Engineers have built machines to scrub CO₂ from the air. But will it halt climate change?

Climeworks

Deanna D’Alessandro, University of Sydney

On Wednesday this week, the concentration of carbon dioxide in the atmosphere was measured at at 415 parts per million (ppm). The level is the highest in human history, and is growing each year.

Amid all the focus on emissions reduction, the Intergovernmental Panel on Climate Change (IPCC) says it will not be enough to avoid dangerous levels of global warming. The world must actively remove historical CO₂ already in the atmosphere – a process often described as “negative emissions”.

CO₂ removal can be done in two ways. The first is by enhancing carbon storage in natural ecosystems, such as planting more forests or storing more carbon in soil. The second is by using direct air capture (DAC) technology that strips CO₂ from the ambient air, then either stores it underground or turns it into products.

US research published last week suggested global warming could be slowed with an emergency deployment of a fleet of “CO₂ scrubbers” using DAC technology. However a wartime level of funding from government and business would be needed. So is direct air capture worth the time and money?

Direct air capture of CO2 will be needed to address climate change.
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What’s DAC all about?

Direct air capture refers to any mechanical system capturing CO₂ from the atmosphere. Plants operating today use a liquid solvent or solid sorbent to separate CO₂ from other gases.

Swiss company Climeworks operates 15 direct air capture machines across Europe, comprising the world’s first commercial DAC system. The operation is powered by renewable geothermal energy or energy produced by burning waste.

The machines use a fan to draw air into a “collector”, inside which a selective filter captures CO₂. Once the filter is full, the collector is closed and the CO₂ is sequestered underground.

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Canadian company Carbon Engineering uses giant fans to pull air into a tower-like structure. The air passes over a potassium hydroxide solution which chemically binds to the CO₂ molecules, and removes them from the air. The CO₂ is then concentrated, purified and compressed.

Captured CO₂ can be injected into the ground to extract oil, in some cases helping to counteract the emissions produced by burning the oil.

The proponents of the Climeworks and Carbon Engineering technology say their projects are set for large-scale investment and deployment in coming years. Globally, the potential market value of DAC technology could reach US$100bn by 2030, on some estimates.

Artist impression of a DAC facility to be built in the US state of Texas. If built, it would be the largest of its kind in the world.
Carbon Engineering

Big challenges ahead

Direct air capture faces many hurdles and challenges before it can make a real dent in climate change.

DAC technology is currently expensive, relative to many alternative ways of capturing CO₂, but is expected to become cheaper as the technology scales up. The economic feasibility will be helped by the recent emergence of new carbon markets where negative emissions can be traded.

DAC machines process an enormous volume of air, and as such are very energy-intensive. In fact, research has suggested direct air capture machines could use a quarter of global energy in 2100. However new DAC methods being developed could cut the technology’s energy use.

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While the challenges to direct air capture are great, the technology uses less land and water than other negative emissions technologies such as planting forests or storing CO₂ in soils or oceans.

DAC technology is also increasingly gaining the backing of big business. Microsoft, for example, last year included the technology in its carbon negative plan.

Direct air capture is touted as a way to offset emissions from industry and elsewhere.
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Opportunities for Australia

Australia is uniquely positioned to be a world leader in direct air capture. It boasts large areas of land not suitable for growing crops. It has ample sunlight, meaning there is great potential to host DAC facilities powered by solar energy. Australia also has some of the world’s best sites in which to “sequester” or store carbon in underground reservoirs.

Direct air capture is a relatively new concept in Australia. Australian company Southern Green Gas, as well as the CSIRO, are developing solar-powered DAC technologies. The SGG project, with which I am involved, involves modular units potentially deployed in large numbers, including close to sites where captured CO₂ can be used in oil recovery or permanently stored.

If DAC technology can overcome its hurdles, the benefits will extend beyond tackling climate change. It would create a new manufacturing sector and potentially re-employ workers displaced by the decline of fossil fuels.

Australia has ample sunlight and plenty of non-arable land where DAC facilities could be built.
Shutterstock

Looking ahead

The urgency of removing CO₂ from the atmosphere seems like an enormous challenge. But not acting will bring far greater challenges: more climate and weather extremes, irreversible damage to biodiversity and ecosystems, species extinction and threats to health, food, water and economic growth.

