Blog post

Will gas upgrading technology save European biogas?

Biogas, 25 November 2025

I used to be a vinyl nerd. My angsty teenage self hoarded hundreds of scratched LPs in faded sleeves, and they’ve sat unplayed on my shelves for decades because my turntable was also 40 years old. Then, someone invented the smart turntable: digital conversion, auto-levelling, and other technical wizardry I don’t pretend to understand. Suddenly, the whole collection had a second life, no more skipping, no more ‘underwater sound’. The old obsolescent kit was reinvented by bolting on something new and clever.

You see the same pattern everywhere. The bicycle becomes an e-bike. Mechanical watches morph into smartwatches. Dusty Victorian novels find new purpose as audiobooks are read by breathy actors between gigs. The theme is consistent; infrastructure that looked obsolete becomes valuable again once technology catches up to repurpose it.

European biogas plants are the energy-sector equivalent of those vinyl records. Across the continent, 20,000 or so plants happily digest organic waste, manure and food residues into raw biogas (CH₄ + CO₂) and burn it in engines to make electricity. Most were built a decade ago under generous feed-in tariffs or CHP schemes, Germany’s EEG, Italy’s Conto Energia, France’s FITs, and Denmark’s incentives – all designed to reward electrons, not molecules. As those schemes come to an end, the economics stop working, and the plants end up quietly rusting away in the farmyard.

Why retrofitting upgraders makes sense

Fast-forward to the 2020s, and the market has flipped. With wind and solar now commonplace, Europe frequently has too many electrons in some regions and too few gas molecules in others. We solve this with something of a contradiction: we pay wind and solar developers not to generate electrons on windy, sunny days, but then import methane molecules from Russia and Qatar pretty much every other day.

The obvious opportunity is to stop turning molecules into electrons, and that’s where our analogy of old vinyl comes in: we can bolt on technology to make the transition. The two key things here are the language and chemistry of biogas (a chemical mixture of CO₂ and CH₄) and biomethane (CH₄). People often use these words interchangeably, which drives me mad, but for our purposes, the semantical distinction is critical.

Biogas can be burned in engines, but biomethane entering the grid must be pure CH₄, so it needs to be purified to remove the CO₂. Thankfully, Mother Nature has helpfully made oxygen molecules much larger than hydrogen ones, so a CO₂ molecule is approximately three times larger than a CH₄ one. Upgraders can separate the two gases by using membrane technology, whereby the little CH₄ molecules go through the holes, and their bigger CO₂ cousins stay stuck on the other side. Similar physics applies when lithe young men can squeeze into the driving seats of low-slung sports cars, but let’s say sturdier middle-aged blokes like me can’t.

Membrane technology is proven, modular and widely available, but the real kicker is this: thanks to legacy tariff schemes, all the expensive infrastructure: reception halls, digesters, and feedstock systems already exist. Retrofitting an upgrader to switch a site from electrons to molecules costs a fraction of building a new biomethane plant.

The emergence of upgrading technology is also cracking news for the original developer, typically a farmer. He/she will have built the plant on the back of the electricity tariff support, so probably didn’t expect a second bite of the revenue cherry. Consequently, owners of biogas plants that are coming to the end of tariff regimes tend to be quite amenable to incoming investors who can extend the life of their plant by another fifteen years.

How to upgrade your plant in five easy steps

While no two European biogas plants are quite alike, the retrofit process is surprisingly consistent:

Check the gas quality
Most plants produce biogas in the 50–65% CH₄ range. Some agricultural sites need minor tweaks to improve that ratio, but nothing drastic.
Choose the upgrading tech
Membranes dominate because they’re compact, modular and tolerant of variable gas compositions. PSA, water scrubbing and amine systems have their niches, but membranes hit the sweet spot on cost, footprint and proven technology.
Add compression and finishing
Once the CO₂ and impurities are scrubbed, operators add compression, drying, odorization, and trace removal. As an interesting aside, because CH₄ is odourless, all countries legislate to add odour and try to reach the same ‘rotten egg’ smell so people can sense gas leaks. The output is grid-spec biomethane indistinguishable from fossil natural gas.
Build the connection
This is often the biggest cost variable. Dutch and French plants tend to sit close to gas networks; parts of Spain, Italy and Eastern Europe face longer pipelines or need liquefaction. Even then, the economics usually work.
Secure support and an offtaker
Each country brings its own alphabet soup of green-gas policies. France’s tariff system, Italy’s CIC biomethane certificates, Germany’s shift to tendered support, Denmark’s biomethane quotas, and the Netherlands’ SDE++ scheme. The details vary, but the ultimate aim is the same: to encourage the creation of green gas molecules and discourage plant owners from turning that gas into electrons.

These retrofits can be completed in 9–15 months, which is an awful lot quicker than building a plant from scratch.

The market potential is huge

As previously discussed, Europe’s biomethane landscape is expanding rapidly:

Europe now has 1,678 biomethane plants—over 1,000 more than in 2018, with many being upgrades rather than new builds
Total capacity stands at 6.4 billion cubic metres per year—a drop in the ocean compared with Europe’s 350 billion cubic metre annual gas demand
However, and here’s the nub, there are still over 20,000 legacy biogas plants across Europe which represent a massive retrofittable base. If we assume that only 25% of these are suitable because of scale and grid access, that’s still 5,000 plants and assuming EUR 2m for an upgrader, we are looking at a EUR 10 billion investment opportunity

Why investors like upgraders

For infrastructure funds, retrofitting gas upgraders to existing biogas plants is firmly in the ‘sounds like a plan’ box because it offers:

Very low permitting risk—plants already exist, and the local communities have ceased caring about them
Low technology risk—mature, proven kit
Established supply chains—digesters have been fed for years
Stable incentive regimes
Long-term offtake certainty

Returns can be surprisingly strong because you’re leveraging existing capex instead of building everything from scratch.

Turning redundant plants into a EUR 10 billion opportunity

Just as my smart turntable revived my vinyl collection, retrofitting Europe’s legacy of biogas plants could turn a rusting asset base into a major plank of energy security. With circa 20,000 plants already on the ground, a €10 billion opportunity to upgrade them from electrons to molecules is sitting in plain sight. My records didn’t die; they simply waited for the right technology to bring them back to life. Europe’s biogas sector can enjoy the same Lazarus-like revival, not through endless new construction, but by upgrading what we already have.

Overview