Axpo has set itself the target of preparing and publishing an environmental declaration for a representative power plant for all of its energy systems. The company wishes to present the ecological advantages and disadvantages associated with each energy system in a transparent manner. With these environmental declarations for various power plants, Axpo wishes to contribute to improved objectivity in the debate about energy systems. Back in 2008, the Beznau nuclear power plant (KKB) was the first nuclear power plant in Switzerland to receive an environmental certificate.

The lifecycle analysis of the Kompogas plant in Otelfingen (canton of Zurich) in December 2009 means that a second Axpo plant has now been certified with an environmental declaration prepared in accordance with the international ISO 14025 standard. It was shown here that fermentation in a Kompogas plant is one of the most environmentally friendly ways of recycling organic waste. With every tonne of organic waste recycled in this way rather than being left to decompose in a landfill, around 200 kilograms of CO₂ equivalent can be saved. The declaration has been updated in 2012.

Certified lifecycle assessment

The main element of an environmental declaration as per ISO 14025 is the lifecycle assessment. This clearly structured method based on international standards makes it possible to quantify and estimate the emissions into the environment and the resource consumption for the overall production of electricity, heat, biogas and fermentation product. For this purpose, numerous environment-related factors were recorded and evaluated for the Kompogas plant in Otelfingen. Taken into account here was the entire lifecycle of the Kompogas system, including the transportation of the organic waste to the Kompogas plant, the construction and operation of the plant, and the treatment of the resulting waste.

The ecological balance must also fulfil the requirements of the international EPD® (Environmental Product Declaration) programme before it can be used in an environmental declaration as per ISO 14025. This also includes independent verification of the results by the Veritas Certification office from Sweden, whose certificate then confirms that all specifications in the standards have been adhered to.

Kompogas process: ecological energy production

The Kompogas process is based on anaerobic fermentation of solid organic materials such as those from municipal organic waste. Biogas (methane) is produced here, which can then be burned in a combined heat and power plant (CHP). The result is green electricity with 'naturmade star' certification that can be fed into the public supply grid on the one hand, and heat on the other. Alternatively, the biogas can be treated for use as motor vehicle fuel. The fermentation product left over by the Kompogas process is certified for use in organic farming (FiBL).