Chinese scientists successfully developed white paper from fly ash, a waste product of black coal combustion in electric power plants.
The result — which passed rigorous tests in actual production lines — is now ready for mass application, with some local paper mills already using the material in their manufacturing process.
The innovation comes nearly a decade after Zhang Meiyun, a professor from the Shaanxi University of Science and Technology (SUST), and colleagues proposed that fly ash could be used as a substitute for wood pulp, the main ingredient in papermaking.
Interestingly, the new paper is nearly indistinguishable from one made of wood pulp, achieving more than 90% match to pure whiteness.
The breakthrough tackles two major environmental issues: the industrial demand for timber and the disposal of millions of tons of fly ash per year.
Most forests in China — the world’s largest paper industry — are protected, so its paper mills source wood pulp from other places such as Canada, Russia and the United States.
China, however, is also the world’s largest electricity producer, which unfortunately yields about 700 million tons of fly ash each year, some 30% of which end up as waste.
In 2010, Zhang and her colleagues realized that fly ash could be used as an alternative for wood pulp, considering that its chemical and physical properties are similar to industrial additives already used in papermaking.
Turning a black coal by-product into white paper immediately posed challenges for the team. For starters, fly ash contained unburnt carbon particles, which reduced the paper’s brightness.
“The first sheets that came out in our lab looked grey,” Song Shunxi, one of the scientists involved, told the South China Morning Post. “We had a Cinderella but the paper industry wanted a Snow White. It didn’t work out very well.”
In solving the problem, the team relied on a chemical process that extracted aluminum from fly ash. They eventually succeeded in improving its whiteness, but the paper became too fragile.
“Plant fibre is organic, fly ash is not. Blending them together is difficult, and there are lots of gaps to fill between the fibres,” Song told SCMP. “Nobody wants to use paper on which the ink spreads or which has dust coming off.”
In 2014, after further research, the team finally managed to address all papermaking concerns. The only problem was that no factory wanted to try making their paper.
“Thankfully we had the government behind us,” Song said. Aside from funding their work, public officials helped them test and improve the technology at paper mills in multiple cities.
“We will continue to improve the technology until one day it can be used in every paper mill,” Song added.
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