Operational case: Recovering spent caustic to cut costs and support a zero-waste ambition
Spent caustic is a highly alkaline, contaminated wastewater composed of sodium hydroxide (NaOH or KOH), water, and various organic and inorganic pollutants. It is generated in processes that use caustic for cleaning, extraction, or neutralization, resulting in lower concentration streams that often contain impurities challenging to treat due to their high pH and suspended matter. Some years ago, we partnered with an industrial plant facing precisely this challenge. The main driver behind the project was clear: support the company’s corporate target of becoming a zero-waste facility.
DATE 2026-06-30The challenge
Spent caustic from the customer’s process unit is a valuable but difficult stream to manage. It contains reusable caustic, but part of it is chemically consumed during the process and converted into byproducts. Without a recovery solution, this creates a costly waste stream and increases the need for fresh caustic purchases.
Before the evaporation system, the customer had no established at-scale handling route, as previous volumes had only been managed at lab scale through disposal and/or limited reuse.
With a typical caustic consumption of approximately 12,000 kg/day of 50% caustic, the financial impact of off-site handling was significant, so the customer wanted a reliable partner that could deliver on a tight timeline and had proven experience with caustic evaporation systems.
Why evaporation made sense
The objective was to recover as much caustic as possible and reduce the customer’s dependency on fresh chemical purchases and off-site waste management. The customer targeted 80% caustic recovery, with the remaining 20% loss linked to the chemistry of the process itself.
By implementing an evaporation skid, the customer was able to recycle caustic back into the process instead of treating the stream only as waste. This approach directly supports both cost reduction and waste minimization, while improving resource efficiency in production.
The results
With the evaporation system in place, the customer now achieves approximately 80% caustic recovery. This generates major economic benefits thanks to lower fresh caustic demand and off-site waste handling requirements.
In addition, the customer estimates:
- EUR 0.9 million saved by recycling 80% of caustic internally
- EUR 1.9 million avoided through reduced third-party recycling costs
- EUR 2.2 million avoided through reduced disposal costs
Based on the project calculations:
Damien Vernede
Role at Alfa Laval: Global Sales and Business Development
Area of expertise: ZLD; evaporation and crystallization technologies
Scenario 1: Recycling by a third party
- Annual savings: EUR 1.9 million
- Payback time: 5 months
Scenario 2: Fresh caustic recharge + disposal of used caustic by a third party
- Annual savings: EUR 3.0 million (0.9+2.2)
- Payback time: 3 months
These numbers demonstrate that caustic recovery has a strong financial case, while also helping the customer reduce waste and improve resource efficiency.
Key success factors
For the customer, selecting the right supplier was critical. Since this was the company’s first production line, the top priorities were:
- Timeline
- Ability to perform
- Proven experience
The customer placed high importance on working with a supplier that could move quickly and had real-world expertise, both in evaporation technology and in handling the specific challenges of the process. Alfa Laval’s experience and support during the project were key reasons for moving forward without a lengthy comparison process.
Supporting growth and sustainability
Spent caustic recovery delivers value beyond waste treatment alone. By recovering and reusing caustic internally, the customer has taken an important step towards its zero-waste goal, while also reducing chemical consumption and improving the economics of its production line.
For companies managing high-volume spent caustic streams, evaporation can be a practical way to turn a difficult waste stream into a recoverable resource, with fast payback, high return, and clear sustainability benefits.
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