Because what the Institute for Applied Material Flow Management (IfaS) of the Environmental Campus Birkenfeld presented made some committee members turn away from the idea. The technical, but also the economic feasibility, was illuminated. The confectionery factory and the former mine are 2.7 kilometres apart, so the question arises, for example, of how the heat gets to the heat storage facility.

One of three options favoured is "biogas transport" with a pre-treatment plant close to production and a biogas pipeline to the combined heat and power plant at the site of the heat storage facility. The exact amount of production water was not available to IfaS, but a data basis according to which a calorific value of 8.8 megawatt hours is assumed for the current state of expansion of the Haribo plant; with a possible complete expansion in the coming years, the assumption rises to 17.7 megawatt hours.

If we look at the four surrounding villages around the pit, their heat demand is higher, although IfaS does not expect a 100 per cent connection rate. It is recommended that ground-mounted solar thermal plants be included in the supply concept, as even with a 70 per cent connection rate and full Haribo expansion stage, not enough heat would be produced. In the end, IfaS defined a total of eight study variants: with and without solar thermal, with hot water or gravel water storage, with Haribo expansion stage II or IV.

To convert the wastewater into electricity and heat, the institute recommends combined heat and power in a biogas cogeneration plant. In the best case scenario, 2;500 households could ultimately be supplied with electricity and 440 with heat; in the current expansion stage of the plant, the biogas potential is half. The plant is to be supplemented with an open-space solar thermal system. Such a combination would be unique in Germany, but similar plants already exist in Denmark. The combination could eventually supply 85 percent of the households in Oeverich, Niederich, Leimersdorf and Nierendorf with heat. Without solar thermal energy, up to 70 percent of the households could be supplied.

The question of economic viability remains. The investment requirement alone is enormous, assuming about 800,000 Euro for the CHP unit, a good nine million Euro for the solar thermal system and up to 11.3 million Euro for the underground storage tank. 360,000 Euro are needed for the micro gas pipeline and more than ten million Euro for the development of the four villages, including house connections. With all the ancillary costs, the total is up to 40 million Euro. For comparison: the entire municipal budget for 2022 amounts to 32 million Euro in expenditure.

In the environment committee, opinions differed. Andreas Ackermann (CDU) questioned the economic viability of the project. Günter Bach (SPD) cannot imagine being able to attract enough interested parties, especially as only recently a campaign in Nierendorf led to new gas connections.

Reinhold Hermann (FWG), who in the end voted against the continuation of the project, also sees the reduction of greenhouse gases as important, but does not consider the economic viability of the project as given. Michael Schneider (CDU), who chaired the meeting on behalf of Mayor Achim Juchem, emphasised the necessity of promoting such a project, whose continuation was also advocated by Economic Development Officer Klaus Becker: "The task of the study was to find out whether the idea is spinning or actually feasible, not the economic viability, about which nothing can be said today. We have to continue and readjust," said Becker.

(Original text: Thomas Weber; Translation: Mareike Graepel)