Cases / Oil, gas and coal operations · Iran · 2020–2026

Mazut burning in Iranian power plants, 2020–2025

Nature's voice · report

My air in Tehran had SO2 that doubled in a week because of mazut, according to the head of the Tehran City Council (January 2021).

Did nature suffer? Yes. Harm is on record. Disputed

Recorded

Power plants burned mazut of 3.5% sulfur, up to seven times the Clean Air Act limit, in the winter of 2022/23, according to Oil Ministry reports cited by RFE/RL. RFE/RL
My air at Shazand had 27 unhealthy SO2 days in the Iranian year 1402 and five in 1403 after low-sulfur mazut was used, according to the Department of Environment. Shana (Ministry of Petroleum)
NASA's catalogue lists the Neka power plant at 68.6 kt of SO2 and the Bandar Abbas oil power plant at 86.2 kt in 2025. NASA Goddard Space Flight Center

What the record lacks: 3 none on record · 1 not disclosed · 1 insufficient · 1 not measured · 3 disputed See the gaps

Accounts of the harm differ

Whether mazut use was halted or expanded in the winter of 2024/25

Government and regulators President Masoud Pezeshkian (20 January 2025): Mazut was not supposed to be burned at all and this had been announced, but the government got stuck; without it gas to households would have been cut. Iran International
Government and regulators Somayeh Rafiei, spokesperson of the parliamentary agriculture committee (February 2025): All thermal plants had shifted to mazut. Iran International
Government and regulators Ministry of Petroleum (4 February 2025): Mazut deliveries to power plants were up 53% year on year. Shana (Ministry of Petroleum)

When gas runs short in winter, Iranian power plants burn mazut, a high-sulfur heavy fuel oil. The Ministry of Petroleum reported 4.941 billion litres delivered to power plants between 22 October 2024 and 31 January 2025, up 53% on the year before; the head of the Tehran Province Judiciary said five former managers were convicted over non-enforcement of the Clean Air Law.

4.941 billion litresMazut delivered to power plants, 22 Oct 2024 to 31 Jan 2025
Up 53% (1.718 billion litres) on the same period a year earlier, according to the Ministry of Petroleum (Shana, 4 February 2025).

Status As of February 2026: the Department of Environment said 420 million litres of low-sulfur mazut were allocated to four plants; five former managers were reported convicted over Clean Air Law non-enforcement, and the case against ecologist Esmail Kahrom had no verdict on record.

What?

Iranian power plants burn mazut, a high-sulfur heavy fuel oil, when gas is short; the Ministry of Petroleum reported 4.941 billion litres delivered in the winter of 2024/25, up 53% on the year before, and five former managers were reported convicted over Clean Air Law non-enforcement. Shana (Ministry of Petroleum)

Where?

Power plants named by officials and press at Shazand (Arak), Karaj, Isfahan, Neka, Hamedan, Tous, Sahand Bonab, Montazer Ghaem and Bandar Abbas. Iran International

When?

Winters of 2020/21, 2022/23, 2023/24, 2024/25 and 2025/26. Radio Farda

Who?

Gained

Households — Kept gas supply in winter 2024/25, according to President Pezeshkian Iran International

Lost

Five former managers — Convicted of dereliction of duty under the Clean Air Law, as stated by the head of the Tehran Province Judiciary; sentences not disclosed Mehr News Agency

Harmed

Air in Tehran, Arak, Isfahan, Neka and other plant cities — SO2 doubled in a week in Tehran in January 2021; NASA lists power-plant sources at 16.6 to 86.2 kt SO2 in 2025 NASA Goddard Space Flight Center
Residents near power plants — Four plants in residential areas were allocated 420 million litres of low-sulfur mazut in 2026 Shana (Ministry of Petroleum)

Why?

Gas shortages in winter; President Pezeshkian said that without mazut gas supply to households would have been cut, and the Energy Minister said plants are forced to burn it when gas is scarce. Iran International

How?

Mazut is delivered to power plants by the Ministry of Petroleum at government-set conditions; the Department of Environment and the Oil Ministry began a low-sulfur mazut programme. Shana (Ministry of Petroleum)

6 of 6 questions answered from the record

What happened

The record, in order.

