Welcome to the second Block of the course.
The underlying question in this block is 'What makes CCS different from
other low-carbon technology options?'
We now briefly review the key messages from Block 1 and introduce what
is coming next in Block 2.
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Carbon Capture and Storage can protect the atmosphere from an excess of emissions of
carbon, and help to avoid dangerous levels of climate change.
It can decarbonise our energy and decarbonise our industries,
where there is no alternative to the use of fossil fuels.
It can also contribute to remove excess carbon already in the atmosphere,
in the likely event that we exceed the carbon budget within our lifetime.
CCS offers a very unique option in the toolbox against climate change
to complement other technologies such as energy efficiency,
renewable energy and nuclear.
So how is CCS different?
And what are its key applications throughout the sectors of the economy?
A Unique Value Proposition
We now look at how Carbon Capture and Storage compares to other low-carbon options to 1)
reduce CO2 emissions, and 2) guarantee that the atmosphere's carbon budget won't be
exceeded. Then, we introduce important sectors of the economy for the applications of CCS:

Manufacturing industries. In particular, two of the most common materials in the modern
world: Concrete and Steel.

The energy supply chain. Notably, two energy vectors that do not contain
carbon: Hydrogen and Electricity.
Erratum: At 2'07 in the video, the rate of use of fossil fuels should be less than 1% per year in the last
column of the table (in line with the audio)
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Carbon Capture and Storage offers a unique proposition complementary to other
measures to prevent 2ºC of global warming.
So let’s compare CCS to other options to achieve deep cut in carbon dioxide
emissions: Energy efficiency, renewable energy and nuclear energy.
Energy efficiency measures allow us to use less energy,
therefore less carbon-containing fossil fuels, and
to keep carbon in the ground as unused fossil fuels.
Renewable and
nuclear energy can replace the use of fossil fuels to produce low carbon energy,
and, like energy efficiency, keep carbon in the ground as unused fossil fuels.
CCS in itself does not produce any energy per se.
Its sole purpose is to avoid climate change.
It can be added to produce low carbon energy from fossil fuels.
But unlike other options,
it also allows low carbon manufacturing in many industries.
And it can also be used to create carbon sinks or carbon negative emissions.
At the very end, the carbon in fossil fuels used with CCS returns to the ground
to stay as carbon dioxide.
It can no longer be used.
These three options are very important options to achieve the first of two steps
of decarbonisation of the global economy: Peak and the reduce global CO2 emissions.
However, once we reach our atmospheric carbon budget,
the question as to whether carbon is actually going to stay in the ground
becomes critical to ensure we stay below that budget.
We have seen previously that it is likely that we will reach our carbon budget
within our lifetime.
If we were to rely only on energy efficiency, renewable and
nuclear, we would not be able to decarbonise many industries and
remove carbon from the atmosphere.
Very importantly,
we would have to guarantee that unused fossil fuels stay in the ground forever,
and we would have to guarantee extremely limited use at the scale of the planet
over thousands of years, at a rate of use well below 1% per year.
This would be extremely difficult to justify on ethical grounds
in poorer countries with limited access to energy, and to enforce globally.
With CCS, what matters instead,
is how long we can keep carbon dioxide geologically stored in the ground.
The challenge shifts to ensuring that we can achieve
permanent storage over thousands of years, and
ensure that well over 90% of the carbon dioxide injected stays underground.
We will see in Block 4 what types and combinations of rocks are prime
candidates, and the physical mechanisms to ensure permanent storage.
So we don’t have to guarantee that the world won’t use fossil fuels, but instead
that fossil fuels are used with CCS, and that the CO2 is permanently stored.
It is a very different proposition.
We have previously touched on the versatility of CCS.
Two of the most important low carbon energy vectors are one: electricity and
two: hydrogen.
They can both be produced with CCS to decarbonise how we heat our homes and
our industrial processes, and our modes of transportation,
cars, airplanes, heavy trucks, in different ways.
We can use electricity to heat and cook in our homes, with electric heating,
domestic heat pumps powered by electricity, and electric cookers.
We could use hydrogen to heat and cook in our homes,
to replace natural gas, oil or coal-based solid fuels.
We could also use hydrogen to power vehicles using a technology called
hydrogen fuel cells.
And, finally, we can decarbonise many industrial sectors,
such as iron and steel, cement, chemicals, paper,
where there is no alternative to the use of fossil fuels.
This makes CCS unique, and creates a pathway towards a neutral balance of
carbon, which cannot be achieved with a combination of energy efficiency and
other forms of low carbon energy alone.
But this will only be possible if CCS becomes a routine technology added to any
process using fossil fuels.
