Biogas & RNG Online – March 2026
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VFA and LCFA concentrations?
VFA and LCFA concentrations?
Curious what benchmark or threshold total-VFA and / or total-LCFA concentrations values folks consider to be triggers for further investigation or action when operating their AD plants?
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Total VFA concentration above 2,000–4,000 mg/L (as acetic acid) or a VFA/Alkalinity ratio (FOS/TAC) above 0.3–0.4. More then 0.4 ratio indicates High risk of acidification/failure; immediate reduction in organic loading rate (OLR) is required. Long-Chain Fatty Acids (LCFAs) are particularly dangerous as they can cause sludge flotation (washout) and inhibit methane bacteria. Recommended Concentrations around 150-250 mg/L of LCFAs.
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