Membranes play a key role in the human body, filtering out bacteria and viruses and also ensuring cells absorb essential nutrients. They are immensely efficient. For example, the total absorptive surface area of the small intestine membranes is roughly 250 square meters – the size of a tennis court!
Membranes play an equally important role in the cost-competitive sustainable biorefinery industries – facilities that use different biomass feedstocks – plant and algal materials – to produce biofuels, value-added chemicals, power and heat. When compared to the already well established petroleum-based industry, biorefineries are ripe for optimization. Recreating even a fraction of the efficiency membranes provide the human body would provide a major competitive advantage to bioindustries.
Due to the variety of compounds (carbohydrates, proteins, fibers, lignin and others) present in biomass, only efficient and selective technologies bring the process proficiency needed to compete with petroleum-based chemical and fuel production. Each compound present in biomass must be selectively separated in order to maximize its utilization while reducing waste generation. A clear example of this is a cellulose-based biorefinery platform where carbohydrates are transformed into fermentable sugars for subsequent conversion to biofuels (ethanol or butanol) or high value-added biochemicals and other platform chemicals as organic acids and even biopolymers.
Nowadays, there are many different biorefinery facilities around the world, however, only a few can be considered as competitive as their petroleum-based counterparts. This weakness can be associated with poor biomass separation processes, low biosynthesis rates and the current inability to recover expensive materials that are commonly lost in waste streams. Essential process compounds are often lost as waste and cannot be recovered, hurting the competitiveness of bioindustries.
For example, in cellulosic biorefineries enzymes produced from fungi are added during a hydrolysis process in order to break the cellulose carbohydrates down into small sugars. A commercial cellulosic ethanol plant spends millions of dollars annually on enzymes that are completely lost in waste streams during the process and must be replaced, a waste of energy and resources for the plant.
Reducing enzyme waste through cellulose hydrolysis
Imagine now a membrane process able to recover enzymes after cellulose hydrolysis, greatly reducing the amount of enzymes that have to be replaced at the beginning of every cycle. This would reduce waste and be a significant competitive advantage for the biorefinery.
Teams of researchers at GE Global Research in Niskayuna and Rio de Janeiro tackled this problem over the past two years. We found that by using polymeric membranes just after the hydrolysis process, a considerable portion of the enzymes can be recovered. The approach also generated downstream benefits to the process.
The approach is not unlike the way membranes in the kidney recycle glucose, the primary energy source for cells throughout the body. Once absorbed, our body recycles and uses all glucose with 0% losses. Membranes in the kidneys excrete wastes while simultaneously recycling glucose together with amino acids and water. Key molecules are maintained inside the body and losses are not allowed.
The research teams’ work on membranes to recover enzymes lost during cellulosic hydrolisis generated a patent application accepted by the Brazilian Patent and Trademark Office (INPI) and surely will serve as initial step for improving the efficiency of biorefining processes. It is clear that biorefineries will represent an important part of the future world economy once oil-based industries become less competitive as a function of petroleum price and availability. The success of this bioindustry will depend on how scientists and researchers can learn to mimic body and natural processes to increase productivity while reducing energy requirements.