For its 80th anniversary, this French site that builds monstrous 320‑tonne engines is getting a “nice gift” from its German owner Everllence

On France’s Atlantic coastline, an ageing works that once epitomised brute diesel might is quietly preparing for an industrial revival.

In Saint-Nazaire, a long‑established engine factory is being reshaped into a strategic pillar for nuclear safety, greener shipping and next‑generation biofuels, as its German owner Everllence marks the site’s 80th anniversary with fresh capital and bigger plans.

From diesel powerhouse to modern industrial platform: Saint-Nazaire at 80

The story begins in 1946 with the founding of S.E.M.T. (the Company for the Study of Thermal Machines). From the post‑war expansion through to the mid‑2000s, S.E.M.T. became a benchmark name for high‑output diesel engines used in ships and power stations-built from its base in Saint‑Nazaire on the Atlantic.

S.E.M.T. ceased to exist as an independent company in 2006, yet the know‑how never left the site. Today the facility belongs to the German energy and engineering group Everllence (previously MAN Energy Solutions) and still turns out engines so large that a dedicated quay is required to ship them.

By 2026, the plant employs about 600 people and builds huge four‑stroke engines weighing up to 320 tonnes apiece. To celebrate 80 years of operations, Everllence is lining up what managers describe as a “nice gift”: a major investment push, a stronger order book, and a comprehensive modernisation of both workshops and office space.

Everllence is targeting roughly 40% growth at Saint‑Nazaire by 2028, powered by rising demand for nuclear safety equipment and cleaner maritime propulsion.

Nuclear boom: engines designed for the worst day imaginable

Last‑resort electricity when the grid collapses

Within a nuclear power station, Everllence’s engines are not there to drive the main turbines. Their role is quieter-and far more vital: they act as the ultimate back‑up when external power fails.

These large units operate as:

• emergency diesel generators,
• backup power systems,
• independent electricity sources if the outside grid collapses.

If a station loses its usual supply, the engines must auto‑start within seconds. They then keep essential systems operating, including:

• reactor cooling systems,
• safety pumps,
• control and monitoring equipment.

They are engineered for the situation nobody wants to face: a major grid failure or an accident in which seconds matter. That translates into exceptionally high reliability, redundancy, and the ability to run for hours or even days under intense operating stress.

Everllence’s timing at Saint‑Nazaire is deliberate. The International Atomic Energy Agency (IAEA) forecasts that global nuclear capacity could rise from around 377 gigawatts today to nearly 1,000 gigawatts by 2050. New builds, life‑extension programmes and small modular reactors all increase the need for emergency power packages.

Nuclear growth does not only mean more reactors; it also means additional layers of ultra‑reliable backup engines, control systems and safety architecture.

Added context: For equipment used in nuclear safety chains, the commercial differentiator is not just output, but assurance-traceable manufacturing, documented testing regimes and long‑term maintainability. As more countries extend reactor lifetimes, operators increasingly value suppliers that can deliver upgrades, spares and service support over decades, not merely one‑off deliveries.

Maritime pressure: cleaner propulsion becomes non‑negotiable

Shipping under tightening climate rules

At sea, the rulebook is shifting quickly. The International Maritime Organization (IMO) is aiming to reduce the carbon intensity of shipping by 40% by 2030 and 70% by 2040, with an ambition of climate neutrality around mid‑century. In parallel, the European Union is folding shipping into its carbon market, progressively pricing emissions from large vessels above 5,000 tonnes, which are responsible for the bulk of maritime pollution.

The cost implications are substantial:

• new low‑carbon ships can be 30–50% more expensive than conventional designs,
• low‑carbon fuels are frequently two to five times the price of standard fuel oil,
• fleet renewal could demand up to US$28 billion per year (about £22 billion),
• fuels and associated infrastructure may require as much as US$90 billion annually (about £71 billion).

Shipowners are left with an uncomfortable decision: retire vessels early and replace them, or convert existing propulsion systems to run on cleaner fuels. Everllence is backing the conversion route rather than wholesale scrappage.

Added context: Regulatory compliance is also becoming more granular than “CO₂ only”. Ports and coastal states increasingly focus on local air quality-nitrogen oxides, particulates and sulphur-so multi‑fuel solutions that can be tuned for different operational profiles (port approaches, coastal waters and open ocean) are gaining importance alongside headline carbon targets.

Everllence and the 51/60DF: a multi‑fuel future in 320 tonnes of metal

Central to this approach is the 51/60DF engine family, produced and upgraded in Saint‑Nazaire. While “DF” stands for dual fuel, in practice these engines are built to handle a wider range of fuel pathways.

