A MATERIALS WORLD#02
Moral fiber: sugar cane replaces petroleum to make eco-friendly polyester fabrics
The development of plant-based polyester could help save the earth by changing what we wear, while significant sales figures suggest consumers are all too happy to make the switch to eco-apparel.
Plant-based polyester may sound like a contradiction in terms. But the parka you take on your next skiing trip, the uniform worn by your cinema attendant and the fabric lining your car seats may soon be made from polyester derived largely from sugar cane.
It’s a ground-breaking technology that could help save the planet by reducing our dependence on petroleum-derived fabrics that contribute to global warming through CO2 pumped into the atmosphere.
The need to wean ourselves off fossil fuels has reached critical levels, with the latest report from the Intergovernmental Panel on Climate Change warning of calamitous consequences – such as epic human displacement and ice-free Arctic summers – if global temperatures rise by 1.5C or more. Meanwhile, some experts predict proven petroleum reserves will run out within 50 years at current rates of extraction, meaning alternative sources are needed for the energy we consume. The same goes for petroleum-derived products, including the plastics and fabrics we use in our everyday lives.
“The global environment and economic security are indelibly intertwined,” says the World Economic Forum, citing “greenhouse gases, environmental degradation and natural-resource depletion” as risks to sustainable growth.
The challenge to go green
The plant-based polyester developed by Japan’s Toray is one way to promote green living in our work and leisure. It’s already used in waterproof, breathable jackets designed for hiking and skiing. And applications are expected to spread greatly in years to come as costs come down and the ecodear fiber’s benefits become more widely known. “We may expect to see a future in which bio-polyesters will be worn in many schools around the world,” Toray says.
The technology takes molasses left over from processing sugar cane and turns it into ethylene glycol, one of two main raw materials used in the manufacture of polyester. The organic compound is combined with petroleum-derived terephthalic acid and undergoes polymerization – a process of chaining simple molecules into three-dimensional networks – and is spun into polyester thread. Currently, the polyester is 30 percent derived from molasses and 70 percent from petroleum; Toray’s ambition is to develop a polyester made from 100 percent plant-based sources. The breakthrough will come in finding a way to produce terephthalic acid – polyester’s other main raw material – from plant-based sources.
Plant-based polyester significantly reduces greenhouse-gas emissions because the CO2 produced at the end of the product’s life – for example, if it is burned – is balanced out by CO2 absorbed by the original plant source while it was growing, as a result of photosynthesis.
The eco-fiber yields the same performance as polyester derived entirely from petroleum. Partially plant-derived polyester resin – before it is spun into yarn – reduces CO2 emissions by more than 13 percent compared to its petroleum-based equivalent. A 100 percent plant-based polyester would cut CO2 pumped into the atmosphere by up to 58 percent.
“As environmental issues gain prominence, the adoption of biomass-based polyesters is increasing and is projected to continue rising”
The trend for sustainable solutions
While the technology is still in its early stages, plant-based polyester is making rapid strides in the apparel industry. Toray’s ecodear fiber recorded a three-fold rise in sales last year compared to the previous year. “As environmental issues gain prominence, the adoption of biomass-based polyesters is increasing and is projected to continue rising,” says Toray.
Plant-based polyester costs more than petroleum-derived polyester. But the relative cost of organic polyester is steadily decreasing as the technology evolves. Moreover, petroleum prices are on a long-term upward trend as reserves are depleted and energy consumption rises with emerging nations’ economic development. That means the cost of biomass-derived materials will become more competitive over time – particularly if trading nations introduce a global carbon tax to curb emissions.
Will there be a day when all polyester is made from organic sources? For that to happen, the cost will have to come below that of the petroleum-based product and manufacturing capacity correspond to a global production volume of roughly 50 million tons per year. “The challenge is great, but if we clear these conditions, replacement is possible,” Toray says. The benefits of taking up this challenge are equally huge: a 13 percent reduction of CO2 emissions from current polyester production would take 30 million tons of greenhouse gases out of the atmosphere every year – the equivalent of the CO2 emitted by 6.5 million cars in a year, or the energy consumed by 3.3 million homes, according to the United States Environmental Protection Agency’s emissions calculator.
The dream of achieving a sustainable society can take a step forward with plant-based polyesters developed through chemical innovation. Climbing a mountain wearing a jacket that keeps you warm, shields you from raw gusts and allows your body to breathe can also help to protect the planet. The UN Sustainable Development Goals of responsible consumption and production (Goal 12) and climate action (Goal 13) have an unlikely space to flourish in a field of sugar cane.