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View of Canberra from Mount Ainslie lookout, Australia. Credit: Piter Lenk / Alamy Stock Photo. M8TY9H
View of Canberra from Mount Ainslie lookout, Australia. Credit: Piter Lenk / Alamy Stock Photo.
1 November 2018 12:20

Negative emissions: Scientists meet in Australia to discuss removing CO2 from air

Daisy Dunne


Daisy Dunne

01.11.2018 | 12:20pm
GeoengineeringNegative emissions: Scientists meet in Australia to discuss removing CO2 from air

An international group of researchers and policymakers met in Australia’s capital this week for the country’s first major conference dedicated to the topic of “negative emissions”.

The two-day event, held at the Australian Academy of Science’s Shine Dome in Canberra, played host to a range of ideas for removing CO2 from the atmosphere and storing it on land, underground or in the oceans.

The topics discussed ranged from “natural” solutions, such as boosting the carbon stores of soils and giant kelp forests, to the more experimental, including “fertilising” the world’s oceans.

Carbon Brief was at the conference, which was organised by researchers from Australian National University and the University of Tasmania, to take in the presentations, talks and discussions.

The Australian perspective

This year has seen a ramping up of interest in negative emissions technologies (NETs) on both national and international levels.

In January, the European Academies Science Advisory Council (EASAC) – an independent group that offers science advice to EU policymakers – published a report looking at the feasibility and overall potential of NETs from a European perspective.

This was followed by the world’s first international conference on NETs, which was held in Sweden in May. The three-day event, which was covered in depth by Carbon Brief, saw scientists debate a range of issues, with a particular focus given to land-based methods such as afforestation and bioenergy with carbon capture and storage (BECCS).

In September, the Royal Society and the Royal Academy of Engineering jointly published a report looking at NETs from a UK perspective and, in October, the US National Academies of Science, Engineering and Medicine published a national research agenda for NETs.

Australia’s offering to the growing field comes at a time when its government is facing criticism for inaction over climate change. Concerns over political apathy were articulated by Prof John Hewson, a former leader of the country’s conservative Liberal Party and prominent voice on climate change within Australia.

In a rousing introductory talk, Hewson said he was “personally embarrassed” by the government’s lack of emissions reduction policies and raised a round of applause from the audience after saying: “If a government doesn’t have a climate action plan, it forfeits the right to be a government.”

Speakers at the conference also alluded to the harsh impacts that Australians are already facing as a result of climate change and how NETs could play a role in alleviating these effects.

In a plenary talk, Major General the Honourable Michael Jeffery, a former governor-general for Australia and founder of the non-profit Soils for Life, spoke of the threats to Australian farmers caused by record droughts and increasing soil infertility. Efforts to boost soil carbon could offer a lifeline to farmers, he said.

Across the two days, Carbon Brief spoke to a range of scientists about the possible positive and negative impacts that could be caused by negative emissions, both in Australia and globally.

In the video below, Carbon Brief asked delegates to comment on whether large-scale negative emissions could be achieved without side-effects for humans and the natural world. The speakers include:

Natural solutions

A major topic of conversation among delegates was the potential of “natural climate solutions” to remove CO2 from the atmosphere.

These methods are typically aimed at enhancing the carbon stores of soil and plants, which currently soak up around 40% of the CO2 emissions resulting from human activity.

Perhaps reflecting Australia’s position as an island in the southern hemisphere, several discussions were devoted to the potential of enhancing “blue carbon”– the carbon stored by seagrass, mangroves and saltmarshes.

Prof Catherine Lovelock, a marine ecologist from the University of Queensland, spoke on the wide-ranging potential co-benefits of boosting blue carbon stores by restoring coastal wetlands. These co-benefits could include improving natural flood defences and water quality and, in Australia, providing job opportunities for Indigenous communities, she said.

Although wetlands can store large amounts of carbon on a per area basis, their activities can also cause the release of large amounts of methane – a greenhouse gas that is 34 times more potent than CO2 over a 100-year period.

However, Lovelock pointed to research released in 2017 which suggests that the methane emissions of wetlands can be minimised by reintroducing saltwater to restored areas.

The possible co-benefits of enhancing blue carbon stores were also discussed by Prof Todd Michael, a scientist from the J Craig Venter Institute. His research is focused on giant kelp – the world’s largest species of marine algae –  which is found along the coast of California, western South America and parts of Australia.

Giant kelp absorb CO2 in a similar way to trees. However, because kelp absorbs CO2 directly from seawater, it could also play a role in tackling ocean acidification. The restoration of kelp habitats could also benefit a wide range of species, ranging from small invertebrates to large mammals, Michael said.

Another natural solution up for discussion was afforestation – planting new forests in areas with no previous tree cover. (As a forest grows, it naturally removes CO2 from the atmosphere and stores it in its trees.)

Prof Justin Borevitz, a biologist from Australian National University, discussed the potential benefits of agroforestry, a type of afforestation where trees are incorporated into farmland.

His research is focused on “regenerative agriculture” – which would see agroforestry combined with other technologies such as drones and real-time data collection. The video below shows a demonstration of this in action.

An advantage of this type of agriculture is that it allows land to be used for food production and carbon storage simultaneously, he said. This could help address what he called “the land-use paradox” – the growing need for both food production and conservation of green spaces. He told the conference:

“The solution is to try to overlap the food production area with the carbon sequestration area and biodiversity areas. This is how we solve this land-use paradox.”

Incorporating trees into agricultural land could also help Australian farmers manage “the intensifying cycle of droughts, fires and floods” caused by climate change, he added.

Another way to boost the productivity of agricultural land while enhancing carbon stores could be through the use of “biochar”, according to Dr Wolfram Buss, a biologist from Australian National University.

