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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There aren’t enough trees in the world to offset society’s carbon emissions – and there never will be

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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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More livestock, more carbon dioxide, less ice: the world’s climate change progress since 2019 is (mostly) bad news

Thomas Newsome, University of Sydney; Christopher Wolf, Oregon State University, and William Ripple, Oregon State UniversityBack in 2019, more than 11,000 scientists declared a global climate emergency. They established a comprehensive set of vital signs that impact or reflect the planet’s health, such as forest loss, fossil fuel subsidies, glacier thickness, ocean acidity and surface temperature.

In a new paper published today, we show how these vital signs have changed since the original publication, including through the COVID-19 pandemic. In general, while we’ve seen lots of positive talk and commitments from some governments, our vital signs are mostly not trending in the right direction.

So, let’s look at how things have progressed since 2019, from the growing number of livestock to the meagre influence of the pandemic.

Is it all bad news?

No, thankfully. Fossil fuel divestment and fossil fuel subsidies have improved in record-setting ways, potentially signalling an economic shift to a renewable energy future.

The graph on the left shows an increase in fossil fuel divestment by 1,117 organisations based on data from 350.org, and the graph on the right shows a decrease in subsidies for fossil fuels based on the International Energy Agency subsidies database. The red lines show changes since our original publication in 2019.

However, most of the other vital signs reflect the consequences of the so far unrelenting “business as usual” approach to climate change policy worldwide.

Especially troubling is the unprecedented surge in climate-related disasters since 2019. This includes devastating flash floods in the South Kalimantan province of Indonesia, record heatwaves in the southwestern United States, extraordinary storms in India and, of course, the 2019-2020 megafires in Australia.

In addition, three main greenhouse gases — carbon dioxide, methane and nitrous oxide — set records for atmospheric concentrations in 2020 and again in 2021. In April this year, carbon dioxide concentration reached 416 parts per million, the highest monthly global average concentration ever recorded.

Time series of three climate-related responses. The red lines show changes since our original publication in 2019.

Last year was also the second hottest year in recorded history, with the five hottest years on record all occurring since 2015.

Ruminant livestock — cattle, buffalo, sheep, and goats — now number more than 4 billion, and their total mass is more than that of all humans and wild mammals combined. This is a problem because these animals are responsible for impacting biodiversity, releasing huge amounts of methane emissions, and land continues to be cleared to make room for them.

There are now more than 4 billion livestock on Earth.
Flickr

In better news, recent per capita meat production declined by about 5.7% (2.9 kilograms per person) between 2018 and 2020. But this is likely because of an outbreak of African swine fever in China that reduced the pork supply, and possibly also as one of the impacts of the pandemic.

Tragically, Brazilian Amazon annual forest loss rates increased in both 2019 and 2020. It reached a 12-year high of 1.11 million hectares deforested in 2020.

Ocean acidification is also near an all-time record. Together with heat stress from warming waters, acidification threatens the coral reefs that more than half a billion people depend on for food, tourism dollars and storm surge protection.

Map of land-ocean temperature index anomaly in June, relative to the 1951-1980 baseline.
Oregon State/NASA

What about the pandemic?

With its myriad economic interruptions, the COVID-19 pandemic had the side effect of providing some climate relief, but only of the ephemeral variety.

For example, fossil-fuel consumption has gone down since 2019 as did airline travel levels.

But all of these are expected to significantly rise as the economy reopens. While global gross domestic product dropped by 3.6% in 2020, it is projected to rebound to an all-time high.

So, a major lesson of the pandemic is that even when fossil-fuel consumption and transportation sharply decrease, it’s still insufficient to tackle climate change.

There is growing evidence we’re getting close to or have already gone beyond tipping points associated with important parts of the Earth system, including warm-water coral reefs, the Amazon rainforest and the West Antarctic and Greenland ice sheets.

Warming waters are threatening West Antarctic and Greenland ice sheets.
Flickr

OK, so what do we do about it?

In our 2019 paper, we urged six critical and interrelated steps governments — and the rest of humanity — can take to lessen the worst effects of climate change:

1. prioritise energy efficiency, and replace fossil fuels with low-carbon renewable energy
2. reduce emissions of short-lived pollutants such as methane and soot
3. curb land clearing to protect and restore the Earth’s ecosystems
4. reduce our meat consumption
5. move away from unsustainable ideas of ever-increasing economic and resource consumption
6. stabilise and, ideally, gradually reduce human populations while improving human well-being especially by educating girls and women globally.

These solutions still apply. But in our updated 2021 paper, we go further, highlighting the potential for a three-pronged approach for near-term policy:

1. a globally implemented carbon price
2. a phase-out and eventual ban of fossil fuels
3. strategic environmental reserves to safeguard and restore natural carbon sinks and biodiversity.

A global price for carbon needs to be high enough to induce decarbonisation across industry.

And our suggestion to create strategic environmental reserves, such as forests and wetlands, reflects the need to stop treating the climate emergency as a stand-alone issue.

By stopping the unsustainable exploitation of natural habitats through, for example, creeping urbanisation, and land degradation for mining, agriculture and forestry, we can reduce animal-borne disease risks, protect carbon stocks and conserve biodiversity — all at the same time.

