Wet waste management: Puttur CMC junks lazy landfill approach, aids CNG production

Mangaluru: The Puttur city municipal council (CMC) has taken a step toward sustainable waste management by producing Compressed Natural Gas (CNG) from wet waste.

By converting biodegradable waste into clean energy, the initiative has not only reduced the burden on landfills, but also helped in cutting down greenhouse gas emissions.

The generated CNG is presently used as fuel for six vehicles, including the vehicle of the CMC commissioner and waste collection vehicles.

BOOT mode

The bio-CNG plant was set up by the Rotary Club East Puttur Swachh Bharath Trust, Krishna Muliya Green Energy LLP and Retap Solutions under build, own, operate and transfer (BOOT) mode at a cost of Rs 3 crore at Bannur in Puttur.

“Puttur town generates 20 to 22 tonnes of wet waste daily. The plant has a capacity to produce 350 kg of CNG daily. However, currently six to 10 tonnes of wet waste is being used for CNG production. At present, 100-120 kg of CNG is produced daily. This is the first time in the state that a municipality is producing CNG,” CMC commissioner Madhu S Manohar told DH.

Pure methane

“The quality of methane gas produced is 97% to 99% pure,” he said. “As per the agreement, a royalty of Rs 1 per kg is paid to the CMC. Further, CNG is given for the CMC vehicles at Rs 5 less than the market price. At present, the CNG price is around Rs 88 per kg,” said the commissioner.

Officials said wet and dry waste is collected separately from households. If there is any mixture of plastic, eggshells in the wet waste, they are manually separated by municipal staff.

The organic waste is then shredded into five-cm pieces and ground into a fine slurry using a machine.

Water is added to prepare the slurry. The slurry is subjected to anaerobic digestion (decomposition in the absence of oxygen). Microorganisms break down the organic particles to produce biogas containing methane and carbon dioxide. 

CO2 removed

Later, carbon dioxide is removed and the remaining gas is compressed to produce CNG, which is filled into cylinders.

The plant has received a licence from the Petroleum and Explosives Safety Organisation (PESO). The final order for commercial sales is awaited. 

Plant project director Rajesh Bijjangala said the municipality provided the land and the waste for the project, while Rotary Swachh Bharat Trust and Krishna Muliya Green Energy invested Rs 3 crore in the project. 

Six staff members operate the unit. The plant is yet to operate in a fully-fledged manner, he added.