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.
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:
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.
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.
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.
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.
Plant material can be burned for energy – known as bioenergy. In a BECCS system, the resulting CO₂ is captured and stored deep underground.
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.
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.
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.
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.
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.
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
The Morrison government will tell its refocused clean energy agencies and the clean energy regulator to give priority to investment in five low emissions technologies and report how they are accelerating them.
The technologies are clean hydrogen, energy storage, low carbon steel and aluminium, carbon capture and storage, and soil carbon.
The government last week announced it would legislate to extend the remit of the Australian Renewable Energy Agency (ARENA) and the Clean Energy Finance Corporation (CEFC) beyond renewables.
On Tuesday it will indicate the “priority low emissions technologies” they, and the Clean Energy Regulator (CER) – which is responsible for administering the government’s emissions reduction fund – should concentrate on.
Energy Minister Angus Taylor, in a Tuesday speech on low emissions technology, will say the government is putting technologies into four categories. Apart from the priority low emissions technologies, the other categories are emerging and enabling technologies, “watching brief” technologies, and mature technologies.
Priority technologies “are those expected to have transformational impacts here and globally and are not yet mature,” Taylor says in his speech, released ahead of delivery.
“They are priorities where government investments can make a difference in reducing costs and improving technology readiness.
“Technologies where we, as a government, will not only prioritise our investments but where we will streamline regulation and legislation to encourage investment.
“Investors will have confidence that identified priority technologies are of long-term strategic importance for the government.”
Emerging and enabling technologies, such as those for energy efficiency and infrastructure for electric and hydrogen vehicle charging/ refuelling, will also be included in the mandate of the government’s investment agencies.
In the “watching brief” category are those that are for the longer run or are longer odds, such as direct air capture and small nuclear modular reactors. (There is a moratorium on nuclear power in Australia at the moment but the government is watching developments in Europe and the United Kingdom.)
Notably, key renewables and key fossil fuels are in the “mature” category, which includes coal, gas, solar and wind.
The government says it will only invest in them where there is market failure or where such investments secure jobs in key industries.
Last week Scott Morrison threatened to build a gas power station in the Hunter region if private investors left a supply gap for when the Liddell coal-fired station closes, while he also indicated renewables could now stand on their own feet.
Taylor will release an overarching technology roadmap, which he says “arms the government with “four levers to enact change”: an investment lever, a legislative lever, a regulator lever, and international co-operation and collaboration.
“The roadmap will guide the deployment of the $18 billion that will be invested, including through the CEFC, ARENA, the Climate Solutions Fund [which will evolve from the Emissions Reduction Fund] and the CER.
“This will turn that into at least $50 billion through the private sector, state governments, research institutions and other publicly funded bodies. That will drive around 130 000 jobs to 2030,” Taylor says.
The legislative level “is about flexibility and accountability.
“We don’t currently have that. Our agencies are restricted by legislation and regulation to invest in the new technologies of 2010 not the emerging technologies of 2020.”
The regulator lever “is about enablement”.
Taylor says the government’s plan is not based on ideology but “balance and outcomes”.
The government is announcing several “stretch goals” (see table for details). Stretch goals are the point at which new technologies become competitive with existing alternatives. The government announced the hydrogen stretch goal earlier in the year.
“Getting these technologies right will strengthen our economy and create jobs,” Taylor says.
“This will significantly reduce global emissions, across sectors that emit 45 billion tonnes annually.
“Australia alone will avoid 250 million tonnes of emissions by 2040.”
He says “Australia can’t and shouldn’t damage its economy to reduce emissions”.