Last summer, the UK became the first G7 country to legislate for net zero carbon – the state of overall balance between carbon dioxide (CO2) emissions produced and emissions taken out of the atmosphere. An amendment to the Climate Change Act increased the target to reduce greenhouse gas emissions from 80 per cent to 100 per cent by 2050. It is an ambitious objective, and not one that can be reached by reducing emissions alone.
“Reducing emissions becomes harder and harder to do once we reach a certain level: in the UK (where total emissions were around 364 million tonnes in 2018), we might get to a low emissions economy with between 80 to 150 million tons of carbon dioxide equivalent still being released to the atmosphere,” says Professor Nilay Shah (MEng Chemical Engineering 1988, PhD 1991), Head of the Department of Chemical Engineering. “To go from there to net zero means having technologies that will take in air and scrub out the greenhouse gases.”
Carbon capture essentially means trapping carbon dioxide at its emission source, transporting it to a storage location – usually deep underground – and isolating it. But achieving net zero is a huge task. From the fine details of tree-planting to technical breakthroughs in underground storage, and from global financial implications to the details of translation, there are any number of problems, processes and pathways.
In short, it’s just the kind of challenge that Imperial’s experts relish. However, according to Professor Shah, the simplest solutions to carbon capture are right here now, all around us.
“It doesn’t require us to invent anything exotic. It’s more a question of practical landscape management.” Take trees, for example: along with getting rid of carbon dioxide, they also provide a multitude of other benefits, including improving the climate and biodiversity of an area.
"A well-managed forest with trees grown in rotation will produce wood that can be used in construction, and that’s yet another way of capturing carbon. The carbon that was in the atmosphere goes into the wood. Then the wood goes into a building, and that carbon is locked away for a long time,” says Professor Shah. “The only downside is that trees aren’t going to be enough on their own. We’d need an awful lot of trees!”
Then there’s biochar, a charcoal-like material produced when agricultural materials are partially combusted. It’s carbon-negative: when biochar is used in soil, it traps carbon there while also improving the soil’s quality. Restoring coastal wetlands and peatlands will also improve the landscape’s ability to take up carbon dioxide, as will reducing ploughing in order to disturb the soil less.
“In the last two years, I’ve seen a big change in the attitude of large companies,” says Professor Shah. He cites the example of the Drax power station, a large biomass and coal-fired power station in North Yorkshire that aims to get to net zero in 2030 by burning wood pellets from sustainable forests and utilising carbon storage technology. “We’re also working with a very big company I can’t name yet that has made a huge commitment in this area. For many aspects of science and technology, this will be a golden age. Carbon capture is a big and complex thing but it is also really exciting, enthusing and engaging.”
Core carbon capture and storage technologies are nothing new, says Dr Niall Mac Dowell, Reader in Energy Systems. Most of them were first deployed between 1900 and 1930, and are used all over the world today. “But there’s more to this kind of system transformation than just engineering technology,” Dr Mac Dowell points out.
“Nobody is doing this for charity. The service being provided will be for removing CO2 from the atmosphere. And to do that effectively, we need to develop the institutions and frameworks for the monetisation and commercialisation of these services, and for appropriately valuing them.”
For example, a ton of carbon stored underground will eventually become rock. The risk associated with its removal is zero. Use trees to capture carbon, however, and the risk rises: trees can die from pests, disease or fire. “So how do we design a level of risk to that stored carbon, and price it appropriately? How many trees do you have to plan for to remove a ton of CO2?”
Last year, Dr Mac Dowell’s lab won a grant from the EU’s Horizon 2020 research and innovation programme to grapple with questions such as these, working out how this new system might be designed – and how to make it fair, equitable and, most importantly, practical. “We’ll be looking into how deploying negative emission technologies interacts with the rest of the energy system,” he says. “And we’ll also be studying how we can make this transition in a way that benefits our broader society.”
The transition is often framed in terms of trade-offs, Dr Mac Dowell points out, but it doesn’t have to be that way. “I would argue that it’s unlikely – even with the experience of the current crisis – to be broadly socially acceptable that we have to drastically and rapidly change our lifestyles. So, we need to design transitions that aim to maximise growth. “We are creating new industries and economies that will result in the creation and preservation of jobs and communities across the world.”
