A team of researchers from the University of California in the US have found a method of making wood-composites from sewage waste.
Wastewater purification uses microbes to form unwanted carbon, nitrogen and phosphorus into a cell mass that settles out, but the disposal of the material can cause greenhouse gases. The team has found a way to prompt the bacteria to grow small granules of plastic within the cell mass, a substance that can then be mixed with natural fibres like straw, wood or hemp to create a wood-composite.
Dr Frank Loge, leading the research at University of California at Davis said the wood-composite has identical properties to conventional materials made using oil-based plastics. ‘The cell mass does make the wood-composite a little bit more flexible however. It’s a property we’re not used to getting out of these materials.
The material would also be biodegradable, thus restricting it to indoor applications such as furniture, doors or interior building structures.
Loge said the material is cost-competitive against established products, because the main cost of producing a wood-composite conventionally is in the plastic manufacture, whereas the cell mass is produced ‘essentially for free’. He acknowledged that convincing the public to buy a household material made from sewage could prove difficult however.
The researchers found the cell mass needed a strict oxidation cycle and had to be heated correctly, said Loge. ‘The product you can end up with if you’re not careful with the heating would look and smell a lot like burnt sugar,’ he said. ‘It’s all a matter of creating the right conditions and turning the right knobs, rather than supplementing the cell mass with any new compounds or genetically-modified organisms.’
The team plans to achieve full-scale operation in a wastewater plant within two years using National Science Foundation funding, in partnership with wood-composites company Strandex and sustainable engineering firm Ecologic. The team is seeking European collaboration. ‘This is one of the first times anyone has been able to implement the concepts of sustainability in a manufacturing context,’ said Loge. ‘This truly is a green technology.’
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