Biogas production bacteria need >15°C to produce methane. This limits biogas use in colder climates. However in winter, people need energy most. A cheap heating/insulation source is needed.
The innovation: Around a standard fermenter design a compartment is built and filled with compost (mixed straw and manure). The compartment outer wall is insulated with rice-shell ash or equivalent material. Good compost reaches a temperature of up to 60°C and heats the fermenter for 3-4 months. With permanent sub-zero temperatures of more than 2 weeks, the biogas plant is to be covered by a greenhouse. Cold-climate agriculture needs greenhouses to cultivate seedling to prepare for the planting season. The greenhouse is added-value and the fermented manure (alkaline fertilizer) can be used to fertilize greenhouse soil.
To improve the efficiency of fermentation, the greenhouse back wall is built with heat storing material and painted black to heat up at day time and radiate at night time. The front side is covered by rice straw mats during night time.
This organic heated fermenter has been developed and tested in North Korea because of random energy shortage. Most of the countries forest is logged and people have to walk for days to collect fuel wood for cooking their daily menu.
Erosion and the disappearance of springs robs many farmers their livelihood and perspective of life. Quite Often a person burns more calories to collect fuel wood for cooking and heating than the low caloric meal provides energy to keep going. A daily struggle to survive starts and many do not survive, especially when the winter is harsh and longer than expected. Conventional Biogas plants would not work as the climate is too cold, so this special technology was developed.
North Korea is not the only country lacking energy with a rapid environmental damage, Nepal, Mongolia, Buthan, northern China, the Caucasus region and the east block countries may profit.
Fermenter: Cement, Sand, Gravel, steel bar, rice husk 280 €
Greenhouse: wood, nails, painting, roof tiles, glass 230 €
System supplies: pipes, valves, stove, lamp, gas tank 140 €
Transportation: diesel 80 €
Total: 730 €
Greenhouse: insulated wall and glass front (30 m2) 900 €
The Biogas plant is affordable without the greenhouse. For very cold climate ADRA provides interest free loans. Beneficiaries can generate income from seedling production and reduce household budget on cooking fuel.
• Waste for digestion: Human, Animal, Organic
• Plant: Volume: 5 m3, all year production (can be up to 20 m3)
• Insulation: 60 cm, Rice Husk (efficient up to -15°C)
• Anaerobic process: < 25°C (Psychrophilic)
• Heating system: Aerobic 30 – 65ºC (composting layer of 50 cm keeps temperature for 2-3 month)
• Output: Gas Volume per day 4 – 9 m3
• Any type of digester design is appropriate, heating layer around the fermenter to be designed accordingly
• Design without greenhouse for ambient temperature above zero
• Design with greenhouse for climatic conditions with sub-zero temperature up to -15°C temperature under ground