Mazut is residual fuel oil that Iranian power plants burn when gas supply runs short. In January 2021 the head of the Department of Environment, Eisa Kalantari, said a directive from a deputy prosecutor-general had told provinces not to block mazut burning on security grounds, and gave the sulfur content of Iranian mazut as about 30,000 ppm (3%); the prosecutor-general's deputy for public rights denied issuing such a directive. Oil Minister Bijan Namdar Zanganeh said he did not want mazut to be used but had no choice but to deliver it to power plants. The head of the Tehran City Council said SO2 in Tehran had doubled in a week because of mazut.

In the winter of 2022/23, Oil Ministry reports cited by RFE/RL showed mazut use rising to 38.5 million litres a day in December 2022 (up 22%) and 42 million litres a day in January 2023, with mazut of 3.5% sulfur, 'up to seven times' the Clean Air Act limit. A report of the parliamentary Article 90 Commission presented on 27 June 2023 said the Ministry of Petroleum had not enforced standards for mazut use in power plants, and that the Ministry of Energy reported rising use, with 14 of 16 power plants reportedly burning it.

On 4 February 2025 the Ministry of Petroleum said 4.941 billion litres of mazut had been delivered to power plants from 22 October 2024 to 31 January 2025, up 53% on the year before, and that the 30 days to 19 January 2025 averaged 53.9 million litres a day against 40.9 million a year earlier. On 20 January 2025 President Masoud Pezeshkian said on state television that mazut was not supposed to be burned at all, that this had been announced, that the government 'got stuck', and that without mazut gas supplies to households would have had to be cut. In February 2025 Somayeh Rafiei, spokesperson of the parliamentary agriculture committee, said all thermal plants had shifted to mazut. On 14 November 2025 power plants burned more than 21 million litres of mazut, according to Fars, with Hamedan, Neka and Arak the biggest consumers; Energy Minister Abbas Aliabadi said the ministry did not want to burn mazut because it damages plants and is an expensive commodity, but was forced to use it when gas was scarce.

On 15 February 2026 the head of the Department of Environment, Shina Ansari, said 420 million litres of low-sulfur mazut had been allocated that year to four power plants in residential areas, and that after low-sulfur mazut was used at Shazand unhealthy SO2 days fell 'from 27 days in 1402 to five days in 1403'. NASA's SO2 catalogue lists power-plant sources including Shahid Rajaee, Shahid Mofateh, Bandar Abbas, Neka, Arak, Isfahan and Tehran (Besat); the figures below are totals per plant and the catalogue assigns no fuel type.

On the legal side, Ali Alghasi-Mehr, head of the Tehran Province Judiciary, said on 3 December 2023 and again on 12 January 2025 that five former managers had been convicted of dereliction of duty under the Clean Air Law; sentences were not disclosed. RFE/RL reported in May 2023 that the Tehran Prosecutor's Office had charged five unidentified officials with failing to enforce Clean Air Act standards on vehicle emissions, gasoline quality and mazut-fuelled plants. In December 2025, Iran International reported that the judiciary had opened a case against the ecologist Esmail Kahrom, with charges reported as 'false statements' and acts 'against national security', after he criticised mazut use and spending priorities.

2021Department of Environment head says a prosecutor-general's deputy directed provinces not to block mazut; the deputy for public rights denies it (3 Jan); Oil Minister says plants must be supplied
2023Oil Ministry reports mazut use at 38.5 million litres a day in December 2022 and 42 million in January 2023; prosecutor charges five officials (RFE/RL, May); Article 90 Commission report (27 Jun); Tehran judiciary announces five managers convicted (3 Dec)
2025Ministry of Petroleum reports 4.941 billion litres delivered 22 Oct 2024–31 Jan 2025 (4 Feb); President says the government 'got stuck' (20 Jan); judiciary head repeats that five managers were convicted (12 Jan); mazut burned at more than 21 million litres in a day (14 Nov); ecologist Esmail Kahrom interviewed (30 Nov); judiciary case against him reported (Dec)
2026Department of Environment head reports 420 million litres of low-sulfur mazut allocated to four plants in residential areas (15 Feb)

What was said

Claims, in the words of those who made them.

