Ban the non-bio polybag!
Join the campaign to ban plastic bags - by not using those nasty mailing bags!
There are alternatives if you still want your customers to see your brochure as it lands on the doormat:
Try not only biodegradable but compostable bags from Natureplas:
www.polypostalpackaging.co.uk/index.php?page=Eco_bags
or
www.polymailplastics.com/
biodegradableplastics.htm
Or try recyclable envelopes. Or a wraparound cover and stick a 'stamp' directly on the brochure back.
Get your mailing house on the case. Think how many bags your organisation won't be inflicting on the environment...