The bubbles in your drinks come from fossil fuels – why not make them from “slash” instead?

University of Canterbury researcher Karan Titus is conceptualising how to make the bubbles in drinks without using fossil fuels.

Planet-friendly carbon dioxide for our favourite foods and beverages could be made from waste wood, which can become debris in extreme weather events.

Rather than crashing through communities and bridges during storms, slash would be better used with our favourite foods and drinks, say scientific researchers.

At the moment, the fizz in most carbonated soft drinks and beers come from fossil fuels. In New Zealand, a Taranaki plant purifies the fossil gas coming from the Earth: carbon dioxide is separated from the natural gas, with the latter entering the piped network to businesses and homes.

The refined carbon dioxide is dissolved into fizzy drinks and beer, and forms bubbles when opened. The fossil gas is widely used across the grocery store: it boosts the growth of fruit and veggies in greenhouses, and is also pumped into containers and trays to preserve fresh meat.  As dry ice, it keeps fruit, vegetables and dairy products cold and fresh during transportation.

But as New Zealand transitions to clean energy, we have a growing opportunity to use “green” carbon dioxide: gas that doesn’t add to the problem of climate change.

This green carbon dioxide would come from trees, which breathe in the gas when they grow. That means when wood waste is burned for energy, the carbon dioxide that is released doesn’t add to the blanket of heat around our planet the way fossil fuels do.

Even better, a green carbon dioxide plant could solve another environmental problem – by using the “slash” or waste left behind from forest harvesting, which often smashes its way downstream during floods, say researchers Rebecca Peer and Karan Titus.

Across the motu, companies already burn wood pellets in large boilers, creating lots of green carbon dioxide. But no large producer captures this gas. While there are small initiatives to reuse green carbon dioxide made in beer brewing and horticulture, the vast majority is simply released.

University of Canterbury's Rebecca Peer thinks businesses would be keen to use fossil fuel-free dry ice to store and transport fresh food.

The country should take advantage of this opportunity as soon as possible, Peer said. “I think most businesses would embrace the greener option, over fossil gas.”

In recent years, New Zealand suffered a serious shortage of refined fossil carbon dioxide. After the refining plant malfunctioned in 2023, prices shot up 600%, leaving desperate companies paying thousands of dollars per tonne for the limited and often imported supply.

The challenge, Titus said, is that food and drink makers require a very pure supply of carbon dioxide: at least 99.5%. That’s likely what has stopped anyone from collecting and selling green carbon dioxide to date, he said.

However, in an engineered pure-oxygen environment, a biomass boiler would produce a rich source of green carbon dioxide, Titus said. He is currently conceptualising a pilot plant to test out the idea.

“There is a major opportunity for a company planning to burn a lot of biomass, such as wood pellets,” he said. “This gas could be a much more valuable product than the energy made.”

Bubbles made from organic waste would have a lower carbon footprint than fossil-derived gas.

Beyond food and drink, many other industries regularly use carbon dioxide. Water treatment plants use it to fight pathogens. In factories, it is used for cleaning and purification.

Peer said green carbon dioxide could also be used in emerging clean technologies, such as the production of net-zero aviation fuel. Alternatively, it could be pumped and stored underground, she said. This would actively fight against climate change.

Green carbon dioxide might not directly reduce the production of fossil fuels, Peer warned – but taking away one income stream from a fossil gas producer might make them “a little bit less attractive”.

Rebecca Peer is the co-leader of the Sustainable Energy Research Group and Karan Titus is a postdoctoral researcher. Both work for the University of Canterbury, and are part of the Government-funded Carbon Removal research project.