From jet fuel to clothes, microbes can help us recycle carbon dioxide into everyday products

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Jamin Wood, The University of Queensland; Bernardino Virdis, The University of Queensland, and Shihu Hu, The University of QueenslandThe Intergovernmental Panel on Climate Change (IPCC) report released earlier this month sounded a “code red for humanity”. At such a crucial time, we should draw on all possible solutions to combating global warming.

About one-quarter of greenhouse gas emissions are associated with the manufacture of the products we use. While a small number of commercial uses for carbon dioxide exist — for instance in the beverage and chemical industries — the current demand isn’t enough to achieve meaningful carbon dioxide reduction.

As such, we need to find new ways to transform industrial manufacturing from being a carbon dioxide source to a carbon dioxide user.

The good news is that plastics, chemicals, cosmetics and many other products need a carbon source. If we could produce them using carbon dioxide instead of fossil hydrocarbons, we would be able to sequester billions of tonnes of greenhouse gases per year.

How, you may ask? Well, biology already has a solution.

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Gas fermentation

You may have heard of microscopic organisms, or microbes — we use them to make beer, spirits and bread. But we can also use them to create biofuels such as ethanol.

They typically need sugar as an input, which competes with human food consumption. However, there are other microbes called “acetogens” which can use carbon dioxide as their input to make several chemicals including ethanol.

Acetogens are thought to be one of the first life-forms on Earth. The ancient Earth’s atmosphere was very different to the atmosphere today — there was no oxygen, yet plentiful carbon dioxide.

Acetogens were able to recycle this carbon using chemical energy sources, such as hydrogen, in a process called gas fermentation. Today, acetogens are found in many anaerobic environments, such as in animals’ guts.

Not being able to use oxygen makes acetogens less efficient at building biomass; they are slow growers. But interestingly, it makes them more efficient producers.

For example, a typical food crop’s energy efficiency (where sunlight is turned into a product) may be around 1%. On the other hand, if solar energy was used to provide renewable hydrogen for use in gas fermentation (via acetogens), this process would have an overall energy efficiency closer to 10-15%.

This means acetogens are potentially up to twice as efficient as most current industrial processes — which makes them a cheaper and more environmentally friendly option. That is, if we can bring the technology to scale.

About one-quarter of greenhouse gas emissions come from the manufacture of everyday products, while one-third come from electricity generation and another one-fifth come from transport.

Sustainable carbon recycling

Gas fermentation is scaling up in China, the United States and Europe. Industrial emissions of carbon monoxide and hydrogen are being recycled into ethanol to commercially produce aviation fuel from 2022, plastic bottles from 2024 and even polyester clothes.

In the future this could be expanded to produce chemicals needed to make rubber, plastics, paints and cosmetics, too.

But gas fermentation currently isn’t done commercially with carbon dioxide, despite this being a much larger emission source than carbon monoxide. In part this is because it poses an engineering and bioengineering challenge, but also because it’s expensive.

We recently published an economic assessment in Water Research to help chart a pathway towards widespread acetogen-carbon dioxide recycling.

We found economic barriers in producing some products, but not all. For instance, it is viable today to use carbon dioxide-acetogen fermentation to produce chemicals required to make perspex.

But unlike current commercial operations, this would be enabled by renewable hydrogen production. Increasing the availability of green hydrogen will greatly increase what we can do with gas fermentation.

Looking ahead

Australia has a competitive advantage and could be a leader in this technology. As host to the world’s largest green-hydrogen projects, we have the capacity to produce low-cost renewable hydrogen.

Underused renewable waste streams could also enable carbon recycling with acetogens. For instance, large amounts of biogas is produced at wastewater treatment plants and landfills. Currently it’s either burned as waste, or to generate heat and power.

Past research shows us biogas can be converted (or “reformed”) into renewable hydrogen and carbon in a carbon-neutral process.

And we found this carbon and hydrogen could then be used in gas fermentation to make carbon-neutral products. This would provide as much as 12 times more value than just burning biogas to generate heat and power.

