pH Importance in Biogas Production

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pH Importance in Biogas Production

Why is the pH Important?

The correct mix of feedstock such as slurry, food waste and processed plant material is important to ensure efficient biomethane production.

This combined feedstock (media) is broken down by microorganisms in a series of steps, resulting in the production of methane (methanogenesis).

The pH of the media is an important consideration during this process. Values in a production environment may range from pH6.0 to pH8.0, with a pH closer to 7.0 often being cited as best for efficient digestion and methane production.

The pH of the media is just one factor to consider.

FOS/TAC Where Does This Come in?

The digestion (anaerobic digestion) process is dynamic, and plant operators will want to know whether there is sufficient nutrition to maintain a healthy bacterial load. In addition, the waste mix needs to have an adequate buffering capacity to protect against changes in pH.

The most important measurement within the process itself is to determine the volatile organic acids (FOS) and total inorganic carbon (TAC) or alkalinity ratio. The FOS/TAC ratio is an ongoing indicator of the bio-fermenters stability based on the Volatile Fatty Acids content (FOS) and buffer capacity (TAC) that prevents acidification in the reactor. It is key in measuring the risk of acidification of a biogas plant.

FOS/TAC is a ratio that, when used in conjunction with the overall pH of the system, enables operators to assess and take remedial action where necessary to maintain the digester as close to maximum performance as possible.

Daily monitoring is the key to preventing plant underperformance due to an imbalance of feedstock load. In a worst-case scenario, this imbalance may cause a whole process restart, which translates to a great loss of time and biogas production. For further information on biogas monitoring, check out BIOGAS WORLD's article.

How to Analysis FOS/TAC?

The SI Analytics TitroLine 5000 auto titrator, with a built-in FOS/TAC method, provides an easy-to-use daily analysis of how the fermentation plant performs.

Should chloride concentration be an issue for your process, the SI TitroLine 7000 with interchangeable burette heads and pre-programmed methods, including chloride, will allow rapid analysis of these and other parameters.

For further information on these and other products to help monitor the digestion process, please contact

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