The Different Classes of CCS
CCS facilities can be classified into three types. They differ based on the fate of the carbon that
leaves their boundaries.
We will discuss what they are, and we will look at the evolution of the perception of pollution cleanup technologies.
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CCS technologies are very versatile and
can be utilised in many applications across all sectors of the economy.
Yet, it is important to distinguish between the different types of CCS
applications.
There are 3 classes of applications of CCS facilities: Carbon
negative CCS facilities, Carbon neutral or
near carbon neutral CCS facilities, and Carbon positive CCS facilities.
Carbon negative CCS facilities includes BECCS, Biomass Energy with CCS,
and technologies to process air directly to capture CO2, Direct Air Capture,
which we have discussed in Block 1.
Near carbon neutral CCS consists of producing carbon free energy vectors:
Electricity, hydrogen, or heat from natural gas, oil and coal.
They are near carbon neutral, as opposed to 100% carbon neutral,
due to emissions to the atmosphere during the extraction of primary energy and
its conversion to energy vectors.
For example, the extraction of fossil fuels can
result in emissions of greenhouse gases to the atmosphere,
for example, leakage of methane during the extraction of natural gas, if unmitigated.
The conversion to carbon-free energy vectors results in emissions too.
CCS facilities are typically designed, at present,
to capture 80 to 95% of carbon dioxide emissions.
So 5 to 20% of carbon dioxide leaves these CCS facilities and enters the atmosphere.
Yet, this is in no way a flaw of the technology.
CCS facilities can be engineered today to achieve close to 100% CO2 capture.
We choose not to do so to reduce costs, and
because there is no incentive to do so.
When our climate change policies shift to achieve net zero carbon emissions,
they could achieve close to zero residual emissions.
An example of near carbon neutral CCS is the production of electricity from
natural gas with CCS.
It is also possible to combine a fraction of biomass with fossils fuels to
move from near to fully carbon neutral CCS.
Carbon positive CCS consists of facilities producing processed fuels,
such as liquefied natural gas, coal-to-liquid fuels, or oil sands,
where CCS reduces the carbon footprint of the energy vector.
The carbon contained in the fuel eventually enters the atmosphere when it
is converted to useful energy without the use of CCS.
This is the case in industrial facilities converting coal to liquid transportation
fuels, for example in South Africa or China, two countries with access to large
reserves of coal, which they use to produce transportation fuels.
The carbon footprint of these fuels is several
times higher than the footprint of conventional fuels from oil.
In practice, these industrial facilities, also called coal-to-liquid plants,
routinely emit large quantities of nearly pure carbon dioxide to the atmosphere.
Adding CCS there would greatly reduce their emissions, except for
the carbon remaining in the fuel.
This is why they classify as carbon positive CCS facilities.
The interactive tutorial immediately after this video will help you to recognise
the difference classes of CCS projects.
All three types of projects are currently in operation worldwide.
So CCS has already made extensive progress.
Yet, much more remains to be done to ensure that the full potential of CCS
is truly recognised within the energy industry, within governments,
with politicians and more widely the public.
The confidence in environmental technologies changes with time as
the stakeholders become more aware of their principles.
The evolutionary stages of pollution clean-up technologies typically consist of
four stages.
A first stage where the technology is rejected.
It is considered infeasible, classified as "science fiction".
The second stage consists of the first stage of acceptance of the technology.
It then becomes about costs.
"This technology is impossible expensive and complex".
The third stage is to recognise,
that the "technology is a major investment but necessary".
The perception usually shifts when the consequences of the pollution
that the technology addresses become mainstream.
And finally, the fourth and final stage then becomes "This
technology is now just a routine part of any process".
Throughout time, pollution clean-up technologies now considered routine,
such as catalytic converters to address emissions from the exhaust of cars, or
sulphur removal to address acid rains caused by the pollution of coal-fired
electricity production, have gone through these 4 stages.
Eventually CCS will become, too, a normal iteration of fossil fuel power plants and
industrial processes and manufacturing.
So at what stage do you think CCS is?
I invite you to share your views in the forum,
immediately after the interactive tutorial.
There is no right or wrong answer to that question, so please discuss and
share your views.
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An Illustrative Example: Acid Rain and Flue Gas Desulphurisation
The Evolution of Other Pollution Clean-Up Technologies: The Example of Acid Rains
Because winds can blow the pollutants causing acid rain over long distances and across borders, it
became an important issue in the 1970s and 1980s, not just for those living close to the sources of
emissions.
This problem is now on the mend, thanks, in particular, to the development
of desulphurisation technologies, now routinely installed in coal-fired power stations. These
technologies capture sulphur dioxide at the source and prevent it from entering the atmosphere.