There has been a worrying number of disasters since 2019, including Australia’s megafires.
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Is this actually possible?

Yes, and many opportunities still exist to shift pandemic-related financial support measures into climate friendly activities. Currently, only 17% of such funds had been allocated that way worldwide, as of early March 2021. This percentage could be lifted with serious coordinated, global commitment.

Greening the economy could also address the longer term need for major transformative change to reduce emissions and, more broadly, the over-exploitation of the planet.

Our planetary vital signs make it clear we need urgent action to address climate change. With new commitments getting made by governments all over the world, we hope to see the curves in our graphs changing in the right directions soon.

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Read more:
11,000 scientists warn: climate change isn’t just about temperature

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Thomas Newsome, Academic Fellow, University of Sydney; Christopher Wolf, Postdoctoral Scholar, Oregon State University, and William Ripple, Distinguished Professor and Director, Trophic Cascades Program, Oregon State University

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

Peatlands worldwide are drying out, threatening to release 860 million tonnes of carbon dioxide every year

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Yuanyuan Huang, CSIRO and Yingping Wang, CSIROPeatlands, such as fens, bogs, marshes and swamps, cover just 3% of the Earth’s total land surface, yet store over one-third of the planet’s soil carbon. That’s more than the carbon stored in all other vegetation combined, including the world’s forests.

But peatlands worldwide are running short of water, and the amount of greenhouse gases this could set loose would be devastating for our efforts to curb climate change.

Specifically, our new research in Nature Climate Change found drying peatlands could release an additional 860 million tonnes of carbon dioxide into the atmosphere every year, by around 2100. To put this into perspective, Australia emitted 539 million tonnes in 2019.

To stop this from happening, we need to urgently preserve and restore healthy, water-logged conditions in peatlands. These thirsty peatlands need water.

Peatlands are like natural archives

Peatlands are found across the world: the arctic tundra, coastal marshes, tropical swamp forests, mountainous fens and blanket bogs on subantarctic islands.

They’re characterised by having water-logged soil filled with very slowly decaying plant material (the “peat”) that accumulated over tens of thousands of years, preserved by the low-oxygen environment. This partially decomposed plant debris is locked up in the soils as organic carbon.

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Peatlands can act like natural archives, letting scientists and archaeologists reconstruct past climate, vegetation, and even human lives. In fact, an estimated 20,500 archaeological sites are preserved under or within peat in the UK.

As unique habitats, peatlands are home for many native and endangered species of plants and animals that occur nowhere else, such as the white-bellied cinclodes (Cinclodes palliatus) in Peru and Australia’s giant dragonfly (Petalura gigantea), the world’s largest. They can also act as migration corridors for birds and other animals, and can purify water, regulate floods, retain sediments and so on.

The giant dragonfly (Petalura gigantea) is listed as endangered under NSW environment law.
Christopher Brandis/iNaturalist, CC BY-NC

But over the past several decades, humans have been draining global peatlands for a range of uses. This includes planting trees and crops, harvesting peat to burn for heat, and for other land developments.

For example, some peatlands rely on groundwater, such as portions of the Greater Everglades, the largest freshwater marsh in the United States. Over-pumping groundwater for drinking or irrigation has cut off the peatlands’ source of water.

Together with the regional drier climate due to global warming, our peatlands are drying out worldwide.

What happens when peatlands dry out?

When peat isn’t covered by water, it could be exposed to enough oxygen to fuel aerobic microbes living within. The oxygen allows the microbes to grow extremely fast, enjoy the feast of carbon-rich food, and release carbon dioxide into the atmosphere.

A marsh in Les Sables d Olonne, France. Some peatlands are also a natural sources of methane, which is a more potent greenhouse gas than carbon dioxide.
Arthur Gallois, Author provided

Some peatlands are also a natural source of methane, a potent greenhouse gas with the warming potential up to 100 times stronger than carbon dioxide.

But generating methane actually requires the opposite conditions to generating carbon dioxide. Methane is more frequently released in water-saturated conditions, while carbon dioxide emissions are mostly in unsaturated conditions.

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Emissions of methane – a greenhouse gas far more potent than carbon dioxide – are rising dangerously

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This means if our peatlands are getting drier, we would have an increase in emissions of carbon dioxide, but a reduction in methane emissions.

So what’s the net impact on our climate?

We were part of an international team of scientists across Australia, France, Germany, Netherlands, Switzerland, the US and China. Together, we collected and analysed a large dataset from carefully designed and controlled experiments across 130 peatlands all over the world.

In these experiments, we reduced water under different climate, soil and environmental conditions and, using machine learning algorithms, disentangled the different responses of greenhouse gases.

Our results were striking. Across the peatlands we studied, we found reduced water greatly enhanced the loss of peat as carbon dioxide, with only a mild reduction of methane emissions.

A swamp forest in Peru.
Rupesh Bhomia, Author provided

The net effect — carbon dioxide vs methane — would make our climate warmer. This will seriously hamper global efforts to keep temperature rise under 1.5℃.

