India ranks as the third-largest producer and processor of cashew nut, following Vietnam and Nigeria, contributing approximately 23% of global cashew production. Interestingly, while cashew nuts are edible and highly valued, the shell, which makes up about 67.5% of the fruit, is often consider waste in the processing industry.
However, cashew shells have a significant calorific value of 4800 Kcal/kg, higher than many biomass fuels like groundnut shells, firewood, wood chips, mustard straw, and rice husk. But the question is—can we use cashew shells as a reliable industrial fuel? A high calorific value alone isn’t enough to make a fuel viable. Let’s explore what lies inside the cashew shell and the challenges of using it as a fuel.

Cashew shell and Nut

What’s Inside a Cashew Shell?

Cashew nut shells contain 15-25% of a dark, reddish-brown viscous liquid known as Cashew Nut Shell Liquid (CNSL). CNSL is a low-cost source of phenol and has various industrial applications, especially in polymer-based industries such as paints, brake linings, epoxy resins, and rubber compounds. It has a high calorific value of about 11,380 Kcal/kg, similar to light furnace oil (LFO).

Cashew shell composition

However, CNSL is acidic, with a pH of 4.5 to 5.2, due to anacardic and cardol acids. Because of CNSL’s properties, cashew shells that are combusted pose several risks.

Challenges of Using Cashew Shells as a Fuel

Although cashew shells have high calorific value, using them as an industrial fuel comes with significant drawbacks:

  • Reduction in Furnace Lifetime: Cashew shells are rich in phenols, which can severely damage the refractory bricks in furnaces over time, reducing their lifespan.
  • Toxic and Corrosive Fumes: When cashew shells burn, the acidic CNSL generates toxic fumes, including anacardic acid. These fumes corrode equipment and pose serious health hazards to workers and the environment.
  • Black Smoke Emissions: Due to their high carbon content, cashew shells can produce black smoke during combustion, especially when there’s insufficient air supply.
  • Handling and Feeding Issues: The high oil content of cashew shells creates problems in hoppers and feeders, making the fuel challenging to handle and store. Its acidity also poses safety risks during storage and handling.

Lessons from the Past: A Case Study

In 2016, an FMCG company based in Orissa experimented using cashew de-oiled cake (DOC) as a standalone fuel in their thermic fluid heater. Within 10 to 15 days, the coils were damage beyond repair, forcing the company to shut down the heater for a month to replace the damage parts. Thankfully, a major accident was avoided, but the incident highlighted the risks of using cashew shells as fuel without proper processing.

The Solution: Astillas

At Steamax, we advise against using raw cashew shells as standalone fuel due to the risks mentioned above. To address these challenges, we’ve developed Astillas—a new fuel blend that incorporates cashew shells but processes them to reduce CNSL content and toxicity. This ensures safer combustion without producing toxic fumes or black smoke. Plus, Astillas is easier to handle and store, making it a viable and efficient fuel for industrial use.

If you’re looking for cleaner, more reliable fuel for your operations, Astillas might be the solution you need. Feel free to contact us for more information or inquiries.

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27 Comments

  2. Hello 😉 Thanks heaps for this indeed!… if anyone else has anything, it would be much appreciated. Great website Just wanted to say thanks and keep doing what you’re doing Thx & Regards!

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