Yet the uptake of the technology took two to three decades. It followed the four stages of
environmental technology development explained in the video. Once the third stage - 'it is a major
investment but necessary' - had been reached, desulphurisation became a very successful example
of cost reduction. For example, the costs of desulphurisation reported at the end of the 1990s
were five to ten times lower than initially anticipated. These costs have continued to decline since.
Image: Acid rain diagram, by Siyavula Education, CC BY 2.0, via Flickr
Tutorial - Part 1
All three classes of CCS facilities are in operation today. Yet they do not offer the same benefits in
terms of their contribution to tackling excess CO2 in the atmosphere.
The interactive tutorial below will help you understand these concepts further.
Carbon Positive CCS
An example of a carbon positive CCS facility is the Quest CCS facility near Edmonton, Alberta in
Canada. The refinery transforms oil sands, a type of unconventional petroleum deposit, into more
refined, useful products such as petrol or gasoline. During the process, CO2 is produced and, instead
of being vented to the atmosphere, is captured and geologically stored away from the atmosphere.
Yet, a large fraction of the carbon from the oil sands leaves the refinery contained in the final
petroleum products and therefore enters the global energy system, currently resulting in CO2
emissions to the atmosphere. This type of CCS facility avoids emissions, but the balance of carbon
into the atmosphere remains positive. They remain incompatible with climate change goals in the
long run, unless the energy vectors they produce - for example, carbon containing fuels - are
subsequently converted to useful energy, also with CCS.
Interactive Exercises
To complete the next four interactive exercises, you need to select the elements representing the
input and output of each class of CCS facility, and then move them to their correct position on one of
the grey arrows.
Fossil Fuel and Biomass are represented in brown, Air and 'CO2 in the Atmosphere' are shown in
light blue. CO2 sent to geological storage is shown in purple. Energy Vectors containing carbon, e.g.
gasoline or bio-ethanol, are shown in Orange. Carbon-free Energy Vectors, e.g. electricity, are shown
in yellow.
To finish, you need to click on the blue rectangle 'check' at the bottom on the left-hand side.
Tutorial - Part 2
Near Carbon Neutral CCS
An example of a Near Carbon Neutral CCS facility is the Boundary Dam CCS facility, in the state of
Saskatchewan, also in Canada. It is the very first power station with CCS and started operation in
2014. It uses coal to produce electricity, a carbon-free energy vector. 90% of the CO2 it produces is
captured and sent to geological storage, whilst the residual 10% enters the atmosphere. Overall,
additions of carbon to the atmosphere are greatly reduced and the conversion of the energy vector electricity - into useful energy does not result in any further emissions of CO2 to the atmosphere.
This type of CCS facility is extremely important for achieving climate change goals in the long run.
Tutorial - Part 3
Carbon Negative CCS
Overall, these facilities result in a negative balance of emissions to the atmosphere. The Decatur CCS
facility, in the state of Illinois in the USA, is an example currently in operation. The bio-refinery
converts biomass into ethanol, a chemical that can be blended with petrol/gasoline and used in
motor vehicles.
There are three parts to the carbon balance:

First, CO2 in the atmosphere is transformed into biomass when plants grow.

Second, a fraction of the carbon of the biomass ends up in ethanol. That carbon (of biogenic
origin) eventually enters the global energy system and subsequently the atmosphere as CO2.

Third, the remaining fraction of carbon is transformed into a pure stream of CO2 during the
conversion of biomass into ethanol in the bio-refinery. That CO2 is captured and sent away
to geological storage. It is that fraction of carbon, which is removed from the atmosphere
and makes the carbon balance to be negative.
It is also possible to use biomass to produce electricity, which is a carbon-free energy vector, unlike
ethanol. The second part of the carbon balance is then zero. In both cases (biofuels and electricity),
the more useful energy goes to the end-user, the more carbon has been removed from the
atmosphere.
The other form of Carbon Negative CCS is Direct Air Capture. A proposition is being tested at pilot
scale near Hvergerdi in Iceland, but Direct Air Capture does not exist at an industrial scale yet
(update: the pilot-scale DAC plant was replaced by Orca in Sep 2021, information can be found in
Block 1 here). Air passes through the CCS facility and then leaves containing less CO2. The CO2 that
has been removed from the air is sent to geological storage. For the overall balance of emissions to
be negative, it is important that any energy input into the facility, being electricity or heat, is carbonfree. Likewise, if fossil fuels are used as part of the process, all of the resulting CO2 must be captured
and sent to geological storage.
