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How did this come about?
There was a major power outage in Fürth on September 16, 2025. From 13:28 to 14:12, around 8,640 households in the southern part of the city were affected. The cause was a short circuit on a medium-voltage cable. Our Fürth data center site was also affected. However, thanks to the uninterruptible power supply (UPS) and the emergency power generator, there were no interruptions at the data center. Such incidents illustrate the importance of a reliable emergency power supply for data centers.
Careful preparation pays off
We test our UPS systems monthly in so-called black building tests, in which we completely interrupt the power supply in a controlled manner. This routine has proven its worth - during the Fürth power outage in September, our systems worked smoothly and the power supply for our customers in the data center was ensured without interruption. However, there is a catch to these necessary tests: our generator consumes around 6 % of its tank capacity. This means that the maintenance tests alone generate 4.73 tons of CO₂ emissions per year when using conventional diesel.
However, we have found a good solution: HVO diesel (Hydrotreated Vegetable Oil) is a fuel that is obtained from used fats and waste vegetable oils and can be used up to 90% less CO₂ emissions than conventional diesel. Both fuels behave in the same way and can even be mixed. At the moment, however, HVO diesel is not so easy to obtain. However, HVO diesel is an uncomplicated and more environmentally friendly alternative for scheduled, regular refilling of the diesel tank.
Why is it worth switching to HVO?
During our monthly black building tests, as already mentioned, we use around six percent of the tank capacity, which corresponds to around 1,765 liters per year. If we were to use conventional diesel, we would emit 4.73 tons of CO₂. Thanks to HVO, we reduce these emissions by 90 percent, saving 4.25 tons of CO₂ per year. With minor power interruptions, which our emergency power system compensates for, the figure is even higher.
For comparison: This saving corresponds to the annual climate performance of over 210 mature deciduous trees or the amount of CO₂ that three average cars with petrol engines emit annually (source: based on data from the Federal Environment Agency and the Federal Motor Transport Authority).
Pioneer in Germany
The number of data center operators opting for HVO is still manageable. The data center operator Digital Realty has tested the innovative fuel in Europe and converted its US data centers to HVO diesel in 2024. EcoDataCenter (Sweden) also uses HVO diesel. ScaleUp is now the pioneer among German data centers.
The advantages are obvious:
- Ready for immediate use: No modifications to existing generators necessary
- Drastic CO2 reduction: Up to 90% fewer emissions
- Improved air quality: the release of soot, particulate matter and nitrogen oxides is significantly minimized.
- Proven technology: HVO is chemically very similar to conventional diesel, is suitable for all diesel engines, but is free of fossil components.
- Circular economy: Recycling waste instead of consuming raw materials
Challenges for existing data centers
We encounter typical problems with existing plants such as the site we took over in 2024: Alternative solutions, such as large battery storage systems or biogas plants, often fail due to the space available. Diesel generators are therefore still the most proven and compact solution for emergency power supply.
The HVO supply still presents practical hurdles: the fuel cannot yet be supplied quickly in large quantities. This means that some conventional diesel may have to be refueled in the event of unplanned, prolonged power outages.
Nevertheless, we are consciously taking this path to strengthen the supply chains for sustainable fuels and pave the way for other data center operators. Especially for existing data centers with limited space, HVO is often the only viable option to immediately reduce CO₂.
Sustainability as an investment
HVO fuel is currently around ten percent more expensive than conventional diesel. However, this additional cost is worth the more sustainable approach and the immediate avoidance of emissions. We see it as an investment in the future - both for our company and for future generations.
Looking ahead
The switch to HVO diesel is just one element of our sustainability strategy. It shows: With innovative solutions, data centers can already drastically reduce their ecological footprint without compromising on reliability.
Every liter of conventional fuel saved and every ton of CO2 avoided counts. With HVO-Diesel, we are taking an important step towards climate-neutral data centers - and hope that other operators will follow our example. Further information and answers to frequently asked questions can be found in this FAQ.
In addition to HVO diesel, the ScaleUp data center in Nuremberg relies on other sustainability measures and achieves an impressive PUE value of just 1.2. Innovative open hardware concepts for modern, sustainable data centers can be seen, for example, in the new OCP Experience Center including Liquid Cooling Lab at the Nuremberg-Fürth site.
