Cardboard tents
cnn.com
cnn.com
No amount of greenwashing is going to solve the real problem, which is that too many people just don't care. The greenest solution was probably not to attend the festival to begin with; the second greenest solution was to attend but actually give a shit about the impact of your decisions.
WTF? People just leave their shit on the ground leaving a festival?!
What you mean is "too many brits just don't care".
It's definetely NOT like this in the US. Yes, some thoughtless people do leave some shit behind, but nothing like 100K tents.
I've been to my share of festivals, what I mostly see left on the ground is small trash (equally unacceptable, but on a much smaller scale than this is reporting).
The huge overlap I see with the UK, that the US appears to be missing, is that there's surprisingly few other places to use tents. In most of the UK (ex. Scotland), wild camping is actually illegal. In central europe, camping appears to be surprisingly rare. They have astounding hiking routes, but with amenities provided/expected and just setting up camp is frowned upon.
So we have these super-cheap "pop-up" tents that don't survive much usage at all, and are likely only fit to be abandoned after a few days. Relatively expensive tents for weirdos like me that'll actually appreciate them. And almost zero market for anything in between.
So the markets are roughly €20-40 for a tent that'll survive this festival maybe. €200-400 for a tent that'll make it to next year, if this year doesn't get rained out, and you don't bother spend a few days at home drying it out so it's not a mouldfest when you go to use it next year, and €400+ for something you'll care about.
The huge disconnect between UK/EU usage and US usage is that there's often very little other reason to own a tent here. Even if you don't go camping in the US, you could, and that hypothetical is enough to get you to spend a few bucks more on something that's worth taking home with you.
(This comment offered without suggestions - perhaps a why, probably not a how.)