Easy trick turns wood waste into biofuels

One easy step could convert the lignin in wood, considered an annoying waste, into a source of biofuel. A team of researchers in Switzerland and the US has found that adding formaldehyde during wood pretreatment converts up to 80 percent of lignin into molecules that are used to make fuels and chemicals.

Widespread, fast-growing trees such as poplar could be a sustainable source of biofuels that don’t affect food supply. The first step in today’s biofuels production process is to remove the fibrous lignin that surrounds the sugary cellulose, which is fermented to make fuels.

This is done via a costly process that requires high temperatures and harsh chemicals. That changes the chemical bonds in the lignin polymers, so it cannot be used and is discarded as waste. . Millions of tons of lignin waste are similarly produced by the paper industry.

Researchers have been trying to engineer trees that produce altered forms of lignin and self-destructing lignin. But lignin makes up almost a third of a plant’s biomass, and could be an abundant source of fuel if there was an easy way to extract and transform it.

Jeremy Luterbacher, a chemical engineer at the Swiss Federal Institute of Technology, and his colleagues report in Science that adding formaldehye to the pretreatment step is all it takes to preserve lignin, so that it can be converted into useful building blocks for chemicals and biofuels.

The researchers were able to extract 50 percent of useful lignin when using beech wood, and almost 80 percent when using poplar. That’s three to seven times more than when not using formaldehyde, they say in the paper.

Formaldehyde is a relatively inexpensive bulk chemical that can be derived from biomass, the researchers say. Its addition could be easily integrated into today’s biorefinery processes. “The chemistry is relatively straightforward,” said Luterbacher in a press release. “The real challenge is actually finding investors for a pilot facility to demonstrate this.”

Source: Li Shuai et al. Formaldehyde stabilization facilitates lignin monomer production during biomass depolymerization. Science. 2016.
Photo: ©Dennis Wise/University of Washington (AHB)

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