DAC technology undoubtedly faces stiff headwinds. But with the right policy incentives and market drivers, it may be one of a suite of measures that start reversing climate change.

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Deanna D’Alessandro, Professor & ARC Future Fellow, University of Sydney

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

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The Morrison government wants to suck CO₂ out of the atmosphere. Here are 7 ways to do it

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Annette Cowie, University of New England; Han Weng, The University of Queensland; Lukas Van Zwieten, Southern Cross University; Stephen Joseph, UNSW, and Wolfram Buss, Australian National University

Federal Energy Minister Angus Taylor is on Tuesday expected to outline the Morrison government’s first Low Emissions Technology Statement, plotting Australia’s way forward on climate action. It’s likely to include “negative emissions” technologies, which remove carbon dioxide (CO₂) from the air.

The Intergovernmental Panel on Climate Change says negative emissions technologies will be needed to meet the Paris Agreement goal of limiting warming to well below 2℃. In other words, just cutting emissions is not enough – we must also take existing greenhouse gases from the air.

Last week, the government broadened the remit of the Australian Renewable Energy Agency (ARENA) and the Clean Energy Finance Corporation (CEFC). It flagged negative emissions technologies, such as soil carbon, as one avenue for investment.

Some negative emissions ventures are operating in Australia at a small scale, including carbon capture, reforestation and soil carbon management. Here, we examine seven ways to remove CO₂ from the atmosphere, including their pros and cons.

Graphic showing seven negative emissions technologies.
Anders Claassens

1. Managing soil carbon

Up to 150 billion tonnes of soil carbon has been lost globally since farming began to replace natural forests and grasslands. Improved land management could store or “sequester” up to nine billion tonnes of CO₂ each year. It could also improve soil health.

Soil carbon can be built through methods such as:

• “no-till” farming, using techniques that don’t disturb soil
• planting cover crops, which protect soil between normal cropping periods
• grazing livestock on perennial pastures, which last longer than annual plants
• applying lime to encourage plant growth
• using compost and manure.

It’s important to remember though, that carbon can be hard to store in soils for long periods. This is because microbes consume organic matter, which releases carbon back to the atmosphere.

Intensive farming has led to global loss of soil carbon.
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2. Biochar

Biochar is a charcoal-like material produced from organic matter such as green waste or straw. It is added to soil to boost carbon stores, by promoting microbial activity and aggregation (soil clumps) which prevents organic plant matter breaking down and releasing carbon.

Biochar has been used by indigenous people in the Amazon to increase food production. More than 14,000 biochar studies have been published since 2005. This includes work by Australian researchers showing how biochar reacts with soil minerals, microbes and plants to improve soil and stimulate plant growth.

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On average, biochar increases crop yields by about 16% and halves emissions of nitrous oxide, a potent greenhouse gas. The production of biochar releases gases that can generate renewable heat and electricity. Research suggests that globally, biochar could store up to 4.6 billion tonnes of CO₂ each year.

However its potential depends on the availability of organic material and land on which to grow it. Also, the type of biochar used must be suitable for the site, or crop yields may fall.

Added to soil, biochar increases carbon stores.
Shutterstock

3. Reforestation

Planting trees is the simplest way to take CO₂ from the atmosphere. Reforestation is limited only by land availability and environmental constraints to growth.

Reforestation could sequester up to ten billion tonnes a year of CO₂. However, carbon sequestered through reforestation is vulnerable to loss. For example, last summer’s devastating bushfires released around 830 million tonnes CO₂.

4. Bioenergy with carbon capture and storage (BECCS)

Plant material can be burned for energy – known as bioenergy. In a BECCS system, the resulting CO₂ is captured and stored deep underground.

Currently, carbon capture and storage (CCS) is only viable at large scale, and opportunities for storage are limited. Only a few CCS facilities operate internationally.

BECCS has the potential to sequester 11 billion tonnes annually. But this is limited by availability of material to burn – which in theory could come from forestry and crop waste, and purpose-grown plants.

