Converting biomass to biogas is simple. Fill a digester with manure and rotten vegetables – just about any kind of biomass – seal it, and unleash trillions of methane-producing bacteria to convert worthless waste into valuable fuel.


The production of biogas is booming in Germany. The German Biogas Association projects that biogas will provide 17 percent of the country’s electricity by 2020. While the conversion of biomass to biogas is accessible and simple, the issue most farmers face is finding the best way to economically use the biogas that’s generated.

Farmer Thomas Karle, owner of the Kupferzell agricultural biogas plant in Germany, is putting waste to work. Using Capstone Turbine Corporation’s MicroTurbine® technology, organic waste is turned to fertilizer that’s used by Kupferzell farms spanning more than 100 hectares (10.7-million-square-feet).

The biogas plant on Karle’s farm in Kupferzell, a town in the district of Hohenlohe in Baden-Würtemberg, opened in 2001. In 2007, the facility adopted microturbine technology and a sludge drying system. At that time, two Capstone CR65 microturbines were commissioned and successfully converted pig and cow slurry, along with crop and food residues from Karle’s farm, into electricity and heat.

Two years later, the facility’s growing demand for electricity fueled the need to upgrade to a Capstone CR200. In July 2009, the updated combined heat and power (CHP) system was commissioned.

The Capstone CR200 runs solely on renewable products and is expected to produce 1,500MW of electricity and 2,800MW of heat each year. The unit is operating year-round at maximum capacity with an average availability of 97 percent.

The methane gas that fuels the microturbine is produced at the farm in two digesters that break down the slurry and crop waste. While the microturbine’s clean-and-green electricity is fed directly into the utility grid, 100 percent of its waste heat is efficiently used to dry the sludge. In addition, the hot, lowemission exhaust from the microturbine flows directly into a dryer building to produce high-quality, natural fertilizer from fermentation residue. A heat exchanger is not required since the exhaust is used for direct drying, something that cannot be accomplished with a traditional genset motor. This organic and highly effective mineral fertilizer is then sold to local farmers and gardeners.

“The installation of the microturbine helps Kupferzell farmers focus on their core competence –farming.” — Radu Anghel, Managing Director, Greenvironment

The plant requires accurate biogas flow measurements and analysis. Operators use a biogas measurement device and a SCADA system, both developed by Capstone German distributor Greenvironment. The SCADA system allows central supervision, monitoring, and control of the CHP system, and facilitates preventive maintenance actions.

“Using biogas at the Kupferzell plant will help the European Union meet its emission trading and obligations in the Kyoto Accord,”said Radu Anghel, Greenvironment Managing Director. “Capstone’s microturbines now have a sizable presence in the fast-growing European biogas market.”

The Kupferzell plant receives a financial bonus from Erneuerbare-Energien-Gesetz (EEG), the German law for renewable energies. Under the EEG, the plant is guaranteed an electricity price for power it supplies to the local utility and a separate technology bonus for using microturbines.

In addition to government incentives for feeding energy into the grid, the Kupferzell biogas plant meets and far exceeds standards set in the “Technische Anleitung zur Reinhaltung der Luft” (TA Luft), a regulation covering air-quality requirements from stationary sources.

“The environment is winning as microturbines’ exhaust emission levels are far below those of traditional gas engines,” said Thomas Karle. “We’re winning because we’re saving money as our energy and fertilizer bills are significantly lower.”

“In addition to reducing greenhouse gas emissions and increasing fuel efficiency, the microturbines only require eight hours of maintenance annually,” Greenvironment’s Anghel said. “The installation of the microturbine helps Kupferzell farmers focus on their core competence – farming.”

At A Glance

Location: Kupferzell, Germany
Commissioned: 2007 – 2 CR65 Capstone microturbines; 2009 – Upgraded to a CR200 microturbine
Fuel: Biogas

• Beginning in 2007, 2 Capstone CR65 microturbines converted biogas into heat and electricity onsite. In 2009 the plant upgraded to a CR200 microturbine.
• The CHP system allows the hot, low emission exhaust air of the CR200 microturbine to flow directly into a dryer building to make high-quality natural fertilizer from fermentation residue.
• Operators use a biogas measurement device and a SCADA (Supervisory Control and Data Acquisition) system for accurate biogas flow measurement analysis, both developed by Capstone German distributor Greenvironment.

• Each year, the Kupferzell plant is expected to produce 1,500MW of electricity and 2,800MW of heat.
• CO2 emissions avoided through the CHP system are 500 – 1160 kg CO2 per MW-hour.
• Under the Erneuerbare-Energien-Gesetz EEG) the Kupferzell farm is guaranteed an electricity price for power supplied to the grid. In addition, the farm receives a technology bonus for using microturbine technology.