Environmental Engineering Reference
In-Depth Information
digestate as biofertilizer, many countries have set up regulatory frameworks
for the quality of the produced digestate (Al Seadi and Lukehurst, 2012).
The quality and use of digestate as a biofertilizer or soil improver are often
regulated by soil protection legislation, fertilizer or waste legislation or
combinations thereof. In Europe, increasingly strict regulations have been in
place for more than 20 years, prescribing limit values for heavy metals,
organic pollutants and pathogens in materials used as crops fertilizers and
soil improvers, both as EU regulations and national regulations. The
national regulations are, in many cases, stricter than the corresponding EU
regulation (Al Seadi and Lukehurst, 2012). Countries with developed biogas
sectors, such as Austria, Denmark, Germany, Sweden, Switzerland and the
UK have taken a step further and implemented specific regulatory
frameworks for the quality of digestate aimed to be used as fertilizer.
Such frameworks include inter alia positive lists of materials suitable as AD
feedstock, digestate certification systems and quality standards as well as
good practice guidelines. Their aim is to guarantee that digestate intended to
be used as fertilizer is of the highest quality and, by this, to encourage its use
for agricultural purposes and ensure safe and sustainable practices.
12.2.1 High-quality digestate
High-quality digestate suitable for fertilization purposes is defined by some
essential features related to its properties such as: declared content of
nutrients, pH value, content of dry matter and organic dry matter, and
homogeneity. Equally important are features related to health and safety,
including
.
purity, requiring that digestate is free of physical impurities (plastic,
stones, glass, non-digestible matter, etc.)
.
hygiene or sanitization, ensuring that digestate is free of any pathogenic
and other undesired biological content
.
safety, ensuring it is safe for living organisms and for the environment.
These concerns necessitate strict controls and limitations on the
undesirable content of chemical pollutants, both organic and inorganic.
From both technical and economic points of view, the only feasible way to
ensure production of high-quality digestate, suitable as fertilizer, is to use
high-quality feedstock as a substrate for AD. An increasing number of
countries in Europe have implemented specific digestate regulations and
measures of quality assurance (certification systems for digestate, positive
lists of suitable feedstock materials, etc.), aiming to unify the approaches
and develop a healthy market for this valuable product (Al Seadi and
Lukehurst, 2012). It is important to highlight that the positive lists of
feedstock must never exclude the ongoing quality control of the feedstock
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