Waste-to-energy: Science and thermodynamics

Why India's wet rubbish so often refuses to burn

Why India's wet rubbish so often refuses to burn What this tab covers The thermodynamics: the grade (temperature or pressure) of the energy being recovered, energy versus exergy efficiency, and how harsh the waste stream is on equipment.

Waste-to-energy turns the chemical energy in rubbish, residues and spent oil back into heat, power or reusable product. The fuel is poor and variable: Indian mixed waste often sits below the heating value needed to burn without support fuel.

Grade of energy

Mixed

Unlike most recovery tiles the source here is a fuel, so combustion temperatures are high and grade is not the problem; fuel quality is. Indian municipal solid waste (MSW) is wet and organic-rich: a Centre for Science and Environment (CSE) analysis put its heating value at roughly 1,411 to 2,150 kcal/kg (about 5.9 to 9.0 MJ/kg), against about 1,800 kcal/kg needed for self-sustaining combustion and 1,900 to 3,800 kcal/kg in Sweden, Norway and the US. Refuse-derived fuel (RDF), made by drying and sorting waste, reaches 2,500 to 3,000 kcal/kg, which is why cement kilns prefer it to raw waste.¹²

Indian MSW heating value (CSE analysis, 2019) 1,411-2,150 kcal/kg (5.9-9.0 MJ/kg, calculated)¹ Minimum for unsupported combustion about 1,800 kcal/kg¹ Nordic and US MSW 1,900-3,800 kcal/kg¹ RDF for cement kilns (JSW Cement authors) 2,500-3,000 kcal/kg²

Exergy versus energy efficiency

Mixed

Burning waste for electricity alone wastes most of the energy as low-temperature condenser heat; plants that also sell heat to a district network (combined heat and power) use far more of it. Waste boilers keep steam at around 4 MPa and 400 C, well below coal plants, because the flue gas corrodes superheaters at higher temperatures; at those conditions net electrical efficiency in condensing mode is about 20% at most. Used-oil re-refining and co-processing score better on exergy because they replace a refined product or a high-quality fuel rather than producing low-grade steam.³⁴

European WtE plants (2023) 499 plants treating 101 Mt residual waste³ Typical WtE steam conditions about 4 MPa, 400 C⁴ Net electrical efficiency, condensing about 20% or less⁴

Media compatibility and corrosiveness

Unfavourable

Waste flue gas carries hydrochloric acid, sulphur oxides, heavy metals, dioxin precursors and fly ash, so boilers need corrosion-resistant superheater alloys and the plant needs a substantial gas-cleaning train with continuous emission monitoring (CEMS). CSE found that Indian plants it assessed between 2016 and 2018 mostly suffered from weak equipment standards, faulty installation and poor maintenance, and that CEMS data could easily be manipulated. Cement kilns tolerate many wastes because of long residence times and alkaline clinker, but chlorine and moisture in RDF still limit how much fossil fuel can be replaced.¹⁴

Indian plants closed for low heating value (as of 2019) Vijayawada, Bengaluru, Kanpur, Hyderabad, Lucknow, Karimnagar¹ Okhla (Delhi) NGT fine Rs 25 lakh (2016)¹

Variants compared²⁵⁸⁹¹⁰¹⁵

Variant	What it recovers	Key figure	Main constraint
Mass-burn incineration (WtE)	Electricity, sometimes district heat	India: 13 operational plants, about 127 MW excluding Uttar Pradesh (FY2021-22); 21 operational in 10 states and UTs (CPCB, April 2025)	Low heating value of Indian waste; emissions control
RDF and cement co-processing	Kiln fuel replacing coal and petcoke	India average thermal substitution about 6%; some plants above 20%	RDF quality, chlorine, supply logistics
Pyrolysis and gasification	Oil, syngas, char	No reliable fleet data sourced	Feedstock sorting, tar, unproven economics at scale
Used oil re-refining	Re-refined base oil (RRBO)	India makes about 27 kt RRBO a year; about 400 small processors (consultant estimate, 2023)	Informal collection; quality standards
Agricultural residue (co-firing)	Pellets replacing coal in power plants	71 coal plants co-firing (Aug 2025); about 230 Mt/yr surplus residue	Pellet supply chain and price

Sources

Trash-fired power plants wasted in India Down To Earth (Centre for Science and Environment), 2019
Advancing Cement Sector Decarbonization via RDF Co-Processing (authors from JSW Cement) NBM&CW, 2026
EU Map 2023: Waste-to-Energy plants in Europe CEWEP, 2026
Energy efficient processing of waste (Pavlas, Tous, Bebar), Chemical Engineering Transactions 21: 841-846 AIDIC, 2010
Annual Report 2021-22 on implementation of Solid Waste Management Rules 2016 Central Pollution Control Board, 2023
India's RRBO EPR targets: feasibility concerns raised (Kline presentation at ALIA seminar) Fuels & Lubes, 2023
Decarbonising Coal: Co-firing as a viable pathway to cleaner thermal power generation Power Line (citing CAQM and Ministry of Power), 2025
India's cement sector embraces decarbonisation amidst robust outlook (citing GCCA India) Global Cement, 2025
Report filed by the Central Pollution Control Board on waste to energy plants, 15 April 2025 India Environment Portal (CSE), reproducing CPCB filing to NGT, 2025