Mega-cities are running out of places to put their waste

A city of 10 million people produces waste faster than any landfill can absorb it. Delhi, Lagos, Jakarta and Mexico City all face the same arithmetic. The population grows, the consumption grows, and the ground set aside for dumping does not.

The World Bank estimates the world generated about 2 billion tonnes of municipal solid waste in 2016 and projects 3.4 billion tonnes by 2050. Most of that growth will come from cities in low and middle income countries, where collection is already stretched.

When collection fails, waste goes to open dumps. Open dumps leak liquid into groundwater, release methane and burn in the open. Neighbouring communities breathe the smoke.

Hauling waste farther is not a fix. Trucks cost money and burn diesel, and every new landfill site faces local opposition. Cities need treatment close to where the waste starts.

That is the design thinking behind the Nexus Biofuel Carbon-to-Carbon (C2C) plant. The system is compact. It takes in solid and liquid waste and converts it to low-sulfur fuel, syngas, hydrogen and inorganic fertilizer. A plant sized for 100 tonnes of municipal solid waste per day can sit on a small industrial site inside a metro region instead of at the end of a long haul route.

Mega-cities will not stop producing waste. They can change what the waste becomes.