Specification	51/60DF details
Configuration	6L, 12V or 18V
Maximum power	up to 20,700 kW at 500/514 rpm
Fuel flexibility	diesel, heavy fuel oil, natural gas, liquid biofuels
Combustion	can start directly in gas mode with roughly 1% “pilot” fuel
Bore and stroke	510 mm × 600 mm
Weight	up to about 416.8 tonnes for the 18‑cylinder version

This adaptability matters for owners trying to plan amid volatile fuel availability. A ship can begin life on conventional fuel and then transition-step by step-to gas or biofuels as supply chains, pricing and port infrastructure mature.

Everllence also intends to convert more of these XXL engines so they can run on liquid fuels derived from biomass. In many cases, this is quicker and cheaper than commissioning brand‑new vessels, while still delivering a meaningful reduction in emissions.

Converting a 320‑tonne engine to burn biomass‑based fuels can, in some cases, reduce lifetime emissions far more cost‑effectively than building a new low‑carbon ship from scratch.

The consequence is rising workload in Saint‑Nazaire. Everllence plans to increase production from 48 to 72 engines a year-an extra 24 units annually-as early as 2025. That expansion gives the French site a global role in helping shipping meet tightening climate obligations.

Beyond the shop floor: 6,000 m² of offices modernised

A site upgrade aimed at engineering, not only equipment

The investment programme goes beyond heavy tooling and test facilities. Everllence is beginning a two‑year refurbishment of around 6,000 square metres of office space at Saint‑Nazaire.

The renovation has three main objectives:

• improve working conditions for existing teams,
• help recruit scarce engineering and technical specialists,
• underpin a move towards more design work, digitalisation and innovation.

This shift is significant. Upcoming contracts are less about repeating standard diesel builds and more about engineering tailored, multi‑fuel systems for nuclear plants, LNG terminals, ferries or cruise ships operating under strict emissions limits.

The 80th‑anniversary “gift” is not just more orders; it is a deliberate move up the value chain-from heavy fabrication to higher‑value engineering.

Saint-Nazaire: an Atlantic energy and industry crossroads

A port ecosystem linked to global trade

Everllence operates within a tightly connected industrial and port cluster. In 2025, the Port of Nantes–Saint‑Nazaire handled 26.4 million tonnes of cargo, up 2.6% on the previous year. About 18 million tonnes were energy flows such as oil and liquefied natural gas.

Around 3,068 ships call at the port each year, supporting roughly 28,700 direct jobs across 1,460 hectares. Saint‑Nazaire also hosts the renowned Atlantic Shipyards and major customers such as EDF, TotalEnergies and ArcelorMittal.

Everllence makes use of a dedicated quay to load 48/60 and 51/60 engines, some weighing up to 320 tonnes. Only a small number of sites worldwide can build, test and dispatch machinery of this size at industrial scale.

The plant also connects to France’s “France 2030” strategy via the ZIBaC Loire Estuary programme, which allocates €8.2 million to projects spanning hydrogen, carbon capture and biofuels. This provides a platform to trial future low‑carbon solutions around the engines themselves-covering fuel logistics, storage and integration with port energy networks.

What biomass-based marine fuels actually are

“Biofuel” is an umbrella term covering several different products. In marine use, it can span everything from used‑cooking‑oil derivatives (such as HVO) to advanced bio‑oils made from forestry residues or agricultural waste. While these fuels are intended to cut lifecycle emissions, their real‑world benefit depends heavily on how the feedstock is sourced and how the fuel is processed.

Typical pathways include:

• Short term: blending biofuels with conventional marine diesel to reduce emissions without changing hardware.
• Medium term: retrofitting engines and fuel systems to run largely on biofuels or biomethane.
• Long term: moving towards synthetic fuels such as e‑methanol or e‑ammonia produced using renewable electricity.

Engines like the 51/60DF function as a bridge technology, coping with different mixtures while regulators, ports and fuel suppliers decide which low‑carbon route scales fastest.

Scenarios: what if decarbonisation in shipping accelerates?

If regulators tighten requirements sooner than expected, shipowners may be forced to bring retrofit schedules forward. In that scenario, facilities like Saint‑Nazaire could face a growing pipeline of conversion work-not only for newbuilds but also for existing fleets across Europe, Asia and the Middle East.

There are clear downsides. Shortages in skilled labour, constraints in component supply, or limited test capacity could stretch lead times. Engine manufacturers also take on technology risk if policy and infrastructure swing rapidly towards a single fuel-ammonia, for example-faster than product portfolios can adjust.

On the positive side, a successful move to multi‑fuel, high‑efficiency engines can compound advantages. Ports reduce local air pollution, shipowners lower carbon‑related costs, and countries such as France strengthen energy and industrial sovereignty by keeping critical capabilities anchored domestically.

By modernising an 80‑year‑old engine factory, Everllence is effectively wagering that heavy industry still belongs in a low‑carbon economy-provided it can evolve quickly enough.