A second life for waste wood
About 100 million tonnes of wood waste go unrecycled every year in the EU and the United States alone. Burned or landfilled, this material poses a major environmental challenge. The novel Dendronic process is turning this and other unwanted materials into a valuable resource. “Wood and other agricultural residues are made up of biopolymers called cellulose, hemicellulose and lignin. We have developed a chemical process, based on an environmentally friendly solvent called an ionic liquid, to separate these polymers. This means they can be used for new products,” explains Florence Gschwend, CTO and co-founder of the Imperial College London spin-out company, Lixea. The EU-funded Bioflex project enabled Lixea to build a pilot plant in Sweden – the world’s third largest exporter of forestry products – where the team demonstrated the technology and its various applications.
A versatile process: pick and mix
The process can be applied to different types of waste, including discarded construction wood, sawdust, and also agricultural residue such as sugar cane bagasse. “We can work with a number of different input materials, and there are many different things you can potentially make from the outputs: we offer a platform that enables a lot of different new value chains,” Gschwend adds. For instance, cellulose can be used to produce moulded fibre products, the packaging material egg cartons and food trays are typically made out of. It can also be hydrolysed into sugars and then fermented to produce for example the biofuel ethanol. Lignin is isolated to produce biomaterials such as resins, which are a part of many composite materials, often used in furniture. Hemicellulose is converted into specialty chemicals used in different industrial processes, for instance to create paints or adhesives. At the Bäckhammar plant, the Lixea team has been working with industry pathfinders to explore different applications. For instance, it applied the process to sawmill residues, producing a cellulosic pulp which was then hydrolysed into sugars used as a substrate for fermentation processes, such as bioethanol and food production. In another case study, bagasse from a sugar cane mill will be used to produce moulded fibre products as well as furfural, a chemical used for instance in inks and fertilisers.
Less waste, more value
There are a few notable differences that set Bioflex’s process apart from those currently used in the paper and textile industries, Gschwend notes. “These involve harsh chemicals, and often only create value from part of the wood, as they do not utilise all three components. Moreover, these processes require plantations of one single tree species, while ours uses waste material.” Another currently available recycling option is the use of sawdust waste in fuel pellets. Although these are sometimes promoted as a renewable energy source, their use considerably contributes to air pollution, Gschwend points out.
A green solution with big potential
The Lixea team believes its process can contribute to environmental protection and help reduce CO2 emissions in a number of ways. In addition to helping reduce waste, large-scale deployment could have a significant impact on air quality globally. “This especially true for South-East Asia where agricultural residues are often burned in the field without any energy recovery, resulting in air pollution and causing major health problems,” explains Gschwend. Analysis in a Swedish context comparing the production of moulded fibre to polypropylene trays showed that the process could potentially save up to four tonnes of CO2 per tonne of packaging produced. With the market for bio-derived chemicals expected to reach about EUR 75 billion by 2027, the economic potential of the different value chains is huge, according to Gschwend. Her team is currently exploring partnerships with a view to launching a demonstration plant, the next key step towards market deployment.
Keywords
Bioflex, waste wood, biopolymers, cellulose, hemicellulose, lignin, sawdust, moulded fibre, fuel pellets, bio-derived chemicals
