Turning food scraps into fuel and light

Households and municipalities in southern India are converting their organic waste into biogas. Behind the sustainability scheme is Biotech, a Kerala-based NGO and 2007 Ashden Awards winner. Maryann Bird explains.

In a growing number of municipalities in the south Indian state of Kerala, an innovative biogas programme is helping to resolve several problems at once. Fetid odours that once emanated from food waste dumped in public places – not to mention the scavenging dogs, rats and crows it attracted – are disappearing. Declining, too, are associated health risks – a particular concern in southern India’s hot climate. Thanks to an Indian NGO called Biotech, food scraps and other kinds of organic waste are being used to produce gas for cooking and, in some cases, electricity for lighting.

Biotech, founded in 1998 by A Sajidas, has developed a line of biogas digesters that, so far, are cleanly and hygienically managing wastes in 12,000 households, 220 institutions (including schools, hospitals and hotels) and 20 municipal sites. An estimated 60,000 people already are benefiting. Among its clean-energy advantages, the gas, when used directly for cooking, offers a 50% savings over the use of liquefied petroleum gas (LPG), as well as greater safety. And the waste residue can serve as a fertiliser, contributing to greater food production. 

“A huge quantity of waste is accumulated daily,” says Sajidas, a sociologist who was concerned about health and environmental problems stemming from the dumping of waste. “We can clean any type of biodegradable material to generate biogas.”

For its innovation, Biotech has received the £30,000 ($60,000) first prize in the food security category of the 2007 Ashden Awards for Sustainable Energy. With its biogas plants, the Ashden judges found, “Biotech has succeeded in tackling the problem of the dumping of food waste in the streets of Kerala”. A clear health hazard, such dumping is no longer considered acceptable in densely populated areas, including relatively prosperous Kerala, where a middle-class population is expanding. (In rural India, however, there is a long tradition of throwing food waste onto roads for animals to eat.) 

At the individual household level, says Sajidas, “a one square-metre space is enough” for installation of a domestic bio-waste treatment plant. Set-up up takes just a few hours, at a cost of around $200 for a basic system. The daily waste of a five-person family, according to Biotech, can generate enough gas to operate a single-burner stove for two hours.

Easily biodegradable waste, mixed with kitchen wastewater (like that in which rice has been cooked), is fed into the airtight plant. Through the breakdown action of anaerobic bacteria, it is converted into cooking gas, the main component of which is methane. The resulting biogas – mainly a mixture of methane (CH4) and carbon dioxide (CO2) — can be burned as a fuel, while the solid residue can be used as organic compost. (For technical details, see here.)

While methane and CO2 are greenhouse gases, which contribute to global warming, use of biogas is nevertheless considered less harmful than burning fossil fuels. In general, photosynthetic plants have recently extracted the carbon in biogas; releasing it back into the atmosphere in a controlled way, therefore, contributes less total atmospheric carbon than burning coal or petroleum.

Of Biotech’s 12,000 domestic biogas plants, 160 also use human waste from latrines, avoiding contamination of ground water, while municipal plants employ waste from fish markets to power electricity generators, which then provide light for the market. (As with the fish-market waste, blood and wash-water from abattoirs also can also be used, but a separate digester is required.)

Among the scheme’s benefits, Biotech plants replace the equivalent of about 3.7 tonnes per day of LPG and diesel, resulting in a saving of about 3,700 tonnes a year of CO2, the most plentiful greenhouse gas. Additional savings come from the decreased production of methane – the most harmful of the greenhouse gases – as a result of uncontrolled waste decomposition (such as in landfills), and from the transport of LPG.

“Anybody can install a biogas plant,” says Sajidas. “It is the scheme of the common man.” Biotech’s technology could be used in many other hot countries with rapidly growing urban areas, he adds. For hygiene and cleanliness, safe disposal of organic waste at source is critical. The greater potential, however, is for big municipal systems, particularly in areas where large volumes of organic waste threaten public health – for example, where water supplies can be polluted.

In Sajidas’s words: “Now it is high time that we open our eyes to ensure scientific treatment and disposal of waste without causing any harm to the atmosphere. Otherwise, the lives of the people of the next generation on the planet Earth will be affected very adversely.”

Homepage photo by Huggy47