This suggests if sustainable developments to restore these ecosystems aren’t implemented in future, drying peatlands would add the equivalent of 860 million tonnes of carbon dioxide to the atmosphere every year by 2100. This projection is for a “high emissions scenario”, which assumes global greenhouse gas emissions aren’t cut any further.

Protecting our peatlands

It’s not too late to stop this from happening. In fact, many countries are already establishing peatland restoration projects.

For example, the Central Kalimantan Peatlands Project in Indonesia aims to rehabilitate these ecosystems by, for instance, damming drainage canals, revegetating areas with native trees, and improving local socio-economic conditions and introducing more sustainable agricultural techniques.

Likewise, the Life Peat Restore project aims to restore 5,300 hectares of peatlands back to their natural function as carbon sinks across Poland, Germany and the Baltic states, over five years.

But protecting peatlands is a global issue. To effectively take care of our peatlands and our climate, we must work together urgently and efficiently.

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People, palm oil, pulp and planet: four perspectives on Indonesia’s fire-stricken peatlands

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Yuanyuan Huang, Research Scientist , CSIRO and Yingping Wang, Chief research scientist, CSIRO

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

Carbon dioxide levels over Australia rose even after COVID-19 forced global emissions down. Here’s why

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Zoe Loh, CSIRO; Helen Cleugh, CSIRO; Paul Krummel, CSIRO, and Ray Langenfelds, CSIRO

COVID-19 has curtailed the activities of millions of people across the world and with it, greenhouse gas emissions. As climate scientists at the Cape Grim Baseline Air Pollution Station, we are routinely asked: does this mean carbon dioxide concentrations in the atmosphere have fallen?

The answer, disappointingly, is no. Throughout the pandemic, atmospheric carbon dioxide (CO₂) levels continued to rise.

In fact, our measurements show more CO₂ accumulated in the atmosphere between January and July 2020 than during the same period in 2017 or 2018.

Emissions from last summer’s bushfires may have contributed to this. But there are several other reasons why COVID-19 has not brought CO₂ concentrations down at Cape Grim – let’s take a look at them.

Measuring the cleanest air in the world

Cape Grim is on the northwest tip of Tasmania. Scientists at the station, run by the CSIRO and Bureau of Meteorology, have monitored and studied the global atmosphere for the past 44 years.

The air we monitor is the cleanest in the world when it blows from the southwest, off the Southern Ocean. Measurements taken during these conditions are known as “baseline concentrations”, and represent the underlying level of carbon dioxide in the Southern Hemisphere’s atmosphere.

The Cape Grim station measures the cleanest air in the world.
Bureau of Meteorology

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A drop in the CO₂ ocean

Emissions reductions due to COVID-19 started in China in January, and peaked globally in April. Our measurements show atmospheric CO₂ levels rose during that period. In January 2020, baseline CO₂ was 408.3 parts per million (ppm) at Cape Grim. By July that had risen to 410 ppm.

Since the station first began measurements in 1976, carbon dioxide levels in the atmosphere have increased by 25%, as shown in the graph below. The slowdown in the rate of carbon emissions during the pandemic is a mere tug against this overall upward trend.

The CO₂ increase is due to the burning of fossil fuels for energy, and land use change such as deforestation which leaves fewer trees to absorb CO₂ from the air, and changes the uptake and release of carbon in the soils.

Baseline CO₂ record from Cape Grim.
Author provided

Atmospheric transport

Large air circulation patterns in the atmosphere spread gases such as CO₂ around the world, but this process takes time.

Most emissions reduction due to COVID-19 occurred in the Northern Hemisphere, because that’s where most of the world’s population lives. Direct measurements of CO₂ in cities where strict lockdown measures were imposed show emissions reductions of up to 75%. This would have reduced atmospheric CO₂ concentrations locally.

But it will take many months for this change to manifest in the Southern Hemisphere atmosphere – and by the time it does, the effect will be significantly diluted.

Natural ups and downs

Emissions reductions during COVID-19 are a tiny component of a very large carbon cycle. This cycle is so dynamic that even when the emissions slowdown is reflected in atmospheric CO₂ levels, the reduction will be well within the cycle’s natural ebb and flow.

Here’s why. Global carbon emissions have grown by about 1% a year over the past decade. This has triggered growth in atmospheric CO₂ levels of between 2 and 3 ppm per year in that time, as shown in the graph below. In fact, since our measurements began, CO₂ has accumulated more rapidly in the atmosphere with every passing decade, as emissions have grown.

Annual growth in CO₂ at Cape Grim since 1976. Red horizontal bars show the average growth rate in ppm/year each decade.
Author provided

But although CO₂ emissions have grown consistently, the resulting rate of accumulation in the atmosphere varies considerably each year. This is because roughly half of human emissions are mopped up by ecosystems and the oceans, and these processes change from year to year.

For example, in southeast Australia, last summer’s extensive and prolonged bushfires emitted unusually large amounts of CO₂, as well as changing the capacity of ecosystems to absorb it. And during strong El Niño events, reduced rainfall in some regions limits the productivity of grasslands and forests, so they take up less CO₂.

The graph below visualises this variability. It shows the baseline CO₂ concentrations for each year, relative to January 1. Note how the baseline level changes through a natural seasonal cycle, how that change varies from year to year and how much CO₂ has been added to the atmosphere by the end of the year.

