Enviro-Chem METHA – Advanced H₂S Biogas Control for Anaerobic Digesters
Enviro-Chem METHA is a next-generation solution designed specifically for anaerobic digestion processes. Its innovative mode of action targets the root causes of hydrogen sulfide (H₂S) formation and supports optimal methane (CH₄) production. Unlike traditional iron-based treatments that simply neutralize H₂S after it is formed, METHA works upstream – directly inhibiting the activity of sulfate-reducing bacteria (SRB), the primary biological source of H₂S in digesters.
In addition to its preventive properties, METHA improves the stability of the microbial environment, supports pH regulation, and reduces inhibitory compounds such as volatile fatty acids (VFAs) and dissolved H₂S. These combined effects contribute to better digester health, more stable biogas composition, and increased methane yields over time.
METHA is easy to implement, compatible with most feedstocks, and suitable for a wide range of biogas plants – from agricultural units to wastewater treatment and industrial digesters. Its effectiveness has been validated across numerous facilities in Europe, consistently delivering significant H₂S reductions and measurable gains in CH₄ content.
How Enviro-Chem METHA Works
Enviro-Chem METHA is a specialised formulation designed to act at the source of hydrogen sulfide (H₂S) formation within anaerobic digesters. Unlike conventional products that only neutralise already-formed H₂S, METHA prevents H₂S generation by targeting the biological activity of sulfate-reducing bacteria (SRB). In parallel, it creates a more favourable environment for methanogenic bacteria, supporting the efficient conversion of organic matter into biogas — particularly methane (CH₄).
Inhibition of SRB: Reducing Competition for Substrates
Sulfate-reducing bacteria compete directly with methanogens for key substrates such as acetate and hydrogen (H₂). When SRBs dominate, they divert these substrates away from methane production, converting sulfate into toxic H₂S instead. Enviro-Chem METHA contains active components that selectively inhibit SRB enzymes and metabolic activity, drastically reducing their population and activity inside the digester.
This inhibition of SRB has two major effects:
• Less H₂S is produced, reducing the need for chemical neutralisation.
• More acetate and hydrogen are available for methanogens, directly improving CH₄ production.
Stabilisation of pH and Anaerobic Conditions
Methanogenic archaea are highly sensitive to pH fluctuations and acidification, often caused by the accumulation of volatile fatty acids (VFAs). Enviro-Chem METHA provides a mild buffering effect that helps stabilise the pH around 6.8–7.2, the optimal range for methanogenesis. This stability improves methanogenic enzyme activity and prevents digester imbalance, particularly under high organic loading.
Reduction of Inhibitory Compounds
Hydrogen sulfide is not only corrosive but also toxic to methanogens at relatively low concentrations. By preventing its formation at the microbial level and neutralising any residual H₂S through selective precipitation, Enviro-Chem METHA improves the biological conditions within the digester. This helps maintain a healthy, dominant population of methanogens, which directly translates to higher CH₄ yields.
Positive Feedback Loop
Once SRB activity is reduced, the copper-based inhibition mechanism in METHA becomes more effective, as less copper is consumed by direct precipitation with sulfides. This initiates a positive feedback loop:
• Less H₂S → Less copper consumption (precipitation) → More active copper available (inhibition) → Stronger SRB inhibition → Even less H₂S AND More CH₄.
Result: Increased CH₄, Lower H₂S
Field results have consistently shown that after the full retention time, METHA treatment leads to:
• H₂S reductions of 70–90% in most cases.
• CH₄ increases of 3–6% (relative), depending on the baseline condition and digester stability.
These gains are achieved without disrupting the microbial balance or requiring major changes in process control, making Enviro-Chem METHA an efficient, low-dose, high-impact additive for anaerobic digestion systems.
Product Injection Options
Enviro-Chem METHA can be injected into the digester feed using one of the three following systems, depending on the available infrastructure and the client’s preferences. The goal is to ensure homogeneous mixing with raw substrates, ideally in the premix tank, feed hopper, or any location where thorough mixing can be guaranteed.
1. Dosing Pump with IBC of Pre-Diluted Product
This system uses a dosing pump that draws from an IBC (1000 L) containing pre-diluted METHA. The product is diluted manually to the required concentration and then injected continuously.
✅ Advantages: Simple to install, cost-effective, suitable for small to medium-scale installations.
2. Complete Cabinet with Automatic Dilution Pump
This is a self-contained cabinet housing an automatic Dosatron-type dilution pump, which mixes the product with water on demand. It ensures consistent dilution and controlled injection flow, offering high reliability.
