Global Waste Management : Rotting vegetables into electricity

Tons of food goes unsold every day at a market in Hyderabad, India. But instead of throwing it into a landfill, it is turned into electricity that will power street lights, buildings and a kitchen that prepares meals for 800 people. This is called biogas. It is plentiful, low tech and experts say that it is cleaner than any fossil fuel. So why can we make energy from the 1.3 billion tons of food that gets thrown out every year.

The first step is to chop up the large vegetables and load them onto a conveyor belt. Some of the vegetables are spoiled and others are thrown away because it costs farmers too much to transport them back home. These vegetables are useless if they rot so that is why they are used in the biogas plant.The conveyor belt carries the material to a shredder which further breaks down the food into smaller, more uniform particles. In a single day it handles the same amount of vegetables that 150 people eat in a year.

A grinder crushes the mixture into pulp which is pumped through underground tanks and into two digesters. So anaerobic digesters basically have bacteria which operate in the absence of oxygen and they essentially eat the food waste that we are putting in there and give out methane and carbon dioxide. Any organic material emits these planet warming gases as they decompose but the massive amounts of food waste makes landfills the third largest source of human caused methane emissions just behind fossil fuels and agriculture.

Burning biogas to make electricity is a way to harvest those gases before they enter the atmosphere. The fuel is stored in large containers before it is ready to use. Aside from energy, the plant creates another valuable by-product and that is fertilizer. Farmers who sell their wares at the market buy it back and spread it on the same fields where their vegetables grow. By using this fertilizer, the crop yield gets better. It is helping to reduce landfill waste at a large level. It is an essential step towards sustainable living.