Karachi's green buses to be powered by dung.

Not in their wildest dreams did the residents of Karachi's Cattle Colony think that the filth they were living in for over four decades would generate wealth as well as energy.

'Just the fact that the dung will be removed from our roads and by-lanes makes me excited,' said 35-year old dairy farmer, Yasmeen Barkat, who took over her father's business after his death in 2007. There are associated benefits. 'Getting rid of the flies, reduction in diseases among our cattle, spending less on the water that we consume to wash the dung away from our farm and into the drains, and hopefully getting cheaper electricity,' are some of the advantages Barkat lists.

She has over 100 cows, buffaloes and goats, which seems a large number, but is a quarter of the size of the herd her father managed while he was alive.

The colony provides milk to many across Karachi -Image by Zofeen T. Ebrahim

Observing purdah, Barkat, happily manages the farm in Malir district, with her husband and eight workers. They sell up to 374 litres of milk every day to Ambala Sweets and Bakers with three outlets in Karachi. She pointed out that they use up huge amounts of water to clean their farm every day. 'If we don't, our animals will fall sick and die,' she said. All of this slurry eventually flows through the drains, untreated, into the Arabian Sea.

Her hopes, though, now rest on the biogas plant that is being planned on the huge tract of land next to the abattoir which will be powered by the dung when it is ready in two years.

What she had no idea about was that the dung from her cattle would help run the 213 buses of the Karachi Breeze Red Line. This is one of the five bus rapid transit (BRT) lines that Karachi, a metropolis without adequate public transport system, will be getting in the next two years. 'By then the biogas plant would also have started working,' said Masood Alam Farooqui, the director of City Fuel Gas Company, a biogas specialist with the BRT Red Line Project.

In addition the project documents state that the cheap, clean bus network will reduce planet-warming emissions by 2.6 million tonnes of carbon dioxide equivalent over 30 years.

The process

The cow manure will be put in a digester where the dung reacts with bacteria and produces different gases including sulphur dioxide, nitrogen, carbon dioxide, oxygen and methane. 'The idea is to separate methane, which is a liquefied natural gas, and transport it to CNG tanks at two designated bus depots,' said...