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Japanese Researchers Develop Membrane For More Efficient Ethanol Production

Nikkei. Researchers from Japan’s National Food Research Institute and the University of Tokyo have developed a membrane that supports the more energy-efficient production of high-concentration bioethanol.

Conventional ethanol production typically uses a two-stage distillation process to deliver the final ethanol output at a concentration of nearly 100%. The process can consume the equivalent of 55% of the energy that the bioethanol provides as a fuel.

The new membrane has a two-layer structure. The underlying membrane allows ethanol to pass like a selective filter, while the upper membrane acts like a gatekeeper, only allowing the ethanol to pass when it is present in a sufficiently high concentration. As a result, the distillation process only needs to be conducted once.

The gatekeeper membrane is made from a sheet of polyethylene with tiny holes that are coated with a special polymer. The polymer blocks the holes until the ethanol reaches sufficient concentration. At that point, the polymer contracts and allows the ethanol to pass.

Use of the membrane can produce ethanol at 90% concentration while using less than 70% of the energy normally required.


Rafael Seidl

If I read this right, with the new membrane the distillation process requires only the equivalent of 0.7 * 0.55 = 0.385 of the energy contained in the end product. Put another way, you have to put in 1/(1-0.385) = 1.626 units of energy to get one out as fuel.

Previously, you needed 1/(1-0.55) = 2.222 units of energy in for the same result. In relative terms, this means the energy input requirement for the distillation process is reduced by 27% when using the new membrane.

Note that all of the above refer to th distillation process only, not the whole chain from agriculture to fuel.


No what it means is before the distillation process ate over half the total energy of the fuel itself but with this method they can getto 90 percent pire ethanol using about 40 percent of the end fuels energy to do so.

Problem is its only 90 percent pure.


link to intresting letter on ethanol verses electricity from biomass


This gatekeeper membrane remembers me the "Maxwell´s demon" we´ve seen in thermodynamics and it would be a marvel, but I note some ambiguousness in the article like others over biofuels.
Reading the last paragraph we can not deduce what´s the final product and all the mathematics are trivial.
¿Somebody have real yield numbers in ethanol and diesel from biomass (actual processes)?

Rafael Seidl

Wintermane -

ok, there obviously is a difference between >99% pure (anhydrous) and 90% pure ethanol, the rest being mostly water. Only the anhydrous type is suitable for blends containing mostly gasoline.

However, ethanol is highly hygrospcopic, so it's very hard to keep it pure in the distribution chain - especially in humid climate. Brazilians have resigned themselves to using a 93% pure (azeotropic) alcohol/water mix as a gasoline-free alternate fuel.

So perhaps this new membrane will be useful primarily in tropical countries that can emulate Brazil's model.


Perhaps they could use reverse osmosis, or flash evaporators to finish the distillation. Waste heat from powerplants could heat the solution to near boiling temps. Then, the pressure is lowered, and causing the solution to boil away. Ethanol is then distilled from the gas. Some of the heat given off can be used to preheat the incoming liquids, or run heat engines to power the pumps (some of the time).

Warren Heath

The fact still remains that it is much more efficient to simply burn the biomass in thermal power plants to produce electricity. And plants are terribly inefficient as energy producers. The focus should be on converting 100% of biomass carbon to liquid fuel carbon, as this is the one thing plants do very well, fix carbon out of the atmosphere. The only two processes that do that efficiently, that I know about, are the Fischer Tropsch process and a possible approach of using CO2 to feed algae, see:


Fuel ethanol is usually double distilled to concentration close to 96% (it is theoretical limit of ethanol purification from water solution by distillation), and then dehydrated on molecular sieve – kind of membrane separation technology. As I understand it, new membrane allows to produce 90% proof ethanol in one distillation step. It is indeed great achievement.


As Andrey mentioned, what the article does not mention or inaccurately states is that distillation is not the only process involved in purifying the "beer" or 3-5% ethanol produced during fermentation. Typically distillation is used to reach the azeotrope (ie the point where no further separation can occur or 92% for ethanol-water mixtures), from there a molecular sieve (packed bed of material that absorbs water, ie a sophisticated desiccant) purifies the ethanol up to 99.5%

So the potential of this Japanese technology is that if it is efficient (low pressure requirement, high separation efficiency, etc), then maybe some amount of distillation can be avoided altogether and this membrane could be coupled with a molecular sieve to get pure ethanol.
The article is very unclear on how the membrane works with distillation. I imagine that it simply makes it possible to take a lower concentration of ethanol (say 70% ethanol) and concentrate it to 90%.
Either way this is a poorly written article


I think this is great, low costs for producing ethanol. Also I think 90 percent ethanol means 180 proof.

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