5 surprising ways major cities are going green 

What do cow dung, cockroaches, wood pellets and empty plastic bottles have in common? It’s not a trick question. The answer is that they could help us save the planet.

When the Pakistan port city of Karachi had to shut down its public transport authority, the 14.9 million people who live there were left without a formal bus service. An informal network of brightly decorated but often overcrowded private buses struggles to keep people moving.

Now the UN-backed Green Climate Fund and the Asian Development Bank have stepped in to fund a 30km zero-emission bus network that will be safe and accessible to all. Buses will be powered by methane from cow dung, making it the world’s first biomethane hybrid bus fleet.

A new plant is being built outside the city to generate methane from dung which would otherwise find its way into the Arabian Sea. The $584 million project includes 25 new bus stations, secure pedestrian crossings, cycle lanes and segregated bus lanes to speed buses past Karachi’s notoriously slow traffic.

Cockroaches to the rescue

If the idea of cow dung makes you hold your nose, how about a billion cockroaches? That’s how many they have at a plant in Jinan, capital of eastern Shandong province, China and they are eating their way through 50 tonnes of food waste every day.

The city, in common with many others, produces more food waste than can be accomodated in local landfill. So the Shandong Qiaobin Agricultural Technology Co came up with the idea of feeding it to cockroaches, which can in turn be fed to pigs.

China bans the feeding of food waste to pigs to prevent transmission of African swine fever. By next year, the Shandong Qiaobin Agricultural Technology plans to have three more plants operating that will be capable of handling a third of the kitchen waste produced by Jinan’s 7 million people.

As well as a protein-rich food for pigs, cockroaches are also believed to provide a cure for oral and peptic ulcers and heal skin wounds and other conditions. In Sichuan, a company called Gooddoctor is rearing 6 billion cockroaches for medicinal use.

Pay with plastic

In China’s capital, Beijing, and Surabaya, Indonesia’s second largest city, you can buy your ticket for the bus or metro with a bag of recycling plastic.

In Surabaya, a two-hour bus ticket costs 10 plastic cups or up to five plastic bottles, depending on their size. Each bus can collect up to 250kg of plastic bottles a day, helping the city towards its target of eliminating plastic waste by next year.

Plastic is a big issue for Indonesia. A study in the journal Science named the country’s archipelago of a thousand islands as a major source of plastic in the world’s oceans, second only to China.

In Beijing, ticket machines in the city’s subway system now take plastic bottles as well as more conventional payment methods. Passengers receive a credit of between five and 15 cents for each bottle and can top up their fare with cash. China’s rivers are among the 10 major sources of plastic pollution. Eight of the 10 are in Asia.

World’s first carbon neutral city

As nations take action to reduce waste and their environmental footprints, one of the greenest cities in the world is on the verge of becoming fully carbon neutral. Copenhagen plans to be carbon neutral - meaning it will produce no more carbon emissions than it can offset elsewhere - by 2025, a quarter of a century ahead of the targets set in the Paris climate agreement.

It helps that the city owns its electricity generation, which is mostly wind powered. A happy legacy of the last century is that most buildings in the city are on a district heating system, where heat is supplied to homes from a single neighbourhood plant, instead of by each household having its own system.

Virtually all of Copenhagen’s 600,000 residents own a bicycle, and the city has 375km of cycle lanes. But what happens if the wind fails to blow? The city-owned energy company HOFOR is converting a coal-fired plant to burn renewable wood pellets. They will still emit some carbon but the city expects to be 95% carbon neutral even if it has to fall back on pellet power.