In a 6 July analysis presented by Mouvement Ecologique on Thursday, Germany’s Öko-Institut challenged the environmental design of the planned Google data centre in Bissen, saying the project could sharply reduce its emissions under a different technical setup.
“The proposed Google data centre does not yet reflect the current state of best available technology (BAT) in several key aspects of its design,” the analysis said.
The paper examined the planned centre’s energy efficiency, electricity supply, waste-heat use, emergency power, refrigerants and water consumption. Mouvement Ecologique is presenting it as part of its long-running challenge to the Bissen project, after earlier objections over planning, transparency and access to environmental data.
The analysis also included a warning on the figures. “Consequently, the environmental impacts and improvement potentials presented here should be regarded as indicative estimates rather than precise calculations,” Öko-Institut said.
A 950GWh project
Öko-Institut put the planned data centre’s IT power capacity at 100MW and its annual electricity use at around 950GWh, roughly equivalent, it said, to the electricity used by Luxembourg’s private households in a year.
The planned site would cover around 34 hectares near the Creos substation in Bissen, according to the paper. The project has been discussed since 2016, with Google securing the land in 2017, years of procedural delays following, and Bissen council completing the special development plan process in January 2025.
The institute’s first technical criticism concerned power usage effectiveness, or PUE, a standard measure of data-centre efficiency. The analysis said the Bissen plan had a PUE of 1.3, meaning that cooling, power distribution and other supporting systems would add energy use equal to around 30% of the IT load.
“Replacing conventional air cooling with direct-to-chip liquid cooling, in which the coolant circulates in a closed loop, can substantially reduce cooling-related energy losses,” the analysis said.
Öko-Institut said this could bring PUE down to 1.1 and reduce annual electricity use from around 950GWh to about 800GWh. It said Google already reaches some stronger efficiency standards at other sites, but not in the current plans for Bissen.
How the estimate works
The 97% emissions-reduction figure was built from several changes. Öko-Institut first modelled a scenario in which electricity imported from the average German power mix would produce around 315,000 tonnes of CO₂ equivalent emissions a year.
It then modelled an alternative supply based mainly on additional renewable generation. Under that scenario, the paper assumed 5% on-site solar power, 80% newly developed onshore wind power and 15% electricity from the Luxembourg grid, cutting annual emissions to around 28,000 tonnes.
The final step is heat recovery. The analysis said the data centre could supply at least 40GWh of waste heat a year to households in Bissen, Diekirch and Ettelbruck, municipalities with a combined population of about 20,000.
“To realise this potential, Google should begin engaging with prospective heat users at an early stage and incorporate the necessary technical infrastructure into the project design,” Öko-Institut said.
By replacing some fossil-fuel heating, the institute estimated this would save around 20,000 tonnes of CO₂ equivalent a year. That would leave the modelled project with around 8,000 tonnes of annual emissions, or 97% below the starting scenario.
Heat and backup power
Waste heat has already become a political point in the project. In June, Green MP Joëlle Welfring questioned Economy Minister Lex Delles on the Google project’s energy efficiency, electricity use and heat recovery.
Delles defended the strategic value of data centres for Luxembourg and Europe, while saying heat from data centres should be treated as a local resource and integrated into district heating where possible. That was a prior parliamentary position, not a response to the July Öko-Institut analysis.
The analysis also questioned the planned emergency-power system, saying the current concept includes 46 diesel generators. Öko-Institut estimated that routine testing would consume around 200,000 litres of diesel a year under normal conditions, and argued that battery storage could reduce noise, diesel soot and local emissions.
The paper also recommended replacing the planned refrigerant R-1234ze with natural refrigerants such as propane or ammonia. On water, it said planned annual use of around 3,800 cubic metres suggested the centre was not relying on large-scale evaporative cooling, though it argued the remaining demand could be met through rainwater collection.
Meco’s wider campaign
Mouvement Ecologique is using the analysis to support a broader argument about whether the project still makes sense under current energy, climate, land-use and digital-sovereignty concerns. Those points are part of Meco’s political case, not findings of the Öko-Institut paper.
The NGO said the environment and economy ministries should require Google to meet the best available technical standard, publish environmental data and ensure objections are addressed before the operating-permit stage. Meco argued that none of this had happened to date.
Meco also repeated its criticism of confidentiality around energy, emissions and carbon-balance data, a dispute it had already escalated through a solicitor in May 2026. It lost an earlier challenge to the rezoning of the Bissen site in March 2022.
Google has previously pointed to its sustainability commitments. In February 2025, Google Cloud executive Anthony Cirot told Paperjam the group was ready for Bissen if the need arose, and said that if Google moved forward on data-centre issues in Luxembourg, it could guarantee a fully decarbonised approach.
Delles has also previously defended the project as part of a broader digital-sovereignty strategy. The source pack does not include a fresh response from Google, the economy ministry or the environment ministry to the July analysis.
