Delta Air Lines has unveiled a new plan to reduce the use of fossil fuels on its planes in an effort to address climate change. The goal, the airline said, is for sustainable aviation fuel (SAF) to account for at least 95 percent of its fuel consumption by 2050.

SAF is made from waste or crops through a process that is supposed to cancel out much of the greenhouse gas emissions a plane produces. It is not a perfect system and could create new environmental problems. And with very little SAF produced today, it’s going to be an uphill climb for Delta to reach its 2050 goal. However, SAF is largely considered by the industry to be the most viable alternative to fossil fuels for now.

SAF is a biofuel made from plant or animal material. A plane running on SAF will still produce planet-warming carbon dioxide emissions, but the goal is to write off much of that pollution in the form that the fuel is produced. If it’s made from plants like corn or soybeans, the climate benefit is supposed to come from photosynthesis. Plants absorb carbon dioxide during photosynthesis, which is supposed to remove some of the pollution that comes from burning fuel. When SAF is made from food waste or other organic matter in the trash, it is assumed that the climate benefit comes from avoiding the greenhouse gas emissions that would have resulted from that food or waste ending up in landfills.

Airlines also like the idea that SAF can be used like traditional kerosene, without much change to aircraft or fueling infrastructure. That is not the case with electric planes or hydrogen jets. Aircraft running on hydrogen would have to be redesigned to accommodate larger fuel tanks. And today’s batteries are too heavy for electric planes to fly long distances on.

Delta is also investigating those technologies. It is partnering with Airbus to develop a hydrogen-powered aircraft and with Joby Aviation on electric air taxis for short-range flights. Delta says “breakthrough aircraft” should account for 25 percent of its fleet by 2050. Still, Delta says in its new sustainability plan announced yesterday that SAF “is at the forefront” of its medium-term strategy.

So far, Delta has committed to 200 million gallons worth of SAF purchase agreements with around 50 corporate customers. That is still a drop in the ocean. The world does not currently produce enough SAF to power Delta’s operations for even a single day, the airline said in its announcement.

The company has set incremental milestones on its way to reaching net-zero greenhouse gas emissions by 2050. By the end of the decade, Delta expects SAF to offset 10 percent of its fuel use and says it is already “on half” of that goal. . SAF usage reaches 35 percent by 2035 under Delta’s plan. Then you have to make a big leap to over 95 percent SAF by 2050.

The company covers itself by saying it will need help from lawmakers and the rest of the industry to get sustainable jet fuels off the ground. Creating supply chains for SAF and making it more affordable than traditional jet fuel will require more investment and demand.

On the other hand, the increasing demand for SAF could have harmful side effects for the environment. Without reducing the demand for air travel, feedstocks for biofuels could occupy an area as large as 19 percent of the world’s farmland today. That has some environmental advocates concerned about how SAF could contribute to deforestation in the future.

All of these challenges make aviation one of the hardest sectors to clean up Delta generated approximately 27 million metric tons of carbon dioxide in 2021, according to its latest ESG report. That’s roughly the amount of climate pollution 68 gas power plants could create in a year. Jet fuel alone is responsible for 98 percent of Delta’s emissions, the company says.

Until recently, airlines, including Delta, relied heavily on carbon offset schemes to tackle their pollution. With carbon offsets, companies often pay to support forestry or other conservation projects to offset their emissions. The idea is that trees and plants capture climate pollution through photosynthesis.

The bad news is that carbon offset projects, often due to poor planning and management, fail to reduce the amount of CO2 entering the atmosphere. In light of those failures, other airlines, including JetBlue, Air France and easyJet, have also begun to prioritize the transition to SAF.