When Russia invaded Ukraine in 2022, Germany realized that its dependency on natural gas piped from Russia had endangered its energy security. It had no ports to bring in alternative energy sources needed to keep its factories running and homes warm. Three years on, it now has four.

The most recent began operating in late May when a tanker called the Energy Endurance pulled in close to shore at the harbor town Wilhelmshaven and began unloading its cargo: liquefied natural gas from the Gulf Coast of the United States.

Watching from a dike, where lambs and their mothers grazed on spring grass, was Marco Alverà, chief executive of TES, a green energy company in the Netherlands that helped construct the terminal, estimated to have cost 400 million euros, at the request of the German government, which now operates it.

“This is the icebreaker,” Mr. Alverà said.

Mr. Alverà and his colleagues have been eyeing Wilhelmshaven for years and initially planned to focus on importing a cleaner form of fuel made with renewable hydrogen to help the country meet its target of reaching climate neutrality by 2045.