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Large-scale vegetable waste disposal case
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Project background
Songming County, Kunming, Yunnan Province, produces nearly 1500 tons of waste vegetable leaves every day, with a peak of more than 3000 tons. Only a few of these fruit and vegetable wastes were handled by the professional clearance personnel to the county and township waste landfill plants, and most of them were lost to the roadside, edge and field. A large amount of leachate from abandoned vegetable leaf landfill and roadside stacking has caused direct pollution of surface water and groundwater, threatening the water quality of Niulanjiang River.
The "abandoned fruit and vegetable organic waste treatment project", a large-scale biogas project supported by "Shanghai Ji Xing Energy Environmental Technology Co., Ltd.", has been started and completed from June 2017 to June 2018. The project takes the biogas project as the link to make the energy environment construction and the recycling of resources organic The integration of land and resources can realize the resource utilization of agricultural wastes. After the completion of the project, we can create a certain economic benefit while reducing the emission of pollutants, and form a pollution-free and sustainable ecological cycle economic system.
Project overview
In this project, the anaerobic facility covers an area of about 8 mu, and a single fermentation tank of 3300 cubic meters, a total of 4. The medium temperature fermentation is 35 degrees Celsius. A semi dry biogas fermentation process was used to treat vegetable waste 1200t daily. The daily output of biogas was about 24000 cubic meters. The whole plant includes feeding system, pretreatment system, anaerobic fermentation system, dehydration system, biogas purification-storage system, sewage treatment system.
Process selection
The water content of vegetable refuse treated in this project is high, but due to the large scale of treatment, if the traditional wet process is adopted, the amount of biogas liquid produced is large and it is difficult to eliminate, especially in the non fertilization season in winter. Because of the large scale of the treatment, the scale of the anaerobic fermentation system is larger, the investment and the area are large. In order to maximize the benefit of the project, the biogas output of the project will be increased, the discharge of the biogas liquid is reduced, and the scum and sands produced by the wet fermentation process are avoided. Therefore, the semi dry anaerobic fermentation technology is recommended as the core technology of the biogas engineering.
Comparison of Low Solid and Semi-dry Anaerobic Digestion
| Low Solid Anaerobic Digestion | Semi-dry Anaerobic Digestion | |
| Fermentation concentration | 5%-10% | 10%-15% |
| Hydraulic retention time | 15~20 days | 20~30 days |
| Pool capacity and gas production rate | 0.8~1.2m3/m3.d | 2.0~2.5m3/m3.d |
| Heat consumption | Higher, about 20~30% of biogas production capacity | Lower, about 10~15% of biogas production capacity |
| water demand | large | Little or no need |
| Quantity of biogas slurry | large | Little or no basic |
| Fermenting tank operation | The possibility of producing scum and precipitation in the tank threatens the stable operation of the fermenter. | Basically, no scum and sediment will be generated in the tank, so as to ensure the stable operation of the fermentr. |
Technological process
After the vegetable waste is transported to the factory, it will first enter the pretreatment system to crush and dehydrate. The vegetable squeezing liquid enters the sewage treatment system, and the effluent is discharged after purification. Vegetable dregs enter the fermentation tank system and produce biogas through anaerobic fermentation. Biogas into the whole plant biogas utilization system. After the anaerobic fermentation, the slurry enters the sludge dewatering system to separate solid and liquid, and produce dewatered biogas residue and biogas slurry. The dehydrated biogas residue is used to produce organic fertilizer by compost. Biogas slurry is used as liquid fertilizer to supply the surrounding planting area.
Project summary
1, the project after anaerobic fermentation of solid residue into excellent organic matter, these organic matter can be provided to the flower enterprises in the agricultural park, flower enterprises no longer need to buy organic matter from abroad, but also help enterprises to save the cost of disposal of abandoned fruits and vegetables.
2. In the whole process of production, the waste fruits and vegetables can be used in the comprehensive utilization of resources, more energy saving and more environmental protection. In the whole process, there will be no two pollution. At the same time, the planting industry, biogas organic fertilizer and organic farming recycling economy model has also been formed.