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Next generation recycling (Dec.)

Deccan Herald, Bangalore Tuesday 3rd December 2013

Waste disposal and recycling have taken new meanings altogether, with the Bhabha Atomic Research Centre (BARC), Mumbai, developing a two-stage process, called Nisargruna (which is Sanskrit for ‘repaying nature’s debt’), which efficiently turns domestic waste into high-quality manure and odour-free methane, which can be used as fuel.

This was revealed recently at an interaction with professor and Padmashree Dr Sharad Kale, Head, Pesticide Residue and Soil Sciences Division, BARC, on how social media could help the government deliver its schemes and technology to more beneficiaries.

An eye on the future

Nisargruna is a next generation version of the traditional Gobar Gas plant. In the traditional plant, cattle waste and other organic waste is confined to a digester. In the absence of oxygen, bacteria breaks down the organic matter into gas rich in methane and a slurry which is rich in nitrogen, phosphorus and potassium, and is valuable as compost.

As it is a one-stage process and anaerobic, or a ‘sealed off from air’ fermentation process, it takes as long as 40 days for the waste to be digested. Nisargruna splits the process into two stages. The first stage is an aerobic, or ‘open to air’ phase in the first chamber, before the methane producing fermentation begins in the second chamber.

The waste is pulverised before it is mixed with hot water and kept in the first chamber for three-four days. The structure of the chamber helps the aerobic phase effectively degrade the biomass into a homogenous and only slightly acidic liquid. This preparation enables more efficient fermentation by methane bacteria in the next, anaerobic phase, which now lasts only some 15 days.

The process consists essentially of the complex molecules in organic waste being broken down to simple components, which then react and recombine as methane gas and carbon dioxide, the remainder being left rich in nitrogen and other plant nutrients.

Thus, in the first stages of anaerobic fermentation, carbohydrates, fats and proteins are broken down into sugars, fatty acids and amino acids, respectively. In the next stage, the volatile fatty acids arising from the products of the first stage are reduced to acetic acid, carbon dioxide and hydrogen, in a process that is similar to the souring of milk.

The next stage of fermentation is where the acetates and products of the earlier stages are converted into methane, with the hydrogen being used up, leaving largely methane and carbon dioxide gas.

In Nisargruna, there is control over the different bacteria that bring about the changes, and the methane production is mainly in the second chamber.

The bacteria that bring about the first changes, of complex molecules being broken down, reproduce and act faster in the first chamber.

The bacteria that act to form methane need more stable acid levels and temperature, and they find optimum conditions in the second chamber.

Natural recycling

Dr Kale also brought home the concept of the value of waste and the efficiency of natural recycling with a captivating account of an ongoing experiment he has carried out for the last 14 years.

He has, in his flat, a glass jar in which he had placed soil and a plant, and watered the plant till it had taken roots and was growing.

He then sealed the jar so that the bio-system in the jar became isolated. He placed the jar near a west-facing window so that it received sunlight every evening. The sunlight enabled photosynthesis and generation of oxygen.

The water in the jar was recycled from the soil, the root, the leaves and back to the soil. The insect and other life forms in the soil thrived and when the leaves withered, they enriched the soil.

Now, even after 14 years, the ecosystem in the jar is thriving well, with all ‘waste’ recycled as ‘resource’. Such ‘ecosystems in a jar’ are now commonplace and go under the name of ‘terrariums’. “If recycling can work perfectly in a jar, why not on Earth?” Dr Kale asked.

The only difference is that garbage in cities contains man-made materials like used torch cells, toothpaste tubes or plastic bags. When different materials like this are mixed, one kind of waste poisons the other, taking away its value as a resource. The two components hence need to be separated, Dr Kale said, stressing on the need for segregation of waste at home.

With rising pressure on natural resources, such green innovations are indeed the need of the hour.

What’s even more imperative is adapting such technologies in our daily life, ensuring that the coming generations are taken care of.