WPI researchers put ‘red mud’ to use turning food waste into biofuel

WPI researchers put ‘red mud’ to use turning food waste into biofuel

By mcomo April 27, 2018

WORCESTER – The shopping list for Price Chopper includes unsalted butter, applesauce, cheese, mashed potatoes, rice, canned chicken and green beans.

The result?

Not a meal, but a bio oil that researchers at Worcester Polytechnic Institute have combined with a new catalyst, called “red mud,” to improve its energy yield.

“What it comes down to is food waste has carbon in it,” explained Michael T. Timko, an associate professor of chemical engineering at WPI. “We ideally want to maximize the carbon that goes to the oil … red mud seems to be maximizing that carbon.”

About a third of the food produced for human consumption – representing about 1.3 billion tons a year – is lost or wasted, according to the Food and Agriculture Organization of the United Nations. In the United States, approximately 30 million tons of food goes into the trash, costing the country about $161 billion.

“The question is, what can we do with it?” asked Mr. Timko. He explained that food in landfills is not only wasted as an energy source, but decomposes and releases greenhouse gases and creates water pollution. “There is really nothing good that comes of it. But it is a potential resource that could be useful.”

For about the last 40 years, scientists have used the process of hydrothermal liquefaction to convert food waste into a bio oil. The process places wet biomass such as waste food in a pressure cooker-like reactor and exposes it to high temperatures and pressure. The hydrocarbons in the biomass break down to produce a bio oil similar to crude oil. This can be refined to produce biofuel.

But the process is not energy efficient, recovering only about 25 percent of the energy in the food waste, and is expensive, according to Mr. Timko.

Researchers are looking at ways to improve this process.

Graduate student Alex Maag first experimented with using a metal oxide catalyst called cerium-zirconia. The yield of oil from the conversion process went from under 40 percent to 50 percent. The results were published in the March 6 edition of the journal Energies.

But it was red mud – a waste product of aluminum refining being studied by a colleague at WPI – that worked as an even better catalyst. Students Jeremy Hemingway, Marianna Bailey and Nicholas Carabillo, all seniors at the school, began working with the red mud as a catalyst in October.

Initial results have yielded more than 80 percent energy recovery. “We were happy with getting 40 percent before,” noted Mr. Timko.

Red mud is also inexpensive and abundant as a waste product, the researchers noted.

The research, funded by a one-year $168,373 Small Business Innovative Research grant from the U.S. Department of Energy, still has a long way to go before it’s ready to convert WPI cafeteria cast-offs into a sustainable energy source.

Initial results are promising and need to be replicated, Mr. Timko said. Moreover, it isn’t exactly clear what “instrument” in the red mud is causing the catalyzation.

“The basic hypothesis is if we put (the ingredients) together they work in concert – they produce a nice symphony effect,” Mr. Timko said.

But students and researchers are enthusiastic, hoping that their work can eventually tackle problems such as food waste, alternative energy production and reducing greenhouse gases.

“We wanted to do something with renewable energy,” said Mr. Carabillo.

“And food waste is a big issue right now,” added Ms. Bailey. “So this is something that could have a big impact in the long run.”