The construction and operation of biogas digesters require careful planning, skilled labor, and proper maintenance to ensure safety, efficiency, and long-term performance. Below is a comprehensive guide to the key aspects involved in building and using a biogas system.
**I. Site Selection and Excavation**
In southern regions where the climate is warm, freezing is generally not a concern. However, site selection remains crucial for the durability and quality of the biogas digester. The location should be close to the toilet, pigpen, and gas outlet, following the "three-in-one" principle to streamline waste management. It’s best to avoid areas with trees or bamboo, as their roots can damage the structure. If unavoidable, cut and seal the roots with lime to prevent intrusion. Choose a site with firm soil, low groundwater levels, and no heavy traffic nearby. If space is limited, consider installing the biogas tank within the pigpen.
Before excavation, mark the center point and draw a circular line based on the design plans. In loose soil, increase the slope to prevent collapse. Start by digging the upper part (the dome), then proceed to the lower section. Avoid disturbing the original soil, and move excavated earth away from the pit to prevent wall collapse and ensure worker safety.
**II. Labor and Material Preparation**
The quality of the biogas digester largely depends on the skill of the workers. Trained technicians with proper certification are essential to ensure both quality and cost-effectiveness. They should commit to three guarantees: construction, quality, and post-installation maintenance.
Key materials include sand, gravel, bricks, cement, some rebar, a gas pipe, and a PVC feed tube. These must be of good quality to ensure structural integrity and long-term use.
**III. Biogas Tank Design and Capacity**
Biogas tanks should be designed for safety and ease of use. Common types include cylindrical and ellipsoidal models, which follow the principles of “three combinations,†“small and shallow,†movable covers, and straight feeding. These designs align with national standards (GB 4750–4752-84).
The tank size should match the amount of organic waste available. A 1 cubic meter digester can typically process the waste from 1.5 pigs, producing enough biogas to meet one person’s daily energy needs. Proper sizing ensures efficient gas production and storage.
**IV. Testing the New Digester**
After installation, the first step is to check for leaks. Fill the digester with water up to more than 50% capacity and observe for 24 hours. If the water level remains stable, there is no leakage. Next, test the airtightness by pressurizing the system with water and measuring the pressure drop over 24 hours. A small drop (less than 2 cm) indicates a properly sealed system ready for use.
**V. Preparing Fermentation Materials**
The success of biogas production depends on the type and quantity of raw materials. Human and animal waste, along with organic wastewater, are ideal because they break down easily. When using grass or straw, it's important to chop and soak them before adding to the pool to prevent floating and incomplete digestion.
**VI. Key Conditions for Maximum Biogas Production**
To maximize gas output, four factors must be controlled:
1. **Fermentation Concentration:** 5–7% in summer, 10% or more in winter.
2. **Temperature:** Optimal range is 4–65°C, with natural fermentation in rural systems averaging 15–28°C.
3. **pH Level:** Neutral pH (6.5–7.5) is ideal. Adjust if acidic materials like chicken manure are used.
4. **Effective Volume:** Regular cleaning is needed to remove sludge and scum that reduce usable space.
**VII. Increasing Winter Gas Output**
During colder months, increase the concentration of the slurry to over 10%, use warm water for feeding, cover the pool to retain heat, and build the digester inside the pigpen for better insulation.
**VIII. Efficient Use of Biogas**
Ensure smooth gas flow by using appropriately sized pipes and preventing condensation buildup. Install desulfurizers to protect appliances from corrosion. Use high-efficiency stoves and lamps, and manage gas usage to maintain pressure balance in the tank.
**IX. Safe Operation and Maintenance**
Biogas is flammable and potentially dangerous. Always cover inlet and outlet ports to prevent accidents. Never light the gas directly at the outlet. Before entering the digester for maintenance, ventilate the area thoroughly and use safety equipment. Keep gas switches out of reach of children and install desulfurizers to reduce harmful gases.
**X. Emergency Procedures**
In case of a digester collapse, never attempt rescue without proper ventilation. Avoid smoking near the tank, as even small amounts of biogas can be deadly. Always prioritize safety when handling biogas systems.
By following these guidelines, households can safely and efficiently utilize biogas for cooking, lighting, and other energy needs while minimizing risks and maximizing output.
Greenhouse Wiggle Wire
Wiggle wire lock is designed to be used with poly lock base cap- sold separately. Greenhouse wiggle wire and base care are an effective method of attaching your poly film roof and or shade cloth. The greenhouse wiggle wire lock will hold form 4 mil to 20 mil thickness of material. Use one wire to hold the roof in place and then add a second wire to hold your shade cloth. When it is time to remove the shade cloth, you will not disturb the roof plastic.
Universal Base (WIG2000)- used on the curved surface, i.e. the arch for attaching the end wall covering.
Standard Base (WIG1000) - used along the straight lengths of your greenhouse.
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