Quarnbek - Germany
Built by Xergi in 2007. Biogas plant based on manure and energy crops.
Quarnbek biogas plant is situated at Quarnbek manor in Schleswig-Holstein in Northern Germany.
Quarnbek manor is solely engaged in arable farming with 1,000-1,200 ha of cultivated land. The energy crops for the biogas production are cultivated on approx. 180 ha. Apart from their own energy crops a smaller amount of cow manure from the neighbouring farms is added to the biogas plant.
Biogas and energy production
Quarnbek biogas uses 5 tons manure, 25 tons maize/GPS silage and 1-2 tons chicken manure on a daily basis. 95 % of the total gas production comes from the added silage.
The biogas facility is a so-called NAWARO plant, which means that only agricultural material such as manure and energy crops are used.
By running the plant as a NAWARO plant the owners are awarded a bonus in the price of the electricity sold to the grid as well as a bonus if
the surplus heat from the plant is utilised.
After the biogas process the digestate can be used on the land as a fertilizer. The digestate has a relatively high content of ammonium-N, which is easily absorbed by plants.
Optimum process temperature
The biogas plant is designed with one primary steel digester with an operating temperature at 50°C and one secondary digester with an operating temperature at 37°C. As silage degrades slowly the plant operates with a retention time of 50 days in the primary digester and 90 days in the secondary digester.
In total there is a very high exploitation of the biomass, which by far exceeds similar NAWARO plants.
The methane gas (CH4) is used in a gas engine with a heat efficiency of 50 % and electrical efficiency of 40 %.
Xergi's experience shows that energy crops are very suitable for the high process temperature.
This experience with high process temperature has built a solid basis for establishing biogas plants with a high, stable gas production and a healthy operational economy. The plant in Quarnbek is built based on this know-how.
The owner, Christoph Schöller, states:"With the construction of this biogas plant I have decided to invest in the future of the farming industry and have thus become an energy supplier. It was not an easy decision for me, but today I am convinced it was the right thing to do for my business".
Gas production: 1.9 mil. m3/yr
Electricity production: 4.3 mil. kWh/yr
Biomass: 8,700 ts/yr
Primary digester: 1,500 m3
Secondary digester:3,000 m3
Final storage: 3,000 m3
Gas engine: 536 kWe
Boiler: 500 kW