Icarus’ Legacy — Episode 7 — Carbon Capture
“Do the right thing, reduce your carbon footprint… Think of the world we’ll be leaving behind for Willie Nelson and Keith Richards.” Anonymous
(Google Slides version more suitable for large screens here)
In the previous episodes
We have learned that there is nothing straightforward in the energy transformation towards net zero carbon emissions, and this is why we will need unprecedented commitment and collaboration in the international community to achieve success. Our challenges include:
- Reducing emissions while increasing energy production, to support population growth and reducing poverty, especially in Asia and Africa.
- Producing more and more clean and renewable energy from solar and wind, but doing it without creating environmental and societal disasters due to the mining and production of rare earths and other materials for the new plants.
- Revisiting the importance of nuclear energy, but with advanced technologies that can reduce costs, projects’ duration, safety risks and make them accessible to a larger number of countries.
- Increasing production of modern biomass to displace fossil fuels, but without taking land away from food production or natural habitats, that would threaten humanity and biodiversity
- Scaling up renewable energy production but also investing in research and improvements in areas that will be dearly required over the next 5–10 years, like energy storage and hydrogen.
A last major challenge remains to be discussed in our quest to net zero.
No matter how good we will be at decarbonizing energy production, human activities will continue to generate greenhouse gas emissions. Think of farm animals, fertilizers, the depletion of soil, the leaks from melting permafrost, the release of carbon dioxide stored in oceans and forests, the production and disposal of materials.
Global warming caused by high concentration of greenhouse gases in the atmosphere goes well beyond energy production and use.
We have a last resource at our disposal: Carbon Capture. Let’s discover it.
The full sixth episode is here, the fifth is here, the fourth is here, the third here, the second here.
Seeing CO2 allows to explore a virtual world where amounts of CO2 are side by side with real life objects and monuments
Our planet is able to capture and sequester carbon through natural processes, which primarily consist of plants photosynthesis. Think of trees, grassland, crops and even phytoplankton. The captured carbon is stored within the plants themselves (think of the trunk of a tree — it is roughly 50% carbon) and also deposited in soil and oceans.
But the scale of emissions from human activities has been far superior to the natural capture capabilities of the planet for at least the past 70 years, and this is confirmed by the accelerating increase in CO2 concentrations in the atmosphere. Concentrations will continue to increase while our net emissions remain positive.
Natural processes and carbon sinks can capture carbon, but they can also release it, and this is something we are only now starting to understand with sufficient detail. Soil, oceans and forests contain enough carbon that, if released, could cancel out any decarbonization effort in our quest to net zero. And the bad news are that global warming is causing these natural sinks to become unstable and leak more and more CO2 from their ancient stores, in a spiralling pattern that is speeding up the warming process.
Two obvious reflections are:
- There’s one more reason to accelerate our actions against climate change, as the longer we wait, the more emissions will be generated from natural sinks, in addition to human activities
- It won’t be enough to reduce our emissions — we will need to start removing carbon through artificial means, so we can compensate for any residual emissions (human or natural) and eventually start going negative, to reduce CO2 concentrations in the atmosphere
Carbon Cycle
When we mix human and natural activities, the carbon cycle becomes incredibly complex, with so many variables at play. Various models exist and consider the exchanges and capacities in the various sinks, activities and ecosystems. These models are being continuously revised, as we acquire more and more real world data (including satellite measurements, in recent times) and advance our research.
What is striking is that the quantities at stake are incredibly large, and what is making a huge difference to our climate, is in comparison relatively small. We know that our atmosphere, what makes our planet unique and keeps us alive, is a very fragile and thin layer, and this is another demonstration of this.
Let’s try to make sense of all these Gt (billions of tons) figures in the chart: the quantity of CO2 contained in biosphere, hydrosphere and lithosphere is, respectively, 5 times, 50 times and 90,000 times the current quantity of CO2 contained in the atmosphere.
