Brands are promising to plant a tree for each can of beer, tshirt, or pair of trainers you buy, offsetting their carbon emissions so they can put an attractive ‘carbon negative’ sticker on a product to show green they - and you - truly are. But how effective is a new forest at offsetting a company’s emissions, what does ‘carbon negative’ really mean, and how do they go about proving they’ve achieved it?

Trees are just one type of carbon offset. Another, albeit promising but expensive, option is Direct Air Capture. Could that be the future of long term carbon offsetting? Greg Foot finds out.

This series, we’re testing your suggested wonder-products. If you’ve seen an ad, trend or fad and wonder if there's any evidence to back up a claim drop us an email to sliced.bread@bbc.co.uk or you can send us a voice note to our new WhatsApp number: 07543 306807

PRESENTER: Greg Foot PRODUCER: Simon Hoban