Compatibility between boilers and low carbon and renewable heating fuels: what did German field tests taught us?

The climate targets can also be achieved with a modern oil condensing boiler. Renewable liquid fuels play an important role here. This is shown by corresponding practical tests with proportionately "green" heating oil.

Around 5.2 million oil-fired heating systems supply almost a quarter of the population in Germany with heat. This is a challenge for achieving the goal - climate neutrality in 2045 - because about three million of the corresponding buildings are located away from the heating grids. To switch to another heating system, the technical and financial hurdles are often too high. And that is not even necessary: The climate targets can also be achieved with a modern oil condensing boiler. Renewable liquid fuels play an important role here. This is shown by corresponding practical tests with proportionately "green" heating oil.

A study by the Institut für Technische Gebäudeausrüstung Dresden (ITG) in 2019 already showed that it is possible to gradually reduce the CO2 emissions of buildings with oil heating systems in line with climate targets:

  • Energy efficiency can already be greatly improved by heating modernization with condensing technology and measures on the building envelope.
  • Another step is the direct integration of renewable energies in hybrid heating systems. In this way, the fuel demand can already be significantly reduced.
  • Alternative fuels could then be used for the remaining low demand: “Green” heating oil is increasingly replacing fossil heating oil.


Prospects with oil heating systems for rural areas

Practical tests with green house gas reduced heating oil in Germany and throughout Europe show that this works: numerous residential buildings with oil heating systems prove how the energy transition can be implemented in Germany, especially in rural areas. This is because most oil heating systems are located outside of urban centres.

In Germany, around 61,000 litres of greenhouse gas-reduced heating oil were delivered to 13 detached and semi-detached houses with oil condensing boilers from 2017 to 2020. Operation has thus proven to be just as reliable as with classic heating oil. Paraffinic fuels from hydrogenated residues, so-called waste-based biofuels of the second generation whose production does not compete with food cultivation, were used.


Different variants for “greener” heating oil

Based on the results, an additional 21 heating systems were then operated with alternative fuel for an initial two heating periods - a joint campaign with various heating appliance and tank manufacturers organised in the Federal Association of the German Heating Industry (BDH). A so-called R33 fuel combination is used. It consists of 26 percent hydrogenated residues, such as used fats or vegetable and wood waste, and seven percent esterified bio-oils, Fatty Acid Methyl Ester, or FAME for short. If this combination also proves itself in practice, it would expand the range of liquid energy sources that are suitable for oil heating and reduce greenhouse gas emissions.

In addition, the regulatory framework for use in the heating market should also be prepared. The practical test is closely linked to a transnational project of the European umbrella organisation of the heating industry EHI and Eurofuel.


Green fuels ready label makes future-proofing visible

Manufacturers of condensing boilers, tanks and other heating components have launched a "Green Fuels Ready" product label in Germany 2021. The label was created by BDH in cooperation with en2x - Wirtschaftsverband Fuels und Energie. The core message behind it is that if you buy products such as a heating appliance, a tank and other components of an oil installation and make sure that they bear the label, you can be sure that these products are suitable for greenhouse gas-neutral liquid fuels and any mixtures with fossil liquid fuels.

The new fuels are not yet available as standard in the portfolios of energy traders in Germany - but especially for long-term investments, future security plays an important role. After all, most people do not want to buy a new television, a new kitchen or a new heating system after only a few years. The label gives them the security they need. Your heating system will also be able to meet climate targets in the long term - the technology to use these energy sources is ready.

An example: The Kreeb family lives in a small town in Rems Valley, about 40 kilometres east of Stuttgart. Their house was built in the mid-1970s and was supplied with heat by an oil heating system from the very beginning. A piped natural gas connection would have been disproportionately long and thus too expensive. Over the decades, the family has replaced the boiler twice, most recently in March 2021. Since then, the heat supply has been provided by a hybrid combination consisting of an oil condensing boiler and an electric heat pump. This has already noticeably reduced the need for fossil energy. But that's not all: the new condensing boiler in the house is one of those that can now boast the "Green Fuels Ready" label. And so the Kreebs received a fuel that consists proportionately of "Green Fuels", i.e. an alternative fuel based on renewable energies. The fuel mixture currently used in the tank already ensures a quarter less greenhouse gas emissions. But the use of a 100 per cent paraffinic liquid energy source would also be feasible.

And so numerous households within Europe prove that the climate targets are also feasible with liquid fuels.