Earlier this year, a global thematic research firm said that every electric vehicle leaves the factory with a lot more embedded carbon than an equivalent ICE vehicle. Put simply, the EV production process releases more carbon which directly clashes with the greater goal of producing a zero-emission car. In some cases, you'll have to cover tens of thousands of miles in your Tesla Model 3 before it becomes less harmful to the environment than a similar ICE car. That's why a number of manufacturers are pushing towards carbon neutrality in their production processes by powering their factories with solar energy and making sure the supply chain is green.

This uncomfortable truth about carbon emissions during production now applies to supposedly green hydrogen-powered vehicles too, according to new research that exposes the damaging impact of producing hydrogen using specific methods.

There aren't many new vehicles that use hydrogen fuel cell technology, but new models like the Hyundai Nexo and Toyota Mirai successfully combine the quick refueling times of ICE cars with the zero-emissions of normal EVs - at least in theory. But a new peer-reviewed study published in the Energy Science & Engineering journal points to a worrying amount of carbon dioxide being released when hydrogen is extracted from natural gas, the main method of production used in the US.

Known as "blue hydrogen", this process also releases methane, a damaging greenhouse gas. The researchers found that blue hydrogen has a 20 percent larger greenhouse gas footprint relative to burning natural gas or coal. It was assumed that 3.5% of gas drilled from the ground leaks into the atmosphere.

"To call it a zero-emissions fuel is totally wrong," said Robert W. Howarth, a biogeochemist and ecosystem scientist from Cornell University and who is the study's lead author. In an even more damning statement, he said: "What we found is that it's not even a low-emissions fuel, either."

Less damaging green hydrogen is produced on a much smaller scale. It requires electrolyzing water to separate hydrogen atoms from oxygen in a process that is highly energy-intensive. With hydrogen touted as a clean energy source to drastically cut global emissions and power everything from cars to planes and homes, the method of its production is likely to come under further scrutiny as research like this latest study intensifies.