Turning manure into sustainable electricity

A planning application from Biomasse Energie AG was available in the municipality of Hünenberg until last Tuesday. Due to requirements imposed by the Office for the Environment, adjustments have to be made to the plant.

The objection period for the construction project of Biomasse Energie AG (BiEAG) ended on 30 January. The biomass cogeneration plant near Fildern in Hünenberg generates sustainable energy extracted from biogenic waste and residues from the surrounding area. The company, which has a licence agreement with the Hünenberg municipality, has now been ordered to carry out conversion measures by the Office for the Environment (Amt für Umwelt).

The agricultural fermentation plant was built in 2011. It produces biogas from manure and compost, as well as generating electricity and heat from this biogas, procesed together with wood chips and storage water. The main output of the plant is the processing of biomass into gas. Biogas is produced when animal manure and other biological waste is broken down. According to the BiEAG, this fermentation process can also be found in bogs, swamps or the large intestine of ruminants. The biogas produced can be used as an ecological fuel.

Information on the plant and the planned modifications was available in the planning application. The original concept of the plant envisaged the transport of fresh slurry via underground pressurised slurry pipes (Gülledruckleitungen), and the subsequent return transport of the fermentation slurry. Since its foundation, however, there have been increasing deviations in this process. In particular, the delivery radius of the plant has increased.

The plant originally had capacity for 28,400 ton of input material from local farms and surrounding industrial plants and businesses. By 2022, the delivery volume had risen to 51,000 tons. One of the consequences of the increase in material is that there is no longer sufficient storage capacity, and that more material is being transported by road.

The Office for the Environment calls for adjustments
Changes have already been made to the plant and buildings in recent years as a result of the expansion, but the Office for the Environment is now imposing further requirements on BiEAG. In this regard, an environmental impact report (EIR:  Umweltverträglichkeitsbericht UVB) has been drawn up regarding the most important environmental aspects. The report focuses on water protection and the containment of gas and odour emissions, as well as pollutants and foreign substances from the fermentation slurry. The Office for the Environment has thereby prescribed a number of measures.

The BiEAG biomass power plant in Hünenberg with the two fermenters for fermentation                  Archive photo: Laura Büchler

According to the Office for the Environment, the biogas plant must be operated and adapted in such a way that the retention time of the material is at least 100 days. The slurry pressure pipes must be extended and the hammer mill that is used for the management of foreign matter must be upgraded in accordance with the state of the art. In addition, the input and output quantities of the BiEAG must be balanced.

Biomasse Energie AG is obliged to comply with and implement the measures set out in the EIR. The form in which the necessary adjustments will be made and the extent of the reorganisation are not yet known, and the management of BiEAG has thereby so far refrained from making a public statement.

In addition, the  Hünenberg municipality has received four objections. It remains to be seen whether these will result in any changes to the planning.