The energy transition cannot happen immediately, points out Geoff Maitland, Professor of Energy Engineering – even by 2050, at least 20 per cent of our energy sources globally, and maybe up to 50 per cent, will still be fossil fuels. So how do we decarbonise these fossil fuels? Ten years ago, Maitland founded the Qatar Carbonate and Carbon Storage Research Centre (QCCSRC), a collaboration between Imperial College London, Qatar Petroleum, Shell and the Qatar Science and Technology Park, part of Qatar Foundation. It aimed to deepen understanding of how carbon can be efficiently stored underground in depleted oil and gas reservoirs and water-permeable rock formations called deep saline aquifers.
“This programme focused on how we can ensure both depleted oil and gas reservoirs and deep saline aquifers have the capacity to safely store the ten gigatons of CO2 that we’ve got to store by 2050,” says Professor Maitland. “The big concern with this method is that when you put the CO2 down there, it stays there.”
They used x-ray imaging tomography at both the micropore scale and the larger core scale to examine the fluids inside rocks. “And we identified the trapping mechanisms in a way people hadn’t understood before,” says Professor Maitland. “The natural seals of low-permeability rocks have kept oil and gas in place for millions of years. The CO2 gets trapped by capillary forces in the same way that oil does; it’s trapped by surface tension. Injecting it requires high pressure, but not too much, otherwise you fracture the rock, and we did a lot of work identifying this window.” Once injected, the CO2 gradually dissolves into the fluids in the rock, and eventually turns into carbonate minerals, trapping it permanently.
The project has already spawned numerous papers and take-ups in the field and paved the way for the large-scale adoption that will be needed by 2050. “We have 20 to 25 large-scale projects worldwide now, and by 2050 we’re going to need about 5,000 or more,” says Professor Maitland. “That’s a big jump – but the technology exists.”
Having practical knowledge and solutions to reach net zero is one thing: getting them out there into the real world is quite another. That’s where the Grantham Institute for Climate Change and the Environment comes in.
“We are a bridge between the technical knowledge that we have at the university, the business and the policy community, and the general public,” says Alyssa Gilbert, the Institute’s Director of Policy and Translation. “We help them to make use of all that knowledge to make evidence-based decisions that can help deliver solutions today and in the future. We listen to those people so we can understand their queries and then we design information responses.”
The recent Science in the City programme, for example, took Imperial’s experts into different City firms to talk about the technologies that will need to be implemented to deliver net zero emissions goals. “We got some very good, insightful questions about the technology’s strengths and weaknesses,” Gilbert says.
“That informs a firm’s ability to make investments in those technologies. And that’s what we want to see – the shift of finance and investment from the things that damage our environment to the things that can solve our environmental challenges. It’s really exciting when we’re in the room with people who have access to funding decisions, asking us questions that we think can move the tide of money in the right direction.
The route to carbon neutral
Greenhouse gas removal methods in the natural world include forestation, habitat restoration, biochar and soil carbon sequestration, as well as enhanced terrestrial weathering and mineral carbonation (accelerating the conversion of silicate rocks to carbonates to provide permanent storage for CO2).
Capture and storage
Some greenhouse gas removal methods have built-in storage, while others require a separate activity to store the CO2, such as bioenergy with carbon capture and storage (BECCS), which utilises biomass for energy and captures the CO2 emissions, and direct air capture and carbon storage (DACCS).
Many of the greenhouse gas removals methods in discussion are expensive to deploy. The rate of roll-out will need to be rapid, particularly in the 2030s and 2040s, and will require significant policy support. Economic mechanisms could establish markets and assist efficient resource allocation.
A key action is to pursue research into the greenhouse gas removal potential of various activities not yet demonstrated at scale (for instance, biochar) as well as carbon capture and storage options, along with Imperial's own research efforts in the carbon and electric car industries.
Science and technology
Includes solar power and wind power, along with electrolysers. Cost, scalability, security and environmental impacts of greenhouse gas removal methods are often poorly understood, limiting their application and requiring research and development.
National and international regulations/policy
Emissions and removals (and their reporting) are governed under national and international legislation, and these will all have a significant impact on outcomes, particularly in terms of, for example, the supply chain of international trade.
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This story was published originally in Imperial 48/Summer 2020.