Biomethane EN 16723 is biogas purified to natural-gas quality for injection into the grid. The standard sets strict limits: methane above 96%, oxygen below 1% and traces of H2S, siloxanes and water reduced to a minimum. Reaching them is not only a matter of the upgrading equipment: biomethane quality starts in the digester. The dirtier the biogas comes in, the more expensive it is to clean. This article summarises what the standard requires, the critical parameters, the upgrading technologies and why siloxanes are the contaminant that causes the most headaches.
Biomethane EN 16723 is the most profitable destination for biogas when there is a natural gas grid nearby: it is sold as renewable natural gas, with premiums and certificates. But the jump from biogas to grid biomethane comes with a demanding regulatory bar.
The European standard EN 16723 defines what can and cannot be injected. And its limits are an order of magnitude stricter than those of a cogeneration engine.
Here «more or less clean» is not enough: either you meet every parameter, or you don’t inject. This article explains what the standard requires, how you get there and where the real cost lies.
What the biomethane EN 16723 standard requires (part 1 and part 2)
EN 16723 has two parts. Part 1 regulates biomethane for injection into the grid of natural gas. Part 2 regulates it as an automotive fuel.
Both set composition and contaminant limits, but the grid-injection one is what affects most plants making the jump.
The underlying idea: biomethane has to behave like natural gas in the grid. The same calorific value, the same safety and without damaging pipes or consumers’ equipment.
The 12 critical parameters of biomethane EN 16723
Beyond methane, the standard monitors a dozen parameters. These are the ones that decide whether a plant injects or not:
| Parameter | Reference limit | Why it matters |
|---|---|---|
| Methane (CH₄) | ≥ 96% | Calorific value equivalent to natural gas |
| CO₂ | ≤ 2.5-3% | Dilutes the calorific value |
| Oxygen (O₂) | ≤ 1% | Corrosion risk and grid safety |
| H₂S | ≤ 5 mg/m³ | Corrosion and toxicity |
| Total sulphur | low (mg/m³) | Odour, corrosion, catalysts |
| Siloxanes | ≤ 0.3-0.5 mg Si/m³ | Abrasive silica in consumer equipment |
| Water dew point | -10 °C at grid pressure | Prevents condensation and corrosion |
| Ammonia (NH₃) | traces | Corrosion |
| Halogenated compounds | traces | Corrosion and combustion by-products |
| Odorant / mercaptans | controlled | Leak detection (safety) |
| Particles | absent | Grid clogging |
| Hydrogen (H₂) | grid-dependent | Compatibility of the gas system |
The exact values are set by each grid operator in its connection protocol, within the framework of the standard. Before designing the upgrading, you must request the specific specification of your injection point.
Upgrading technologies: PSA, scrubbing, membranes, cryogenic
Upgrading separates the CO₂ (and fine-tunes traces) to raise the methane above 96%. Four families dominate the market.
- PSA (pressure swing adsorption): sieves that retain the CO₂. Mature and modular, good for medium-sized plants; it loses some methane in the purge.
- Water or amine scrubbing: washes the CO₂ in a column. High efficiency; the amine one recovers almost all the methane, but consumes heat.
- Membranes: separate the CO₂ by permeability. Compact, chemical-free and scalable; the most widespread in new plants.
- Cryogenic: liquefies to separate. Very pure and it allows selling liquid CO₂, but with high CAPEX; for large plants.
None on its own removes the H2S, the siloxanes or the water: that is removed in previous polishing stages. Upgrading raises the methane; polishing guarantees the traces.
Why the quality of the incoming biogas decides the OPEX
The expensive mistake is to design the upgrading as if the incoming biogas were stable and clean. It is not.
If the biogas arrives with a lot of H2S or siloxanes, the polishing stages (activated carbon, beds) saturate sooner and the replacement cost soars. Upstream biogas desulphurisation is not optional: it protects the upgrading.
The operational rule: every mg of H2S or siloxane you avoid in the digester is money you don’t spend on polishing consumables. Biomethane quality starts in the digester’s diet, not in the membrane.
This is especially true in biogas at WWTPs and in co-digestion with sulphur-bearing substrates, where the contaminant regime changes with the diet.
Siloxanes in biomethane EN 16723: the critical contaminant
Siloxanes are silicon compounds that arrive with certain substrates (WWTP sludge, OFMSW with cosmetics and detergents). In combustion they form abrasive silica that destroys engines and turbines.
For grid injection the limit is very low: of the order of 0.3-0.5 mg Si/m³. It is one of the hardest and most expensive parameters to meet.
They are removed with specific activated carbon or regenerable beds, and measured by gas chromatography after cartridge capture. They cannot be detected by eye: they have to be analysed.
Frequently asked questions about biomethane EN 16723
What is the EN 16723 standard and what does it require?
EN 16723 is the European standard that defines biomethane quality. Part 1 regulates injection into the natural gas grid and part 2, use as an automotive fuel. It requires meeting strict limits for methane (≥ 96%), oxygen (≤ 1%), H2S (≤ 5 mg/m³), siloxanes, water and other contaminants. The exact values are set by each grid operator within that framework.
What are the main contaminants in the upgrade to biomethane?
The ones that most drive the cost are CO₂ (separated in the upgrading), H2S and total sulphur, siloxanes (especially in WWTP sludge and OFMSW), water (dew point) and oxygen. Siloxanes are usually the bottleneck because of their very low limit and their removal cost.
Which upgrading technology is best?
It depends on size and context. Membranes are today the most common in new plants because they are compact and chemical-free; PSA is solid in medium-sized plants; amine scrubbing maximises methane recovery at the cost of thermal consumption; and cryogenic pays off in large plants that want to sell liquid CO₂. The choice is made against the flow rate, the inlet quality and the destination of the CO₂.
How is the presence of siloxanes measured?
Siloxanes are captured in an adsorbent or solvent cartridge and analysed by gas chromatography with mass spectrometry (GC-MS). They cannot be detected with field sensors like H2S: they require sampling and a laboratory. In plants with WWTP sludge it is advisable to measure them periodically, because their concentration varies with the diet.
How Smallops audits the biogas-biomethane chain
Meeting EN 16723 cost-effectively is a whole-chain problem, from the digester to the membrane. A biogas plant diagnosis measures the real contaminant regime, sizes the polishing and avoids consumable cost overruns.
Are you making the jump to grid biomethane?
Before investing in upgrading, audit the quality of your incoming biogas. Request a Smallops Operational Excellence Diagnosis and we calculate what you need to meet EN 16723 without paying more than necessary.
References and standards
EN 16723-1:2016. Natural gas and biomethane for use in transport and biomethane for injection in the natural gas network.
EN 16723-2:2017. Natural gas and biomethane for use in transport.
Adnan, A.I. et al. (2019). Technologies for biogas upgrading to biomethane: a review. Bioengineering, 6 (4), 92. doi.org/10.3390/bioengineering6040092