“We do not want mazut to be used, but we have no choice but to deliver it to power plants”
Bijan Namdar Zanganeh, Oil Minister, as reported by Radio Farda · January 2021 · translated from Persian · Radio Farda

“producing poison”
Fatemeh Mohajerani, government spokeswoman, on scheduled outages as the alternative · November 2024 · translated from Persian · Al Jazeera

“We were not supposed to burn mazut at all, and we announced this. But then we got stuck.”
Masoud Pezeshkian, President, on state television · 20 January 2025 · translated from Persian · Iran International

“If we hadn't used it, we would have had to cut off gas supplies to households.”
Masoud Pezeshkian, President, on state television · 20 January 2025 · translated from Persian · Iran International

“We do not want to burn mazut because it damages plants and is an expensive commodity. But when gas is scarce, we are forced to use it.”
Abbas Aliabadi, Energy Minister · November 2025 · translated from Persian · Iran International

“420 million liters of low-sulfur mazut were allocated this year to four power plants located in residential areas”
Shina Ansari, head of the Department of Environment · 15 February 2026 · Shana (Ministry of Petroleum)

“seven times the global standard”
Esmail Kahrom, ecologist, on the sulfur content of mazut, as reported by Iran International · 30 November 2025 · translated from Persian · Iran International

Where accounts differ

Each party's account, side by side, with its source. The record does not settle these points; it shows them.

Whether a directive allowed mazut burning on security grounds (January 2021)

Government and regulators

Eisa Kalantari, head of the Department of Environment

A deputy prosecutor-general's directive told provinces not to block mazut burning on security grounds.

Radio Farda

Government and regulators

Prosecutor-general's deputy for public rights

Denied issuing such a directive.

Radio Farda

Whether mazut use was halted or expanded in the winter of 2024/25

Government and regulators

President Masoud Pezeshkian (20 January 2025)

Mazut was not supposed to be burned at all and this had been announced, but the government got stuck; without it gas to households would have been cut.

Iran International

Government and regulators

Somayeh Rafiei, spokesperson of the parliamentary agriculture committee (February 2025)

All thermal plants had shifted to mazut.

Iran International

Government and regulators

Ministry of Petroleum (4 February 2025)

Mazut deliveries to power plants were up 53% year on year.

Shana (Ministry of Petroleum)

How it looked

What was shown, beside what was recorded.

Shown

Scheduled outages described as replacing 'producing poison'
Government spokeswoman Fatemeh Mohajerani, November 2024, as reported by Al Jazeera and Iran International · Al Jazeera
Mazut-burning power plants described as low priority because liquid fuel is valuable and kept as a last resort
Energy Minister Abbas Aliabadi, as reported by Al Jazeera, November 2025 · Al Jazeera
A low-sulfur mazut programme with the Oil Ministry, with unhealthy SO2 days at Shazand falling from 27 to five
Department of Environment head Shina Ansari, 15 February 2026 · Shana (Ministry of Petroleum)