The large-scale deployment of CCS will also have to overcome barriers such as high costs, challenges in dealing with leaks, and determining who takes long-term responsibility for the stored carbon.

Bioenergy has big potential but is limited by the amount of material available to burn.
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5. Enhanced weathering of rocks

Silicate rocks naturally capture and store CO₂ from the atmosphere when they weather due to rain and other natural processes. This capturing can be accelerated through “enhanced weathering” – crushing rock and spreading it on land.

The preferred rock type for this method is basalt – nutrient-rich and abundant in Australia and elsewhere. A recent study estimated enhanced weathering could store up to four billion tonnes of CO₂ globally each year.

However low rainfall in many parts of Australia limits the rate of carbon capture via basalt weathering.

6. Direct air carbon capture and storage (DACCS)

Direct air carbon capture and storage (DACCS) uses chemicals that bond to ambient air to remove CO₂. After capture, the CO₂ can be injected underground or used in products such as building materials and plastics.

DACCS is in early stages of commercialisation, with few plants operating globally. In theory, its potential is unlimited. However major barriers include high costs, and the large amount of energy needed to operate large fans required in the process.

7. Ocean fertilisation and alkalinisation

The ocean absorbs around nine billion tonnes of CO₂ from the air each year.

The uptake can be enhanced by fertilisation – adding iron to stimulate growth of marine algae, similar to reforestation on land. The ocean can also take up more CO₂ if we add alkaline materials, such as silicate minerals or lime.

However ocean fertilisation is seen as a risk to marine life, and will be challenging to regulate in international waters.

Negative emissions technologies will be needed to address climate change, but deep emissions reductions are the highest priority.
Dan Himbrechts/AAP

Looking ahead to a zero-carbon world

The foreshadowed government investment in negative emissions technologies is a positive step, and will help to overcome some of the challenges we’ve described. Each of the technologies we outlined has the potential to help mitigate climate change, and some offer additional benefits.

But all have limitations, and alone they will not solve the climate crisis. Deep emissions reduction across the economy will also be required.

Correction: a previous version of this article said biochar could store up to 4.6 million tonnes of CO₂ each year. The correct figure is 4.6 billion tonnes.

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Annette Cowie, Adjunct Professor, University of New England; Han Weng, Research academic, The University of Queensland; Lukas Van Zwieten, Adjunct Professor, Southern Cross University; Stephen Joseph, Visiting Professor, School of Material Science and Engineering, UNSW, and Wolfram Buss, Postdoctoral fellow, Australian National University

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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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.

Exaggerating how much CO₂ can be absorbed by tree planting risks deterring crucial climate action

A long way to go…
Amenic181/Shutterstock

Duncan McLaren, Lancaster University

Planting almost a billion hectares of trees worldwide is the “biggest and cheapest tool” for tackling climate change, according to a new study. The researchers claimed that reforestation could remove 205 gigatonnes of carbon from the atmosphere – equivalent to about 20 years’ worth of the world’s current emissions. This has criticised as an exaggeration. It could actually be dangerous.

While the paper itself included no costings, the researchers suggested a best-case estimate of just US$300 billion to plant trees on 0.9 billion hectares. That’s just 40 US cents per tonne of carbon dioxide (CO₂) removed. More detailed studies on the costs of carbon removal through reforestation put the figure closer to US$20-50 per tonne – and even this may be optimistic at such large scales.

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Our research suggests that the promises implied in such studies could actually set back meaningful action on climate change. This is because of what we call “mitigation deterrence” – promises of cheap and easy CO₂ removal in future make it less likely that time and money will be invested in reducing emissions now.

Why would anyone expect governments or the finance sector to invest in renewable energy, or mass transit like high-speed rail, at costs of tens or hundreds of dollars a tonne if they – and shareholders and voters – are told that huge amounts of CO₂ can be absorbed from the atmosphere for a few dollars a tonne by planting trees?

Why should anyone expect energy companies and airlines to reduce their emissions if they anticipate being able to pay to plant trees to offset everything they emit, for the paltry price of less than 50 cents a tonne. If studies like this suggest removing carbon is cheap and easy, the price of emitting carbon for businesses – in emissions trading schemes – will remain very low, rather than rising to the levels needed to trigger more challenging, yet urgently needed, forms of emission reduction.