The Cement Industry
Concrete is everywhere in the modern world. And we keep making more of it. Concrete is made by
mixing water, sand or stones and, very importantly, cement. We now discuss the use of Carbon
Capture and Storage in the production of cement.
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Cement is a very common product.
It is one of the foundations of the infrastructures of modern civilisation.
Portland Cement, the generic name,
was invented in the 19th century in the United Kingdom.
It is the basic ingredient of concrete.
A glue used to create a paste with water, which allows sand, gravel,
and/or crushed stone to bind together and to harden to form concrete.
And concrete is everywhere, highways, bridges, buildings of all sorts and sizes.
Over 4 billions tonnes of cement are manufactured every year worldwide.
That is roughly half a tonne for every person on the planet.
It currently has a huge carbon footprint.
For each tonne of cement produced, 800 kilograms of carbon dioxide are emitted.
Cement production represents a fifth of the average emissions of every person on
the planet.
Cement is manufactured through a closely controlled combination of chemical
elements such as calcium, silicon, aluminium, iron and other ingredients.
The most common materials used to manufacture cement are limestone,
a hard rock, and clay, a finely-grained rock.
They are combined with other minerals, which requires heat at very high
temperatures – up to 1400ºC – for the chemical reactions to occur.
At the end of the process a new rock-like mineral is formed.
It is then ground into the fine powder that we commonly think of as cement.
The cement kiln is where a large amount of heat is needed and
carbon dioxide emissions occur.
It consists of a huge steel cylinder lined with special fire-brick.
Kilns can be as big as 3 metres in diameter and 15 to 60 metres in length.
They rotate on an axis slightly inclined from the horizontal.
The finely ground raw material is fed into the higher end.
At the lower end is a roaring blast of flame,
produced by precisely controlled burning of powdered coal, oil, or natural gas.
That is fossil fuels containing carbon.
CO2 emissions from cement production are reported to account for
5 to 7%, and even up to roughly 8% of global emissions in 2015.
Half of that, so
up to 4% of global emissions, comes from the use of fossil fuels in the rotary
kilns to create direct exposure of the raw material to that roaring flame.
There is no alternative to using a fuel to create that flame.
The other half comes from the nature of the very core material used to make
cement: Limestone.
It consists primarily of calcium carbonate.
At a temperature around 1100ºC in the kiln,
calcium carbonate decomposes into calcium oxide and carbon dioxide.
The calcium oxide further reacts to eventually form the final product of
cement, and the carbon dioxide, initially trapped in the rock, is
released within the flame and then leaves the process to return to the atmosphere.
There is no alternative to using limestone there either, and
the associated release of carbon dioxide is inevitable.
The use of blended cement is increasing, where waste from other industries such as
fly ash from coal-fired power plants, or s.lag from steel making, reduces
the quantities of limestone required, and contributes to reduce CO2 emissions.
Alternatives to Portland cement, with a lower carbon footprint,
are just about to start to enter the marketplace,
but currently only represent a very small fraction of total production.
They will eventually contribute to help to reduce CO2 emissions too.
But both options do not achieve the deep cuts
in emissions necessary to reach net zero carbon emissions globally.
They may not prove to be able to deal with the emissions of existing
Portland cement facilities.
For example, the International Energy Agency estimates,
that the lowest cost pathway to meet 2ºC of global temperature increase would
include CCS on 20 to 30% of cement production facilities worldwide in 2050.
And the carbon neutral balance of the Paris Climate Change Agreement will
require that most facilities are fitted with CCS beyond 2050.
In the end, there is no alternative to Carbon Capture and
Storage in the cement industry.
The video explains that half of the emissions of the cement industry originate from the use of
limestone, a commonly found type of rock. Limestone contains over 50% of Calcium Carbonate
(CaCO3), which decomposes at high temperature in the cement kiln into Calcium Oxide (CaO) and
Carbon Dioxide (CO2). These molecules of carbon dioxide, which do not come from fossil fuels,
currently account for 3 to 4% of global emissions and cannot be eliminated.
The cement industry is developing carbon capture technologies, yet there is no commercial scale
facility currently in operation. Using the global map of CCS, identify one of the largest research and
development activities in that industry at the Norcem Brevik facility in Norway. Click on the blue flag
located near Oslo, in the South of Norway (in Northern Europe).
The Steel Industry
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Like the cement industry,
the steel industry is a key sector of the global economy.
It is the largest energy consuming manufacturing sector in the world and
provides another fundamental material to modern civilisation.
Steel is everywhere and in almost everything we do, in our buildings, our
vehicles or in large industrial equipment, such as power stations and ships.
It is also part of our everyday life: in modern appliances,
electronics, toys, tools, etc.
