There are not far off 7bn people in the world and between us we generate between 2.5bn and 4bn tonnes of waste a year. That, at least, is the estimated waste collected each year – which excludes waste generated by the construction, demolition, mining and agricultural industries.

It is difficult to gather accurate information on the global waste market, because so much of it is informal. Outside the developed world and the more affluent parts of developing countries, waste collection is patchy and frequently unreliable. Waste may be simply left in the streets to rot or be scooped up by scavengers who scrape a living by reusing or recycling what they can.