The IPCC report shows carbon dioxide removal is required to limit global warming to less than 2℃.

Carbon capture and storage is on most governments’ agendas. But if we change our mindset from viewing carbon as a waste product, then we can change our economic incentive from carbon disposal to carbon reuse.

Carbon dioxide stored underground has no value. If we harness its full potential by using it to manufacture products, this could support myriad industries as they move to sustainable production.

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Jamin Wood, PhD Candidate at the Australian Centre for Water and Environmental Biotechnology (formerly Advanced Water Management Centre), The University of Queensland; Bernardino Virdis, Senior Researcher at the Australian Centre for Water and Environmental Biotechnology (formerly Advanced Water Management Centre), The University of Queensland, and Shihu Hu, Senior Research fellow at the Australian Centre for Water and Environmental Biotechnology (formerly Advanced Water Management Centre), The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Healthy microbes make for a resilient Great Barrier Reef

Maxine Gatt, The Conversation

Healthy microbes make for a healthy coral reef. And if that microbiological community is disrupted by overfishing, pollution or climate change, it can contribute to the decline of reefs.

A three-year study
published this month in Nature Communications, conducted on a reef in the Florida Keys, United States, has shed light on how microbes living on corals are instrumental to keeping coral reefs healthy, and how overfishing, pollution and climate change can destabilise the coral’s natural defence and disrupt ecological communities.

According to the lead author of the study Dr Rebecca Thurber, from Oregon State University, healthy corals normally recover easily from small injuries, such as fish bites.

“In our experiment, 100% of the corals bitten in normal waters recovered. But in the presence of elevated nutrients, 66% died after they were bitten by fish, showing that nutrient pollution increases the vulnerability of corals to normal every day events,” she said.

Although this study focused on Caribbean ecosystems, it can inform threats to the Great Barrier Reef, said Dr Jon Brodie from James Cook University, who was not involved in the study.

Coral bleaching and warming ocean temperatures are already affecting tropical reefs, with coral cover already on the decline.

The addition of overfishing and nutrient pollution interact with the elevated temperatures creating more disease-causing bacteria, and this may make reefs less resilient to disruptive events such as cyclones.

According to Dr Zoe Richards, from Western Australian Museum, who was not involved in the study, the study shows “how easily an innocuous interaction like a fish feeding on a coral can turn deadly in overfished and polluted habitats, especially in summer”.

Adding protection

The results suggest it’s especially important to manage overfishing around important reefs, says Richards. This will help sustain the population of fish that feed on microbes that might otherwise increase in numbers and disrupt the normal microbial ecology.

“This will help suppress algal overgrowth and blooms of harmful bacteria, which are major drivers of coral mortality,” said Richards.

Another strategy to protect reefs is to protect the environment around them.

“Rehabilitating catchment areas, preventing clearing and erosion, along with protecting natural waterways and limiting herbicide and pesticide run-off are integral components of reducing nutrient pollution,” said Richards.

Even though climate change is warming the Great Barrier Reef, reducing the impact of other stressors could help maintain a healthy microbial balance.

“If we reduce ocean pollution and ensure that there are abundant fishes to remove the algae on reefs, corals can likely tolerate some increases in water temperatures,” said Thurber

Maxine Gatt, Editor, The Conversation

This article was originally published on The Conversation. Read the original article.

Microbes: the tiny sentinels that can help us diagnose sick oceans

Katherine Dafforn, UNSW Australia; Emma Johnston, UNSW Australia; Inke Falkner, and Melanie Sun, UNSW Australia

Microbes – bacteria and other single-celled organisms – may be tiny, but they come in huge numbers and we rely on them for clean water, the air we breathe and the food we eat.

They are nature’s powerhouses but they have often been ignored. We previously lacked the capacity to appreciate truly their diversity, from micro-scales right up to entire oceans.

Recent advancements in genetic sequencing have revealed this diversity, and our research, published in Frontiers in Aquatic Microbiology this week, shows how we can use this information to understand human impacts on an unseen world – making microbes the new sentinels of the sea.

