European Commission chief Ursula von der Leyen cannot repeat often enough how close stepping up climate action is to her heart.

She described the European Green Deal as "Europe's man on the moon moment." She has called climate neutrality "our European destiny." And she solemnly proclaimed that no effort will be spared for Europe to become the world's first continent with net-zero emissions.

But as often, the devil is in the detail. 

The big question is how exactly the European Union intends to achieve its goals.

One measure being put into place is a so-called taxonomy, "a classification system, establishing a list of environmentally sustainable economic activities," according to the European Commission.

This taxonomy could be described as the EU's green investment rulebook, intended to serve the goal of allowing the continent to become climate neutral by 2050.

Can gas and nuclear be green? 

Critics say the objective of climate neutrality could be under threat, as the European Commission, the EU's executive arm, decided to give nuclear energy and natural gas a green label under this taxonomy.

In a proposal presented this Wednesday, the EU Commission stated that certain strings remained attached. For example, gas plants could only be considered green if the facility switched to low-carbon or renewable gases, such as biomass or hydrogen produced with renewable energy, by 2035.

Nuclear power plants would be deemed green if the sites can manage to safely dispose of radioactive waste. So far, worldwide, no permanent disposal site, has gone into operation though.

At a news conference in Brussels, Mairead McGuinness, the EU commissioner responsible for financial services, said her institution was not guilty of "greenwashing," as gas and nuclear were labeled as "transitional" energy sources in the taxonomy. "Our credibility is still strong," McGuinness added.

Environmental organizations most certainly see this critically, saying the proposal could jeopardize the EU's aim to reach climate neutrality by 2050. The Climate Action Network Europe wrote that the EU Commission "sacrifices the scientific integrity of the taxonomy on the altar of fossil gas and nuclear lobbies" and failed to "reorient financial flows towards genuinely climate-positive investments."

And it's not just climate activists: Also a group of experts advising the EU on the matter had announced how they are worried about "the environmental impacts that may result," for example the consequences of a nuclear accident. Building new nuclear plants would also take too long to contribute to the 2050 neutrality goals, they believe.

The proposal was preceded by a heated debate among EU countries. While some consider nuclear to be a good bridging technology, others are strongly opposed, and prefer gas instead.

Germany pro-gas, France pro-nuclear

France, which derives about 70 percent of its electricity from nuclear plants, is — unsurprisingly — heading up the pro-nuclear fraction. It is supported by a group of EU states including Poland, Hungary, the Czech Republic, Bulgaria, Slovakia and Finland. 

Especially France wants to invest in new nuclear power plants, particularly in new generation, so-called small modular reactors.

Energy expert Nicolas Mazzucchi, who works for the Foundation of Strategic Research think tank in Paris, supports the French government's plans. "These reactors can be produced on an industrial level at factories, as automated as possible, to make it cheaper and guarantee quality," Mazzucchi told DW.

Germany, however, has argued against nuclear power — also unsurprisingly, as it decided to shut down all its nuclear power plants by the end of 2022 following the Fukushima disaster in 2011.

Denmark, Austria and Luxembourg share this view, highlighting the controversial point of where to safely store highly radioactive nuclear waste. 

In a letter to the European Commission, Germany's current governing coalition has clearly said that gas is needed as an interim energy source until enough renewables are available.

To avoid a clash with its EU neighbor France, German Chancellor Olaf Scholz downplayed the importance of the taxonomy at an EU leaders' meeting last year, saying the debate was "completely overrated."

Georg Zachmann, a senior fellow at the Brussels-based Bruegel think tank, has been following the EU's energy and climate policy for years. He said that, in the end, he was relatively sure no decision would be taken in Brussels to prevent France, for example, from investing in and building new nuclear reactors. 

The Commission is keen to have the taxonomy viewed as the "gold standard" for guiding private investment toward measures that help fight climate change. 

But in Zachmann's view, no investor would be interested in nuclear or gas if the EU "invested political capital" in getting member states to substantially expand their renewable energy production.

"We know that onshore wind and solar power are not very costly in most European countries," he pointed out.

What happens next?

The European Commission's taxonomy proposal will now be reviewed by the 27 EU member states and by the European Parliament. 

As the EU's executive opted for a delegated act, a type of fast-track legislative procedure, only a total of 20 EU countries, or a majority of EU lawmakers at the European Parliament, would be able to reject it.

While EU states are not likely to turn down the taxonomy, a win in the European Parliament is not yet certain. Parliamentarians from across the political spectrum have expressed anger over the inclusion of fossil gas and nuclear power in the EU taxonomy.

Green lawmaker Rasmus Andresen said he was "disappointed" by the proposal, adding that the Green parliamentary fraction would fight hard to gather a majority against the taxonomy.

German Social Democrat Joachim Schuster told DW he thought it possible that the European Parliament could vote against the act. 

And even if lawmakers were to support it, there is another threat looming: Austria and Luxembourg have already threatened to sue  the European Commission over the taxonomy rules.

Edited by: Sonya Diehn