Daily baseline values for CO2 for each year from 1977 relative to 1 January for that year.
Author provided

The growth rate has been as much as 3 ppm per year. The black line represents 2020 and lines for the preceding five years are coloured. All show recent annual growth rates of about 2-3 ppm/year – a variability in the range of about 1 ppm/year.

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Research in May estimated that due to the COVID-19 lockdowns, global annual average emissions for 2020 would be between 4.2% and 7.5% lower than for 2019.

Let’s simplistically assume CO₂ concentration growth reduces by the same amount. There would be 0.08-0.23 ppm less CO₂ in the atmosphere by the end of 2020 than if no pandemic occurred. This variation is well within the natural 1 ppm/year annual variability in CO₂ growth.

CO₂ levels in the atmosphere are increasing due to fossil fuel burning and land use change.
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The road ahead

It’s clear COVID-19 has not solved the climate change problem. But this fact helps us understand the magnitude of change required if we’re to stabilise the global climate system.

The central aim of the Paris climate agreement is to limit global warming to well below 2℃, and pursue efforts to keep it below 1.5℃. To achieve this, global CO₂ emissions must decline by 3% and 7% each year, respectively, until 2030, according to the United Nations Emissions Gap Report.

Thanks to COVID-19, we may achieve this reduction in 2020. But to lock in year-on-year emissions reductions that will be reflected in the atmosphere, we must act now to make deep, significant and permanent changes to global energy and economic systems.

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The lead author, Zoe Loh, discusses the CO₂ record from Cape Grim in Fight for Planet A, showing now on the ABC.

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Why there’s more greenhouse gas in the atmosphere than you may have realised

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Zoe Loh, Senior Research Scientist, CSIRO; Helen Cleugh, Senior research scientist, CSIRO Climate Science Centre, CSIRO; Paul Krummel, Research Group Leader, CSIRO, and Ray Langenfelds, Scientist at CSIRO Atmospheric Research, CSIRO

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

Climate explained: why higher carbon dioxide levels aren’t good news, even if some plants grow faster

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Sebastian Leuzinger, Auckland University of Technology

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

If carbon dioxide levels were to double, how much increase in plant growth would this cause? How much of the world’s deserts would disappear due to plants’ increased drought tolerance in a high carbon dioxide environment?

Compared to pre-industrial levels, the concentration of carbon dioxide (CO₂) in the atmosphere will have doubled in about 20 to 30 years, depending on how much CO₂ we emit over the coming years. More CO₂ generally leads to higher rates of photosynthesis and less water consumption in plants.

At first sight, it seems more CO₂ can only be beneficial to plants, but things are a lot more complex than that.

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Climate explained: why plants don’t simply grow faster with more carbon dioxide in air

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Let’s look at the first part of the question.

Some plants do grow faster under elevated levels of atmospheric CO₂, but this happens mostly in crops and young trees, and generally not in mature forests.

Even if plants grew twice as fast under doubled CO₂ levels, it would not mean they strip twice as much CO₂ from the atmosphere. Plants take carbon from the atmosphere as they grow, but that carbon is going straight back via natural decomposition when plants die or when they are harvested and consumed.

At best, you might be mowing your lawn twice as often or harvesting your plantation forests earlier.

The most important aspect is how long the carbon stays locked away from the atmosphere – and this is where we have to make a clear distinction between increased carbon flux (faster growth) or an increasing carbon pool (actual carbon sequestration). Your bank account is a useful analogy to illustrate this difference: fluxes are transfers, pools are balances.

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The global carbon budget

Of the almost 10 billion tonnes (gigatonnes, or Gt) of carbon we emit every year through the burning of fossil fuels, only about half accumulates in the atmosphere. Around a quarter ends up in the ocean (about 2.4 Gt), and the remainder (about 3 Gt) is thought to be taken up by terrestrial plants.

While the ocean and the atmospheric sinks are relatively easy to quantify, the terrestrial sink isn’t. In fact, the 3 Gt can be thought of more as an unaccounted residual. Ultimately, the emitted carbon needs to go somewhere, and if it isn’t the ocean or the atmosphere, it must be the land.

So yes, the terrestrial system takes up a substantial proportion of the carbon we emit, but the attribution of this sink to elevated levels of CO₂ is difficult. This is because many other factors may contribute to the land carbon sink: rising temperature, increased use of fertilisers and atmospheric nitrogen deposition, changed land management (including land abandonment), and changes in species composition.

Current estimates assign about a quarter of this land sink to elevated levels of CO₂, but estimates are very uncertain.

In summary, rising CO₂ leads to faster plant growth – sometimes. And this increased growth only partly contributes to sequestering carbon from the atmosphere. The important questions are how long this carbon is locked away from the atmosphere, and how much longer the currently observed land sink will continue.

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The second part of the question refers to a side-effect of rising levels of CO₂ in the air: the fact that it enables plants to save water.

Plants regulate the exchange of carbon dioxide and water vapour by opening or closing small pores, called stomata, on the surface of their leaves. Under higher concentrations of CO₂, they can reduce the opening of these pores, and that in turn means they lose less water.