Tree planting is cheaper but less effective at reducing emissions than building zero-carbon infrastructure like electric high-speed rail.
Pedrosala/Shutterstock

A false carbon economy

The promises of cheap and powerful tech fixes help to sideline thorny issues of politics, economics and culture. But when promises that look great in models and spreadsheets meet the real world, failure is often more likely. This has been seen before in the expectations around carbon capture and storage.

Despite promises of its future potential in the early 2000s, commercial development of the technology has scarcely progressed in the last decade. That’s despite many modelled pathways for limiting global warming still assuming – increasingly optimistically – that it will be deployed at a large scale in coming decades.

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This model of tackling climate change goes hand in hand with another tool – pricing carbon emissions. This potentially allows companies to go on emitting by paying someone else to cut emissions or remove CO₂ elsewhere – an approach called climate offsetting. But offsetting makes exaggerated promises of carbon removal even more risky.

Tree planting financed through offset markets would guarantee the polluter could continue emitting carbon, but the market couldn’t guarantee removals to match those emissions. Trees might be planted and subsequently lost to wildfire or logging, or never planted at all.

Trusting in trees to remove carbon in future is particularly dangerous because trees are slow to grow and how much carbon they absorb is hard to measure. They’re also less likely to be able to do this as the climate warms. In many regions of the world but particularly in the tropics, growth rates are predicted to fall as the climate warms and devastating wildfires become more frequent.

Relying on trees to absorb CO₂ from the atmosphere in the future also appears misleadingly cheap because of the effects of economic discounting. Economists discount the current value of costs or benefits more deeply, the further in the future they occur. Models which determine the cheapest mix of policies available all use some form of discounting.

When researchers add carbon removal options like tree planting to these models, they tend to generate pathways for slowing temperature rise which reduce the role of short term action and replace it with imaginary removals late in the century.

This is because discounting over 30 to 60 years makes the removal options look incredibly cheap in today’s prices. Priming models to focus on minimising cost causes them to maximise the use of discounted future removals and reduce the use of more expensive near term emissions reduction.

I am not arguing against reforestation, nor for a purely technological response to climate change. Trees can help for many reasons – reducing flooding, shading and cooling communities, and providing habitat for biodiversity. Incentives for reforestation are important, and so are incentives for removing carbon. But we shouldn’t make trees or technology carry the whole burden of tackling climate change. That demands moving beyond technical questions, to deliver immediate political action to cut emissions, and to begin to transform economies and societies.

This article was amended on July 13 2019 to clarify the proposed costs of carbon removal by reforestation.

Duncan McLaren, Professor in Practice, Lancaster University

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

New technology offers hope for storing carbon dioxide underground

Dom Wolff-Boenisch, Curtin University

To halt climate change and prevent dangerous warming, we ultimately have to stop pumping greenhouse gases into the atmosphere. While the world is making slow progress on reducing emissions, there are more radical options, such as removing greenhouse gases from the atmosphere and storing them underground.

In a paper published today in Science my colleagues and I report on a successful trial converting carbon dioxide (CO₂) to rock and storing it underground in Iceland. Although we trialled only a small amount of CO₂, this method has enormous potential.

Here’s how it works.

Turning CO₂ to rock

Our paper is the culmination of a decade of scientific field and laboratory work known as CarbFix in Iceland, working with a group of international scientists, among them Wallace Broecker who coined the expression “global warming” in the 1970s. We also worked with the Icelandic geothermal energy company Reykjavik Energy.

The idea itself to convert CO₂ into carbonate minerals, the basis of limestone, is not new. In fact, Earth itself has been using this conversion technique for aeons to control atmospheric CO₂ levels.

However, scientific opinion had it up to now that converting CO₂ from a gas to a solid (known as mineralisation) would take thousands (or tens of thousands) of years, and would be too slow to be used on an industrial scale.

