Biogas Upgrading Chemistry & Dosing

Upgrading concentrates biogas to >96–98% CH₄ (CO₂ <2–3%, O₂ <0.2–0.5%, controlled water dew point) so it meets grid specs such as EN 16723 / EASEE-gas CBP in Europe or interconnect tariff specs in North America. Four technologies dominate — and each has a chemistry vulnerability that addresses.

The four upgrading routes and their chemistry

Technology	How it separates CO₂	Chemistry vulnerability	Dosing response
Membrane	Selective permeation	Condensate, fouling, corrosion, sulfide carryover	Corrosion inhibitor, antiscalant, upstream drying
Water scrubbing	CO₂/H₂S absorb into pressurized water	Scaling, biofouling, corrosion in water loop	Antiscalant, biocide, corrosion inhibitor, pH control
Amine (chemical)	CO₂ chemically bound in amine solvent	Foaming, corrosion, solvent degradation	Antifoam, corrosion inhibitor, solvent-management dosing
PSA	CO₂ adsorbed on molecular sieve	Moisture & sulfur poison the sieve	Upstream H₂S/moisture control chemistry

Why methane recovery is a chemistry problem

Every upgrading route has a methane slip — CH₄ lost with the off-gas. Best-in-class systems hold slip below 1–2%, but fouled membranes, scaled scrubber packing, foaming amine or a poisoned PSA sieve all push slip up and recovery down. Because RNG revenue rides on environmental credits (RFS RINs, LCFS, or Guarantees of Origin), a 1% recovery loss is a direct, compounding hit to project economics. Support chemistry that keeps the separation surface clean is, in effect, revenue protection.

Water-loop and utility chemistry

Water scrubbing and cooling/utility loops need the same discipline as any industrial water system: antiscalant matched to feed hardness, corrosion inhibitor for carbon-steel wetted parts, biocide to prevent biofilm, and pH trim. Neglect it and you trade a chemical line-item for capital repair.

Optimization targets

Methane recovery > 98% / slip < 1–2% — protected by clean separation surfaces.
CO₂ removal to grid/vehicle spec — stable, on-spec product gas.
Asset uptime — corrosion and fouling controlled, media/membrane life extended.
Lowest total chemical cost — precise dosing, not blanket overdosing.

Where Milton Roy fits

Precision metering pumps and skids for antiscalant, corrosion inhibitor, antifoam and utility-water chemistry.
Materials and turndown suited to low-flow, high-accuracy specialty dosing on upgrading skids.
Automated control tied to loop conductivity/pH for hands-off protection.

Chemical Dosing for Biogas Upgrading Systems