A cardboard bicycle is a bicycle composed mostly of cardboard. Only prototypes have been made as of 2012[update].[1][2][3] Reported benefits include low cost,[1] and construction from recyclable[3] and renewable materials.[4] The low cost is also expected to act as a theft deterrent.[5][6]
And because it is made of cardboard, it will also be cheap
First, he folds the cardboard—commercial-grade material, made from recycled paper
Renewable materials are sustainable materials, which means, according to the Rutgers University Center for Sustainable Materials, these materials do not use up non-renewable resources. These raw materials are abundant and biodegradable, and are used to make diverse products such as adhesives and cardboard.
If you make a bicycle from cardboard, no-one will want to steal it!
If someone stole the bike (and it's hard to believe that something so cheap would have appeal to thieves), the replacement cost would be negligible.