Cities using bioenergy - Freiburg as an example

The city of Freiburg’s concept of the regenerative production of power firmly includes the use of bioenergy. Currently, 1.6 percent of total power in Freiburg is produced from bioenergy. Up until 2010, it is planned to increase this to 2.7 percent. In addition, bioenergy is also used for the production of heat, the amount of which cannot, however, be provided in concrete figures since the heat is not fed into the public power supply system.

Wood is an important component of bioenergy. This is particularly the case in Freiburg because it and the Upper Rhine region are closely related to the Black Forest (Photo: Hoppe)

The energy supply concept was developed in Freiburg in 1986, which was the same year as the Chernobyl nuclear disaster. It was then the declared aim of Freiburg to find alternatives to nuclear power and to protect energy resources. This concept relies heavily on three major pillars, which the city’s energy policy still uses for its foundation. In 1996, Freiburg committed itself to reducing its carbon dioxide emissions by 25 percent by 2010.

Eight years later, the city declared that it would replace ten percent of the power used with renewable energy sources by 2010. The aim also included the increase of the proportion of heat produced with renewable energies. In this sector, bioenergy will play an even greater role than in the generation of electricity, since wind and water are of subordinate importance in heat production.

Landfill gas – refined use of a troublesome substance

Freiburg has realised three major and some smaller projects involving bioenergy in solid, liquid or gaseous form. The Landwasser district is supplied by a combined heat and power station (CHP) that produces power and heat from the methane gas that is obtained from the Eichelbuck landfill, which has in the meantime been shut down. “By doing so, we can use the relatively troublesome landfill gas in an environmentally-friendly way in order to produce energy,” explained Klaus Hoppe, head of the Energy Division in Freiburg’s Office of Environmental Affairs. A second project uses waste for the production of energy. In the biological waste fermentation plant, the biological waste from the city of Freiburg and the district of Breisgau-Hochschwarzwald, has been used since 1999 to produce electricity. Biological waste is fermented under anaerobic conditions and the resulting gases are used to operate power-producing turbines.

Pilot project with “childhood diseases”: nevertheless, the Vauban wood heating plant will soon supply more than 3500 people with power and warmth. (Photo: Hoppe)

Nevertheless, the Vauban wood heating plant has attracted the most attention. It supplies the Vaubun city district with heating and electricity. The last construction works will soon be completed in the new area. Subsequently, more than 70 percent of the district’s 5,000 residents will receive energy from the biomass power plant, which has been operative since 2002. Nevertheless, the operation of the plant is not simple. “The regional energy supplier “badenova”, which is the operator of the power plant, had to deal with ‘childhood diseases’ that are common to any such pilot project,” said Hoppe referring to the lack of experience with wood as the energy carrier in a CHP of this size at this time.

The power station has so far not been able to fulfil expectations in terms of power production. Hoppe explained that ‘badenova’ is continuously working on optimising the system.

Mixture of rapeseed oil, biodiesel and wood

In addition to these large projects, Freiburg runs several small facilities that use bioenergy. The solar factory supplies a CHP with rapeseed oil, and the ‘Stadtbau’ building society operates a small CHP with biodiesel that supplies several blocks of flats with energy. In addition, ‘Stadtbau’ has established a CHP that uses wood pellets for the exclusive production of heat. A heat generating station that utilises wood is operated by the well-known football school of the SC Freiburg. There is still no time-tested technology available that can enable simultaneous power and heat generation by small CHPs using pellets or wood chips,” explained Hoppe.

The city of Freiburg also promotes biomass. The city council declared that all heating systems that are managed by the city and need to be replaced must be evaluated for the potential use of biomass. For each ton of carbon dioxide that is not emitted from a bioenergy plant compared to a conventional heat generation plant, the alternative concept is awarded 50 €. If the bioenergy plant ends up with a positive balance compared to using gas boilers, then the city will construct a more expensive bioheating system. “This is an excellent example of how cities can set an example for its inhabitants,” said Hoppe.

Are wood-firing systems more problematic because of fine particulates?

Freiburg’s energy supply concept is complemented by two ongoing studies. In the scope of the “BioRegion – strategies for the sustainable use of biomass in selected model regions”, the Öko-Institut is evaluating how bioenergy can contribute to the energy supply at the Southern Upper Rhine. Hoppe explained that a first rough estimate suggests that bioenergy can contribute up to ten percent to the energy supply. A second study, which overlaps partially with the examinations undertaken by the Öko-Institut, is being jointly carried out by the energy agencies of the cities of Ortenau and Freiburg, developing regional development concepts for the regional Southern Upper Rhine (RVSO) association. An energy atlas is already available, including information on the energy demand, energy suppliers and the potentials of regenerative energies.

One problem is still unsolved and might become even larger: wood-firing plants are not without problems in terms of the smallest of fine particulates. “There is of course a big difference between a single oven and an enormous, modern pellet-firing plant,” explained Hoppe. Nevertheless, it now needs to be decided at the national level as to whether, and if so which, wood-firing plants are dangerous in terms of fine particulates. Reliable answers are still unavailable. What is known for sure is that wood and biomass generally achieve better values than natural gas CHPs in terms of the reduction of carbon dioxide emissions. However, the sulphur dioxide, nitrogen oxides and fine particulate emissions from wood and biomass are higher.

kb – 24.5.06
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Further information:

Klaus Hoppe

City of Freiburg

Office of Environmental Affairs

Head of Energy Division

Talstr. 4

79102 Freiburg

Phone: [phone]

Fax: [phone]

E-mail: [e-mail]