To settle this question, we prepared a field trial using Reykjavik Energy’s injection and monitoring wells. In 2012, after many years of preparation, we injected 248 tonnes of CO₂ in two separate phases into basalt rocks around 550m underground.

Most CO₂ sequestration projects inject and store “supercritical CO₂”, which is CO₂ gas that has been compressed under pressure to considerably decrease its volume*. However, supercritical CO₂ is buoyant, like a gas, and this approach has thus proved controversial due to the possibility of leaks from the storage reservoir upwards into groundwater and eventually back to the atmosphere.

In fact, some European countries such as the Netherlands have stopped their efforts to store supercritical CO₂ on land because of lack of public acceptance, driven by the fear of possible leaks in the unforeseeable future. Austria went even so far as to ban underground storage of carbon dioxide outright.

The injection well with monitoring station in the background.
Dom Wolff-Boenisch, Author provided

Our Icelandic trial worked in a different way. We first dissolved CO₂ in water to create sparkling water. This carbonated water has two advantages over supercritical CO₂ gas.

First, it is acidic, and attacks basalt which is prone to dissolve under acidic conditions.

Second, the CO₂ cannot escape because it is dissolved and will not rise to the surface. As long as it remains under pressure it will not rise to the surface (you can see the same effect when you crack open a soda can; only then is the dissolved CO₂ released back into the air).

Dissolving basalt means elements such as calcium, magnesium, and iron are released into pore water. Basaltic rocks are rich in these metals that team up with the dissolved CO₂ and form solid carbonate minerals.

Through observations and tracer studies at the monitoring well, we found that over 95% of the injected CO₂ (around 235 tonnes) was converted to carbonate minerals in less than two years. While the initial amount of injected CO₂ was small, the Icelandic field trial clearly shows that mineralisation of CO₂ is feasible and more importantly, fast.

Storing CO₂ under the oceans

The good news is this technology need not be exclusive to Iceland. Mineralisation of CO₂ requires basaltic or peridotitic rocks because these types of rocks are rich in the metals required to form carbonates and bind the CO₂.

As it turns out the entire vast ocean floor is made up of kilometre-thick oceanic basaltic crust, as are large areas on the continental margins. There are also vast land areas covered with basalt (so-called igneous provinces) or peridotite (so-called “ophiolitic complexes”).

The overall potential storage capacity for CO₂ is much larger than the global CO₂ emissions of many centuries. The mineralisation process removes the crucial problem of buoyancy and the need for permanent monitoring of the injected CO₂ to stop and remedy potential leakage to the surface, an issue that supercritical CO₂ injection sites will face for centuries or even millennia to come.

On the downside, CO₂ mineralisation with carbonated water requires substantial amounts of water, meaning that this mineralisation technique can only succeed where vast supplies of water are available.

However, there is no shortage of seawater on the ocean floor or continental margins. Rather, the costs involved present a major hurdle to this kind of permanent storage option, for the time being at least.

In the case of our trial, a tonne of mineralised CO₂ via carbonated water cost about US$17, roughly twice that of using supercritical CO₂ for storage.

It means that as long as there are no financial incentives such as a carbon tax or higher price on carbon emissions, there is no real driving force for carbon storage, irrespective of the technique we use.

*Correction: The sentence has been corrected to note that gas volume rather than density decreases when it is compressed. Thankyou to the readers who pointed out the error.

Dom Wolff-Boenisch, Senior Lecturer, Western Australian School of Mines, Curtin University

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

Removing CO2 from the atmosphere won’t save us: we have to cut emissions now

Pete Smith, University of Aberdeen and Pep Canadell, CSIRO

Over 190 countries are negotiating in Paris a global agreement to stabilise climate change at less than 2℃ above pre-industrial global average temperatures.

For a reasonable chance of keeping warming under 2℃ we can emit a further 865 billion tonnes of carbon dioxide (CO₂). The climate commitments to reduce greenhouse gas emissions to 2030 are a first step, but recent analyses show they are not enough.

So what are the options if we cannot limit emissions to remain within our carbon budget?

Emitting more than the allowance would mean we have to remove carbon from the atmosphere. The more carbon we emit over the coming years, the more we will need to remove in future.

