at the margin

22:46 Mar 23, 2017 

Let's note first of all the rather unusual wording:
"...make consumers more knowledgeable at the margin..."

Now assuming this is correct EN written by a native speaker, I would not normally understand that to mean 'marginally — to me, it's particularly the use of the preposition 'at' that might at first sight appear curious.

I think the answer is actually simple: I believe the writer is not talking here about 'the margin of the knowledge', but rather, those consumers who are "at the margin" — i.e. between the two groups of consumers: those who are already deeply aware of and commited to environmental issues; and those who don't give a damn about saving the planet, there is a marginal group of people who are faintly aware of environmental issues, maybe have a nagging guilty conscience about it, but perhaps don't actually take any concrete action. I believe it's these people who are being referred to here — of course, they represent a far smaller group of people than either of the 2 major groups.
After all, there's no point campaigning to those who are already committed — "preaching to the converted"; there's probably not a lot that can be done to win over the others.