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This episode of Real Engineering is brought to you by Skillshare. Home to over twenty
five thousand classes that could teach you a new life skill.
We rarely witness evolution on a timeframe short enough for a single human life to take
notice. These changes usually occur over many lifetimes, the gradual drift of a creatures
DNA to best survive their environment. But in one case in the 1700s humans witnessed
evolution with their own eyes, and they caused it. This metamorphosis coincided with human’s
rapid industrialization. We began burning coal on levels never before seen, and it’s
bi-products rapidly changed the landscape for not just humans, but for the animals that
shared the planet with them.
The peppered moth was one of those animals, getting its name from its speckled white and
black colouring, designed to camouflage the moth while it lay on lichen covered tree barks.
A black variant was first observed in 1811, many decades into the industrial revolution.
At first the mutation was rare, but human’s influence on the environment grew, so did
their numbers. By 1895, 98% of the peppered moths in Manchester had this black colouring
[1] Surely this black colouring would leave them exposed, making them easier to spot for
hungry birds. In reality, these moths had adapted to be harder to spot in this newly
industrialised world, one stained by soot.
And it may be time for humans to follow their lead. To evolve, or die. The rate we have
been spewing these pollutants into our atmosphere has only risen since this discover. Our carbon
dioxide emissions have risen from one thousand six hundred million metric tonnes to thirty
six thousand million metric tonnes since 1865 [2] And despite our best efforts, that number
is not declining. Human population and development are continuing to outpace our efforts to curbed
our carbon dioxide emissions.
Just as alcohol producing yeast will eventually create an environment too toxic for itself
to survive, humans are pumping the world’s atmosphere with a gas that will eventually
render the world unlivable for many, if something is not done. So we have to ask ourselves now,
are going the way of a mindless single cell fungi that continue to poison their habitat
until they die, or are we going to recognise that the survival of the next generation is
more important?
Our previous videos have discussed ways to mitigate climate change, by planting trees
in the Sahara or by using aerosols to block out the sun. Both are pretty extreme methods,
and come with some big risks that could lead to some unforeseen consequences. Instead of
some risky engineering tactic, what if we could just suck the CO₂ right out of the
air, undoing some of the damage that has been done?
Well, in certain circumstances, this is already happening. Carbon capture and storage (CCS)
has been around for years. There are a few main types of carbon capture, almost all of
which happens at power plants, capturing the carbon that comes directly from the plant.
In post-combustion ­carbon capture, the CO₂ is captured after the fossil fuel is burned.
In this method, CO₂ is separated from the flue gas, which includes CO₂, water vapor,
sulfur dioxides and nitrogen oxides, by bubbling the gas through an absorber column packed
with liquid solvents, such as ammonia. In the most widely used system, once the chemicals
in the absorber column become saturated, a stream of superheated steam at around 120C
is passed through it. This releases the trapped CO₂, which can then be transported for storage
elsewhere. [3]
In pre-combustion carbon capture,­ CO₂ is trapped before it's diluted by other flue
gases. The fossil fuel is heated in pure oxygen, resulting in a mix of carbon monoxide and
hydrogen. [4]The carbon monoxide is reacted with water to produce carbon dioxide, which
is captured, along with hydrogen. The hydrogen can be used to produce electricity, and the
carbon dioxide is stored. [5]
Pre- and post-combustion carbon capture can prevent 80 to 90 percent of a power plant's
carbon emissions from entering the atmosphere. [6] This is a big deal. The IPCC estimates
that carbon capture and storage has the potential to make up between 10% and 55% of the total
carbon mitigation effort until year 2100. [7]
However, this carbon has to be stored somewhere. It is most often stored underground in a process
called geological sequestration, which involves injecting CO₂ into underground rock formations.
