Researchers at Oak Ridge National Laboratory set out to determine what could increase production speeds and improve the quality of biofuels and bioproducts. What they discovered is a new class of porous membranes—a high performance architecture surface-selective (HIPAS) membrane technology.

Supported by the U.S. Department of Energy’s (DOE’s) Bioenergy Technologies Office (BETO), this new class of high-performance membrane technology can be used to improve the efficiency of biofuel separations, effectively lowering the cost of biofuel production and helping BETO advance its goal of creating cost-competitive, domestically-produced fuels.

HiPAS BETO membranes blog

HiPAS membranes can be manufactured as disks or tubes with tunable surfaces that attract or repel water, allowing energy efficient separations for biofuel production. | Photo Credit: Oak Ridge National Laboratory 

Many challenging separations are required to convert biomass to biofuels. These include removing water from algae or taking contaminants out of sugar streams before microbes or catalysts can further process the chemical intermediates into fuels or products. Membranes can be used in one method to perform these separations. A porous membrane is an engineered barrier that works by allowing certain particles to pass through while preventing others from doing so.

Researchers can use ORNL’s new HiPAS membrane technology to separate carbon, the main building block for biofuels, from both aqueous and vapor-phase materials. These separations can account for as much as 50% of the cost of converting biomass to useful products, which is why researchers at ORNL set out to design a membrane that could be used to efficiently separate carbon from water at higher yields than traditional membranes. 

aqueous bio-oil solution

The effectiveness of the HiPAS membrane can be seen by comparing the initial feed of aqueous bio-oil solution (left) with the membrane-extracted water (right), enabling more efficient carbon recovery for fuel and chemical production. 

Traditional membrane separations rely exclusively on pore size to recover carbon from aqueous streams. As the pore size decreases, the speed of the separations process, known as flux, slows down because fewer particles are able to permeate the smaller pores. Membrane flux is the most sensitive parameter impacting the minimum fuel selling price (MFSP) of biofuels, and achieving high flux is a key element of an effective membrane. ORNL’s HiPAS membranes are innovative in that they do not rely solely on pore size to separate carbon. Instead, the new membranes use nanotechnology coatings to change the shape of the pores, allowing for 10-fold larger pore size with the same separation efficiency as traditional membranes.

The work has multiple possible applications in the production of biofuels. Recent analysis by ORNL, in conjunction with the National Renewable Energy Laboratory, determined that the HiPAS membrane technology has the greatest impact on the BETO portfolio when used to create bio-oil from algae in a process called hydrothermal liquefaction. This has the potential to reduce the biofuel MFSP by 12%. Additionally, the benefits of the new membrane technology could potentially extend to similar applications in the biochemical, pharmaceutical, or petrochemical industries.

The ORNL scientists are continuing their research to determine the best possible and most efficient applications for biofuel production and the BETO portfolio. Plans for future work include continuously improving the membrane flux, developing chemically stable coating materials, and reducing the membrane surface area required while simultaneously working to optimize the process and its scalability.

ORNL is part of BETO’s new Bioenergy Separations Consortium—a consortium of eight DOE national laboratories leading coordinated research on cost-effective, high-performing separations technologies. This consortium is supported by BETO’s Conversion Research and Development Program, which advances the development of technologies for converting biomass feedstocks into viable biofuels and bioproducts, moving the U.S. toward an economically competitive and environmentally sustainable bioeconomy.

membranes separate water vapor

This figure shows the selective permeability and higher throughput of HiPAS membranes in a biomass to bioproduct conversion process. In this example, the membranes separate water vapor from high value chemicals in the product stream.