Environmental Engineering Reference
In-Depth Information
12
Biogas digestate quality and utilization
TEODORI TA AL SEADI , B IOSANTECH , Denmark,
BERNHARDDROSG andWERNER FUCHS,
University of Natural Resources and Life Sciences, Austria and
DOMINIKRUTZ andRAINER JANSSEN,
WIP Renewable Energies, Germany
DOI: 10.1533/9780857097415.2.267
Abstract: Recycling of the nutrients and organic matter contained in
digestate back to the soil is considered the most sustainable utilization of
digestate. Safe recycling requires digestate to be of highest quality, not
only rich in plant nutrients, but also unpolluted by undesirable matter and
compounds of physical, chemical or biological nature. The most
important premise of producing high-quality digestate is utilization of
high-quality feedstock for the digestion process. Measures for quality
management of digestate are implemented in a number of countries as
part of national environmental, waste or agricultural legislations. More
recently, digestate quality assurance systems are also increasingly used.
The overall aim is to secure the production of high-quality digestate and
to enhance its subsequent use for agricultural purposes. Digestate can be
utilized as it is produced, or it can be further refined through various
treatments and technologies commonly known as digestate processing. By
digestate processing, marketable biofertilizers can be produced or the
nutrient load of the remaining effluent can be decisively reduced, up to
discharge quality. A common technology is solid-liquid separation, using
screw press separators and decanter centrifuges. Further treatments and
technologies can be applied for stabilization of the solid fraction or further
refining of the liquid. This chapter emphasizes the main issues related to
the quality management of digestate use as a fertilizer, with references to
the regulatory framework. The possibilities of improving digestate quality,
transportability and marketability through digestate processing are also
emphasized. A brief overview of other possible utilizations of digestate
and digestate fractions (side streams in digestate processing) is given.
Key words: digestate, quality management, AD feedstock quality, sanitation,
heavy metals, organic pollutants, persistent organic pollutants (POPs),
physical impurities, pathogen, digestate processing, separation of digestate,
decanter centrifuge, screw press, utilization of digestate, biofertilizer.
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