FAQ: Note

Plug-in hybrids play a very minor role in the reference scenario. Accordingly, they can only be used to a limited extent and as a transitional technology. In the reference scenario, their use will already peak in 2030, with a 26% share of new vehicle registrations.

Fuel cell vehicles play practically no role in the reference scenario, since their main energy carrier, hydrogen, is needed more in other sectors and can be used more efficiently. In the reference scenario, they will already reach their peak in 2020 with 2% of new registrations.

Heat pumps must be operated with electricity from renewable energies in order to achieve the necessary reduction effect assumed in the tool. In addition, it should be considered that the heating requirement of a building should be particularly low for the installation of a heat pump. In existing buildings, the installation of a heat pump is therefore usually linked to the energy-related refurbishment. Structural restrictions (e.g. monument protection, lack of skilled workers) can make the installation of a heat pump difficult or even impossible.

For district heating, the tool uses the decarbonization rate that the reference scenario estimates for the electricity sector. District heating is developing based on its current average emission intensity. The reduction effect specified in the tool is only achieved if the district heating network used meets these assumptions. In addition, the feasibility must be checked on a site-specific basis, since (district) heating networks are natural monopolies and their expansion depends on the regulatory framework.

Hydrogen is only available to a very limited extent and other solutions exist in the building sector. Therefore, hydrogen should first be used for other (industrial) purposes where less low-emission alternatives exist. In the reference scenario, hydrogen therefore plays practically no role in building heating.

As envisaged in the reference scenario, the average energy demand of buildings must fall before an efficient conversion of energy sources can take place. Energetic refurbishment is therefore often a condition for switching to alternative energy sources, which is reflected in the tool. At the same time, energy-related refurbishments can be delayed by various factors, including a lack of skilled workers, material shortages or structural restrictions.

The tool only takes into account the emissions that arise from the use of heating energy sources. When selecting a heating technology, the upstream chain should also be taken into account.

For the production of the required biochar, no green areas with a high level of biodiversity, forest areas or peat bogs may be used for cultivation. This ensures an almost CO2-neutral production of the biochar and averts negative economies of scale. The possibility of these negative economies of scale stems from the fact that biochar (like biogas) is seen as a decarbonisation opportunity in many sectors, but sustainable biochar is not sufficient to supply all interested sectors. Biomass should be used based on the use of residues according to the cascade principle, i.e. primarily as food and in material use. Energetic use should primarily take place in industrial heat use and must not be at the expense of the sink function of the forest.

When using hydrogen, green hydrogen must be used to ensure sustainability and the required GHG reduction rates.

Due to their high costs and very limited availability, synthetic fuels are mainly used in air and sea transport and play a very limited role in road freight transport – their maximum of 3% is reached in the 2040 scenario. The energy required for their production comes solely from renewable energy sources, the required CO2 from direct air capture.

Biofuels are only obtained from waste and residues (slurry, hydrogenated vegetable oil) and are subject to temporary use restrictions until 2030 as a bridging solution. They are only produced using renewable energy.

The electricity for electricity-based drive systems must be provided solely from renewable energies in order to ensure the emission reductions estimated in the tool.

Only CCS is anchored in the reference scenario as a solution technology. Carbon capture and usage is explicitly not intended, as CO2 captured in this way is delayed but still enters the atmosphere. CCS is currently not permitted by law in Germany. If CCS were to be approved, the energy-intensive capture and compression plants would need to be powered by renewable energy. The captured CO2 must not escape when it is stored. The infrastructure required for CO2 transport would have to be created. It is not yet clear which industrial regions will be connected and when.

The additional firing of coal-fired power plants must take place exclusively using biomass. For the production of the required biomass, no green areas with a high level of biodiversity, forest areas or peat bogs may be used for cultivation. Otherwise, negative economies of scale can occur, since biogas and biomass (such as biochar) are seen as a possibility for decarbonization in many sectors, but both are not sufficient to supply all interested sectors. Biomass should be used based on the use of residues according to the cascade principle, i.e. primarily as food and in material use. Energetic use should primarily take place in industrial heat use and must not be at the expense of the sink function of the forest. Overall, bioenergy can be seen as a niche solution: In the reference scenario, its use falls in absolute terms from 38 TWh net electricity generation in 2030 to 10 TWh in 2050. The latter corresponds to 1% of renewable energy production in 2050.

For the production of the required biomass, no green areas with a high level of biodiversity, forest areas or peat bogs may be used for cultivation. This ensures an almost CO2-neutral production of the biogas and averts negative economies of scale. The possibility of these negative economies of scale stems from the fact that biogas (like biochar) is seen as an opportunity for decarbonisation in many sectors, but sustainable biogas is not sufficient to supply all interested sectors on a large scale. Biomass should be used based on the use of residues according to the cascade principle, i.e. primarily as food and in material use. Energetic use should primarily take place in industrial heat use and must not be at the expense of the sink function of the forest.

PtG energy sources used must be produced with green hydrogen in order to achieve the required (and assumed in the tool) GHG reduction.

The availability of blast furnace slag as a by-product of steel production is expected to decrease as production switches to alternative processes. In this case, local availability must be taken into account.