That is most likely not the reason it is cleaner as releasing captured carbon dioxide back into the atmosphere is kind of polluting isn’t it! I think it’s supposedly cleaner because the alternatives like blasting the tracks with additives and sand is worse but they don’t really say why.
And they mention it's better than the sand approach since they're not leaving a contaminate around afterwards, since the CO2 will just sublimate back into gas, both which improves the cleaning and makes it more consistent when done repeatedly.
The movie is still borderline sales-pitch, so I'd take it with a grain of salt, but it adds some detail.
By any chance, does money change hands? "Carbon credits"?
Guess what! I'll start a brewery and brew billions of tons of CO2 unless you pay me!
The carbon credit industry is a scam, and it does not actually affect the CO2 concentration in the atmosphere.
Cap and trade worked very well for CFCs. In your example, why doesn't the brewery need to pay a tax for the CO2 released both in manufacture and as part of product-use?
They needed something solid that can sublimate and be relatively safe. Media blasting with CO2 is really a super common thing everywhere in industry. I could drive over to Grainger and buy a CO2 blasting machine today.
Far too many people worry about the 100lbs of CO2 emitted because of rail cleaning while ignoring the fact that a diesel train is spewing (literally) tons of CO2 in the atmosphere. And the trains are one of the best options for low carbon shipping!