The formation of foams is an undesirable effect for the operators of "wet" biogas plants which can lead to a decrease in electricity production (biogas trapped and consequently not sent to the cogenerator), to obstruct pipes and ducts, and, in cases more serious occurred, to an overflow of the digestion tank.
The term foam defines a two-phase system consisting of a part of biogas over a very thin layer of liquid, called the lamellar layer.
The formation of foams derives mainly from the formatting substrate, or, more in detail, from the composition of the substrate in fermentation; in the lamellar phase, some macromolecules may be present deriving from the digestion of the matrices used in nutrition, such as proteins, saponins (partially soluble glycosides in water and oil) and some sugars, such as pectins.
Some plant by-products containing saponins are for example:
NB: pomace is a completely different by-product which, on the contrary, helps in the abatement of foam thanks to their oily content.
Some vegetable by-products with high protein content are:
Even if the highest protein content is certainly found in the By-products of Animal Origin, with peaks, for some types such as flours, higher than 40% on as it is.
Some plant products containing pectins are:
The formation of foam from imbalance of the C / N ratio (carbon / nitrogen) caused by sewage or high dosages of manure is also interesting.
In case you notice the formation of foam in the digester it is necessary:
To reduce the possibility of foaming, it is not recommended to abruptly change the substrates in feeding; a gradual change allows the bacterial flora to adapt, keeping gas production constant.
Doubts or questions? Send us an email by clicking here or call us