Axpo reserve power plant in Muttenz (BL) Strengthening security of supply on a CO₂-neutral basis

Given the potentially dramatic consequences of large-scale and prolonged power outages, energy supply security is of the utmost importance. The Federal Office of Energy therefore aims to strengthen electricity supply security – particularly during the winter months – through measures such as reserve power plants. With its planned reserve power plant, Axpo intends to make a substantial contribution to this effort. As Switzerland's largest producer of renewable energy, Axpo is deeply committed to a climate-friendly energy supply. Thanks to the planned use of HVO (a biodiesel) and later – following a potential federal decision – eMethanol as fuels, CO₂-neutral energy supply in emergency situations will be strengthened. To ensure that the reserve power plant is called upon as rarely as possible, the expansion of renewable energies in Switzerland must be accelerated.

The reserve power plant in Muttenz has an installed capacity of 291 MW. In full operation, it produces enough electricity to meet the needs of around 600,000 four-person households.

With the potential use of eMethanol in a power plant, Axpo and the power plant manufacturers are doing technological pioneering work. As a first step, it will be ensured that eMethanol, with its somewhat different properties, can be used as a fuel (development of eMethanol capability). Furthermore, it is expected that the availability of eMethanol will increase rapidly. On the basis of the completed technical development and sufficient availability, the introduction of eMethanol can be implemented in a second step, provided that the federal government makes a corresponding decision. Until that point, HVO (a biodiesel) will be used.

As the electricity produced is only used for emergency preparedness and the power plant is not allowed to participate in the electricity market, Axpo receives compensation for the construction and operation of the power plant.

The planned site for the reserve power plant in Auhafen Muttenz is ideally suited due to its location in an industrial zone with no direct impact on neighbouring residential areas, the infrastructure already in place there and optimal transport links, particularly to rail and water.

In concrete terms, this means:

• The Muttenz Auhafen harbour is already an isolated transshipment and industrial zone with no direct impact on the surrounding residential areas.
• The power plant can utilize the existing infrastructure and primarily water and rail transport routes for the delivery, removal, and handling of fuels. This also has the advantage of avoiding any additional impact on surrounding residential areas.
• Thanks to the proximity to the existing fuel storage facility, the costs for storage, handling, and supply of the required fuels can be kept low.
• The generated electricity can be fed into the nearby Primeo Energie power grid.

Axpo intends to prepare and submit the building permit documents to the Canton of Basel-Landschaft before the end of 2026. This will also include proof that all limit values regarding noise and emissions are being met. The project will subsequently be put on public display. Following construction approval, the actual construction period will be just over 3 years, meaning that commissioning could take place at the earliest in 2030/2031.

The rededication of part of the Auhafen port away from fossil fuels and towards CO₂-neutral energy sources is an important first step in transitioning the port to the post-fossil era. This will enable the port to maintain its position as an important logistics hub for energy carriers. In addition, 17 per cent of the current tank storage capacity will be dismantled to make room for the new power plant.

Axpo will operate the power plant using CO₂-neutral fuels: initially with HVO (a biodiesel). If the federal government makes the corresponding decision and eMethanol becomes available on the market, the use of eMethanol can be introduced in a second step. As a secondary fuel – in the event that HVO and eMethanol are unavailable – conventional diesel or, at a later stage, conventional methanol would be used. In the event of operation with conventional fuel, the power plant will offset its CO₂ emissions.

The abbreviation HVO stands for "Hydrotreated Vegetable Oils". The HVO biodiesel intended for the reserve power plant is a synthetic diesel fuel that is produced from recylced vegetable oils (e.g. used cooking oils) or animal fats (e.g. slaughterhouse waste). If production is carried out using renewable energy, HVO biodiesel is completely CO₂-neutral.

Methanol is a clear, colourless liquid from the alcohol group of substances. eMethanol is methanol produced in an environmentally friendly way from hydrogen and carbon dioxide. The hydrogen is produced using renewable energies and the carbon dioxide comes from industrial processes or the atmosphere. eMethanol is CO₂-neutral, as only the previously bound CO_₂is released during combustion, and is ideal for generating clean energy and as a climate-friendly alternative in areas where a liquid fuel is still required.

The technology of such power plants is basically well proven. The applicable strict emission limits are complied with at all times. The technology used guarantees very low-emission combustion compared to emergency power generators. In addition, nitrogen oxides are reduced to a minimum by a catalytic converter, which goes well beyond the standard power plant technology used in Europe. Part of the authorisation process is an environmental impact assessment (EIA), in which the environmental protection measures taken and the remaining emissions and expected immissions are presented. By using HVO biodiesel and later eMethanol as fuels, the reserve power plant provides CO₂-neutral emergency precautions. 

Thanks to optimized combustion and exhaust gas purification, only a fraction of the nitrogen oxide (NOx) and carbon monoxide (CO) emissions caused by emergency power generators are produced. By using HVO biodiesel and later, presumably, eMethanol as fuels, the reserve power plant provides CO₂-neutral emergency preparedness.

The actual power plant section is located inside a building, so noise emissions will not be high even in the immediate vicinity of the power plant. It is also located in an isolated transshipment and industrial zone and far away from any residential areas. Compliance with the applicable noise protection limits can therefore be guaranteed. Based on a provisional environmental impact report that has already been drawn up, it can be stated that the plant is on track in terms of noise protection.

Commissioning is not expected until 2030/2031 at the earliest, with the reserve power plant functioning like an insurance policy and only being commissioned by the federal government in the event of imminent power shortages. Only a few operating hours are therefore to be expected. The electricity produced is only used for emergency supply and is not part of the regular electricity market.

In a first phase from commissioning, Axpo plans to use HVO (a biodiesel) as the primary fuel. Conventional diesel will only be used if HVO is unavailable. Through the development of the power plant's methanol capability, and once the federal government makes a corresponding decision and the availability of eMethanol is sufficient, the transition from HVO to eMethanol can be implemented. Conventional methanol would then serve as a secondary fuel in the event that eMethanol is unavailable.

The amount of HVO biodiesel required for continuous operation over 16 days is 32,000 m³; for eMethanol, the amount would be 68,000 m³ due to its lower energy density. For comparison: the Auhafen port can currently store approximately 540,000 m³ of fuels and propellants. The power plant is designed as a reserve power plant, and the actual operating hours are expected to be very low.

Primeo Energie will feed the electricity into the existing Münchenstein-Schweizerhalle line via a new substation, whereby the grid will be reinforced.

The Auhafen reserve power plant will have no impact on groundwater. From today's perspective, no structures will be built in the groundwater area (no basements under buildings) and no lowering of the groundwater level is planned at any time during soil improvement work in the foundation area.

Mobile pumps may be used locally during the construction phase to prevent the groundwater level from rising.

The planned reserve power plant will have no impact on the drinking water supply. The Auweg drinking water pumping station, which supplies up to 6,000 m3 of drinking water per day, is located near the project site (in the inflow of the Auhafen). However, it can remain in operation without interruption or restrictions during the construction phase and afterwards. Any long-term impairment of the drinking water pumping station or the quality of the drinking water can be ruled out.

The planned reserve power plant will have no impact on the drinking water supply. The water level in the reservoir will remain unchanged during construction and afterwards if the reserve power plant is operated. At most, it may be necessary to lower the water level locally in a small area during the construction period. This area would be lowered for a short period of time and separated from the groundwater, but this would have no impact on the drinking water supply.