This alleviates drought stress in already dry areas. But again, the issue is more complex because CO₂ is not the only parameter that changes. Dry areas also get warmer, which means that more water evaporates and this often compensates for the water-saving effect.

Overall, rising CO₂ has contributed to some degree to the greening of Earth, but it is likely that this trend will not continue under the much more complex combination of global change drivers, particularly in arid regions.

Sebastian Leuzinger, Professor, Auckland University of Technology

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

Yes, more carbon dioxide in the atmosphere helps plants grow, but it’s no excuse to downplay climate change

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Vanessa Haverd, CSIRO; Benjamin Smith, Western Sydney University; Matthias Cuntz, Université de Lorraine, and Pep Canadell, CSIRO

The alarming rate of carbon dioxide flowing into our atmosphere is affecting plant life in interesting ways – but perhaps not in the way you’d expect.

Despite large losses of vegetation to land clearing, drought and wildfires, carbon dioxide is absorbed and stored in vegetation and soils at a growing rate.

This is called the “land carbon sink”, a term describing how vegetation and soils around the world absorb more carbon dioxide from photosynthesis than they release. And over the past 50 years, the sink (the difference between uptake and release of carbon dioxide by those plants) has been increasing, absorbing at least a quarter of human emissions in an average year.

The sink is getting larger because of a rapid increase in plant photosynthesis, and our new research shows rising carbon dioxide concentrations largely drive this increase.

So, to put it simply, humans are producing more carbon dioxide. This carbon dioxide is causing more plant growth, and a higher capacity to suck up carbon dioxide. This process is called the “carbon dioxide fertilisation effect” – a phenomenon when carbon emissions boost photosynthesis and, in turn, plant growth.

What we didn’t know until our study is just how much the carbon dioxide fertilisation effect contributes to the increase in global photosynthesis on land.

But don’t get confused, our discovery doesn’t mean emitting carbon dioxide is a good thing and we should pump out more carbon dioxide, or that land-based ecosystems are removing more carbon dioxide emissions than we previously thought (we already know how much this is from scientific measurements).

And it definitely doesn’t mean mean we should, as climate sceptics have done, use the concept of carbon dioxide fertilisation to downplay the severity of climate change.

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Rather, our findings provide a new and clearer explanation of what causes vegetation around the world to absorb more carbon than it releases.

What’s more, we highlight the capacity of vegetation to absorb a proportion of human emissions, slowing the rate of climate change. This underscores the urgency to protect and restore terrestrial ecosystems like forests, savannas and grasslands and secure their carbon stocks.

And while more carbon dioxide in the atmosphere does allow landscapes to absorb more carbon dioxide, almost half (44%) of our emissions remain in the atmosphere.

More carbon dioxide makes plants more efficient

Since the beginning of the last century, photosynthesis on a global scale has increased in nearly constant proportion to the rise in atmospheric carbon dioxide. Both are now around 30% higher than in the 19th century, before industrialisation began to generate significant emissions.

Carbon dioxide fertilisation is responsible for at least 80% of this increase in photosynthesis. Most of the rest is attributed to a longer growing season in the rapidly warming boreal forest and Arctic.

Ecosystems such as forests act as a natural weapon against climate change by absorbing carbon from the atmosphere.
Shutterstock

So how does more carbon dioxide lead to more plant growth anyway?

Higher concentrations of carbon dioxide make plants more productive because photosynthesis relies on using the sun’s energy to synthesise sugar out of carbon dioxide and water. Plants and ecosystems use the sugar both as an energy source and as the basic building block for growth.

When the concentration of carbon dioxide in the air outside a plant leaf goes up, it can be taken up faster, super-charging the rate of photosynthesis.

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More carbon dioxide also means water savings for plants. More carbon dioxide available means pores on the surface of plant leaves regulating evaporation (called the stomata) can close slightly. They still absorb the same amount or more of carbon dioxide, but lose less water.

The resulting water savings can benefit vegetation in semi-arid landscapes that dominate much of Australia.

We saw this happen in a 2013 study, which analysed satellite data measuring changes in the overall greenness of Australia. It showed more leaf area in places where the amount of rain hadn’t changed over time. This suggests water efficiency of plants increases in a carbon dioxide-richer world.

Young forests help to capture carbon dioxide

In other research published recently, we mapped the carbon uptake of forests of different ages around the world. We showed forests regrowing on abandoned agricultural land occupy a larger area, and draw down even more carbon dioxide than old-growth forests, globally. But why?

Young forests need carbon to grow, so they’re a significant contributor to the carbon sink.
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In a mature forest, the death of old trees balances the amount of new wood grown each year. The old trees lose their wood to the soil and, eventually, to the atmosphere through decomposition.

A regrowing forest, on the other hand, is still accumulating wood, and that means it can act as a considerable sink for carbon until tree mortality and decomposition catch up with the rate of growth.

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This age effect is superimposed on the carbon dioxide fertilisation effect, making young forests potentially very strong sinks.

In fact, globally, we found such regrowing forests are responsible for around 60% of the total carbon dioxide removal by forests overall. Their expansion by reforestation should be encouraged.

