Understanding waste-to-energy plants
What kind of waste do these plants use to generate electricity? Why is segregation of waste important? How is the Kozhikode municipality planning to
implement the plant project? What are the various challenges such plants face?
The story so far:
The Kerala government recently announced the State’s first waste-to-energy project in Kozhikode. The planned facility is expected to be built in two years and generate about 6 MW of power. There are around 100 waste-to-energy projects around the country but only a handful of them are operational, thanks to various production and operational challenges.
What do waste-to-energy projects do?
Waste-to-energy projects use non-recyclable dry waste to generate electricity. The process increases the State’s power generation capacity and eases the solid waste management (SWM) burden.
Generally, solid waste in India is 55-60% biodegradable organic waste, which can be converted into organic compost or biogas; 25-30% non-biodegradable dry waste; and around 15% silt, stones, and drain waste. Of the non-biodegradable dry waste, only 2-3% — including hard plastics, metals, and e-waste — is recyclable. The remainder consists of low-grade plastic, rags, and cloth that can’t be recycled. This fraction of the non-recyclable dry waste is the most challenging portion of the present SWM system; the presence of these materials also reduces the efficiency of recycling other dry and wet waste.
It is this portion that waste-to-energy plants use to generate power. The waste is combusted to generate heat, which is converted into electricity.
What is the Kozhikode project?
Kozhikode has a population of about 6.3 lakh and generates approximately 300 tonnes per day (TPD) of waste. Of this, around 205 TPD is biodegradable and 95 TPD is non-biodegradable.
The municipality is currently using the biodegradable material to generate organic compost in various composting plants. Of the non-biodegradable waste, only about 5 TPD out of the 95 TPD is recycled; the remaining non-recyclable dry waste could be used to generate power at the waste-to-energy plant.
Why do waste-to-energy plants fail?
While waste-to-energy plants seem like a simple solution, they have several challenges en route to becoming feasible.
First is the low calorific value of solid waste in India due to improper segregation. The calorific value of mixed Indian waste is about 1,500 kcal/kg, which is not suitable for power generation. (Coal’s calorific value is around 8,000 kcal/kg.) Biodegradable waste has high moisture content and cannot be used for power generation. The calorific value of segregated and dried non-recyclable dry waste is much higher, at 2,800-3,000 kcal/kg, sufficient to generate power. However, segregation (ideally at the source, if not at the processing plant) should be streamlined to ensure the waste coming to the facility has this calorific value.
Second is the high costs of energy production. The cost of generating power from waste is around ₹7-8/unit, while the cost at which the States’ electricity boards buy power from coal, hydroelectric, and solar power plants is around ₹3-4/unit. While State electricity boards are considering purchasing power from newer renewable energy sources like waste-to-energy, the price of the power generated needs to halve. Finally, many waste-to-energy projects have failed because of improper assessments, high expectations, improper characterisation studies, and other on-ground conditions.
Waste-to-energy projects can consume only non-recyclable dry waste, which is about 25% of the waste; they are expected to only use segregated non-recyclable dry waste as well, which is the only type of waste with a sufficiently high calorific value. But often these projects are expected to manage all types of waste generated in the city which is is not good.
How can the plant tackle challenges?
Kozhikode’s projected population and waste generation rate could avail around 100 TPD of non-recyclable dry waste to generate power. The proposed plant could absorb another 40-50 tonnes of such waste from nearby urban local bodies (ULBs). But this quantity of material, around 150 TPD, will be available only when the people follow strict segregation practices and also process biodegradable waste. Typically, waste-to-energy projects consume 50 TPD of material to generate 1 MW of power. At this rate, the potential to generate power from Kozhikode’s and other ULBs’ waste is around 3 MW. A higher capacity than this, such as the planned 6 MW, will be risky because enough material may not be available.
Operating waste-to-energy projects also depends on parameters like the municipal collection efficiency, waste segregation, moisture content, and the operational efficiency of existing biodegradable-waste-processing plants. If these plants have operational woes (as is common), the nature of waste will change drastically to have high moisture content and low calorific value, which will compromise power generation. Setting up waste-to-energy projects is complex and needs the full support of the municipality, the State and the people. To overcome its various challenges, the municipality must ensure that only non-biodegradable dry waste is sent to the plant and separately manage the other kinds of waste.
Importantly, the municipality or the department responsible for SWM should be practical about the high cost of power generation, and include the State electricity department, perhaps as a tripartite agreement between the municipality, the plant operator, and the power distribution agency. It is also crucial to conduct field studies and learn from the experience of other projects.
Pushkara S.V. is a practitioner at the Indian Institute for Human Settlements.
The Kerala government recently announced the State’s first waste-to-energy project in Kozhikode. The planned facility is expected to be built in two years and generate about 6 MW of power.
Waste-to-energy projects can consume only non-recyclable dry waste. They are also expected to use segregated non-recyclable dry waste which is the only type of waste with a sufficiently high calorific value.
Setting up waste-to-energy projects is complex and needs the full support of the municipality, the State and the people.