Hydrogen has gained ground in recent years as a potential alternative to fossil fuels because its only byproduct is water.

Both Hyundai and Bosch Mobility announced plans for hydrogen fuel at the Consumer Electronics Show in Las Vegas this month. Hyundai announced a plan to expand existing hydrogen operations. Bosch Mobility showed off a hydrogen combustion engine it intends to launch by the end of this year.

Arizona State University assistant professor Ryan Milcarek said he’s optimistic about the future of hydrogen, particularly in larger applications:

"Batteries work well in those small applications, electric vehicles, but when you start to get to heavy trucking, long transport with trains and other types of applications, there’s just not enough energy usually in batteries," he said, "There's some discussion in trying to make that work, but that's where you start to see fuel cells start to have a better place with long-haul trucking."

Phoenix-based Nikola Motor is doing just that — it manufactures hydrogen-fueled semi trucks in Coolidge. The company recently shipped 35 of the first-ever semis to be powered this way.

Milcarek added that the work to adopt hydrogen as an alternative fuel source is far from over:

"We've still got some things we've got to overcome in order for this to work. And so we need the next generation to get excited about the possibilities and to jump in and try and help us solve some of the things that haven't worked with hydrogen," Milcarek said.