Wednesday, December 28, 2011

How Farm Waste Provides Clean Energy for Homes in Pakistan

By UNEP News Centre, December 27, 2011

A project backed by the United Nations Environment Programme (UNEP) is working to make clean energy a reality for households in a rural region of Pakistan.

Sanghar, a farming district in Sindh province in east-central Pakistan, is home to nearly two million people. Wheat, cotton, sugar cane, rice and maize are grown here, providing livelihoods and food for local communities.

In the villages and towns of the district, access to reliable sources of energy is difficult. Indeed, in households all over Sanghar, women prepare meals and heat water by burning wood or biomass in rudimentary stoves that release choking, black smoke.

Now a new project backed by the United Nations Environment Programme (UNEP) is working to make clean energy a reality for local households.

Realizing that the district was a rich source of agricultural waste, UNEP's International Environmental Technology Centre (IETC), based in Japan, began working on a project to convert agricultural waste left in the fields into clean, sustainable energy.

As a first step, the IETC worked with the Mehran University of Engineering and Technology in Jamshoro to quantify the amount of agricultural waste in the district. A survey found that 2.5 million tonnes of waste ? wheat and canola straw, cotton stalks, cotton gin waste, sugarcane tops, bagasse, rice straw and husks, and banana plant ? was produced in the district, although not all was available for conversion into energy.

A subsequent calculation found that the energy potential of the available waste was equivalent to 1.07 million tonnes of fire wood, or 910 million units of electricity (with a conversion efficiency rate of 20 per cent). If this energy potential was fully realised, the converted waste could meet the energy demands of roughly 400,000 households (at 2400 units per household).

Further research was done to determine how agricultural waste was managed and used, to avoid future conflicts. For instance, it was learnt that 20 per cent of sugarcane tops was being fed to animals, but 80 per cent was being burnt in the fields, along with the entire quantity of banana plant waste and about 70-80 per cent of rice straw. These materials could therefore be used for energy conversion without impacting on food supplies or other needs.

The next step was to decide which technology to use. Several were considered, but after careful analysis a biogas plant was selected, as it had the twin benefits of being able to supply clean fuel (biogas) to surrounding households and produce a good supply of compost, which could be used as fertilizer. A site was chosen at the back of the Sanghar Sugar Mills, which agreed to provide the land and funds to build the plant.

Built at a cost of two million rupees (about US$ 23,000), the biogas plant opened on 1 August 2011. It is producing 50 cubic metres of biogas a day, using 400 kilograms a day of agriculture waste. As well, it produces 200 kilograms a day of liquid fertilizer and 150 kilograms a day of solid fertilizer.

The biogas produced is enough to provide energy to about 20 households, putting to good use a resource that would otherwise have gone to waste.


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