Recorded

Ministry of Petroleum: 4.941 billion litres of mazut delivered to power plants from 22 October 2024 to 31 January 2025, up 53% (1.718 billion litres) on the year before; the 30 days to 19 January 2025 averaged 53.9 million litres a day against 40.9 million.
Shana (Ministry of Petroleum)
Oil Ministry reports cited by RFE/RL: mazut use 38.5 million litres a day in December 2022 (up 22%) and 42 million in January 2023; mazut with 3.5% sulfur, 'up to seven times' the Clean Air Act limit.
RFE/RL
Article 90 Commission (27 June 2023): the Ministry of Petroleum had not enforced standards for mazut use in power plants; the Ministry of Energy reported rising use, with 14 of 16 power plants reportedly using it.
Mizan (Judiciary news agency)
Since the Iranian year 1402, the social-affairs office of the Tehran judiciary sent 94 letters and warnings to agencies including the Energy Ministry on mazut use.
Mehr News Agency
Iran International reported that a decree in November 2024 raising household gas tariffs authorised provinces to use mazut in all power plants and industries.
Iran International
NASA catalogue, selected power-plant sources (kt SO2 a year, 2019 / 2024 / 2025): Shahid Rajaee ('Oil Power Plant') 0.8 / 38.4 / 34.3; Shahid Mofateh 16.2 / 28.6 / 27.0; Bandar Abbas ('Thermal Oil power plant') 141.0 / 106.8 / 86.2; Neka 50.3 / 82.3 / 68.6; Arak refinery and power plant 44.3 / 61.9 / 53.0; Isfahan refinery and power plant 23.3 / 32.9 / 43.2; Tehran (Besat, oil) 15.7 / 14.8 / 16.6.
NASA Goddard Space Flight Center
Ecologist Esmail Kahrom said in a 30 November 2025 interview that each missile costs roughly US$2 million and that the cost of 10 missiles could fund an upgrade of fuel standards; state-affiliated media (YJC) described national security as 'nonnegotiable'.
Iran International
UN Special Rapporteur David Boyd called on Iran in 2023 to stop burning mazut, describing it as a human-rights violation, in a post on X reported by Iran International.
Iran International

Who gained

Money that reached nature, beside money that stayed elsewhere.

Reached nature or the ground

Not published

Priced damage to nature from mazut burning—

None on record.

Gained elsewhere

Not totalled

Economic loss from air-pollution deaths in the Iranian year 1403, Health Ministry (all sources, not mazut-specific)≈ $17.2bn

Currency: USD · Window: 2024–2025. All figures cover the same period. * Estimate built from cited figures.

Responses on record

government-of-iran (January 2025; November 2025): President Masoud Pezeshkian said the government had been forced to burn mazut to avoid cutting gas to households; Energy Minister Abbas Aliabadi said mazut-burning plants are low priority and liquid fuel is kept as a last resort. · Iran International
iran-doe (15 February 2026): Its head Shina Ansari described a low-sulfur mazut programme with the Oil Ministry and reported unhealthy SO2 days at Shazand falling from 27 to five. · Shana (Ministry of Petroleum)
iran-ministry-of-petroleum (4 February 2025): Reported mazut deliveries to power plants of 4.941 billion litres in the winter of 2024/25. · Shana (Ministry of Petroleum)
iran-judiciary (December 2023; January 2025; December 2025): Its Tehran Province head said five former managers were convicted of dereliction of duty under the Clean Air Law; state-affiliated media described national security as 'nonnegotiable' in the Kahrom case. · Mehr News Agency

In court and with insurers

Every proceeding and every insurer decision on record.

Lawsuits and rulings

2023–2023Claimant won
Tehran prosecution of five former managers over Clean Air Law non-enforcement
Tehran courts (as stated by the head of the Tehran Province Judiciary) · Criminal · Tehran Prosecutor's Office → Five former managers (not named in the sources)
RFE/RL reported in May 2023 that the Tehran Prosecutor's Office had charged five unidentified officials with failing to enforce Clean Air Act standards on vehicle emissions, gasoline quality and mazut-fuelled plants. Ali Alghasi-Mehr, head of the Tehran Province Judiciary, said on 3 December 2023 and 12 January 2025 that five former managers had been indicted for abuse of position and convicted of dereliction of duty; sentences were not disclosed. Mehr News Agency
2025–Ongoing
Judiciary case against ecologist Esmail Kahrom
Iranian judiciary (as reported by Iran International) · Criminal · Iranian judiciary and prosecutors → Esmail Kahrom, ecologist
Iran International reported on 8 December 2025 that the judiciary had opened a case against Kahrom after a 30 November 2025 interview in which he criticised mazut use and spending on missiles, with charges reported as 'false statements' and acts 'against national security'; prosecutors also acted against the editor of Jamaran. No verdict is on record. Iran International

Insurers

No insurer decision on record.

What nature saw

Outcomes measured on the ground, and nature's note.

Nature's report opens this page. Below: further outcomes measured on the ground.