Biochar is charcoal made via the pyrolysis of biomass, which could range from wood dust or rice husks to used coffee cups and sewage sludge, according to Buss. When biochar is spread over land, it can boost soil carbon storage while improving soil fertility.

It could also be preferable to other land-based NETS, such as BECCS and afforestation, because it requires relatively low amounts of water and land for its production, he told the conference:

“Biochar has a reasonably low environmental impact, but still has reasonable potential for carbon sequestration.”


The potential for BECCS in Australia was discussed by Prof Peter Cook, a prominent scientist from the Peter Cook Centre for Carbon Capture and Storage at the University of Melbourne.

Put simply, BECCS involves growing crops, burning them in a power plant to generate energy and then capturing the resulting CO2 before it is released into the air. The captured CO2 is then sent to an underground or undersea storage site.

Cook’s talk touched on some of the common concerns about BECCS. This included the worry that growing the amount of crops needed for large-scale BECCS would take up large amounts of land, which could threaten food production and wildlife.

However, he also hit out at claims that BECCS would not work at scale. In his opinion, the main barrier to large-scale BECCS is a lack of available economic incentives. He told the conference:

“There’s absolutely no reason to do it at the moment, you don’t get any more money for electricity that’s produced using CCS, there’s no drivers in the economy to do it.”

Overall, though, BECCS alone cannot solve climate change, he added:

“Let me be clear, BECCS is no silver bullet, it’s part of the rich tapestry of options that we’re going to need.”

BECCS was also discussed by Dr Jessica Strefler, a researcher from the Potsdam Institute for Climate Impacts Research (PIK). In a wide-ranging talk, she discussed the degree to which negative emissions will be needed to meet the goals of the Paris Agreement.

She pointed out that while many describe the land use needs associated with BECCS as unsustainable, it is bioenergy, rather than BECCS, that is likely to drive demand in the future. She told the conference:

“The most important criticism of BECCS in my view is that the large use of bioenergy is unsustainable. I would say that’s certainly true, but it’s really important to distinguish between bioenergy and BECCS.

“If you look at scenarios for energy demand in 2050…if CCS is available, BECCS is used. But, if CCS is not available, the models use just as much bioenergy. The reason for that is it is one of the rare alternatives to oil for liquid fuel.”

Ocean options

A number of the presentations at the conference were devoted to the possibility of enhancing the productivity of the world’s oceans.

The oceans contain millions of microscopic plants – known as phytoplankton – that absorb CO2 as they photosynthesise. Scientists have suggested that artificially increasing the rate at which they photosynthesise could cause CO2 to be removed from the atmosphere.

There are various ways this could be achieved. One idea, known as “ocean fertilisation” involves releasing iron into parts of the ocean where it is currently lacking. This could trigger a bloom of phytoplankton, which would remove CO2 from the air.

Others have suggested that marine plant growth could be stimulated by pumping deep sea water, which is rich in nutrients, up to the ocean’s surface.

Previous NETs assessments have shown limited enthusiasm for these techniques. One reason for this is because they remain largely untested, according to the EASAC report released in January:

“These issues require considerable further research and field trials to be clarified, before [they] could be regarded as a potential contributor to achieving negative emissions.”

However, several speakers argued that more research should be channelled into these techniques.

In a talk focused on options for long-term negative emissions, Prof Andreas Oschlies, from the GEOMAR Helmholtz Centre for Ocean Research at Kiel University, told the conference that research suggests that, in some cases, the “ocean appears less vulnerable than many land systems” to the impacts caused by negative emissions.

This does not mean that ocean fertilisation would come without risks, he added. He pointed to research suggesting fertilisation could lower the availability of oxygen in some parts of the ocean and may have a negative impact on economically-important fish.

Options for increasing the CO2 storage of oceans were also discussed by Dr Phillip Williamson, an honorary reader at the University of East Anglia and science coordinator of the UK government-funded Greenhouse Gas Removal from the Atmosphere research programme.

In his plenary talk, he explained the findings of his recent research which evaluated 13 ocean-based solutions for tackling climate change. (Williamson recently explained each of these 13 ideas in more detail in a guest post for Carbon Brief.)

Governing change

In addition to scientific research into NETs, conference talks also focused on the social issues surrounding the topic.

Several speakers tackled the issue of what terminology should be used when talking about NETs.

In his plenary, Williamson argued that the most preferable term for NETs should be “greenhouse gas removal” – since this could “keep options open for novel approaches”, such as emerging methods for removing methane from the atmosphere.

Terminology was also discussed by Prof Matthew Kearnes, a member of the environmental humanities group at the University of South Wales Sydney. The variety of words used to describe NETs each come with their own connotations, he told the conference.

Several speakers addressed the moral issues surrounding NETs. Dr Clare Heyward, a researcher of philosophy from the University of Warwick and the Arctic University of Norway, argued for an “integrative approach” to NETs.

One way this could be achieved is looking at NETs through the lens of the world’s sustainable development goals (SDGs), she said. (This is the approach that was recently taken by the Intergovernmental Panel on Climate Change’s (IPCC) special report on 1.5C of global warming.)

In another talk, Aaron Tang, a PhD student at Australian National University, addressed the “moral hazard issue” for negative emissions. In this case, the moral hazard issue describes the fear that offering policymakers an option to remove CO2 from the atmosphere could prompt them to backtrack on their commitments to cut emissions.

Despite the prominence given to the idea, there is little empirical evidence for it happening, Tang argued. However, there is evidence that politicians could use such framing to further their own agendas, he added.

The conference ended with an announcement that a follow-up event will be held in the first half of 2019. This event will invite a wider range of stakeholders, according to its organisers, including representatives from the oil and gas industry and farming sector.

The organisers paid Carbon Brief’s travel expenses to attend the conference.

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