It is stored as a supercritical fluid, meaning it has properties between those of a gas and
a liquid. When carbon dioxide is injected at depth, it will remain in the supercritical
condition as long as it stays in excess of 31.1°C and at a pressure in excess of 72.9
atmospheres. Many times, the carbon dioxide is injected into a reservoir which previously
trapped oil and gas, since those areas have natural rock formations that help to contain
the carbon dioxide. While this might be an okay solution, no one knows for sure what
the environmental impact could be if the carbon dioxide were to leak out into the environment
in large quantities. [8] In some instances, leakage of carbon dioxide underground has
been shown to increase plant mortality, reduce growth and create potentially severe localised
damage to ecosystems. For this to be a viable, safe option, the carbon dioxide would need
to remain stored for 100s of years, or even indefinitely, and the feasibility of this
is not certain. [9]
Other methods of storing carbon include sinking it deep below the ocean, at depths under 3500
meters, where it turns into a slushy material that will sink to the ocean floor under that
amount of pressure. [10]But this method is largely untested, and again, there are concerns
about what this could mean for marine life, and uncertainty on whether or not the CO₂
could eventually make its way back into the environment. [11]
There have been more promising experiments in carbon storage in Iceland, where researchers
have shown that pumping carbon dioxide into the volcanic rock underground can speed up
a natural process where the basalts react with the gas to form carbonate minerals, which
make up limestone. This is an encouraging development, but has its limitations. It requires
large amounts of water: 25 tonnes for each tonne of carbon dioxide buried, meaning this
process would have to be limited to coastal sites. Another is that subterranean microbes
might break down carbonate to methane, another powerful greenhouse gas. [12]
And while 80 to 90 percent of a power plant’s carbon emissions can, in theory, be captured
and stored in one of many ways, what about all of the other carbon emitting things in
our world? Only 25% of global greenhouse gas emissions come from electricity and heat production
at power plants. Transportation, general industry, and agriculture collectively make up around
60% of greenhouse gas emissions. [13] Is there a way to capture CO₂ from these sources?
Direct air capture has, up to recently, been a largely theoretical technique in which CO₂
is removed directly from the atmosphere. Theoretical, because doing this on a scale that would even
make a dent has historically been ridiculously expensive - some experts say as much as $600
per metric ton of carbon dioxide. For reference, a typical passenger vehicle emits about 4.6
metric tons of carbon dioxide per year. [14] But recently a team of scientists from Harvard
University and the Bill Gates funded company Carbon Engineering announced that they have
found a method to cheaply pull carbon-dioxide pollution out of the atmosphere - they say
for as little as $94, and for no more than $232 per metric ton of CO₂. This means that
it would cost between $1 and $2.50 to remove the carbon dioxide released by burning a gallon
of gasoline in a modern car. And not only do they suck the CO₂ out of the air with
the ability to store it - they will also transform the carbon back in to gasoline or jet fuel,
creating net-neutral carbon based fuels. [15]
While this sounds too good to be true, the methods they use to pull CO₂ out of the
air is not too different from what has already been done for decades.
This type of direct air capture starts with an air contractor, where air is sucked in
at high volumes. This structure “wet scrubs” the air by using a strong hydroxide solution
to capture CO₂ and convert it into carbonate. The hydroxide solution reacts with carbon
dioxide to form carbonate ions(CO32−.) This occurs within a structure which is much the
same as an industrial cooling tower.
The next step involves a “pellet reactor” where the carbonate ion reacts with calcium(Ca2+)
to form calcium carbonate, in the form of dried pellets.
Then, a circulating fluid heats the calcium carbonate pellets to decomposition temperature,
breaking them apart to release the carbon dioxide as a gas and leave behind calcium
oxide (CaO) [16]
Finally, the carbon dioxide is combined with hydrogen and converted into liquid fuels,
including gasoline, diesel, and jet fuel, using the Fischer-Tropsch process. This is
a process where a mixture of carbon monoxide and hydrogen are converted into liquid hydrocarbons.
These reactions occur in the presence of metal catalysts and typically at temperatures of
150–300 °C. [17]
This means the company can produce carbon-neutral hydrocarbons, meaning if you were to burn
this fuel in your car, you would release carbon-dioxide pollution out of your exhaust and into the
atmosphere. But because this carbon dioxide came from the air in the first place, these
emissions would not introduce any new carbon dioxide to the atmosphere, and no oil would
need to be extracted from the earth to power your car. And perhaps most importantly for
the economic viability of this idea, they can sell the product, which helps to offset
costs, allowing them to capture even more carbon dioxide, to either convert back into
hydrocarbons or ultimately store.
