CSIR-CSMCRI’s Potash Recovery Work Gives Sugar Biorefineries a New Revenue Stream
- Says Dr. Pratyush Maiti at IFGE Webinar
Spent wash is often called a distillery’s biggest headache. Dr. Pratyush Maiti, Senior Scientist at CSIR-Central Salt and Marine Chemicals Research Institute, told the Indian Federation of Green Energy National Webinar that it should be treated as a feedstock instead. At the session on Potash Recovery from Distillery Fly Ash: Technology, Sustainability and Scale, he laid out CSIR-CSMCRI’s integrated recovery technologies, field validation and two commercial plants already running in India.
Treat Spent Wash as a Resource, Not Waste
Dr. Maiti started with scale. Making 1 kilolitre of ethanol produces about 8 to 12 kilolitres of spent wash. Roughly 4.2 to 4.5 tonnes of molasses are needed for that ethanol. Spent wash is dark, high in BOD, COD, TDS and, importantly, 15 to 25 percent potassium.
With more than 400 distilleries in India making about 2.5 billion litres of alcohol a year, the system generates nearly 30 billion litres of spent wash annually. That translates to an estimated 0.29 million tonnes of K2O per year that could be recovered from waste streams.
Spent wash is not just a disposal problem. It is a resource stream with economic value, he said.
What’s Used Today, and Where It Falls Short
He reviewed current routes. Ferti-irrigation gives nutrients to soil but risks groundwater and soil health if not managed well. Bio-methanation produces energy but is biologically sensitive, slow to restart and has methane management issues. Composting with press mud recovers nutrients but creates leachate, is press-mud limited and slows in winter.
Incineration is now the preferred option for ZLD and CPCB compliance. It has its own issues though, including high capex and OPEX, shutdown risk, and potash sublimation that can corrode equipment. Process optimization is still needed.
CSIR-CSMCRI’s Integrated Approach
The institute’s technology is designed for two outcomes at once. Recover potassium as potash fertilizer, and recover potash-free organics for other uses. The potassium recovery efficiency is about 65 percent.
A key co-product is De-Potash Vinasse, DPV. Because potassium is removed, DPV can be used in animal feed and nutritional supplements. To test that, CSIR-CSMCRI worked with ICAR-National Dairy Research Institute. The trial used 15 lactating Murrah buffaloes across three groups for four months. Milk yield and nutrient digestibility were comparable to control, with no adverse health effects. The conclusion was that DPV can safely replace molasses in cattle feed pellets, which improves plant economics.
Commercialization in Practice
The first commercial milestone was Aurangabad Distillery Limited. Technology was licensed in January 2018 and the plant was commissioned in 2019. Current output is about 3,000 tonnes of SOP plus PDM and 7,500 tonnes of DPV per year. It is one of India’s earliest working examples of spent wash potash recovery.
The second is DCM Shriram’s plant at Hariwan, Hardoi, Uttar Pradesh. Licensed in November 2022, it produces 16.5 tonnes of SOP per day. Between January 2024 and March 2026 it produced over 10,000 tonnes of SOP and generated more than 49 crore rupees in revenue, with about 65 direct jobs created. That shows industrial scale and viability.
High-Purity SOP from Ash
Dr. Maiti also presented a route to 100 percent water-soluble Sulphate of Potash from potassium-rich incinerator ash. Product quality from the process includes 0.06 percent moisture, 51.98 percent K2O, 0.44 percent sodium, 0.84 percent chloride and 17.96 percent sulphur. That exceeds FCO specifications.
Economics of Scale
For a reference plant using 60 tonnes of ash per day, the indicative numbers are CAPEX of 45 crore rupees, payback around 4 years, and production cost below 30,000 rupees per tonne of SOP.
Why It Matters for Biorefineries
Dr. Maiti framed potash recovery as a strategic pillar for future sugar biorefineries. It turns waste into products, substitutes imports, adds revenue, improves sustainability and supports circular economy compliance.
His recommendations to speed adoption were faster deployment across distilleries, wider use of advanced recovery technologies, tighter integration into biorefinery flows, promotion of resource recovery models, and stronger industry-research collaboration.
Closing
Potash recovery from spent wash and incinerator ash is no longer experimental, he said. With pilot validation, feed trials and two commercial plants, the technology is proven, viable and scalable. Wider adoption can cut India’s potash import dependence while making sugar-ethanol operations more profitable and sustainable.
