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Feature

Saeid Baroutian: From waste to win

14 June 2021
Baroutian’s research is finding solutions to real-world waste problems by reusing what can be reused and turning things that aren’t useful into things that are.

If traditional Western industry were a diagram, it would be a straight line. Resource extraction leads to production, distribution, consumption and finally disposal.  is working to bend that line into a circle.

Baroutian, an associate professor of chemical and materials engineering, heads the  (WaRe3) at Waipapa Taumata Rau, University of Auckland.

He also leads the , which gets students working closely with industry to solve real-world problems – often leading to jobs for the students.

Fundamentally, Baroutian’s research involves using high-tech processes in the service of principles that would have been familiar to his great-grandparents: minimizing waste, reusing what can be reused and turning things that aren’t useful into things that are.

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Saeid Baroutian

From invasive seaweed to biogas and fertiliser

Sargassum is a type of algae that normally provides a haven for creatures such as turtles, fish and eels. Since 2011, however, for reasons not entirely understood, unprecedented quantities of sargassum have been invading Atlantic and Caribbean coastlines.

Massive carpets of sargassum as much as a metre thick piled up on Caribbean beaches, driving away tourists. It got tangled in fishing nets and boat motors. It smothered coral reefs and killed sea creatures. One young man named Terrell Thompson saw how sargassum affected his native country of Barbados. He turned to Baroutian for help in solving the problem.

Baroutian, Thompson’s PhD supervisor, identified two possible solutions. One was using microorganisms. Certain strains of microbes and fungi can digest organic waste and transform it into useful products. Baroutian had been working on this with materials such as food waste and sewage sludge. Seaweed, however, was a challenge because its physical structure and chemical composition made it difficult for the microorganisms to digest.

Enter Baroutian’s second solution. Hydrothermal processing involves breaking down organic waste using water at high temperature and pressure. Baroutian and Thompson found pre-treating sargassum that way breaks it down so microorganisms can almost completely convert it into biogas and biofertilizer. 

“Biogas is important for small islands like Barbados because they’re importing energy,” says Baroutian. “Biogas can help replace fossil fuels with a clean energy source. Biofertiliser can help agriculture. The process can also help with wastewater and organic solid waste, since lack of technology and treatment facilities often results in the release of contaminants. So we’re tackling two problems, sargassum and other organic waste, and creating valuable products in the process.”

From waste to high-value compounds

A major problem in the linear economy is that valuable compounds such as metals and minerals end up being disposed of along with low-value waste because they’re too hard to separate. Baroutian is working to change that.

Separation processes often involve organic solvents such as hexane, acetone and methanol. These solvents, however, are expensive, toxic and flammable, making storing large quantities a health and safety risk. 

Unlike organic solvents, supercritical and subcritical fluids are cheap, non-toxic, non-flammable and easily reusable. They’re highly specific, dissolving only the desired compound. They also work much faster than organic solvents.

So, what are supercritical and subcritical fluids and why aren’t they in wider use? To explain, let’s look at a familiar concept.

Everyone knows there are three states of matter: solid, liquid and gas, right? However, in-between states can exist.

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Terrell Thompson and Saeid Baroutian

For example, water boils at 100⁰C and turns into vapour under normal circumstances. But under high pressure, water can remain in liquid form above that temperature. This very hot liquid water is called subcritical, and it’s an excellent solvent.

At temperatures above 374⁰C, water becomes neither liquid nor gas but something with the high diffusion rate of a gas but the ability to dissolve substances like a liquid. This substance is called supercritical, and it too is an efficient and specific solvent at specific temperatures.

Carbon dioxide can also be made subcritical and supercritical and used as a solvent.

The challenge is that capital costs are high to start off, because subcritical and supercritical fluids need to be pressurized and pumped. However, the costs can be worthwhile to extract high-value compounds. With mostly renewable electricity used in New Zealand and the ability to keep reusing subcritical and supercritical fluids, it makes for a sustainable solution in the circular economy.

“[Our liquid smoke flavouring] can preserve food because it can completely destroy microorganisms like E. Coli and Listeria. Another advantage is that our product is high in antioxidants and doesn’t contain the toxic compounds that are normally formed when wood is burned.”

Saeid Baroutian

Adding value to an underutilised plant resource

Baroutian is also using supercritical and subcritical water in a project he’s undertaking in collaboration with a Ngāti Porou community of the Whareponga Valley in Ruatōria, East Cape. 

The community has a stand of native forest containing plenty of kānuka. Like its better-known cousin mānuka, kānuka is a tree native to Aotearoa New Zealand. Baroutian has been working with the community to produce high-value products other than honey from the resources it has.

Māori have long used kānuka for its medicinal properties. Baroutian is working with the community to extract bioactive antioxidants and flavours from the leaves using supercritical and subcritical water. The resulting “kānuka juice” is rich in antioxidants, he says.

Another technique, called fast pyrolysis, can produce liquid smoke flavouring. The technique involves burning kānuka wood in the absence of oxygen and collecting the vapours. The lightest vapours become liquid smoke, which has not only a unique flavour profile but strong antibacterial properties. 

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L to R: Wood chips, wood chips broken down using hydrothermal technology; plastic, plastic broken down using hydrothermal technology

With the support from , an investment committee operated by UniServices, and in partnership with the Māori landowners, Baroutian and Business School lecturer  (Ngāti Porou) have formed a company called Kauruki, which means smoke or haze, to market the liquid smoke.

“It can preserve food because it can completely destroy microorganisms like E. Coli and Listeria,” says Baroutian. “Another advantage is that our product is high in antioxidants and doesn’t contain the toxic compounds that are normally formed when wood is burned. We’ve used it on green shelled mussels and cheeses and the flavours are very nice.”

Greener ways of dealing with waste

Despite all Baroutian’s research into recovering materials and producing high-value products, there is inevitably some waste that is of no value or that is highly toxic. It’s typically sent to landfills, where it can result in environmental contamination.

Baroutian says there’s a better way.

In some countries, hazardous waste is incinerated at high temperatures, but this can result in the formation of toxic compounds such as dioxins and in particulate matter that contributes to smog.

Hydrothermal technology involves breaking down waste with hot, pressurized water and oxygen or nitrogen gas.

At high temperatures and pressures, oxygen can be diffused into the water to produce oxidation – that is, burning.

However, it occurs at a far lower temperature than in an incinerator, 200 to 300⁰C compared to the 1000⁰C or higher used in hazardous waste incinerators.

“Oxidising breaks down long chain molecules into smaller molecules, so the final products are water, carbon dioxide and maybe some carbon black that can be recovered,” says Baroutian. “Toxic chemicals like those found in pharmaceutical waste, plastics and tyres can be destroyed within 10 minutes into something that is easily discharged.”

Baroutian didn’t invent the processes he’s working with – he’s optimising them. He’s researching catalysts that could further lower the temperatures needed to destroy hazardous waste such as firefighting foam, agrochemical waste and pesticides. He’s working closely with industry to solve their real problems and meet their needs, whether it’s creating mobile units that can dispose of waste on a small scale or designing large-scale facilities.

Baroutian is currently looking for more companies to join him in addressing waste streams as part of a coalition that will minimize risks and costs. Interested parties are invited to contact him at s.baroutian@auckland.ac.nz.

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