What might seem a relatively small quantity of CO2 in the atmosphere, 3150 Gt (often measured in “concentration”, currently at around 415 parts per million, or 0.415% of all atmospheric gases), is what is impacting our climate.
And what we are trying to affect, with a 30-year “net zero” plan to 2050, is the current net annual increase of around 0.5% of the atmospheric content of CO2 (around 17 Gt)
Just imagine the potential damage if a significant amount of carbon was leaked from plants, ocean or land — all ecosystems that we are disrupting through irresponsible human activity.
A Ton of Carbon Dioxide
Gigatons? To have an idea of what we are talking about, what does 1 ton of CO2 look like?
CO2 has a density of 1.98 Kg/m3. Imagine this gas, 100% pure CO2 in front of you.
To make 1 ton, 1,000 Kg, we need 505 m3. This could be a cube with an 8 meters side, or the equivalent volume of 4 double decker buses, to a Londoner.
What about 1 billion tons? Easy math: 505 Km3. So now we have a cube with an 8 Km (5 miles) side… Or perhaps, easier to visualize, think of a shape with an area of 252,500 Km2 (enough to contain the whole United Kingdom or the state of Michigan) and a height of 2 meters — how long would it take to swim across this massive swimming pool of CO2?
Well, humanity emits around 40 of these billion-ton-United-Kingdom-shaped pools of CO2, every year, and nearly half of that remains in the atmosphere to increase its CO2 concentration, and it will then take thousands of years to be removed through natural means.
A video showing the 54 million metric tons of carbon dioxide New York City added to the atmosphere in 2010
The role of Trees and Depletion of Natural Habitats
The loss of forest land over the past decades (every year an average of 10 billion trees are lost) has contributed to a reduced capacity to naturally capture carbon dioxide, and in fact the increase of wildfires from climate change, artificial fires used for deforestation, loss of grassland, desertification and depletion of soil from poor farming practices has contributed to the spiralling increase of net flows of emissions.
Halting deforestation in Indonesia and Brazil alone could reduce emissions equivalent to those produced by every car and light truck on the road in the United States.
Many initiatives locally and globally look at reforestation (restorative) and afforestation (new areas) as a way to reduce global emissions, but also benefit local communities, improve environments, preserve biodiversity and even improve local weather for agriculture (as forests can attract increased rainfall).
A large initiative called The Trillion Trees aims at ending deforestation, improving protection and restoring forest land. This initiative is working in 120 countries to save and restore forests every day.
Another initiative, The Great Green Wall, is an African led movement in the Sahel region at the Southern edge of the Sahara desert, with the aim to grow an 8,000 km wall of trees and plants to bring degraded landscapes back to life, stop and revert desertification, provide food and water security and improved economy to many of the poorest African countries — it would address, in one project, climate change, drought, famine, conflict and migration issues in the region. By 2030 it plans to restore 100 million hectares of degraded land — the equivalent of the combined area of France and Spain.
More Trees is Not Always a Good Idea
Our understanding of the role of forests as carbon sinks is still relatively limited, and we might have largely overestimated it. While halting deforestation, and restoring lost tree coverage is a must (for many reasons), the impact of planting trees everywhere is not as obvious, in terms of carbon capture ability. Why? Several reasons are emerging from recent research:
- Replacing grassland or crops with trees, in some cases can reduce the overall carbon capture capabilities of plants and soil. The best places to plant new trees are depleted soils and terrains, like in desertic regions, or in busy cities, and specific types of trees should be chosen to reduce the impact on aquifers
- Planting a significant amount of trees in colder latitudes can have the negative effect of absorbing more heat during winter weather, when instead snowy and icy meadows would reflect it back to space. The importance of this offsetting factor is debated
- Mature forests slow down their role as carbon sinks, and often our calculation models refer to the period of fastest growth of trees, which is just a fraction of their life
- Reforestation projects are more complicated than just planting some new trees. Mismanaged projects can create long term damage to the environment, and we have to carefully choose the right kind of trees and management plan for any given area
In recent years companies and even individuals have been “offsetting” their emissions by contributing to planting new trees, but not only we might have overestimated the impact of doing so, if we do this indiscriminately, there won’t be any lasting benefit, we will waste important resources and we will not focus on more important aspects.
