Renmatix uses water to breakdown biomass, specifically the cellulose in it, and convert it into cellulosic sugar. Most technologies that tear apart biomass utilize enzymes, flammable solvents, or rely on strong acids - generally things that are more expensive, or less in line with the principles of green chemistry, than the Plantrose process. The proprietary differentiator of the Plantrose platform is the economical use of our 'secret weapon' - the engine in supercritical hydrolysis, something known as supercritical water.
What is supercritical water?
To understand supercritical water, let's first consider the concept of a supercritical fluid. Supercritical can be thought of as a "fourth state" of a material. It is not a solid, a liquid or a gas.
A supercritical fluid is any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist. It can effuse through solids like a gas, and dissolve materials like a liquid. In addition, close to the critical point, small changes in pressure or temperature result in large changes in density, allowing many properties of a supercritical fluid to be 'fine-tuned'.
Supercritical fluids are suitable as a substitute for organic solvents in a range of industrial and laboratory processes. Carbon dioxide and water are the most commonly used supercritical fluids, being used for applications like decaffeination and power generation, respectively.
— Székely, "What is a supercritical fluid?", Budapest University of Technology and Economics
So, to picture supercritical water, think about a familiar example: boiling water on the stove. When a pot of water starts to boil, you can put pressure on the water and stop it from boiling; this occurs when we put a lid on that pot (or in a more extreme example, what happens in a pressure cooker). That action adds pressure — so the water will actually reach a higher temperature above the normal boiling point — until you get past a certain higher temperature, and then, suddenly it'll start boiling again.
Now imagine if you are in a laboratory and have the equipment to put even more pressure on the water, and it will again stop boiling. You can continue to increase temperature, and then pressure, and temperature until you get to about 373 degrees Celsius. At that time, when you reach the critical point, you can not compress the water back into being liquid - it always stays in something that looks like a vapor form. It’s completely compressible (as opposed to water in a liquid phase, that is not). That’s where water becomes supercritical.
That may not sound very exciting — so why is this important? Yes, it can be compressed - but what really happens is supercritical water behaves differently than normal water. Supercritical water can dissolve organics, like gasoline or cyclohexane would. It can dissolve plastic because you can tune something called the dielectric constant in it — you can make it act more like acid; you can make it more like a base — all by just changing temperature and pressure. All these things change in the water, so water effectively becomes a solvent and a catalyst for us to tear apart the biomass at these conditions.
Paper beats Rock, Scissors beat Paper, Supercritical Water beats Biomass
When we tear apart the biomass, we basically get 3 big chunks: hemicellulose, cellulose, and lignin. The hemicellulose and cellulose create sugars. The lignin is a different molecule altogether.
Plantrose technology is a two-step continuous process that deconstructs a range of plant material into renewable feedstocks to produce separate streams of sugar from the available hemicellulose and cellulose. After sugar extraction, remaining lignin solids can be burned to supply the bulk of the heat energy required for the process (or utilized in higher value applications like adhesives or thermoplastics).
In the first step, biomass and water are pumped together, heated, and fed into a fractionation reactor, where the hemicellulose is solubilized into a sugar stream (5-carbon or 6-carbon sugars, depending on the biomass). In the second step, the cellulose and lignin that were filtered away from the initial sugar steam are pumped into the supercritical hydrolysis reactor.
In the reactor, water acts as both a solvent and catalyst, decrystalizing and dissolving the cellulose and hydrolyzing the cellulose polymers. The temperature and pressure of the supercritical water system can be adjusted for very specific reaction condition control, enabling the use of smaller continuous reactors for large-scale commercial production.