Elected politicians in the west German city of Duisburg have voted to purchase 100 hydrogen buses to replace its existing fleet of diesel vehicles by 2030, after being recommended to do so by a study that will remain secret.

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The buses themselves will cost €76m ($78.5m), and the necessary infrastructure will require a further €15m, according to the city’s publicly owned transport company, Duisburger Verkehrsgesellschaft (DVG).

The order — one of the largest ever seen in Europe — comes after a report commissioned by DVG concluded that fuel-cell buses would be cheaper and greener than battery-electric ones.

“The basis for the decision is a study in which the advantages and disadvantages of battery and fuel cell buses were compared from various aspects,” said a statement from the city of Duisburg. “The result showed that the fuel cell technology not only shows a cost advantage in operation, but also achieves lower CO2 emissions when using green hydrogen than when using green electricity in battery buses.”

The city and DVG have refused to publish the study or any of the information it contains, despite a previous report — commissioned by DVG in 2018 and now publicly available — coming to the opposite conclusion.

Last week, a spokesperson for Cologne-based engineering consultancy Emcel, which produced the study for DVG, told Hydrogen Insight: “The main reason why hydrogen buses are cheaper for the city of Duisburg is that the use of battery-electric buses incurs additional costs, which include the use of more buses, more personnel and additional costs for a higher connection capacity at the depot for the charging infrastructure, compared to diesel and also compared to hydrogen buses.”

The 2018 study found that “fuel cell buses lead to the highest costs”.

Earlier this year, the French city of Montpellier cancelled an order for 51 hydrogen-powered buses after newly elected officials found that electric buses would be six times to cheaper to run.

Duisburg is officially branding itself as “The Hydrogen City” and “the gravitational field for the hydrogen economy”, boasting of its steel factories — which are single-handedly responsible for 5% of of Germany’s CO2 emissions — as well as large inland port and corresponding logistics.

As Hydrogen Insight reported last week, the publicly owned DVG has said it “cannot agree to the publication or forwarding of the study, even in part” due to potentially confidential transport company data.