And backing up their cost estimates of between $94 and $232 per metric ton of carbon dioxide
is the fact that they’ve actually tested the technology in a prototype plant for a
few years in Squamish, British Columbia, which offers a proof of concept that’s way stronger
than simple calculations or computational models. It currently captures and processes
around 1 ton of carbon dioxide per day. [18]
However, for this idea to work on a large scale, the process has to be cost-effective
to implement cheaply around the world, without the massive costs of constructing all-new
factory parts. In the pilot plant, they pulled all this off by designing a factory based
entirely on parts that suppliers could already make cheaply and by keeping careful track
of their emissions and costs at each stage of the design and production process. They
are currently seeking funding for an industrial-scale version of the plant, that will use low-cost
renewable energy, that will produce 200 barrels of synthetic fuel a day, which they hope to
complete by 2021. [19]
But how much carbon can they realistically hope to suck out of the air? In 2017, the
world emitted about 32.5 gigatons of carbon dioxide. If this technology were built at
a scale to suck all that back out of the atmosphere at $93 to $232 per ton, simple math shows
that the total cost would be between about $3 trillion and $7.5 trillion. [20] That seems
like a lot, but many industries are worth more than that, including Apple or the airline
industry. Definitely a tall order, but not impossible.
For this idea to work globally in pulling substantial amounts of carbon dioxide from
the Earth’s air, there would need to be hundreds or thousands of scaled-up plants
producing hundreds of thousands of barrels of carbon-neutral fuel to drive down costs
further, in the same way that solar and wind energy costs have plummeted over the past
decades with increasing scales
However, to keep global warming to less than 2 degrees C, the international target to avoid
the most dangerous impacts, we will need negative emissions, not carbon neutral emissions. We
need carbon to be taken out of the atmosphere and stored permanently, or the problem will
only plateau indefinitely. And if Carbon Engineering is making fuel from their captured carbon,
this is only a carbon-neutral plan.
But the reality of the situation is that when you are only capturing and storing carbon,
there is no market for that. The only way to pay for carbon being captured from the
air and stored, on a large scale, would be government subsidies, and to rely on only
our governments to solve this problem is certainly a mistake. And at $100 per ton at the moment,
there aren’t enough carbon dioxide buyers in the market for any other uses to make a
dent.
Thus, introducing the idea of selling back the carbon as fuel is a way to fund such an
effort. With market demand and money coming in, companies like Carbon Engineering can
improve their technology, expand operations, store some carbon, and work toward making
sure that less oil is extracted from the ground over time.
Critics say that we should simply just not be taking the carbon out of the ground in
the first place, focusing on reducing emissions rather than capture and storage, or capture
and re-use. And some worry that technology like this will allow us to think that we have
no responsibility to reduce emissions. And it is cheaper to not emit a ton of carbon
dioxide in the first place than to capture it. While these are all definitely valid points,
technology like this can and should play a role in how we tackle climate change. It’s
unrealistic to think that every industry, every consumer, and every government in the
world will change their behavior in time to tackle the rising global temperatures, as
much as we wish they would. And technology like this will go a long way to help mitigate
the negative effects of industries where a carbon zero result is next to impossible,
like steel or cement manufacturing, or long-distance air travel.
So this may not be a silver bullet curing the world of climate change, but it is definitely
a technology to be invested in as a tool in the toolbox to help solve the problem. And
with direct air capture able to operate anywhere where there is air, water, and electricity,
every country could in theory, have their own supply of carbon neutral fuel.
In the end, we are not mindless animals who cannot recognise the effect our behaviour
is having on the environment. There are thousands of people working to solve these problems
associated with an ever growing human population, with hundreds of start-ups using technology
for the betterment of humankind. My audience is full of incredibly intelligent people who
are more than capable of contributing to fixing our problems. So, if you think you have what
it takes to improve the world, you have probably thought about starting a company. You may
not know where to start, but this course on Skillshare by a New York venture capital fund
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