A sea of microbes

The great majority of bacteria and other microbes are extremely beneficial, performing vital roles such as recycling nutrients.

The number of bacteria on Earth is estimated at 5×10³⁰ (or 5 nonillion, if you prefer), and many of them live in the ocean. There are 5 million bacteria in every teaspoon of seawater, and more bacteria in the ocean than stars in the known universe.

Guess how many microbes?
Victor Morozov/Wikimedia Commons, FAL

There are yet more bacteria in the world’s soils and sediments, with estimates of between 100 million and 1 billion bacteria per teaspoon. These sediments are vital for recycling nitrogen, particularly in coastal sediments closest to human populations. Without bacteria and other microbes, sediments would turn into unsightly, pungent piles of waste.

Microbial services are not limited to recycling. Many microbes, including cyanobacteria, function like tiny plants by using sunlight to produce oxygen and sugars. Due to their extraordinary number in the world’s oceans, the amount of oxygen these organisms produce is equal to that of all plants on land.

Marine sentinels

Until recently, finding out just how many different types of microbes there are was relatively difficult. How do you identify and study millions of different organisms that are not visible to the naked eye?

Bacteria, for example, had to be grown in the laboratory in large colonies to be seen. But only 1-3% of bacteria can be cultured successfully.

Advances in genetics together with the development of molecular tools have allowed researchers to investigate marine bacteria in their natural environment. Microbial communities can now be grouped by the role they play in ecosystems and how these groups respond to environmental gradients.

We can use these new tools to measure ecosystem health, which is crucial to managing human impacts on our coastlines, particularly in estuaries. Early studies have found shifts in bacterial community composition to be good indicators of contaminants

Different areas of harbours, such as Sydney Harbour, have distinct bacterial communities. These patterns may be driven by circulation. The outer harbour, which is flushed with seawater on every tidal cycle, is dominated by photosynthetic cyanobacteria. The upper harbour, with less flushing and more runoff, is dominated by soil-related bacteria and those adapted to nutrient-rich environments.

In our waterways, pollutants such as metals bind to fine particles and settle as sediment. This exposes sediment-dwelling organisms to a multitude of toxic products. What effect do these toxic substances have on sediment microbes?

Recent evidence from a large survey of eight estuaries suggests that microbes are far more sensitive to contaminants than larger animals and plants. This survey also revealed that toxic substances were linked to changes in community structure and a reduction in community diversity. This is especially alarming given that a diversity of microbes is essential to nutrient recycling.

Diagnosing wounded seas

It would be great if we could use particular microbes to diagnose human impacts. For instance, certain microbes can indicate water quality.

A technique called metagenomics is revealing the true depth of microbial diversity by pooling DNA sequences from all the species in a sample. It then works backwards to construct a genetic overview of the entire community.

However, while metagenomics can give us important information about the identity of microbes in a community, it can’t tell us what they are doing or how their functions change in response to environmental stressors and human activities.

Metatranscriptomics takes the sequencing approach one step further and characterises gene expression in a microbial community, which can be linked to crucial ecosystem services such as nutrient cycling.

Similar to their use for diagnosis of ailments in humans, molecular tools are being used to diagnose human impacts on earth by observing changes in microbes across polluted and unpolluted environments. They can even detect very small amounts of toxic substances. Because of their diversity, they can potentially be used to detect a wide range of human impacts.

This allows us to identify environmental impacts early, potentially limiting greater loss in larger organisms.

With the new tools to “see” microbes and their importance, we are now perfectly poised to advance our understanding of how microbes are responding to environmental change. They are sentinels of our increasingly human-affected waterways.

Katherine Dafforn, Senior Research Associate in Marine Ecology, UNSW Australia; Emma Johnston, Professor of Marine Ecology and Ecotoxicology, Director Sydney Harbour Research Program, UNSW Australia; Inke Falkner, Community Outreach Coordinator for Sydney Harbour Research Program, Sydney Institute of Marine Science, and Melanie Sun, PhD Candidate – Environmental Research, UNSW Australia

This article was originally published on The Conversation. Read the original article.

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