Book 25, Question 118
How does a city turn green-bin scraps into compost and energy?
Trucks bring green-bin scraps to a processing plant.
Workers and machines pull out bags and plastic, and then the scraps go into huge sealed tanks called digesters. With no air inside, tiny microbes break down the food and give off a gas called biogas, which can be used for heat or to fuel trucks. What is left is cured into compost that can enrich soil.