American design brand Artecnica have launched a bag made of discarded billboard posters.
The bags are made by cutting the material so that it lies flat when not in use but can be stretched into a shoulder bag.
Here's some more information from Artecnica:
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Billboard
This August, Los Angeles-based design studio Artecnica announces a new collection born out of an exciting venture recycling advertising billboards.
Impressed by Artecnica’s pioneering Design W/ Conscience program, advertising agency TBWA requested Artecnica to recycle their large format billboards exclusively. 
After a 2-year design process, Artecnica releases the first 2 commercial products of this new collection. They are sustainable, simple and beautiful.
A single cut without glue or a stitch this 100% billboard bag lies flat and weightless but transforms into a shoulder Stretch bag, that can carry up to 33lbs. Perfect for the beach, the gym or market.
In the future artecnica intends on launching the second phase of this venture which focuses on designs and systems for communities in need.