The waste is currently treated by neutralising the acid, which causes most of the metals to drop out in a sludge. The sludge goes to landfill and the liquid is diluted before being released as wastewater. Zinc, however, accumulates in the environment and is extremely toxic to aquatic life, so even a small amount entering waterways is problematic.

“The whole treatment process is a massive waste of resources. It’s so much better to reuse the zinc than pollute the environment with it. Disposal is also expensive. It costs industry 3–4 times as much to dispose of the acid than to purchase it.”

Galvanising waste is not a new problem, but it is a difficult one because of the mix of metals and acid. The existing technologies are either very expensive or fail to recover the zinc. Jonathan became aware of the problem at the end of his bachelor’s degree in chemical and process engineering, and decided to take it on as a master’s research project.

“I tried some unconventional methods and had great success. I used an electrochemical method to separate the iron and zinc at low cost, then applied existing technology to regenerate the acid. The transformation from foul green soup to a vial of clean water and metal was almost comical.”

Feedback from local galvanising industries was positive but highlighted the need to scale up to a pilot plant. This required Zincovery to employ three new engineers in 2021 who are now making serious inroads into the remaining technical challenges.

“What we’re doing here in New Zealand is proving the technology. The opportunities to export the tech and license the intellectual property are huge. The 11 galvanising plants in this country produce about 1.5 tonnes of waste acid per year. That’s about the size of a very small plant in China, where there are 4,000–5,000 galvanising plants.”

Jonathan says more stringent environmental regulations have been favourable from a business perspective by pushing up the cost of disposal. He is also intrigued by the glamour around the circular economy and recycling waste.

“When you get your overalls on, however, handling waste is not quite so pretty – for us its toxic, corrosive chemicals. But I wouldn’t have it any other way. I’m pleased to be able to do something to make a real difference in the world.”