Volume reduction of biomethanated spent wash from distilleries

We recently received a request from Srivathsan, a chemical and industrial engineer providing industrial solutions on resource recovery, who is looking to establish the feasibility of using forward osmosis to reduce the volume of biomethanated spent wash from distilleries.

The overall goal is to partially concentrate the waste stream before it goes to conventional separation of water (evaporation) in order to reduce the thermal load on the evaporator.

According to Srivathsan, a typical distillery will produce 800kL spent wash daily with a chemical composition as outlined below.

Typical chemical composition of biomethanated spent wash

Industrial forward osmosis players capable of delivering technical feasibility studies on biomethanated spent wash are encouraged to leave their comments below.

What is biomethanated spent wash?

Distillery spent wash is a high-organic liquid waste product generated during alcohol production. Typically, the organic load of spent wash is reduced through biomethanation by which organic material is microbiologically converted under anaerobic conditions to biogas. The resulting waste stream is referred to as biomethanated spent wash.


  1. The spent wash has high TDS (91700 ppm) which implies use of very high concentration draw. If the draw is readily available as other waste stream having high TDS, the process may be viable otherwise draw regeneration will be the bottleneck and the energy saved in spent wash concentration may be required to be used for draw regeneration. High concentration of Nitrogen (TAN- ?) is another worry as it may carry over to draw.


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