It is estimated that for every metric dry ton of food waste that goes into a landfill, 0.25 metric tons of methane is emitted into the atmosphere over a period of four months as the waste decomposes anaerobically.
If this food waste was composted instead, emissions would reduce by the equivalent of up to 6 metric tons of carbon dioxide.
“The composting process is always occurring in nature, however we can help improve the efficiency of the process through many means. Through the proper control of temperature and regulation of the carbon to nitrogen ratio, moisture content and oxygen availability, we can enhance the efficiency of the process,” explained Shankara K., Assistant Professor, Department of Civil Engineering at Bengaluru campus.
Shankara is currently studying the effect of seeding on the composting process of the organic fraction of the Municipal Solid Waste obtained from campus. The seed material studied consists of sewage sludge (SS) and digested cow dung (CD).
The waste included vegetable scraps (30%), food left-overs (30%), paper (16%), dry leaves (12%) and grass cuttings (12%).
The sewage sludge was obtained from a sewage treatment plant. This contains a large number of bacteria, just the same as seven-day-old digested cow dung.
The sewage sludge and digested cow dung were used as seeding material in various percentages.
“We used four perforated containers. Container 1 was the control (not seeded), and containers 2, 3 and 4 were seeded with (2%SS+2%CD), (3%SS+3%CD) and (4%SS+4%CD) respectively,” explained Shankara.
“We also intended to learn more about the optimum time required
for the composting process to complete with the use of seeded materials,” he further added.
The containers were monitored for a period of 50 days. A total of 12 samples were collected at different stages of the composting process and were analyzed for various parameters. The tests were performed at the University of Agricultural Sciences in Bengaluru.
“Composting efficiency greatly improved when seeded with digested cow dung and sewage sludge. Not only did the degradation rate increase, but also the release of odorous gases was reduced. We found that carbon content decreased linearly in all aerobic perforated containers, but seeding helped accelerate the composting process and hence reduce the composting period. Nitrogen, phosphorus and potassium content also increased linearly with time in all the containers studied,” he shared.
A paper titled Influence of Seeding on Aerobic Composting of Organic Fraction of Municipal Solid Waste, was presented at an International Conference on Solid Waste Management in August 2012 at the Infosys Campus in Mysore.
“Since this helps safeguard the environment, I feel happy about this work,” Shankara summed up.
June 10, 2013
School of Engineering, Bengaluru
