Cold nights and seasons are considered as an obstacle that keeps biogas solutions away from northern areas and out of permaculture and sustainability projects. The experimental week in August 2015 at the Tamera Solar Village was therefore dedicated to find and try out affordable insulations and heating methods that can be applied throughout the world.
The project continued the work with biogas solutions that Dr. T.H. Culhane had started at Tamera in 2011 with the construction of the floating drum system "Holda" and the construction of the "Black Ladies", two IBC tank based systems that were built as part of the Solar CITIES biogas workshop in April 2015.
For the intent to test different insulations as well as two different gas storage schemes, two additional IBC biodigester systems were constructed during the experimental week. This time Culhane partnered aside from Martin Funk with straw build expert Bee Rowan. As a result of their work, we now can welcome "Sao Paulo" and "Grace Kelly" in the Solar CITIES community.
Sao Paulo is a three IBC tank system. The tank that is used as digester is insulated with straw bales, coated with a straw-clay-quicklime-mixture and a sand rich render on top for water repellency. The gas storage scheme works according to a two IBC gas storage system built in Sao Paulo, Brazil that is at the same time basis for the system's name. The system is modified to avoid the usage of a water pump and instead creating passive gas pressure by feed, fertilizer and gas pipe as high as the water displacement tank which is on top of the gas storage tank.
Grace Kelly is another three IBC tank system. As insulation a similar straw-clay-quicklime-mixture as for the coating of Sao Paulo was applied. Compared to Sao Paulo's about 40 cm (15") thick insulation wall, Grace Kelly has a mixture based wall of about 15 cm (6"). For the gas storage again two tanks were used. The system follows the principle of a floating tank (ARTIBC): one of the tanks was turned by 90 degrees to fit into the second tank of which the top got cut off and which is filled with water. The gas that flows into the floating tank presses the water out and the tank wins of height.
Both systems were able to produce gas shortly after they have been built. Both insulations seem to perform very well so far. To make specific assumptions, Sao Paulo and Grace Kelly as well as the other three biodigesters got temperature probes inserted. That way the project continues by monitoring and analysing results regarding temperature performances in the upcoming colder season.