✅ Advantages: Plug-and-play, durable, protected system ideal for industrial environments.
3. Simplified Wall-Mounted System
A more compact and economical version of the above: the dilution pump is mounted directly on a wall panel with basic plumbing for water and product input. The product is fed from smaller canisters (20L).
✅ Advantages: Low-cost, space-saving, ideal for small biogas plants or pilot trials.
Frequently Asked Questions
1. "Copper is toxic to methanogens."
This is true at high concentrations. However, the copper dosage in Enviro-Chem METHA is precisely calibrated to remain 20 times below the inhibition thresholds for methanogens. At this dose, copper is sufficiently active to inhibit sulfate-reducing bacteria (SRB) without disrupting the activity of methanogens. The result: less H₂S formed, and more substrates (hydrogen, acetate) available for CH₄ production.
2. "If I don't have a copper deficiency, the product is useless."
The goal is not to correct a nutritional copper deficiency, but to inhibit SRB, which impair CH₄ yield and produce H₂S. SRB are more sensitive to copper than methanogens. Even in the absence of deficiency, the copper contained in METHA acts as a targeted inhibitor. This mechanism allows sites with no apparent problems to observe a systematic increase in CH₄ (generally +2 to +5% in relative value).
3. "We already have biological mineral monitoring; everything is balanced."
Good mineral monitoring is important, but it does not always detect microbial competition between SRB and methanogens. METHA is not a simple mineral supplement. It is a multifunctional formula that acts preventively against the formation of H₂S and promotes optimal biological conditions for methanation. Even with a balanced mineral profile, there can be too much SRB activity, which limits the CH₄ potential.
4. "We have had problems with the addition of slurry containing copper."
Cases of copper poisoning involve massive overdoses or uncontrolled intakes. METHA is an industrial product formulated with a controlled concentration. The doses applied are 1 to 2 mg/L of input, which is far from toxic levels. Moreover, unlike the copper in slurry, the copper in METHA is complex and stabilized, which limits its excessive bioavailability.
5. "We prefer to use ferric products, which are safer."
Ferric products are effective in neutralizing the H₂S formed, but they do not act as a preventative measure. They do not reduce H₂S production at the source. METHA acts on both levels: it neutralizes H₂S (thanks to the copper), and, more importantly, it inhibits SRB, which reduces the amount of H₂S produced. In addition to iron, METHA allows for reduced dosages of ferric precipitant while improving energy efficiency.
6. "We don't see an immediate drop in H₂S with METHA."
This is normal. The primary effect of METHA is preventative. It targets sulfate-reducing bacteria and acts with a lag time related to residence time. Typically, a significant drop is observed after two-thirds of the residence time, sometimes earlier if a ferric precipitant is maintained in parallel at startup.
7. "We don't have enough H₂S to justify this type of product."
METHA can also be used as a preventative at low dosages to avoid H₂S spikes, corrosion problems, or to optimize CH₄ conversion. Even at 100-200 ppm H₂S, many customers choose METHA to increase CH₄ yield or reduce desulfurization system maintenance.
8. "Why should I still use an iron-based product at the beginning if I'm already using Enviro-Chem METHA? Isn't copper enough to neutralize H₂S?"
This is a frequent and perfectly legitimate question. Enviro-Chem METHA contains copper (Cu²⁺), which has a dual action: it neutralizes the H₂S already present (by precipitating it in the form of CuS), but more importantly, it inhibits sulfate-reducing bacteria (SRB), responsible for the continuous formation of H₂S in the digester.
However, this preventive action of copper can only be fully effective if the H₂S already present in the digester does not consume all the copper from the outset. Indeed, when the H₂S level is high, a large portion of the copper is precipitated immediately, which limits its biological inhibitory effect on SRB.
This is where iron-based products (such as iron hydroxide) come into play. Their precipitation kinetics are faster than those of copper. Iron reacts immediately with H₂S to form FeS, thus quickly eliminating the malodorous gas. This "cleans" the environment, freeing the copper for its inhibition role.
Result:
• H₂S is quickly neutralized by iron.
• Copper remains active longer, acting at the source by slowing H₂S production.
• This allows for a more effective start to the virtuous circle: less H₂S → less precipitation → more free copper → better inhibition → even less H₂S, etc.
Conclusion:
Temporarily using an iron-based product at the beginning of treatment with METHA maximizes its preventative effectiveness. Once the H₂S level has decreased, the product
