India’s ethanol-blending programme has received considerable attention, with much of the debate centered on its potential as a cleaner fuel and its impact on vehicle mileage. While these concerns are important, they often overshadow the environmental cost of producing ethanol at scale.
Ethanol is not inherently a bad idea. According to a July 2026 government background note, the share of ethanol blended with petrol has increased from less than 1.5% in 2013-14 to 20% in 2025-26. This is an important achievement for a country that imports about 88.5% of the crude oil it consumes. Every litre of domestically produced ethanol blended with petrol replaces a small quantity of imported fuel and reduces India’s dependence on unstable oil markets.
The programme has also created an additional source of income for the agricultural sector. Sugar mills can produce ethanol from molasses, sugarcane juice and syrup, while grain-based distilleries can use maize and certain other approved feedstocks. The government estimates that, between 2014-15 and May 2026, the programme substituted more than 310 lakh metric tonnes of crude oil, saved over ₹1.90 lakh crore in foreign exchange and generated more than ₹1.60 lakh crore in additional earnings for farmers.
These are all the substantial gains, but the question remains if India can expand production without allowing pollution around distilleries to become the hidden cost of its energy policy.
India’s ethanol pollution problem starts at the distillery
The most serious pollution risk associated with conventional ethanol production is a dark, concentrated liquid waste known as spent wash. It remains after the fermented mixture has been distilled and contains large amounts of dissolved organic matter, salts, acids and coloured compounds.
The Ministry of Environment has identified distilleries as one of India’s major polluting industrial categories. Its data describe untreated spent wash as having biochemical oxygen demand, or BOD, of around 45,000-60,000 milligrams per litre and chemical oxygen demand, or COD, of approximately 80,000-1,20,000 milligrams per litre. These measurements indicate the amount of oxygen that would be required to break down the pollutants present in the waste.
If such effluent reaches a river, pond or stream without proper treatment, microorganisms begin consuming the organic material and rapidly reduce the oxygen available in the water. This can damage fish, aquatic plants and other organisms. Its dark colour can also block sunlight from entering the water, reducing photosynthesis. If poorly handled on land, concentrated spent wash can increase soil salinity and damage its fertility. A study published in the Journal of Hazardous Materials showed that older distillery processes could generate roughly 8–15 litres of spent wash for every litre of alcohol produced, although the quantity varies according to feedstock and technology. (Read the study)
The pollution problem is not limited to liquid waste. Ethanol plants require steam and heat for fermentation, distillation, evaporation and drying. Boilers powered by coal, biomass or other fuels can release particulate matter, sulphur dioxide and nitrogen oxides if suitable control equipment is not installed and maintained. Fermentation and distillation can also release volatile organic compounds and strong odours. This means that a plant can technically prevent liquid discharge while still creating air-pollution and odour problems for local communities.
Zero liquid discharge by India’s ethanol distilleries: Is it a myth?
Indian environmental requirements generally expect distilleries to prevent untreated waste from leaving the plant. Grain-based distilleries, for instance, have been directed to achieve zero liquid discharge through processes such as separation, evaporation, concentration and drying. Molasses-based plants may use biomethanation, evaporation, incineration or other approved systems to manage spent wash.
These technologies can significantly reduce pollution. Spent wash can be used to produce biogas, while concentrated residues can be processed or burnt in boilers. Condensate and other wastewater can also be treated and reused inside the plant.
The difficulty lies in ensuring that these systems operate continuously rather than only during inspections. Effluent-treatment equipment consumes electricity, fuel and chemicals, making it expensive to run. Storage lagoons can overflow, pipelines can leak, and untreated waste may be released when treatment capacity is not right. A plant’s description as “zero liquid discharge” in its environmental-clearance documents is therefore a commitment that must be verified and regularly monitored.
The Central Pollution Control Board already maintains an online continuous emissions and effluent monitoring system for industrial units. Although monitoring becomes meaningful only when the equipment is properly built, the data are regularly audited and violations lead to timely action.
Evidence from pollution disputes with India’s ethanol distilleries
Recent cases show why stronger monitoring is necessary. In December 2023, effluent allegedly released from a distillery in Kasauli, Himachal Pradesh, affected a natural water source used by a supply scheme serving about 2,000 people. Officials reported froth and a bad fermentation like odour, and the supply was stopped after the water was found polluted enough for human consumption. The National Green Tribunal later formed a joint committee to inspect the site and determine the extent of pollution. (Read the report)
A more serious case emerged from Zira in Punjab. In a 2025 affidavit submitted to the National Green Tribunal, the Punjab government said that the Malbros International distillery had a documented history of violating environmental norms and causing pollution affecting air, water, soil and public health. The state recommended that the plant be permanently closed and not be allowed to restart ethanol production on the same land. (Read the Indian Express report)
These cases do not state that every ethanol plant is polluting. Many modern distilleries may operate within required lawful standards. But they do show that pollution concerns cannot be dismissed merely because a project has received environmental clearance or claims to follow zero-liquid-discharge practices.
