Liquid wood is a strong, thermoplastic material made from a mixture of lignin and natural fibers called Arboform®. It is often hailed as the eco-friendly alternative to petroleum-based plastics because it is non-toxic, biodegradable, and doesn’t deplete or depend on the non-renewable resource of petroleum. Prior to the invention of liquid wood, bioplastics were not suitable for household use due to the high sulfur content, but the low sulfur content of Arboform® makes it safe even for use in toy manufacturing.
Arboform® is formed from the combination of lignin and natural fibers, like flax or hemp, and additives such as wax. Once the composite of lignin and fibers is complete, the mixture can be heated or put under high pressure for processing and molding into parts. Lignin is a chemical compound produced as a byproduct of the pulp and paper industry and derived abundantly from wood. It is second only to cellulose as the most common natural polymer, and this polymer molecular structure makes it very strong and well suited as a plastic alternative.
Norbert Eisenreich’s team at the Fraunhofer Institute for Chemical Technology in Germany began researching alternatives to plastics in the mid-1990s and finally came up with liquid wood. Plastic is strong, moldable, and capable of mass production, but also has several flaws that have caused concern for consumers and researchers. Plastic’s dependence on crude oil depletes a non-renewable resource, causes pollution in its production, and makes it subject to price increases. Pthalate softeners and heavy metals found in plastics have also raised health objections to the use of plastic. Liquid wood is derived from an abundant resource, may be molded and mass produced, will biodegrade, and is non-toxic.
The Fraunhofer Institute faced the problem, however, of making the material waterproof and low in sulfur, which was achieved through substituting sulfur separation with high pressure hydrolysis. In order to use lignin, it has to first be separated from other fibers in the wood, traditionally done with sulfur. The hydrolysis process uses only high pressure, water, and high temperature to produce a water insoluble lignin. This cut the sulfur content by ninety percent while yielding a product that will not degrade with exposure to water or saliva.
After Eisenreich came up with the material Arboform®, Tecnaro, another German company, refined it to be molded and produced. Tecnaro created plastic-like pellets that, under high pressure can be forced through a nozzle to make more elaborate shapes. Liquid wood has been used to produce watches, car parts, pens, speaker boxes, and a nativity set, amongst other items. Finished, it can look like ordinary plastic found in most household products or like polished wood. Liquid wood can be successfully recycled without changing the chemical make-up of the material or disposed of in the same manner as wood.