Summary
In the traditional production of bast fibres, the biological fibre separation is carried out by means of field or water retting, which exposes the fibre bundles and places them in a condition in which they can be processed. Environmentally sustainable methods must be developed so that water retting can be carried out in accordance with the environmental standards in force in Germany. Otherwise the use of domestic hemp and flax fibres will only remain possible to a limited extent.
The overall aim of the collaborative project was therefore in the development of procedures for:
- the preparation and additional processing of bast fibres;
- environmentally friendly water retting processes;
- the cleaning and re-use of the liquid effluents arising from the retting process;
- the elimination of odour problems arising from the retting processes; and
- the recovery of energy.
Results:
- For the cleaning of liquid effluents from the retting of flax and hemp, the following techniques were tested on a pilot scale:
- Modified aerobic sequencing batch reactor (SBR) process by means of a mixed-loop reactor, modified fixed-bed biology and anaerobic biology in combination with a fixed-bed biology. The results are promising.
- The water retting tests with recycled water corresponded with those with fresh water.
- A bio-filter was successfully tested in connection with the elimination of odour-intensive pollutants in the exhaust air from the water retting.
- The burning of the shives and hurds arising from the manufacturing process in the boiler plants of the retting works lends itself to a reduction in the energy used by the fibre separation process.
- When considering profitability, water retting exhibits a cost advantage over field retting, based among other things on improved fibre properties.
