Distillery Fly Ash Can Be a Domestic Source of Potash
India imports nearly all the potash it uses in agriculture. Dr. Mohan K. Dongare, an independent technology developer and patent holder, told participants at the Indian Federation of Green Energy National Webinar on 03 July 2026 that a large part of that gap can be closed by recovering potassium salts from distillery fly ash. He called the approach technically proven and commercially attractive.
Speaking at the webinar on Potash Recovery from Distillery Fly Ash: Technology, Sustainability and Scale, Dr. Dongare focused on why potash matters, why incineration ash is a practical feedstock, and how his aqueous extraction process works at plant scale.
Why Potash Matters
Potash is a key nutrient for crop health. It helps with root growth, water retention, disease resistance and yield. The main commercial products are Muriate of Potash, MOP, Sulphate of Potash, SOP, and Potassium Magnesium Sulphate. Because India has very little domestic potash, most demand is met through imports. That creates price risk, supply risk and pressure on foreign exchange. Finding a local source, even partially, would improve fertilizer security.
From Waste Problem to Resource
Distilleries generate large volumes of spentwash. Traditional routes like biomethanation or composting are under pressure as environmental norms tighten and Zero Liquid Discharge becomes the norm. Incineration is increasingly preferred because it handles the load and meets ZLD requirements.
The by-product of incineration is fly ash. A typical distillery produces about 40 to 60 tonnes of fly ash per day, and that ash contains roughly 25 to 30 percent potassium. Instead of treating it only as waste, Dr. Dongare said, it should be treated as a potassium resource.
The Scale on the Table
India has more than 125 spentwash incinerators in operation. If each plant can produce about 7,500 tonnes of MOP equivalent in a year, the national potential works out to nearly 10 lakh tonnes per year. That volume would meaningfully reduce import dependence and give mills a new product line.
The Technology: Aqueous Extraction
Dr. Dongare outlined a six-step aqueous process developed for fly ash. First, hot water extraction pulls potassium into solution. A catalyst-assisted leaching step improves recovery. The solution is filtered to remove insolubles. Multi-Effect Evaporators concentrate the liquor. Crystallization yields the potassium salts. A final drying step gives a stable product.
The process recovers both MOP and SOP. Current recovery efficiency is in the 40 to 50 percent range. On about 50 tonnes of fly ash, a plant can recover 20 to 25 tonnes of MOP or SOP per day. That is enough to run a viable unit alongside the distillery.
The Economics
He shared indicative numbers for a 50 tonnes per day ash plant producing 20 tonnes of MOP per day. Capital expenditure is estimated at 7 to 8 crore rupees. Production cost is around 6,000 rupees per tonne. With these assumptions, the return on investment is less than one year.
Residual solids after extraction are not wasted either. They can be used in cement blocks and other construction materials, which improves overall resource use and fits circular economy goals.
From Concept to Commercial
Dr. Dongare said potash recovery from incinerator fly ash is past the experimental stage. The chemistry is established, the equipment is industrial, and the economics are strong. For mills already running incineration for ZLD, adding a recovery unit can turn a compliance cost into revenue, while contributing to India’s fertilizer security.
His takeaway was simple. Ash is not a disposal problem. It is a potassium inventory. If mills capture it, India can substitute imports, stabilize fertilizer supply, and create more resilient sugar-ethanol biorefineries.
