatment, and the stack retting time is controlled at about 30 days. Crush the corn stalks into 1-2cm particles, then mix the composted chicken manure and corn stalks evenly at the ratio of manure: straw = 6: 4 (TS) and adjust the C/N to 20, then adjust the mixed raw materials The moisture content is about 65%. Put the proportioned raw materials into the earthworm breeding bed for processing. The earthworm breeding bed adopts an open-air form, and the stacking height of the raw materials is 15-20 cm. The raw material pile is covered with straw to keep warm and keep moisture. Water is regularly sprinkled on the raw materials every 1-2 days to maintain the moisture content of the raw materials. The species of earthworms is Eisenia chinensis, and the number of earthworms planted is about 8,000 per square meter of worm beds. Collect vermicompost every 15 days, and add new raw materials to the breeding bed at the same time. The collected vermicompost is added to the cylindrical hydraulic biogas digester for anaerobic fermentation to produce biogas. The concentration of vermicompost added is about 15% TS, and when the ambient temperature changes within the range of 22-28°C, the biogas production is continuously recorded for 7 days, and the average gas production rate of the biogas digester is calculated to reach 0.32m ³ /m ³ ·d .

Comparative example 1

Add fresh pig manure from the farm to a cylindrical hydraulic biogas digester and stack it for 5 to 7 days to heat up the biogas digester, then add inoculated sludge and warm water to the biogas digester, and ferment the feed after adding water The concentration of the fermentation liquid reaches 12% TS. Stir the fermentation feed liquid evenly and seal the pond. The ambient temperature ranges from 25 to 30°C. After 7 days, the biogas digester still cannot produce gas normally. After testing, it is found that the fermentation liquid is acidified, and clarification is added to the biogas digester. The pH value of the lime water was adjusted to 6.9, and normal gas production began after 3 days, and then the biogas production was continuously recorded for 7 days, and the average gas production rate of the biogas digester was calculated to be 0.23m ³ /m ³ ·d.

Comparative example 2

Crush the freshly harvested corn stalks into 2-3cm particles, add water to adjust the moisture content to about 60%, and then put them in the cement pool for compaction and stacking. After 20 days, take them out and add inoculation sludge, and then add them to the cylindrical hydraulic pressure In the type biogas digester, add warm water to adjust the concentration of the fermentation feed liquid to 8% TS, stir the fermentation feed liquid evenly and then seal the pond. The ambient temperature ranges from 25 to 30°C. After the biogas digester produces gas normally, record continuously for 7 days The biogas production rate of the biogas digester is calculated to be 0.12m ³ /m ³ ·d on average. Under normal feeding and discharging conditions, the gas production effect of the biogas digester decreased significantly after 60 days of operation, and obvious crusting was found after opening the movable cover.

Claims (5)

1, the anaerobic ferment process of a kind of combined treatment of dejection and stalk, it is characterized in that earlier ight soil being carried out stack retting handles, adjust water ratio to 60%～70% afterwards as the bait of vermiculture with adding water after the stalk of pulverizing mixes then, the earthworm wormcast that produces after the bait of searching for food is added to methane-generating pit anaerobically fermenting output biogas.

2, the anaerobic ferment process of combined treatment of dejection according to claim 1 and stalk, when it is characterized in that stalk and ight soil mix, the shared quality of stalk is 30%～50%, the C/N ratio that mixes the back raw material is 15～25.

3, the anaerobic ferment process of combined treatment of dejection according to claim 1 and stalk is characterized in that described stalk is selected from one or more in cornstalk, wheat straw, straw, sorghum stalk, the rice grass.

4, the anaerobic ferment process of combined treatment of dejection according to claim 1 and stalk is characterized in that described ight soil is selected from a kind of or a few section in cow dung, pig manure, chicken manure, sheep excrement, the rabbit excrement.

5, the anaerobic ferment process of combined treatment of dejection according to claim 1 and stalk, the stack retting time that it is characterized in that ight soil is 20～30 days.

Images