A brewery in Australia is hoping to help fight climate change one beer at a time, with the help of two green bioreactors filled with trillions of micro-algae.

Carbon produced from the fermentation of a six-pack of beer can take a tree up to two days to absorb, experts say.

The co-founders of Young Henrys brewery in Sydney set out to find a way to reduce the carbon footprint of their brewery.

With the help of scientists at the University of Technology Sydney (UTS), they found their answer: micro-algae.

The carbon emitted by the fermenting beer is captured and fed to the algae, which then reproduces and transforms the CO2 into oxygen.

The two 400-litre bioreactors, which each take up around one metre of floor space, produce as much oxygen as two hectares of bushland, Young Henrys co-founder Oscar McMahon told Reuters.

"We could knock down our whole site and plant trees, and those trees, it would take years before they did the same amount of carbon sequestration and oxygen creation as those two bioreactors. We can start them up within a week and they are creating oxygen," McMahon said. "As an urban carbon sequestration and oxygen producing solution, it's mind-blowing."

Along with beer, the Young Henrys team, UTS and Meat & Livestock Australia have joined to investigate whether the algae they farm could be used to offset the methane emissions of the Australian livestock industry.

Currently, Young Henrys sends its leftover grain to farmers as cattle feed. Early research shows promising results that adding micro algae to the mix could reduce the methane emissions from cows by up to 20%.

Algae would play a significant role in the future in a sustainable circular economy, where carbon is reused and the waste from one industry becomes an important product in another, Professor Peter Ralph, the executive director of the Climate Change Cluster at the University of Technology Sydney, said.

"Instead of us digging something up, making a product and then throwing it away, we circularise it and we're actually going to use our carbon effectively and I think that's going to be the future, where industries want to use recycled carbon, not fossil carbon," he said.

Australia, one of the world's top producers of coal and gas, has adopted a target of net zero carbon emissions by 2050, but Prime Minister Scott Morrison said he would not legislate the target.

He rejected a global pledge, led by the European Union and the United States, to cut methane emissions by 30% by 2030.