Biogas production bacteria need temperatures of more than 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 solution: A compartment is built around a standard fermenter design and filled with compost (mixed straw and manure). The compartment's 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 temperatures permanently below zero for more than 2 weeks, the biogas plant needs 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's 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.
Background Information & Social Impact
This organic heated fermenter has been developed and tested in North Korea, as the country experiences random energy shortages. Most of the country's forest is logged and people have to walk for days to collect fuelwood for cooking their daily food. Erosion and the disappearance of springs robs many farmers of their livelihood and perspective of life. Quite often a person burns more calories collecting wood for cooking and heating than the low calorie meals provide. Many do not survive this daily struggle, 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, Bhutan, northern China, the Caucasus region and the east block countries may profit.