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.