BENGALURU: Ethanol is being presented as one of India’s key solutions to reduce its dependence on imported fossil fuels. With E20 petrol becoming the norm, the country’s demand for ethanol is expected to remain high. But there is another question that needs to be asked alongside the climate and energy-security benefits: How sustainable is the water footprint of producing ethanol?
Sugarcane is one of India’s major feedstocks for ethanol. According to NITI Aayog’s ethanol roadmap, the total water footprint of sugarcane-based ethanol is 3,000 litres of water for 1 litre of ethanol. Much of this water is not used inside the ethanol factory — it is associated with growing the sugarcane itself.
That becomes particularly important in India, where agriculture already places enormous pressure on freshwater resources. Take Karnataka as an example. The state is India’s third-largest sugarcane producer, after Uttar Pradesh and Maharashtra. In 2024–25, Karnataka produced about 48.06 million tonnes of sugarcane, accounting for roughly 10.6% of India’s total production. UP produced 220.8 million tonnes and Maharashtra 109.97 million tonnes.
At the same time, Karnataka’s groundwater situation is far from uniform. The latest groundwater assessment report on dynamic groundwater resources of Karnataka in 2024 found that the state was extracting about 11.55 billion cubic metres (BCM) of groundwater a year, equivalent to 68.44 per cent of its annual extractable groundwater resource. Of the state’s 237 groundwater assessment units, 45 — nearly 19 per cent — were classified as over-exploited, another 15 as critical and 33 as semi-critical.
The latest 2025 assessment is even more revealing at the district level. Five districts — Kolar, Bengaluru Urban, Chikkaballapur, Bengaluru Rural and Chitradurga — were classified as over-exploited, while Tumakuru and Bengaluru South were classified as critical. Bagalkot, Belagavi, Davanagere, Gadag, Vijayanagar and Chamarajanagar were classified as semi-critical.
According to a 2024 study conducted by the Government of Karnataka, groundwater levels in more than five taluks of Belagavi district fell by over 20 metres during the pre-monsoon period. Even during the post-monsoon period, several taluks continued to record groundwater-level declines of more than 20 metres.
A groundwater depth exceeding 20 metres below ground level indicates a relatively deep water table and can increase the depth to which wells must be drilled and the energy required for pumping. Among the affected areas are Savadatti, Athani and Ramdurg — regions that are also home to one of India’s major sugar and ethanol producers, Shree Renuka Sugars, including its Munoli distillery.
While acknowledging the environmental benefits of E20, retired professor of the University of Agricultural Sciences, Mandya, Professor Dr KV Keshavaiah highlighted the need for major changes in agricultural practices. He stressed that farmers must shift from surface irrigation to water-efficient drip irrigation and adopt better sugarcane cultivation practices. “We need to stop horizontal expansion of sugarcane cultivation, which places additional pressure on land and water resources,” he said.
According to him, India’s average sugarcane productivity is only about 70T/hectare, compared with a potential 350-375T. “We need to target at least 270T/hectare to improve ethanol production while reducing water use. There is a need to carefully manage water-intensive crops such as sugarcane, maize and rice,” Dr Keshavaiah said.
The scale of water use at the distillery is significant. To produce ethanol, the plant requires approximately 73 lakh litres of water/day, of which around 23 lakh litres is fresh water. The remaining 50 lakh litres is reused within the plant, meaning that approximately 31 per cent is fresh water. For example, Shree Renuka Sugar sources this fresh water from the Malaprabha reservoir, located within 2km of the facility.
However, the reservoir itself faces limitations in maintaining adequate water flow, raising concerns about the reliability and sustainability of drawing such large quantities of water on a regular basis. At the distillery, the company produces approximately 3,80,000 litres of ethanol per day on average. This translates to approximately 19.3 litres of total water/litre of ethanol, including 6.1 litres of fresh water.
This creates a difficult policy paradox. While the Centre is encouraging ethanol production and increasing the mandatory blending of ethanol with petrol, some of the crops used to produce that ethanol require substantial amounts of water. If higher ethanol demand strengthens the market for sugarcane, it could encourage farmers to maintain or expand a water-intensive crop — particularly where irrigation is already heavily dependent on groundwater. Karnataka is not an isolated case. Uttar Pradesh, India’s largest sugarcane-producing state, produced 220.8 million tonnes of sugarcane in 2024–25.
Dr Keshavaiah also emphasised that sugar companies must take greater responsibility for conservation by increasing water recycling and adopting more efficient water-management practices. “Sugar mills can develop water-retention infrastructure, including ponds within their premises, and invest in rainwater harvesting to capture and store runoff.
Such measures could help reduce pressure on local water resources and improve the resilience of sugar-producing regions to periods of water scarcity,” he said. He cautioned that without stronger water-conservation efforts, recurring climatic stresses such as El Niño could further intensify water shortages and pose.
The big question: How much fuel efficiency does it give?
Fuel efficiency remains a key concern for motorists as E20 petrol has lower energy density than conventional petrol, meaning engines may consume more fuel to deliver the same output. Government estimates suggest a 3 to 5 per cent reduction in fuel efficiency, while some automotive tests and user experiences report higher declines.
Kalai Selvan, an IT employee from Whitefield, Bengaluru, said, “I bought the bike in 2020, and one of the major problems I’ve faced is the decline in mileage, which has dropped by around 10–12%.” He also reported instances of stalling and delayed acceleration.
Another daily commuter, Rohan Karmakar, said, “I switched to E10 petrol wherever it was available, despite paying more.” Meanwhile, E20 has not translated into lower petrol prices. Neighbouring Bhutan, which relies heavily on India for fuel supplies, continues to offer pure petrol at comparatively lower prices, raising questions about the benefits reaching consumers.
All agriculture requires water. Now, the question is where that water comes from, whether it is being replenished, and whether ethanol policy is creating additional incentives to cultivate water-intensive feedstocks in places where groundwater is already under stress. If E20 reduces fossil-fuel consumption but increases pressure on groundwater in already water-stressed agricultural regions, can the fuel transition still be called sustainable? The answer may depend on what India uses to make its ethanol.
THE BRAZIL MODEL
Between 1975 and 2018, Brazil transformed ethanol from an emergency oil-substitution measure into a mature transport-fuel system. Brazil’s warm climate, adequate rainfall, and large areas suitable for sugarcane cultivation provided a strong natural advantage for expanding sugarcane production, making it relatively easier to increase the domestic supply of ethanol. In 1975, the government launched Proálcool in response to the oil crisis, providing subsidies, financing, and incentives for sugar mills to produce ethanol.
From 1979, the programme expanded into hydrated ethanol for dedicated ethanol vehicles, leading to rapid growth in ethanol-powered cars during the 1980s. However, falling oil prices, rising ethanol production costs, and supply shortages culminated in an ethanol crisis around 1989-90, after which government controls and subsidies were gradually reduced.
In 1993, a mandatory 22 per cent anhydrous ethanol blend in gasoline helped preserve demand. A breakthrough came in 2003 with flex-fuel vehicles, allowing consumers to use gasoline, ethanol, or mixtures of both. The blend rose to 25% in 2007 and 27% in 2015.
By 2018, RenovaBio established a long-term framework for expanding biofuels and reducing carbon emissions. Today, more than 85% of vehicles on Brazilian roads are flex-fuel vehicles.