Imagine a bike that has been made from plant-based materials or reused and recy cled parts. Imagine that the material wearing from your tyres or brake pads is biodegradable. That the lubricant washing down from your chain no longer pollutes the forest you are riding through, but provides valuable nutrients for the plants in it.You no longer discard your old bike as if it were a piece of rubbish, but return it to the manufacturer so that parts and materials can be reused to make new bikes. Or, alternatively, you could plant your old bike in your garden for it to become part of the circle of life again.You would be living in a world with a circular economy. A world where you ride your bike in an environment without pollution. Through forests larger than today, inhabited by ever more varied species of plants and birds. A world where CO2 emissions no longer contribute to climate change and we no longer dig up finite resources from the Earth, but use our 'waste' or renewable natural sources to make new products.To make the transition from our current linear take-make-waste economy to that circular economy, marginal gains are not sufficient. To get there, we need a revolution.This book is a practical guide to help the world of cycling make that transition.Erik Bronsvoort is a bike nerd, engineer, entrepreneur and trailblazer. Founded Circular Cycling with Matthijs to test circular business models in the cycling industry.Matthijs Gerrits is a bike nerd, historian and IT expert. Founded Circular Cycling with Erik to make sustainability an issue in the cycling industry.