The best principles to keep in mind:
- Prioritize reduction of emissions from activities, rather than offsetting
- Stop deforestation
- Consider reforestation or afforestation carefully, by looking at current condition of soil, other benefits from tree coverage on the local ecosystems (e.g. pollution, local climate), and the ability to properly manage the new forests after planting
The Role of Oceans and Soil
The roles of oceans and of phytoplankton in the carbon cycle have recently emerged as key factors in global warming. New estimates indicate that phytoplankton captures over 4 times the amount of carbon captured by the Amazon forest (the largest carbon sink in our biosphere) and also generates between 50% and 85% of the oxygen we breathe. Vast amounts of carbon is stored as phytoplankton remains drop and accumulate at the bottom of oceans.
Too bad that human activities in our oceans, from overfishing to pollution, are drastically reducing the quantity of phytoplankton and creating massive leaks of historical stores of carbon from the oceans.
Ocean trawlers are constantly dragging the seabed, with larger and larger nets, which are often abandoned at sea. In addition to depleting the fish stock that they mean to catch, this has several effects:
- Removal and dispersion of ocean floor sediments, which contain vast quantities of stored carbon. It has recently been estimated that this causes CO2 emissions in the region of 1 Gt per year, similar to the entire impact of global aviation
- Destruction of marine habitats on the ocean floor, disrupting other marine species and threatening biodiversity, which has an impact on phytoplankton and carbon capture
- Creation of massive amounts of plastic pollution (it has recently been estimated that nearly 50% of plastic dispersed in the ocean is made of discarded fish nets) which eventually degrades to microplastics. Microplastics enter the food chain, from plankton to fish to humans — the most subtle form of pollution
The reality is that we are just discovering how all this is affecting our health, in addition to climate change.
The international community is trying to set a goal of protecting at least 30% of oceans from fishing activities (currently it’s 7%) which would be incredibly beneficial to our planet.
A real time video feed from Bonaire, in the netherland antilles. The webcam is located at a depth of 15 meters on the drop off at the dive site “Something Special”.
Artificial Carbon Capture
Natural sinks like forests, soil and oceans can sequester large quantities of carbon, but are not controllable, and can quickly turn into sources of CO2: they are considered “leaky”, and changing weather, chemistry or other events could reduce their quantity of sequestered carbon.
With artificial means to capture CO2 we can create:
- Near-permanent storage of carbon by producing, as a result of capture, materials for everyday use (e.g. polymers for building materials or cars, enriched concrete or aggregates to replace emission-intensive cement) or for injection back into the earth as solid or gaseous materials, for instance into depleted oil and gas reservoirs, or even in the depths of the ocean
- Closed cycles where carbon is captured into products that will generate emissions, but can then be captured again in a sustainable cycle (e.g. synthetic fuel alternatives to oil for transport or industry, or chemicals produced without the use of fossil fuels, whose emissions are recaptured and recycled into new products)
These processes can offer both climate change mitigation and economic incentives.
When CO2 is permanently locked away, for instance in underground wells or embedded in stones, we talk about “Sequestration” or alternatively, when it is reused as part of materials or to create new fuel, we talk about “Utilization”.
Once considered a distraction by scientists, Carbon Capture and Sequestration (CCS) or the alternative Utilization (CCU) are now seen as essential technology to reach net zero emissions by 2050, and to accelerate the transformation.
New artificial ways to manage carbon cycles at large scale are being researched and deployed
While progress with renewable sources of energy should significantly reduce emissions, it will be virtually impossible to reach zero emissions, especially if we consider other activities, away from energy production and use, such as food and materials production for the growing world population.
