Hello, There are several retting methods such as:

"

• Dew retting (biological)

• Cold water retting (biological)

• Hot water retting (biological)

• Mechanical separation (physical)

• Chemical extraction (chemical)

• Enzymatical extraction (chemical)

• Ultrasonic separation (physical)

• Steam-explosion (physical)

"

Among them;

Cold and water retting techniques are obviously based on water usage. Enzymmatic and chemical fiber extraction may need lower water amount during retting process; however, neutralization and deactivation is needed following these methods. Using high cocentrations of chemicals, higher temperature and higher durations increases effectiveness of the retting procedure.

"During dew retting, agricultural residues such as plant stems are left out in

the field where biological organisms partly degrade some polysaccharides exposing the fiber bundles. "

So, minimal water is needed during retting; however, water may be used during cleaning after the completion of retting.

"Mechanical fiber separation may be carried out in different ways such as beating the fiber source with metal blades (scutching) or combing (hackling). When combined with other separation techniques, mechanical decortication, which is also

known as scutching, leads to production of lighter, softer and finer fibers. " No/minimal water is neeed during mechanical "retting". Use of it may need lower water usage is used combined with another retting process.

Lower amount of water should be needed in ultrasonic and steam explosion techniques compared to conventional water retting techniques.

The excerpts are from 

Yılmaz, N.D. “Agro-Residual Fibers as Potential Reinforcement Elements for Biocomposites”, Chapter 11, in “Lignocellulosic Polymer Composites: Processing, Characterization and Properties”, Ed. Thakur, V.K., Wiley -Scrivener, USA, ISBN 978-1-118-77357-4, s. 233-270. ,2015

Hope this is helpful...

plasma retting and enzyme retting are there is cost constrain