Microbial power-to-X: the bugs turning surplus electricity into methane

3,750 cubic metres of renewable methane every hour. That is the throughput a single Electrochaea reference plant is designed to deliver, built from 3,750 Nm³ of captured CO₂ and the output of a 75-megawatt electrolyser running on surplus wind or solar. The figure matters less than what it represents. Living cells, not steel catalysts, are doing the chemistry of storing renewable power.

Why the gas grid is suddenly a battery

Renewables overbuild. When wind and sun exceed demand, the surplus is curtailed or sold at negative prices. Long-duration storage, the ability to hold that energy for days or seasons, is the missing layer of the grid. Batteries cover hours. Everything beyond that stays unresolved.

Microbial routes attack the problem from an unusual angle. Instead of reversible chemistry, they let organisms metabolise CO₂ and hydrogen into methane, the molecule the existing gas network already moves. The natural gas grid becomes, in effect, the world's largest battery. Its leadership has argued for years that the storage and distribution network already exists.

What is scaling

Electrochaea, a Munich company founded in 2010, is the clearest commercial signal. In February 2025 it finalised a basic engineering design package with Baker Hughes, the energy-services group that has been a strategic investor since 2021, integrating its biomethanation biocatalyst with Baker Hughes carbon-capture equipment. The reference plant generates 3,750 Nm³/h of e-methane from a 75 MWe electrolyser and can scale to hundreds of megawatts. Multiple feasibility studies are already running with prospective clients.

Two further moves pushed the company from pilot to sector participant. It joined the e-NG Coalition in December 2025, a group standardising electric natural gas as a traded commodity. It also signed a licensing agreement with Hitachi to build Japan's first biomethanation plant, with commissioning targeted for 2027, supporting Tokyo's plan to blend synthetic methane into existing infrastructure.

The chemicals path is attracting capital of its own. Again, a Copenhagen and Berlin startup, raised $43 million in a 2024 Series A led by GV, the former Google Ventures. Its pilot ferments CO₂ and hydrogen into acetate, a base chemical for adhesives, solvents and plastics, at roughly one tonne of CO₂ per day, under a ten-year offtake with the distributor HELM. In 2026 Again acquired Genomatica, extending its biomanufacturing platform. As we wrote in August (microbial electrosynthesis: microbes turn surplus electrons into acetate, bioplastics and protein), the same biology pointed at chemicals is advancing on a parallel track.

The academic floor is rising too. Penn State researchers reported a microbial electrosynthesis (MES) reactor producing methane at 45 per cent energy efficiency with coulombic efficiency above 95 per cent, scaled roughly tenfold without losing performance. That is the kind of number that turns a lab curiosity into an engineering target.

What is still uncertain

The efficiency bar is real. Direct catalytic methanation of CO₂ with hydrogen already reaches higher round-trip efficiencies than biology, and thermochemical e-fuel routes are scaling with different backers. Microbial routes win on mild operating conditions and tolerance to impure feed gas, not on raw energy maths.

The harder problem is the one every biobased venture has hit before. C&EN, reporting on Again's raise, quoted an analyst noting that the field "has a lot of dead bodies," because even when the biochemistry works, feedstock supply and product purification have sunk previous projects. Martin Iademarco of the metrics firm judged that improved microbial growth rates could lower production cost at scale, but the caution stands.

Then there is the electrolyser. Every cubic metre of e-methane starts as renewable hydrogen, so the levelised cost tracks electrolyser capital and the price of curtailed power. A biological route only wins if it can ride cheap surplus electricity that nobody else wants. That dependency is the whole investment case, and also its largest risk.

Policy is the third variable nobody can model cleanly. Methanation of any kind benefits from renewable mandates, carbon pricing and blending targets, but those signals shift with election cycles. A plant financed on a subsidy that lapses in year six has a different risk profile than one that clears on curtailed-power arbitrage alone. The projects worth watching are the ones whose spreadsheets stay positive if every incentive disappears, because that is the stress case the next downturn will actually test.

Grid connection is the quiet constraint. A biomethanation plant needs both a steady CO₂ source and access to variable renewable power, ideally at the same site. Cement and steel facilities have the CO₂. Few of them also sit next to gigawatts of curtailed wind. The plants that get built will be the ones that solved siting before they ordered the electrolyser, not the ones that assumed the grid would adapt around them.

What is genuinely new

The interesting shift is not any single plant. It is the framing. Biological power-to-X is being sold as long-duration storage first and as a chemical product second, with carbon capture bolted to the front end rather than treated as a separate compliance cost.

That integration is what the Baker Hughes deal expresses. Carbon capture and e-methane production sit in one engineering package, so a cement works or steel mill can turn its CO₂ stream into a storable, sellable fuel. The e-NG Coalition is doing the less visible but more important work of making electric natural gas a standard commodity that utilities can contract and trade.

For a private investor, the pattern is familiar from other deep-tech waves. The science is demonstrated. The question is whether unit economics clear without subsidies once electrolyser costs fall. The companies that survive will be the ones that signed offtake before they built capacity, not after.

How to read the early signals

The instinct is to track pilot results, and the Penn State efficiency figure is genuinely useful. But pilots have misled investors before. The signals that actually separate a going concern from a grant-funded demo are contractual. A final investment decision on a FEED-stage plant tells you more than a press release about a reference design. An offtake with a creditworthy buyer tells you more than a coalition membership.

That reframes where the money is safest. Its Baker Hughes package is attractive precisely because it bundles capture and methanation, so a single counterparty can be held to delivery. Again's ten-year HELM offtake does the same for the chemicals track. Vertical integration of the CO₂, the power and the buyer is the pattern that has consistently survived the "valley of death" in biobased manufacturing, and it is what a disciplined allocation should screen for first.

The contrarian read is that biology's mild operating conditions are underpriced. Catalytic routes post better round-trip numbers today, but they demand clean feed gas and high temperature, which means their own balance of plant and purification cost. If electrolyser capital keeps falling, the gap in efficiency matters less than the gap in operating simplicity. That is the bet the strategic investors in this space are quietly making, and it is the one most outsiders are still ignoring.

Biological versus catalytic methanation

Sources