In fact, out of 116 scenarios consistent with 2℃ published by the Intergovernmental Panel on Climate Change, 101 scenarios require the removal of CO₂ from the atmosphere during the second half of this century. That’s on top of the large emission reductions required.

So how do we remove carbon from the atmosphere? Several technologies have been proposed to this effect. These are often referred to as “negative emissions technologies” because the carbon is being removed from the atmosphere (in the opposite direction to emissions).

In a study published today in Nature Climate Change, which is part of a broader release by the Global Carbon Project, we investigate how big a role these technologies could play in halting global warming.

We find that these technologies might play a role in climate mitigation. However, the large scales of deployment currently used in most pathways that limit warming to 2℃ will be severely constrained by environmental and socio-economic factors. This increases the pressure to raise the level of ambition in reducing fossil fuel emissions now.

Smith et al. 2015, Nature Climate Change

How to pull carbon out of the atmosphere

The technologies range from relatively simple options, such as planting more trees, which lock up CO₂ as they grow, or crushing rocks that naturally absorb CO₂ and spreading them on soils and oceans so they remove CO₂ more rapidly.

There are also higher-tech options such as using chemicals to absorb CO₂ from the air, or burning plants for energy and capturing the CO₂ that would otherwise be released, then storing it permanently deep below the ground (called bioenergy with carbon capture and storage).

Bioenergy with carbon capture and storage.
Canadell & Schulze 2014, Nature Communications

We examined the impacts of negative emission technologies on land use, greenhouse gas emissions, water use, earth’s reflectivity (or albedo) and soil nutrient loss, as well as the energy and cost requirements for each technology.

One major limitation that we identified is the vast requirements for land.

About 700 million hectares of land are required to grow biomass for bioenergy with carbon capture and storage at the scale needed in many 2℃ pathways. This would remove more than 3 billion tonnes of carbon from the atmosphere every year and would help to compensate an overshoot in emissions earlier this century.

The area required is close to half of current global arable land plus permanent crop area. If bioenergy with carbon capture and storage were deployed at this scale there would be intense competition with food, water and conservation needs.

This land requirement has made other negative emissions technologies attractive, such as direct air capture. However, current cost estimates for such technologies are between US$1,600 and US$2,000 per tonne of carbon removed from the atmosphere. In contrast, the majority of emissions with a carbon price in 40 national jurisdictions have a cost of less than US$10 per tonne of carbon dioxide.

The study shows that there are many such impacts that vary across technologies. These impacts will need to be addressed and should determine the level at which negative emission technologies can play a role in achieving climate mitigation goals.

Plan A: reduce fossil fuel emissions

We conclude that, given the uncertainties around large-scale deployment of negative emissions technologies, we would be taking a big gamble if actions today were based on the expectation of heavy use of unproven technologies tomorrow.

The use of these technologies will likely be limited due to any combination of the environmental, economic or energy constraints we examined. We conclude that “Plan A” must be to reduce greenhouse gas emissions aggressively now. A failure to initiate such a level of emissions cuts may leave us with no “Plan B” to stabilise the climate within the 2℃ target.

The technologies of today are not the technologies of tomorrow. However, a prudent approach must be based on the level of climate abatement required with available technologies, while strongly investing in the research and development that might lead to breakthroughs that will ease the formidable challenge ahead of us.

Pete Smith, Professor of Soils and Global Change, University of Aberdeen and Pep Canadell, CSIRO Scientist, and Executive Director of Global Carbon Project, CSIRO

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

We may have to suck up CO2 to prevent planet from frying, U.N. says

Plants will reach point where they couldn’t possibly take another bite of our CO2

Deserts Growth Spurt

The link below is to an article that reports on the growth explosion in deserts due to the increase in CO2.

For more visit:
http://www.natureworldnews.com/articles/2871/20130709/increasing-carbon-dioxide-levels-causing-desert-bloom-study.htm

China Leads the Way in CO2 Emissions Battle

The link below is to an article reporting on China leading the world in greenhouse gas reductions.

For more visit:
http://reneweconomy.com.au/2013/china-emissions-cap-proposal-seen-as-climate-breakthrough-40529