Forests are important to society for so many reasons – biodiversity, mental health, recreation, water resources. By absorbing emissions they are also part of our available arsenal to combat climate change. It’s vital we protect them.

Vanessa Haverd, Principal research scientist, CSIRO; Benjamin Smith, Director of Research, Hawkesbury Institute for the Environment, Western Sydney University; Matthias Cuntz, Research Director INRAE, Université de Lorraine, and Pep Canadell, Chief research scientist, CSIRO Oceans and Atmosphere; and Executive Director, Global Carbon Project, CSIRO

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

Climate explained: why your backyard lawn doesn’t help reduce carbon dioxide in the atmosphere

While growing grass takes up carbon dioxide, it emits it again back into the atmosphere when it is mowed or eaten.
from http://www.shutterstock.com, CC BY-ND

Sebastian Leuzinger, Auckland University of Technology

CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

I read somewhere that 1,000 square metres of grass absorbs the same amount of carbon dioxide that one person produces. I then think about my small 10ha property. Does that mean that I am covering 100 peoples’ CO₂ emissions every day? What about those large 1,000ha properties then? Do they absorb thousands of tonnes of carbon every year?

In New Zealand, your average carbon footprint will be around four tonnes of carbon, emitted per year (based on the carbon contained in 16.9 tonnes of carbon dioxide equivalent annual per-capita emissions). A 1,000-square-metre area of grass will take up around one tonne of carbon per year. So if you didn’t fly much, lived in a well insulated home, cycled to work etc, you might bring your overall footprint down to around one tonne of carbon per year, the equivalent of what a backyard lawn may take up per year. So far so good.

The big problem (causing tremendous confusion even among scientists) begins right here. In the above, we talk about fluxes, not pools. Using your bank account as an analogy, fluxes are transfers, pools are balances.

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With your own carbon emissions, regardless whether they are one or four tonnes per year, you pay into the atmosphere’s account every year. This means that there is more and more carbon in the atmosphere.

That carbon comes from fossil fuels – an entirely different “account”. Regardless of whether you have 1,000 or 100,000 square metres, this is what grass is doing in this analogy: it takes carbon from the atmosphere every year, but that carbon is going straight back to where it was taken from when you mow the lawn and the biomass is broken down and returned to the atmosphere. In other words, your carbon footprint is a flux that leads to a permanent change in a pool (the atmosphere). This is a bit like a weekly salary. You don’t have to pay it back. What your lawn is doing however, is making payments that are returned a few weeks or months later (when you mow the lawn, a cow eats the grass, or when natural turnover takes place).

The bottom line is that short-term fluxes (as large as they might be) don’t matter if they are reciprocated by an equivalent but opposite flux. If you want, let’s do the experiment. You pay $1,000 onto my account ever odd week, and I pay $1,000 onto yours every even week. None of us will care – as little as the atmosphere will worry about the carbon that your grass patch briefly locks away from it.

So your grass won’t lock away carbon dioxide from the atmosphere in the long run. Neither will any grassland in New Zealand.

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Climate explained: why plants don’t simply grow faster with more carbon dioxide in air

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If you wait long enough, things can become a bit more complicated, namely if my payments back to you start to become a little less or a little more, causing dollars or carbon to accumulate on one account rather than the other. While this is the case in some ecosystems, such as a growing forest, New Zealand grassland is unlikely one of them. So your backyard isn’t helping, there is no way around reducing our greenhouse gas emissions.

Sebastian Leuzinger, Associate Professor, Auckland University of Technology

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

Climate explained: why plants don’t simply grow faster with more carbon dioxide in air

Fast-growing plantation trees store less carbon per surface area than old, undisturbed forests that may show little growth.
from http://www.shutterstock.com, CC BY-ND

Sebastian Leuzinger, Auckland University of Technology

CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

Carbon dioxide is a fertiliser for plants, so if its concentration increases in the atmosphere then plants will grow better. So what is the problem? – a question from Doug in Lower Hutt

Rising atmospheric carbon dioxide (CO₂) is warming our climate, but it also affects plants directly.

A tree planted in the 1850s will have seen its diet (in terms of atmospheric carbon dioxide) double from its early days to the middle of our century. More CO₂ generally leads to higher rates of photosynthesis and less water consumption in plants. So, at first sight, it seems that CO₂ can only be beneficial for our plants.

But things are a lot more complex than that. Higher levels of photosynthesis don’t necessarily lead to more biomass production, let alone to more carbon dioxide sequestration. At night, plants release CO₂ just like animals or humans, and if those respiration rates increase simultaneously, the turnover of carbon increases, but the carbon stock doesn’t. You can think of this like a bank account – if you earn more but also spend more, you’re not becoming any richer.

Even if plants grow more and faster, some studies show there is a risk for them to have shorter lifespans. This again can have negative effects on the carbon locked away in biomass and soils. In fact, fast-growing trees (e.g. plantation forests) store a lot less carbon per surface area than old, undisturbed forests that show very little growth. Another example shows that plants in the deep shade may profit from higher levels of CO₂, leading to more vigorous growth of vines, faster turnover, and, again, less carbon stored per surface area.

