Flying is just about the most polluting thing many of us do.
According to Google Flights, a nonstop flight from New York to San Francisco produces, on average, more carbon dioxide per economy class passenger than a person living in Cameroon does in a year, as my colleague Hiroko Tabuchi wrote recently.
This week the Biden administration announced new moves to make aviation cleaner, proposing guidelines for how fuel producers can qualify for tax credits as part of a program to increase production of more sustainable jet fuel, my colleagues Max Bearak and Dionne Searcey wrote.
The guidelines are not yet final, but what caught my attention is that they allow corn-based ethanol to be part of the answer. Among experts, ethanol can be divisive and its environmental benefits are fiercely debated, even two decades after the U.S. started mixing it with gasoline.
Today, I want to lay out why the aviation industry generates so much pollution and explain the debate over ethanol.
Air travel is responsible for 3 percent of global carbon emissions, and those emissions are growing faster than those of rail, cars and trucks, or ships. Finding a way to lower that number is one of the most difficult pieces of the energy transition, in part because the technology isn’t quite there yet to provide a solution on the scale we need.
Airplanes, Hiroko told me, also emit other pollution like nitrogen oxide and soot, and form contrails, all of which warm the planet further. Scientists estimate that the net warming effect of these may be up to three times as great as the warming caused by aviation’s carbon dioxide emissions alone.
The debate over ethanol
Here’s where the ethanol debate gets tricky: Depending on whom you ask, corn-based ethanol either reduces greenhouses gases or it can increase them.
Why is there such a big disagreement?
The ethanol industry says their product should be considered renewable because, though we burn it to create energy, when new corn grows it captures carbon. That part of the debate is fairly straightforward.
The disagreement over corn-based ethanol is mostly about the carbon impacts of dedicating huge amounts of farmland to produce it. Does it create pressure to expand farming into natural areas that store large amounts of carbon?
Answering that question is difficult because it’s hard to track the consequences of each farm’s production choices. The impact of land-use decisions are indirect and sometimes global. In theory, using corn for biofuels in the U.S. could make Brazil, another big producer, expand corn farms into native grasslands, for example.
At the heart of the debate is the tension between food and fuel. Critics argue that, if we use more cropland to grow fuel, then we need to either accept higher food prices or develop even more land. Still, Max explained to me, it’s also true that corn yields are growing, reducing the need to expand cropland.
I spoke to Tyler Lark, a scientist at the University of Wisconsin-Madison whose 2022 study questioned ethanol’s climate credentials and concluded that it can be more carbon-intensive than gasoline. He told me that the margins on ethanol’s benefits are thin enough that, depending on the model you chose to calculate its effects, the results can be radically different. His paper prompted rebuttals from the Renewable Fuel Association, an industry group, and the United States Department of Agriculture.
Setting targets based on shaky accounting, he said, “leads to a lot of confusion, and that has, I guess, some potential for leading to adverse outcomes that we don’t want.”
Biofuel farming also creates pressure on dwindling water supplies, as a Times investigation found last year.
Geoff Cooper, the president of the Renewable Fuels Association, told me that several studies over recent years, including one conducted by the Department of Energy’s Argonne National Laboratory, have shown that ethanol is better for the environment than gasoline. “We really don’t see it as nearly as contentious and as uncertain as that issue may have been, you know, 12 or 15 years ago,” he said.
What happens next
The Biden administration’s proposal also requires farmers who produce corn-based ethanol to use agricultural techniques that can increase the amount of carbon stored in the soil.
But, while these techniques have various proven benefits, it’s still unclear exactly how much carbon soils can store this way. Allan Rodriguez, a spokesman for the Department of Agriculture, said that the practices “are backed by rigorous scientific analysis that demonstrate their positive climate impact.” But critics believe they add another level of uncertainty to an already difficult accounting challenge.
There are other alternatives to traditional airplane fuel. Sustainable aviation fuel, as my colleague David Gelles wrote, is generally made from used cooking oil and agricultural waste. But it’s unclear if it’s even possible to produce enough of it from waste to power all of the world’s commercial aviation. As scientists and the industry work to find innovative solutions, some old tricks can help, too. Countries are trying to encourage people to fly less by directing them to electric high-speed rail, for example.
What seems clear, Dan Lashof from the World Resource Institute told me, is that “there’s not going to be a single solution to aviation emissions.”
Can forests be more profitable than beef?
I’ve been to the Amazon rainforest to report several times over the years, and I always hear the same grievance from farmers: Putting cattle where there used to be forest is one of the few ways to make a living in a region where economic opportunities are hard to find, they say.
But the last time I went to the Amazon, I heard something completely different. Sadir Schmid, a 62-year old farmer, told me he was excited to reforest a section of his ranch. The trees would cool down the area, he said, and help restore streams. “My dream is to see water start flowing again,” he said.
The difference now is new sources of money. A restoration company called Mombak is working with ranchers like Schmid and buying up Amazon pastures to restore forests. Then, they sell carbon credits tied to planting new trees.
Mombak is one of a handful of companies trying to create a whole new industry in the Amazon rainforest that can make trees, which store planet-warming carbon, more lucrative than the world’s biggest driver of deforestation: cattle ranching.
I wrote about their work in an article published today that I hope you’ll make some time to read. This new industry’s bet hinges on the success of the carbon credit system, and many conservationists worry it could easily be abused by companies that want to appear environmentally conscious while sticking with fossil fuels.
Still, to my surprise, I saw how reforestation projects have created a buzz among ranchers in the region.
“You know that people who handle cattle don’t care much about this reforestation stuff,” Anderson Pina Farias, another rancher, told me. But, he added, “if selling carbon is better than ranching, we can change businesses.” — Manuela Andreoni
Read the full article here.
Source link: https://www.nytimes.com/2024/05/02/climate/jet-fuel-ethanol-flying.html