"cleaner alternatives" refers to options that are not harmful to the environment or human health. It means choosing better and more sustainable options instead of ones that can cause pollution or other negative impacts. Full definition
But again, the point is that if everyone that could also installed some kind of clean alternative system that would add up. (realclimate.org)
To date, natural oil still serves as our primary source of fuel, even though a much cleaner alternative exists in the form of synthetic fuel. (sciencedaily.com)
It's impossible to justify the construction of any new natural gas project when cost - effective, clean alternatives exist. (blogs.sierraclub.org)