Commercial vans add <?> to diesel to reduce carbon?

[DreamingOf]

Hi all,
I was watching Frontline last night and heard a guy talk about commercial vehicles. My understanding of what he said was that 'regulation forces him to add something to his diesel fleet to help reduce carbon and that it cost approx. 63cent per litre'.
Did anyone else hear / see that?
And if so, or otherwise, what is that he must add?? (I thought he said 'blue' something but didn't quite catch it)
Why must he do this and must all companies do this???

Thanks in advance,

 

[sse]

Probably AdBlue. Urea-based diesel additive.

Doesn't reduce carbon but reduces nitrogen oxide emissions.

SSE