The reality is that we have released so much CO2 over the past decades, and that the transition to renewables will take decades to fully materialize, so the reduction of new emissions on its own will not be enough. If we want to reduce the greenhouse effects causing climate change, we need to increase our efforts to remove existing CO2 from the atmosphere.
In practice, carbon capture can be implemented in two different ways:
- Capture from sources of CO2: we capture where emissions are generated, such as fossil fuels power plants, and prevent the most part of CO2 to be released to the atmosphere. Different technologies are employed, including post-combustion, which can be used in existing power plants, as it doesn’t affect the fuel used for combustion, or pre-combustion, which requires special power plants, as the fuels requires a complex conversion before combustion. Once the carbon is captured it will need to be transported to the selected storage site
- Direct air capture: machines are employed to suck and filter large quantities of air, and through a mechanical and chemical process, scrub, remove and capture CO2. This process would allow capturing near storage sites, reducing the carbon transportation requirement. A single large scale plant could filter and store as much CO2 as tens of millions of trees, but using a small fraction of the land. Admittedly, it won’t look as nice as a forest.
While carbon capture has already been deployed in many early projects around the world, its utilization at scale will have to face a number of challenges, especially to contain costs or alternatively generate other economic incentives in the form of new materials produced as a side product of the captured carbon.
In the capture from power plants, these additional costs could be seen as a sort of carbon tax on fossil fuels, directly applied at the point of energy production or consumption, possibly incentivizing the transition to clean fuels.
The Direct air capture instead could be used in a market for carbon offsets, where the capture is paid by the companies or governments whose activities release GHG emissions that cannot be avoided or captured at the source of emissions. This would be an alternative to tree-planting offset schemes that are already in use, but often with dubious results.
But it’s easy to imagine this technology as an excuse to maintain dirty fossil fuel plants in place for longer than necessary and to keep businesses from really reducing emissions, while we should invest towards clean and renewable energy to also eliminate pollution from our cities and ecosystems.
The window for climate action is short, and deployment at scale of these technologies is a must in many scenarios, even well beyond the achievement of net zero. But they should be used wisely, so they don’t detract investments from more effective and sustainable measures.
We have come to an end of our energy transformation journey.
We started from understanding how important energy is to global warming, given the quantity of CO2 emissions generated from the production and use of energy, especially when sourced from fossil fuels. Global warming is causing more frequent extreme events like floods, hurricanes, wildfires, droughts, in addition to melting ice caps and glaciers, which contributes to rising sea waters.
We explored the possible solutions and opportunities we have to reduce the impact of human activities on our climate, and keep temperatures within 1.5’C from pre-industrial times. To do this we need to zero the “net” greenhouse gas emissions over the next two to three decades, and start to make a difference already in the 2020s.
This is a massive undertaking which requires coordinated and decisive action from global institutions, countries, cities, companies, communities and individuals. We will need to generate most of our energy from renewable and/or clean sources, and this will require intelligent allocation of resources to deliver results today (expanding solar, wind and biomass energy), as well as to research and innovate, so other important tools can make a difference in the years to come (like advanced nuclear, energy storage, hydrogen and carbon capture, to name a few critical ones). We will also need a positive attitude and belief. Sometimes we are the worst enemies of ourselves.
On the positive side, there’s a lot of attention from the whole world, increased awareness, substantial funding and very good intentions.
What can we, individuals, do? Whatever shifts energy use towards electricity, or reduces energy use, is a good bet — time to change your petrol or diesel car, gas boiler or gas hob? Think electric vehicles, heat pumps, induction hobs. But also, reduce waste in food, plastic, clothes and other materials; insulate your home, use energy-efficient bulbs, use public transport or cycle and walk whenever possible; consider rooftop solar panels.
And most importantly, learn for yourself, and then spread the word.
This change can create new jobs, reduce toxic pollution in our cities and oceans, safeguard biodiversity and improve the lifestyle of entire populations.
We have a last chance to leave a lasting legacy to the next generations, to work with our children, make them proud, and secure a cleaner, sustainable future to humanity on our planet.
Now let’s do our part.