Mazut delivered to power plants

4.941 bn litres

22 Oct 2024–31 Jan 2025; up 53% on the year before (Ministry of Petroleum)

Sulfur in mazut

3% to 3.5%

About 30,000 ppm (Department of Environment head, 2021); 3.5% (Oil Ministry reports via RFE/RL, 2023)

Unhealthy SO2 days at Shazand

27 to 5

Iranian years 1402 to 1403, after low-sulfur mazut (Department of Environment)

Convictions announced

5 former managers

Dereliction of duty under the Clean Air Law, per the head of the Tehran Province Judiciary; sentences undisclosed

What we don't know

Undisclosed, unproven, untried: recorded as data.

Court ruling exists Key earnings undisclosed

Nature

Disputed Whether mazut use was halted or expanded in the winter of 2024/25

Money

None on record Priced damage to nature from mazut burning — None on record.

Accounts

Disputed Whether a directive allowed mazut burning on security grounds (January 2021)

Record

Not measured Not measured: the share of the power-plant SO2 in NASA's catalogue that comes from mazut; the catalogue gives totals per plant without assigning a fuel.
Disputed Figures differ: the sulfur content of Iranian mazut was given as about 3% (30,000 ppm) by the Department of Environment head in January 2021 and as 3.5% in Oil Ministry reports cited by RFE/RL in 2023.
Not disclosed Not disclosed: the identities of the five managers convicted under the Clean Air Law and their sentences.
Insufficient Insufficient: no published government estimate of the health cost specific to mazut.
None on record None on record: official mazut volumes for the winter of 2025/26 beyond a single daily figure (more than 21 million litres on 14 November 2025, Fars).
None on record None on record: a verdict in the case against Esmail Kahrom reported in December 2025.

Did the harm stop?

Mazut burning continued through the winters of 2024/25 and 2025/26 according to the Ministry of Petroleum and Fars; the Department of Environment reported a low-sulfur mazut programme at four plants in February 2026.

Who paid?

None on record for the air pollution. The Health Ministry's cost of air-pollution deaths in 1403 (about US$17.2 billion) is not specific to mazut; five former managers were reported convicted, with sentences undisclosed.

Sources

Voices on record: — Company or project✓ Government and regulators— Courts✓ Press and investigations— Communities and civil society— Researchers✓ International bodies

Connected cases

Related matters, and cases linked to this one through the same organisations, with the role each played in both.

Case file

Country: Iran
Region: Middle East
Period: 2020–2026
Instrument: Oil, gas and coal operations
Sources: 12
Updated: 2026-10-19

Actors in this case

Ministry of Petroleum (Iran)in 5 casesSupplies mazut to power plants; reports delivery volumes
Ministry of Energy (Iran)Power plant operator; reports rising mazut use
Department of Environment (Iran)in 11 casesEnvironmental regulator; low-sulfur mazut programme
Judiciary of Iranin 3 casesTehran Province Judiciary announced convictions; case against Esmail Kahrom
Government of Iranin 23 casesPresidency; decisions on mazut use
NASAin 10 casesSatellite SO2 point-source catalogue

Key figures

Mazut delivered litres bn: 4.94 bn litres · 2025
Mazut litres per day m: 53.9 m litres per day · 2025
Mazut litres per day m: 38.5 m litres per day · 2022
Mazut litres m: more than 21 m litres · 2025
Low sulfur mazut litres m: 420 m litres · 2026
Unhealthy so2 days: 27 days · 2024
Unhealthy so2 days: 5 days · 2025
Mazut sulfur pct: 3.5 % · 2023
Power plants using mazut: 14 of 16 plants · 2023
So2 kt per year: 34.3 kt SO2 · 2025
So2 kt per year: 27 kt SO2 · 2025
So2 kt per year: 86.2 kt SO2 · 2025
So2 kt per year: 68.6 kt SO2 · 2025
So2 kt per year: 53 kt SO2 · 2025
So2 kt per year: 43.2 kt SO2 · 2025
So2 kt per year: 16.6 kt SO2 · 2025
Managers convicted: 5 people · 2023
Judiciary warnings: 94 letters and warnings · 2025

Use this case

Who Gains from Saving Nature. "Mazut burning in Iranian power plants, 2020–2025." Case file, updated 2026-10-19. https://whogains.org/case/iran-mazut-burning-in-power-plants/

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