Environmental Engineering Reference
In-Depth Information
12.2
The closed cycle of digestate production and utilization and the
main set-points of digestate quality management: A) AD feedstock; B)
AD process; C) digestate declaration, storage and utilization as
biofertilizer. Source: Al Seadi and Lukehurst (2012).
ture, retention times, pH, etc.), digestate declaration, suitable handling and
storage and best practices of application as biofertilizer (Fig. 12.2).
Digestate is normally used as a fertilizer without further processing
(whole digestate), but further refining of the digestate is also possible (see
Section 12.3). Digestate processing must be considered as part of the quality
management of digestate.
12.2.4 Feedstock quality
As stated earlier, the composition and quality of the digestate is primarily
determined by the composition and quality of the feedstock, in combination
with the effect of the AD process. Use of high-quality feedstock is therefore
the most important starting point for producing digestate suitable and safe
to be used as biofertilizer. It is thus crucial that the feedstock materials are
not polluted with any unwanted matter or compounds that are able to pass
unchanged into the digestate. High quality also means that the materials
used as feedstock, by virtue of their composition, supply the anaerobic
microorganisms with important nutrients. Strict quality control of the
feedstock supplied to the AD plant is therefore a must, and the first step is
feedstock description.
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