The modern definition of digestate is that it is a natural fertiliser output from the anaerobic digestion process, with real value when produced and sold as a product.
Digestate has often been defined as the material remaining in the digester after the anaerobic digestion of an organic feedstock. But, that description hugely undervalues the fact that it is really the original “Natural Fertiliser”.
Anaerobic digestion produces two distinct output types: digestate and biogas. Digestate is produced both at the beginning, by acidogenesis and later during the methanogenesis stage and each has different characteristics. The fertiliser product is taken and used from the second (methanogenesis) stage.
Watch our video for our explanation of digestate:
How Digestate Differs from Compost
Digestate is technically not compost although it resembles it in physical and chemical features. Compost is produced by aerobic decomposition by aerobic organisms. Those include fungi and bacteria which are able to break down the lignin and cellulose in the feed materials to a greater degree.
Digestate is the solid residue of the original input product to the digesters that the microbes can not use. It also includes the mineralised remains of the dead bacteria from within the digesters.
3 Kinds of Digestate or Should we say “Natural Fertiliser”
Digestate can can be found in 3 kinds:
- liquor, or a
- sludge based combination of the 2 other fractions.
In 2 stage biogas process systems, various forms of digestate originate from various digestion tanks. In single stage digestion systems, the two portions will certainly be incorporated together and, if preferred, these can be separated by more processing.
Digestate typically consists of substances, such as lignin, that can not be broken down by the anaerobic microbes. The digestate may consist of ammonia that is phytotoxic, and could hamper the development of plants if it is used as a soil enhancing material.
Application of digestate has actually been shown to hinder plant illness and aids in the induction of resistance. Digestate application to farmland has a direct beneficial effect on soil born conditions, and an indirect result by stimulation of biological activity.