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Water savings

The effect of CO₂ on the amount of water plants use may be more important than the primary effect on photosynthesis. Plants tend to close their leaf pores slightly under elevated levels of CO₂, leading to water savings. In certain (dry) areas, this may indeed lead to more plant growth.

But again, things are much more complex and we don’t always see positive responses. Research we published in Nature Plants this year on grasslands around the globe showed that while dry sites can profit from more CO₂, there are complex interactions with rainfall. Depending on when the rain falls, some sites show zero or even negative effects in terms of biomass production.

Currently, a net amount of three gigatons of carbon are thought to be removed from the atmosphere by plants every year. This stands against over 11 gigatons of human-induced release of CO₂. It is also unclear what fraction of the three gigatons plants are taking up due to rising levels of CO₂.

In summary, rising CO₂ is certainly not bad for plants, and if we restored forested land at a global scale, we could help capture additional atmospheric carbon dioxide. But such simulations are optimistic and rely on conversion of much needed agricultural land to forests. Reductions in our emissions are unavoidable, and we have very strong evidence that plants alone will not be able to solve our CO₂ problem.

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Sebastian Leuzinger, Associate Professor, Auckland University of Technology

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

Turning methane into carbon dioxide could help us fight climate change

It’s not cows’ fault they fart, but the methane they produce is warming the planet.
Robert Bye/Unsplash

Pep Canadell, CSIRO and Rob Jackson, Stanford University

Discussions on how to address climate change have focused, very appropriately, on reducing greenhouse gas emissions, particularly those of carbon dioxide, the major contributor to climate change and a long-lived greenhouse gas. Reducing emissions should remain the paramount climate goal.

However, greenhouse gas emissions have been increasing now for two centuries. Damage to the atmosphere is already profound enough that reducing emissions alone won’t be enough to avoid effects like extreme weather and changing weather patterns.

In a paper published today in Nature Sustainability, we propose a new technique to clean the atmosphere of the second most powerful greenhouse gas people produce: methane. The technique could restore the concentration of methane to levels found before the Industrial Revolution, and in doing so, reduce global warming by one-sixth.

Our new technique sounds paradoxical at first: turning methane into carbon dioxide. It’s a concept at this stage, and won’t be cheap, but it would add to the tool kit needed to tackle climate change.

The methane menace

After carbon dioxide, methane is the second most important greenhouse gas leading to human-induced climate change. Methane packs a climate punch: it is 84 times more powerful than carbon dioxide in warming the planet over the first 20 years of its molecular life.

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Methane emissions from human activities are now larger than all natural sources combined. Agriculture and energy production generate most of them, including emissions from cattle, rice paddies and oil and gas wells.

The result is methane concentrations in the atmosphere have increased by 150% from pre-industrial times, and continue to grow. Finding ways to reduce or remove methane will therefore have an outsize and fast-acting effect in the fight against climate change.

Global Carbon Atlas

What we propose

The single biggest challenge for removing methane from the atmosphere is its low concentration, only about 2 parts per million. In contrast, carbon dioxide is now at 415 parts per million, roughly 200 times higher. Both gases are much more diluted in air than when found in the exhaust of a car or in a cow’s burp, and both would be better served by keeping them out of the atmosphere to start with.

Nonetheless, emissions continue. What if we could capture the methane after its release and convert it into something less damaging to climate?

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That is why our paper proposes removing all methane in the atmosphere produced by human activities – by oxidising it to carbon dioxide. Such an approach has not been proposed before: previously, all removal techniques have only been applied to carbon dioxide.

This is the equivalent of turning 3.2 billion tonnes of methane into 8.2 billion tonnes of carbon dioxide (equivalent to several months of global emissions). The surprising aspect to this trade is that it would reduce global warming by 15%, because methane is so much more warming than carbon dioxide.

Proposed industrial array to oxidise methane to carbon dioxide.
Jackson et al. 2019 Nature Sustainability

This reaction yields energy rather than requires it. It does require a catalyst, though, such as a metal, that converts methane from the air and turns it into carbon dioxide.

One fit-for-purpose family of catalysts are zeolites. They are crystalline materials that consist of aluminum, silicon and oxygen, with a very porous molecular structure that can act as a sponge to soak up methane.

They are well known to industrial researchers trying to oxidise methane to methanol, a valuable chemical feedstock.

We envision arrays of electric fans powered by renewable energy to force large volumes of air into chambers, where the catalyst is exposed to air. The catalyst is then heated in oxygen to form and release CO₂. Such arrays of fans could be placed anywhere where renewable energy – and enough space – is available.

We calculate that with removal costs per tonne of CO₂ rising quickly from US$50 to US$500 or more this century, consistent with mitigation scenarios that keep global warming below 2℃, this technique could be economically feasible and even profitable.

We won’t know for sure, though, until future research highlights the precise chemistry and industrial infrastructure needed.

Beyond the clean-up we propose here, methane removal and atmospheric restoration could be an extra tool in humanity’s belt as we aim for stringent climate targets, while providing new economic opportunities.

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Future research and development will determine the technical and economic feasibility of methane removal. Even if successful, methane- and other carbon-removal technologies are no substitute for strong and rapid emissions reductions if we are to avoid the worst impacts of global warming.

