de - Beste verfügbare Techniken (BVT) - Umweltbundesamt

2.7.2 Extraction from natural materials
[62, D1 comments, 2004], *065A,I*
Chapter 2
See also Section 4.1.5.1 “Extraktion von Naturstoffen mit flüssigem CO2” and Section 4.1.5.2
“Gegenstromextraktion”.
Extraction is an important process for obtaining raw materials from natural resources. In a
typical setup, the target substance (e.g. tannic acids, alcaloids, quinine salts, food additives,
APIs or intermediates for APIs, additives for cosmetics) is extracted from natural materials (e.g.
leaves, bark, animal organs) with a solvent and prepared for further processing by distilling off
the solvent.
Extraction yields from the extraction of plant materials can vary from 10 to 0.1 % or even
lower, depending on process technique, plant material quality and targeted compounds. This
means that the amount of waste streams compared to the amount of end-product is considerable.
To reduce the amount of waste streams, it is important to maximise the extraction yield, e.g. by
using countercurrent band extraction.
To maximise re-use of waste plant materials, e.g. by composting and subsequent use as a soil
conditioner, it is important to research and use extractions with non-chlorinated biodegradable
solvents. Re-use of extracted fermentation broth or plant waste materials in feed industry is
often not possible due to residues of harmful plant material, or residual API.
Solvent is re-used by treating plant waste materials by indirect steam heating and/or steam
injection, condensation of the solvent and subsequent purification of the solvent by distillation.
Waste water originating from downstream purification, e.g. with liquid-liquid extraction and
phase transfer, can cause dark coloured waste water with a high load of non-biodegradable
COD, due to soluble macromolecular plant materials (lignins, tannins).
Table 2.20 gives some examples of waste streams from extraction.
Waste stream Properties
Waste water from
liquid-liquid extraction
Extracted fermentation broth
Waste plant materials
High load of non-degradable COD (lignins, tannins)
Table 2.20: Typical examples for waste streams from extractions
*065A,I*
*065A,I*
*006A,I*
OFC_BREF Dezember 2005 73