Renewable Natural Gas (RNG)

Before entering the digester, organic feedstock must be conditioned to maximize biogas yield, stabilize the microbial consortium, and prevent operational upsets:

• pH adjustment — Injection of acid (H₂SO₄, HCl) or base (NaOH, lime) to hold incoming substrate within the 6.8–7.4 window required by methanogens.
• Micronutrient supplementation — Trace dosing of iron, cobalt, nickel, molybdenum, selenium, and tungsten to sustain enzymatic activity, particularly in mono-substrate (manure-only or energy-crop) digesters.
• Defoaming — Silicone- or vegetable-based antifoam injection to prevent digester overflows, foam-outs, and gas-line carryover.
• Substrate dilution & blending — Controlled dosing of process water or recirculated digestate to hit the target dry-solids (TS) content — typically 8–12% for wet AD, 25–35% for dry AD.
• Enzymatic / hydrolysis boosters — Optional dosing of enzymes or pre-hydrolysis acids to accelerate breakdown of lignocellulosic feedstocks.

Inside the digester, four microbial stages hydrolysis → acidogenesis → acetogenesis → methanogenesis convert complex organics into raw biogas. 

This biology is fragile: a 0.3-unit pH drop can collapse methane output within hours.

Critical dosing duties include:

• Continuous pH control — Acid/base injection to buffer volatile fatty acid (VFA) accumulation and protect methanogenic archaea.
• In-situ desulfurization — FeCl₃, FeCl₂, or FeSO₄ dosing to precipitate dissolved sulfide as iron sulfide — reducing H₂S in raw biogas by 70–95%, protecting CHP engines, upgrading membranes, and downstream piping from corrosion.
• Alkalinity management — Sodium bicarbonate, lime, or magnesium hydroxide dosing to maintain a healthy FOS/TAC ratio (<0.3).
• Ammonia / nitrogen control — Strategic dosing in high-nitrogen substrates (poultry manure, slaughterhouse waste) to prevent NH₃ inhibition.
• Struvite control — Dosing of inhibitors or precipitation aids to prevent struvite (MgNH₄PO₄) scaling in heat exchangers and pumps.

Raw biogas must be upgraded to pipeline-quality biomethane using one (or a hybrid) of five mainstream technologies:

Upgraded biomethane must meet strict grid specifications before injection:

• Methane content — typically >97% CH₄
• Wobbe Index — within local network band (e.g., 47.2–51.4 MJ/Nm³ in EU H-gas)
• Dew point — −8 °C or stricter, depending on pipeline pressure
• H₂S — <5 mg/Nm³
• O₂ — <0.5%
• Odorant level — THT, mercaptans (TBM/IPM), or sulfur-free odorants at network-defined ppm targets

The ODOROY odorization system — developed by Milton Roy with YZ Systems — delivers compliant odorant injection at ultra-low flow rates with full automation, leak-free liquid-end design, remote monitoring, and validation from leading European gas DSOs. It is the reference standard for RNG grid injection points, biomethane virtual pipelines (CNG/LNG trailers), and city-gate stations.