Pep Canadell, Chief research scientist, CSIRO Oceans and Atmosphere; and Executive Director, Global Carbon Project, CSIRO and Rob Jackson, Chair, Department of Earth System Science, and Chair of the Global Carbon Project, globalcarbonproject.org, Stanford University

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

Rising carbon dioxide is making the world’s plants more water-wise

Pep Canadell, CSIRO; Francis Chiew, CSIRO; Lei Cheng, CSIRO; Lu Zhang, CSIRO, and Yingping Wang, CSIRO

Land plants are absorbing 17% more carbon dioxide from the atmosphere now than 30 years ago, our research published today shows. Equally extraordinarily, our study also shows that the vegetation is hardly using any extra water to do it, suggesting that global change is causing the world’s plants to grow in a more water-efficient way.

Water is the most precious resource needed for plants to grow, and our research suggests that vegetation is becoming much better at using it in a world in which CO₂ levels continue to rise.

The ratio of carbon uptake to water loss by ecosystems is what we call “water use efficiency”, and it is one of the most important variables when studying these ecosystems.

Our confirmation of a global trend of increasing water use efficiency is a rare piece of good news when it comes to the consequences of global environmental change. It will strengthen plants’ vital role as global carbon sinks, improve food production, and might boost water availability for the well-being of society and the natural world.

Yet more efficient water use by the world’s plants will not solve our current or future water scarcity problems.

Changes in global terrestrial uptake of carbon dioxide, water use efficiency and ecosystem evapotranspiration during 1982-2011.

Boosting carbon uptake

Plants growing in today’s higher-CO₂ conditions can take up more carbon – the so-called CO₂ fertilisation effect. This is the main reason why the terrestrial biosphere has taken up 17% more carbon over the past 30 years.

The enhanced carbon uptake is consistent with the global greening trend observed by satellites, and the growing global land carbon sink which removes about one-third of all CO₂ emissions generated by human activities.

Increasing carbon uptake typically comes at a cost. To let CO₂ in, plants have to open up pores called stomata in their leaves, which in turn allows water to sneak out. Plants thus need to strike a balance between taking up carbon to build new leaves, stems and roots, while minimising water loss in the process. This has led to sophisticated adaptations that has allowed many plant species to conquer a range of arid environments.

One such adaptation is to close the stomata slightly to allow CO₂ to enter with less water getting out. Under increasing atmospheric CO₂, the overall result is that CO₂ uptake increases while water consumption does not. This is exactly what we have found on a global scale in our new study. In fact, we found that rising CO₂ levels are causing the world’s plants to become more water-wise, almost everywhere, whether in dry places or wet ones.

Growth hotspots

We used a combination of plot-scale water flux and atmospheric measurements, and satellite observations of leaf properties, to develop and test a new water use efficiency model. The model enables us to scale up from leaf water use efficiency anywhere in the world to the entire globe.

We found that across the globe, boreal and tropical forests are particularly good at increasing ecosystem water use efficiency and uptake of CO₂. That is due in large part to the CO₂ fertilisation effect and the increase in the total amount of leaf surface area.

Importantly, both types of forests are critical in limiting the rise in atmospheric CO₂ levels. Intact tropical forest removes more atmospheric CO₂ than any other type of forest, and the boreal forests of the planet’s far north hold vast amounts of carbon particularly in their organic soils.

Meanwhile, for the semi-arid ecosystems of the world, increased water savings are a big deal. We found that Australian ecosystems, for example, are increasing their carbon uptake, especially in the northern savannas. This trend may not have been possible without an increase in ecosystem water use efficiency.

Previous studies have also shown how increased water efficiency is greening semi-arid regions and may have contributed to an increase in carbon capture in semi-arid ecosystems in Australia, Africa and South America.

Trends in water use efficiency over 1982-2011.
CREDIT, Author provided

It’s not all good news

These trends will have largely positive outcomes for the plants and the animals (and humans) consuming them. Wood production, bioenergy and crop growth are (and will be) less water-intensive under climate change than they would be without increased vegetation water use efficiency.

But despite these trends, water scarcity will nevertheless continue to constrain carbon sinks, food production and socioeconomic development.

Some studies have suggested that the water savings could also lead to increased runoff and therefore excess water availability. For dry Australia, however, more than half (64%) of the rainfall returning to the atmosphere does not go through vegetation, but through direct soil evaporation. This reduces the potential benefit from increased vegetation water use efficiency and the possibility for more water flowing to rivers and reservoirs. In fact, a recent study shows that while semi-arid regions in Australia are greening, they are also consuming more water, causing river flows to fall by 24-28%.

Our research confirms that plants all over the world are likely to benefit from these increased water savings. However, the question of whether this will translate to more water availability for conservation or for human consumption is much less clear, and will probably vary widely from region to region.

Pep Canadell, CSIRO Scientist, and Executive Director of the Global Carbon Project, CSIRO; Francis Chiew, Senior Principal Research Scientist, CSIRO; Lei Cheng, Postdoctoral research fellow, CSIRO; Lu Zhang, Senior Principal Research Scientist, CSIRO, and Yingping Wang, Chief research scientist, CSIRO

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