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A passenger aircraft during refueling
Photo: Chalabala / iStockphoto / Getty Images
Climate change poses many challenges for humanity.
One of them is the development of new, climate-friendly fuels for aviation.
Because during air travel, the combustion of the petroleum-based fuel produces carbon dioxide and nitrogen oxides.
In addition, clouds of exhaust gas form, which can reflect heat radiation back to the earth.
Researchers have therefore been working on environmentally friendly and climate-neutral alternatives for a long time and often use biomass for this.
High-performance bio-kerosene, so-called Sustainable Aviation Fuels (SAF), should decarbonise aviation - that is the hope.
In a new process, a team of scientists now wants to use food waste for an aircraft fuel.
Since the rotting of the waste usually produces methane (CH4), which is 28 times more effective as a greenhouse gas than carbon dioxide (CO2), this approach has a particularly favorable environmental balance.
In addition, the fuel soots very little, as the group around Derek Vardon from the National Renewable Energy Laboratory in Golden (US state Colorado) reports in the journal Proceedings of the National Academy of Sciences.
"Worldwide, food waste accounts for six percent of greenhouse gas emissions," the researchers write.
On the one hand, your process offers the opportunity to reduce these greenhouse gases.
On the other hand, it could reduce the climate-damaging releases of air traffic, which make up another 2.5 percent of these emissions.
Because leftovers have a high moisture content, they require a different approach to producing climate-friendly jet fuel than biomass, for example.
The scientists first stopped the production of methane using a process that was already in use commercially.
Then they made longer carbon chains from volatile hydrocarbons and linked them together.
In the end, two fuels were created - one with a little more carbon atoms, one with a little less.
The researchers then examined the extent to which the two fuels produced meet the specifications for aircraft fuels.
Because the fuel produced from the longer chains ignites faster
,
a maximum of 20 percent of the
fuel
can be added to fossil aircraft fuel.
If you combine both climate-friendly fuels, this mix can make up 70 percent of an aircraft fuel if the specifications are met.
The machine would then only fly on 30 percent fossil fuel.
The researchers now calculated how much greenhouse gas could be saved with the fuel produced in this way.
By using leftover food and the methane emissions that are eliminated as a result, CO2 equivalents of 154 grams per megajoule are saved - with this unit, the researchers put the energy content of the food in relation.
The manufacturing process of the new fuel leads to exhaust gases, which in turn are quantified at 99 grams of CO2 equivalents per megajoule.
The bottom line is that a total of 55 grams per megajoule is saved.
The use of conventional, fossil jet fuel, on the other hand, produces 85 grams. The researchers calculated a saving of 165 percent for their fuels - this also includes the savings from methane emissions that would otherwise be released by the leftover food.
If the desired mixture of 70 percent sustainable fuel and 30 percent fossil fuel is achieved, a climate-neutral fuel will be within reach, explains Vardon's team.
Less soot during combustion
"The lifecycle analysis shows the significant carbon footprint impact when food waste is diverted from landfill to produce sustainable fuels, and shows the potential for achieving the goals of aircraft fuel safety, serviceability and the environment," the researchers write .
Another advantage of the mixture with 70 percent climate-friendly fuel is that 34 percent less soot is produced when burned than when burning purely fossil fuel.
Soot particles from aircraft engines also contribute to the greenhouse effect.
How future-proof the process is and how easily it can be produced on a large scale in order to use the fuel in practice remains to be seen, as is so often the case with basic research.
This also applies to many other procedures in this area.
Some companies are one step further - planes already run on biofuel today.
So-called Sustainable Aviation Fuel (SAF) are currently mainly produced from biomass.
The developers mainly use old vegetable and edible oils for this.
However, it is still expensive to manufacture.
And the environmental balance is also questioned by some experts, for example palm oil is used in some processes, which has been criticized for its cultivation methods.
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joe / dpa