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Insights into Editorial: Converting waste to energy

waste

 

Context:

Recently, Karnataka Chief Minister laid the foundation stone for a 11.5 MW waste-to-energy plant near Bidadi.

This plant is expected to process 600 tonnes per day of inorganic waste. Bengaluru generates close to 5,000 tonnes of waste daily, of which about 2,500 tonnes is organic, about 1,000 tonnes inert material (sweeping waste) and 1,500 tonnes inorganic.

This inorganic material, which consists of bad quality plastics and used cloth pieces, can be processed as Refuse Derived Fuel (RDF).

This material has a calorific value of more than 2,500 kJ/kg, and can be used to generate steam energy, which can be converted into electric energy instead of burning coal and other materials used in traditional waste-to-energy plants.

What are wastes to energy plants?

Waste-to-Energy (WtE) or Energy-from-Waste (EfW) is a form of energy recovery and the process of generating energy in the form of electricity and/or heat by processing of waste into a fuel source.

Modern waste-to-energy plants are very different from the trash incinerators as the latter plants usually did not remove hazardous or recyclable materials before burning.

Most waste-to-energy plants burn municipal solid waste, but some burn industrial waste or hazardous waste.

A modern, properly run waste-to-energy plant sorts material before burning it and can co-exist with recycling.

Waste-to-energy plants are similar in their design and equipment with other steam-electric power plants, particularly biomass plants.

A few plants use gasification, but most combust the waste directly because it is a mature, efficient technology.

A well-planned plant:

In the context of climate change, focus on renewable source of energy and burgeoning population, the Waste to Energy’s approach is needed to address the growing energy need in a sustainable way. However, it is also important to ensure their effectiveness.

The waste-to-energy plants usually accept the RDF material generated in organic composting plants. They also segregate the wet and inorganic material near the plant, convert organic waste to compost, and inorganic waste to energy.

Typically, about 50 tonnes of RDF generate 1 MW of power, which indicates that the plant at Bidadi has been appropriately designed.

Although about 30%-40% of the material received is segregated organic waste and the remainder is mixed waste, the latter consists of about 40% inorganic waste which can be converted into RDF.

Handling inorganic waste that is not fit for recycling has always been a challenge.

Benefits of wastes to energy plants:

  1. In terms of volume, usually waste-to-energy plants incinerate 80 to 90 percent of waste, thus helping large cities from choking due to unmanageable waste.
  2. Most wastes that are generated find their way into land and water bodies without proper treatment, causing severe water and air pollution.
  3. Waste to energy generates clean, reliable energy from a renewable fuel source, thus reducing dependence on fossil fuels, the combustion of which is a major contributor to Greenhouse Gas (GHG) emissions.
  4. Sometimes, the residue ash is clean enough to be used for some purposes such as raw materials for use in manufacturing cinder blocks or for road construction.
  5. In addition, the metals that may be burned are collected from the bottom of the furnace and sold to foundries.
  6. Some waste-to-energy plants convert salt water to potable fresh water as a by-product of cooling processes.
  7. Waste-to-energy plants cause less air pollution than coal plants.
  8. It is carbon-negative – processing waste into biofuel releases considerably less carbon and methane into the air than having waste decay away in landfills or the lake.

Challenges faced in installing Waste-to-Energy plants:

  1. Over the last decade, several Indian cities have been trying to set up such plants but a good demonstration model is yet to be established.
  2. Technology suppliers are international organisations who struggle with the change in quality and nature of waste generated in Indian cities. A few plants in India have stopped operations for this reason.
  3. Waste-to-Energy is still a new concept in India. Most of the proven and commercial technologies in respect of urban wastes are required to be imported.
  4. The costs of the projects are high as critical equipment for a project is required to be imported.
  5. In view of low level of compliance of Solid Waste Management Rules, 2016 by the Municipal Corporations/ Urban Local Bodies, segregated municipal solid waste is generally not available at the plant site, which leads to non-availability of waste-to-energy plants.
  6. Lack of financial resources with Municipal Corporations/Urban Local Bodies.
  7. Lack of conducive policy guidelines from State Governments in respect of allotment of land, supply of garbage and power purchase / evacuation facilities.
  8. The quality of waste generated in Bengaluru itself could be a hurdle. The plants require fine inorganic material with less than 5% moisture and less than 5% silt and soil contents, whereas the moisture and inert content in the mixed waste generated in the city is more than 15%-20%.
  9. Since segregation at source doesn’t happen in the city, the collected waste material needs to be sieved using 80mm-100 mm sieving machines, which lets through organic material with more than 80mm-100 mm particle sizes into the inorganic waste.
  10. In addition, the sticky silt and soil particles can also reduce the calorific value.
  11. The other big challenge for this plant is the power tariff. Generally, the tariff at which the power is purchased by such plants across the country is around Rs.7-8 KwH which is higher than the Rs.3-4 per KwH generated through coal and other means.
  12. This could be a serious challenge to KPTCL as the selling price of power cannot be increased corresponding to the purchasing price.

Conclusion:

If the plant eases the challenge of handling inorganic waste, the efficiency of organic waste processing/ composting plants would become better.

If it is successful, the city would require three more waste-to-energy plants of similar size or six plants of smaller size considering the potential to recover 2,500-3,000 tonnes per day RDF in the coming years.

Urban local bodies (ULBs) should invest in preparing an action plan on waste management in accordance with the Solid Waste Management (SWM) rules, 2016 within a time-bound approach and promote and adopt the key elements of waste hierarchy as refuse, reduce, reuse, recycle and recover.

It is also important to focus on segregation at source, spreading awareness, preparing an action plan for the city for waste management by adopting decentralised technologies.

This will not only improve effectiveness of Waste To Energy’s, but will also ensure protection and improvement of our environment as envisaged in Article 51 A(g) of our Constitution.