'Wet Waste' Could Lead to 165% Decrease in Aviation Emissions

New research says human waste collected aboard airliners can help to power future flights.
Chris Young
Istanbul Airport, Turkeyguvendemir/iStock

Researchers say that by converting "wet waste" materials into biofuel, the aviation industry could cut greenhouse gases by 165 percent, massively reducing its footprint of 2.5 percent of all the planet's greenhouse gases.

In a study published on Monday, March 16, in the journal Proceedings of the National Academy of Sciences, a team of researchers led by the U.S. National Renewable Energy Laboratory detail how to transform organic waste into paraffin, a combustible hydrocarbon used in aviation fuel.

The researchers say their work has the potential to turn jet fuel green and remove the need for electric aircraft.

"While renewable natural gas targets an enormous US market, producing liquid hydrocarbon fuels from wet waste offers the potential to address the challenge of decarbonizing the aviation sector," write the authors in the study.

Unlike production methods for other biofuels like ethanol or biodiesel, the new approach uses a new chemical process to efficiently remove excess water from the "wet waste."

By manipulating the chain length of the carbon molecules in the "wet waste" — which can include food scraps and human waste — the researchers generated short-chain and medium-chain carboxylic acids. These are precursors for biofuels known as "volatile fatty acids" (VFAs).

They then used a process called ketonization to "elongate the carbon backbone of the VFAs." This process created paraffin-rich hydrocarbons and isoparaffin-rich hydrocarbons that can be used for jet fuel. 

A 'circular manufacturing process'

As an Inverse report reads, the scientists propose a circular manufacturing process with their new fuel method. Essentially, human waste from lavatories aboard planes will be collected to help power future flights.

The paper's authors argue this process has the potential to account for 20 percent of the U.S.'s jet fuel consumption, bringing it closer to its goal of carbon neutrality.

This is another great example of an initiative that tackles two global issues at once: food waste accounts for 6 percent of greenhouse emissions worldwide. Combined with other forms of "wet waste," including human excrement, and animal manure, these byproducts have the potential to vastly change the aviation industry.

In laboratory tests, the new fuel was shown to have minimal impurities and chemical leftovers from the waste that would not be useful for fuel. More research is needed, though companies such as Boom Supersonic, who aim to launch a fleet of supersonic carbon-neutral airliners, will no doubt be looking on from the sidelines.


Editor's Note 17/03/21: The title of an earlier version of this article incorrectly stated that "human waste" could lead to a 175% reduction in aviation emissions. This was changed to more accurately reflect the original statement from the authors of the study. 

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