LAST FEBRUARY, THE Associated Press featured a Mexican startup company that converts plastic wastes into gasoline, diesel and other fuels, including for aviation.
Petgas, a startup firm, shreds plastic wastes in its recycling center in Boca del Rio, Mexico and can produce 1.5 tons of plastic into 356 gallons of fuel.
The company envisioned a circular economy, where plastic is no longer a waste but a resource for production of energy. Petgas donates the fuel it produces to the local fire department and food delivery services.
‘Many plastics are used for packaging. Every day, an equivalent 2,000 garbage trucks full of plastic are dumped into the world’s oceans, rivers and lakes.’
Petgas’ machine uses pyrolysis, a thermodynamic process that heats plastics in the absence of oxygen, breaking it down to produce gasoline, diesel, kerosene, paraffin and coke.
Petgas Chief Technology Officer Carlos Parraguirre Díaz said that the process does require propane to initiate the heating, but once the pyrolysis begins, the gas it produces is used to keep it going. Though the fuel it produces throws off carbon dioxide the company says its net impact is less than comparable fuels as the resultant fuel has less sulfur.
DUMPING PLASTIC
The UN had said that global plastic production of over 400 million tons yearly could surge by 70 percent by 2040 if policies don’t change.
Many plastics are used for packaging. Every day, an equivalent 2,000 garbage trucks full of plastic are dumped into the world’s oceans, rivers and lakes.
Last December, the 5th and final round of negotiations for a global treaty to end plastic pollution ended in Busan, South Korea without reaching an agreement. This was supposed to produce the first legally- binding treaty on plastics pollution, including in the oceans, by the end of 2024.
“The future is being able to really take production to a scale that has impact,” said Díaz.
AVIATION FUEL
SciTech Daily published last January a report by the University of Illinois at Urbana-Champaign of researchers developing a groundbreaking method to produce ethylbenzene, a crucial additive for sustainable aviation fuels, from waste polystyrene, to reduce the carbon footprints and reliance on fossil fuels resulting in cost savings of 50 to 60 percent in carbon emissions of the aviation sector.
A new study addresses a major obstacle in transitioning US commercial aircraft from heavy reliance on fossil fuels to sustainable aviation fuels.
Ethylbenzene — an additive that enhances the performance of sustainable aviation fuels — uses polystyrene, a durable plastic commonly found in consumer products.
The findings were published recently in the journal ACS Sustainable Chemistry and Engineering Fuels made from non-petroleum sources, such as waste fat, oil, grease, or plant biomass, often lack adequate levels of aromatic hydrocarbons.
These compounds are essential for maintaining fuel system performance by lubricating mechanical components and swelling seals to prevent leaks during normal operations, explained Hong Lu, a research scientist at the Illinois Sustainability Technology Center of Illinois University.
SUSTAINABLE FUELS
While ethylbenzene is an aromatic hydrocarbon and can be derived from fossil fuels, finding a sustainable way to produce it would aid the aviation industry’s conversion to sustainable jet fuels.
The US Departments of Energy, Transportation, Agriculture, and other government agencies created a roadmap for addressing the climate-related impacts of fossil-fuel-derived aviation fuels.
The Sustainable Aviation Fuel Grand Challenge sets ambitious goals for the production of domestic sustainable aviation fuels to 3 billion gallons per year by 2030, and 100 percent of projected aviation jet fuel use, or 35 billion gallons per year, by 2050.
Present standards require a minimum of 8.4 percent aromatic hydrocarbons be included in any blend of sustainable aviation fuels and fossil-derived fuels “to maintain compatibility with existing aircraft and related infrastructure,” the researchers reported.
While this rule increases the safety and efficacy of the overall fuel mix, it severely limits the use of sustainable fuels, which currently contain 0.5 percent aromatic hydrocarbons, Lu said.
“Currently, they use a blend of 20 percent to 30 percent sustainable aviation fuels and 70 percent to 80 percent conventional jet fuel,” he said, adding that the lag in converting to sustainable fuels stems from factors like the need for enough aromatic hydrocarbons in the mix; and qualities like the blend’s volatility, acidity, moisture content, and freeze point.
ALTERNATIVES
Lu and colleagues chose to develop ethylbenzene because it has a lower tendency to form soot upon burning than other highly aromatic compounds. They chose to start with polystyrene because it is rich in hydrocarbons and is abundantly available in the waste stream. “We produce in the U.S. about 2.5 million metric tons of polystyrene every year, and almost all of it is disposed of in landfills,” Lu said.
To convert the polystyrene to ethylbenzene, the team used thermal pyrolysis, heating it to break the polymer down into a styrene-rich liquid and then hydrogenation converted it into a crude ethylbenzene and later distillation yielded a product that was 90 percent pure.
When mixed with a sustainable aviation fuel, the polystyrene-derived ethylbenzene performed “almost as well as ethylbenzene derived from fossil fuels,” Lu said, explaining that further purification would improve its performance.
“We did a preliminary cost analysis, and we found that the ethylbenzene produced from waste polystyrene is cheaper than that produced from crude oil. And a lifecycle analysis of our ethylbenzene found it reduced carbon emissions by 50 percent to 60 percent compared with the ethylbenzene made from crude oil.”
Lu and his colleagues hope to further develop this additive to help expand the use of sustainable fuels in aviation.