9 slime-based solutions to make our planet future-ready

Notorious for spreading through oceans and lakes in toxic blooms that can affect humans, livestock, and fish alike, algae can be very bad news. But they also have a good side, and could play a crucial role in how we deal with climate change in the future.

Whether you call it algae, seaweed, or slime, when it comes to coping with the effects of climate change, these primitive aquatic organisms are probably not the first thing you think of.

But researchers at James Cook University (JCU) have been investigating the value of algae in mitigating the effects of a warming, crowded planet, and there’s a surprising array of things that seaweed can do to help us thrive.

9. Sustainable seafood farms

By 2050, humanity could face a food security crisis, and the world will be looking to farmed seafood as a more sustainable source of protein than resource-heavy livestock.

But the problem with aquaculture is that ‘used’ seawater from onshore farms is packed with nitrogen and phosphorus from fish waste, which can pollute our oceans and waterways if not treated.

The answer? Algae.

“Algae are fantastic,” says Professor Rocky de Nys, theme leader of the Centre for Macroalgal Resources and Biotechnology at JCU.

“When they grow in water, they use that nitrogen, phosphorus, and a range of other elements in our water, and they grow and produce biomass.”

By passing wastewater from aquaculture through the right kind of algae, de Nys and his team have found that it can be safely released back into the environment.

In fact, it’ll be as clean as when it was first brought to the farm, which means farmers can go ahead and reuse it time and again.

8. Next-level wastewater treatment

After their success in cleaning salt wastewater, JCU researchers have started using freshwater algae to treat municipal wastewater. And this could have huge implications for water sustainability.

Untreated wastewater typically contains around 50 mg of nitrogen per litre. A sewage treatment plant can get nitrogen levels down to about 10 or 20 mg per litre, but that’s still high compared to the 5 mg per litre needed for water to be considered clean.

Because freshwater macroalgae flourish by scavenging nutrients from wastewater, they’re especially good at cleaning up the remaining nitrogen.

Using our slimy friends, de Nys and his team are able to get the nitrogen and phosphorus levels in fresh wastewater to whatever quality of water the environment needs. With industry partner, MBD Industries, they’ve already run a successful trial at the Townsville City Council wastewater treatment plant.

The hope is that this treatment can be rolled out across the country using locally occurring algae strains. This would allow us to more effectively re-use water, while protecting our environmental resources at the same time.

7. Saving the Great Barrier Reef

Improving water quality in the Great Barrier Reef is one of the main ways we can ensure the survival of this vast and unique environmental asset. And algae can help us here, too.

“Around the Great Barrier Reef, water quality is one of the driving factors that would improve it, so by providing a sustainable mechanism to clean water, you have a significant environmental impact,” de Nys explains.

New aquaculture developments attached to the Great Barrier Reef must ensure that the wastewater leaving their farms is as good as the water being brought in.

An algal cleaning service will not only help safeguard the reef and related tourism ventures, but it also means aquaculture businesses in the area can flourish into the future.

6. Profit!

When you use algae to clean water, it doesn’t just eat the nitrogen and phosphorus – it also creates more algae.

Unlike most crops, which have to be replanted every season, algae is a product that continues to grow indefinitely.

Given the right conditions, algae can grow up to 10 per cent daily, and this new growth can be harvested and sold as a high-value product.

According to de Nys, this is a very rare case of having a financial incentive to clean water and use resources sustainably.

5. Burpin’ beasts

This is a big one.

When cows and other ruminating animals digest grass and wheat, bacterial colonies in their rumen – or stomach – produce methane. This methane is burped out, resulting in the majority of the greenhouse gas emissions produced by the agriculture industry.

As a greenhouse gas, methane is 28 times more powerful than carbon dioxide (CO2), which means if you can reduce these emissions, you’ll make a big impact.

While farmers have been looking for a feed supplement to reduce methane production for years now, most solutions have made only minor changes to methane emission levels.

Not so for seaweed.

In a collaborative project with the CSIRO and Meat and Livestock Australia, researchers discovered a particular species of seaweed that can significantly limit the methane production of the bacteria in the rumen.

While this sounds great from an environmental perspective, reducing these methane emissions could also make livestock feed go further, as less energy is wasted through burping out all that methane.

And those aren’t the only benefits of feeding seaweed to livestock.

4. Boosting animal feed supplements

Seaweed isn’t high in protein, but this slimy substance is bursting with minerals and trace elements, so it’s an excellent nutritional supplement for livestock feed.

Because aquaculture and agriculture usually operate in the same regions, the algae used to clean aquaculture wastewater also has a local application as a feed supplement for agriculture. This adds value to both industries without the need to transport the product across long distances.

3. Green food for plants

Livestock aren’t the only ones who can get a feed from algae. If you’re a keen gardener, chances are you’ve used seaweed extract on your plants to help them flourish.

JCU researchers have investigated the role of algae as a plant stimulant,  and found that adding algae extracts to soil or hydroponics promotes root growth and resistance to stress.

2. Solving fertiliser run-off

Speaking of fertiliser, the run-off from agriculture is full of it. And it’s getting into our waterways and causing major problems.

Cleaning this fertiliser-laden water with algae is more difficult than cleaning water from aquaculture, but according to de Nys, it is possible.

Once irrigation wastewater is filtered for sediment, algae can get in there and remove the nitrogen and phosphorus. The end result is not just clean water, but also more food for plants, as the algae can extract it back out of the water as a usable product.

“Suddenly, you can reduce water usage, and you’re still capturing the nitrogen and phosphorus that you’ve paid to put in the system in the first place,” says de Nys.

1. Quackaponics – bringing it all together

Credit: Bethany Keats, JCU

One researcher at JCU has taken the relationship between aquaculture and agriculture to a whole new level.

In what’s lovingly referred to as “quackaponics”, Dr Kate Hutson uses an algae-based system that applies waste from one product to help grow another.

Like a typical aquaponics setup, fish grow in tanks and their waste feeds microalgae growing in the system. And here’s where it gets creative.

In quackaponics, the wastewater from the fish gets filtered through grow beds where vegetables and herbs flourish. These crops use the nutrients from the fish waste, and in doing so, clean the wastewater so it can be recycled back into the system.

Redclaw, a type of freshwater crayfish, use this water from the grow beds and eat the algae. After this, the water is used by ducks, and they add their faeces to the mix, providing an ultra-rich food that can go back into the grow beds.

This system has been producing freshwater fish, crayfish, veggies, herbs, and duck eggs (these ducks are not for eating!) with minimal ongoing costs and maintenance, and without draining precious, non-renewable resources.

Hutson developed the system to demonstrate the theory of collaborative aquaculture, but by creating and managing it with her students, she’s also shown that it can be adapted in all kinds of environments, from someone’s backyard, to a region with food security issues.

“These kinds of systems are really adaptable, because they’re best suited to species that are eaten and grown locally,” Hutson explains.

“This way, there are minimal transport costs, your eco-footprint is substantially reduced, and you know you’re going to have a local market for the organisms. That means you’re not shipping internationally, and that ultimately reduces the impact of CO2 emissions, and some of the root causes of climate change.”

Featured JCU researcher

Prof Rocky de Nys
Prof Rocky de Nys
The Macroalgal Biofuels and Bioproducts research group provides research, development and implementation for cost-effective delivery of algal biomass to value-add to mining, mineral processing, power generation, aquaculture and agriculture.

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