United Airlines has pledged to reduce its greenhouse gas impact to zero by 2050 - a necessary step to avoid climate catastrophe, scientists say - while walking away from a practice increasingly common among large global companies. “Carbon offsets”, or credits generated by forest conservation or other means, can be purchased in markets or privately to cancel out emissions. Chief executive Scott Kirby said the practice can’t scale up to solve the climate problem in the way many are expecting it to. Instead, United’s multimillion-dollar investment in 1PointFive, a venture of Occidental Petroleum and Rusheen Capital Management, relies on what’s called direct-air capture, or facilities that draw carbon dioxide out of open air so that it can be disposed of underground. Carbon Engineering, a Vancouver company, has developed the technology. United’s contribution to the initiative is expected to draw as much carbon dioxide out of the air every year as 40 million trees do. The project has been in the works before the pandemic. Aviation faces unique difficulties in carbon-cutting. Unlike electricity, which can be produced with renewable power, or road vehicles, which can be electrified, jets require jet fuel. Carbon dioxide emissions from this fast-growing sector make up about 2 per cent of global greenhouse gases. United, despite unprecedented losses during 2020, has the resources to address emissions more directly than by purchasing offsets. “Part of the reason others haven’t done it is because it does cost money to do this,” Mr Kirby said. “If instead you can write a check to an NGO, and say you have offset all your carbon by writing a check, that’s been historically an easier way to get there.” The latest announcement doubles down on the company’s 2018 pledge to halve emissions by 2050. Mr Kirby, who took the helm of the company in May, said he has over time come to believe that there are three elements to a strategic climate fight. There’s renewable energy, which is now economically competitive in much of the world. There’s sustainable fuel, which United put $40 million into last year and has used where it can at least since 2016. And there’s capturing carbon dioxide and storing it underground. The airline currently offers a way for business travellers to offset the emissions related to their flights — and will continue to do so. “We are going to still be emitting carbon,” he said. “It's not possible to get actual carbon emissions to zero. And so the only way you can stop and reverse this is through direct air capture and sequestration.” Globally, airlines are trying their bit to become more eco-friendly. Last year, <a href="https://www.thenationalnews.com/lifestyle/travel/the-skies-are-busier-than-ever-this-means-both-cheaper-fares-and-carbon-challenges-1.893372">EgyptAir</a> made headlines for piloting the world's longest flight powered solely by biofuel from Seattle to Cairo. The fuel used came from World Energy, the first facility designed to manufacture renewable jet fuel on a commercial scale. It proved that the substances needed to help fly more planet-friendly already exist. Now they just need to become an affordable reality.