So global steel production currently amounts to around 1.5 billion tonnes
per year, that is equivalent to around 200kg of steel per person per year.
It is mostly used for the construction of new large scale infrastructures.
Every tonne of steel generates 1.5 to 3 tonnes of carbon dioxide,
depending on in which country it is produced.
That carbon dioxide is currently emitted to the atmosphere in steel making,
resulting in emissions equivalent to 300 to 600 kilograms per person per year.
This represents between one sixth and
one third of the average emission of every person across the planet.
The total emissions from steel production are projected to grow by
2050 by at least a third, once the current pledges by governments
in the Paris Climate Change agreement are taken into account.
Steel is effectively an alloy of predominantly iron, and
a few precent of carbon.
We will focus on the method of production associated with 60% of world's steel
production and therefore most of the carbon dioxide emissions of the sector.
Over two thirds of the emissions take place in the first stage of the overall
process, for the production of nearly pure raw iron metal in a liquid form.
This raw liquid metal is then further purified in a second stage to make crude
steel, which can then be customised to become the final
steel product we are accustomed to and meet specific properties, for
example strength, hardness, or corrosion resistance.
Iron metal is extracted from iron ore,
a type of rock containing minerals with iron.
Iron ore is commonly found in rocks formed in marine and
fresh waters millions years ago.
The two most important minerals in this rock are two types of iron oxides,
where metal iron has chemically reacted with oxygen.
This chemical reaction needs to be reversed at high temperature to obtain
nearly pure iron metal, and
is associated with the majority of carbon dioxide emissions in steel making.
This involves reacting iron ore with a specific form of coal,
coking coal, in a blast furnace and produces large volumes of CO2.
You may have seen these images of giant, red-hot cauldrons,
fed by coal, belching flame and smoke.
Blast furnaces are huge, steel stacks, lined with brick, where iron ore,
pulverised coking coal and powder limestone are dumped into the top, and
preheated air is blown, or blasted, into the bottom.
The purpose of a blast furnace is to reverse the chemical reaction and
physically convert the iron oxides, containing iron ore,
into nearly pure liquid iron.
Coking coal is used exclusively for steel production.
It is an almost pure form of carbon,
made after coal has been cleaned of its impurities and dried.
Pure carbon plays several important roles in the blast furnace.
It acts as a source of heat to take the temperature in sections of the blast
furnace over 2000ºC, and
a controlled fraction of it ends up in the steel to make the alloy.
Importantly, it specifically acts as the agent to take away
the atoms of oxygen from iron oxides and then purify iron.
This final role is the oxidisation of carbon,
which eventually results in the production of carbon dioxide.
So carbon is an essential ingredient of the blast furnace,
for which there is no alternative.
That is why there is no alternative to using fossil fuels in that
industry either.
Many improvements have been made in the iron and
steel sector to increase efficiency and reduce emissions.
The recycling of scrap metal avoids the need for
the iron making process and avoids around three quarters of the emissions.
The steel industry will continue to reduce its emissions through that route.
However, the ongoing demand for steel will remain high, so
the processing of iron ore will continue for many more decades to come.
This industry is one of the biggest emitters of carbon dioxide,
accounting for close to 7% of global emissions.
Reductions in emissions greater than 80% are required in the sector, to meet
global emission reductions consistent with 2ºC of temperature increase and
then achieve a neutral carbon balance.
Like the cement industry,
it is clear that there is no alternative to Carbon Capture and Storage either.
And the unavoidable, residual emissions of existing blast furnaces
with CCS are predicted to remain as high as 40%.
New low carbon production technologies may be developed, but emissions of existing
blast furnaces will have to be compensated for, perhaps with the use of biomass
instead of coal in the future, with the prospect of negative emissions with CCS.
So what is happening in CCS for the iron and steel sector?
Please have a look at the information provided next,
to find out about the very first CCS project in the steel sector.
The video explains that coking coal, a nearly pure form of carbon, and one of the essential
ingredients in steelmaking cannot be replaced. Coking coal takes away the atoms of oxygen in iron
ore (Fe3O4 or Fe2O3), the raw material of steelmaking, to transform it into purified iron (Fe). This
makes the use of CCS in that industry unavoidable to achieve deep cuts in CO2 emissions.
We will use again the global map of CCS to find out about the first large-scale commercial facility in
the Steel industry.
Click on the map and identify the Al Reyadah facility in the United Arab Emirates, in the Middle East,
by clicking on the green flag.
Commercial CCS Facilities
Many other industries rely on carbon as an essential ingredient of their process, or as an essential
building block of their final product. There is no alternative to CCS in these industries to achieve
significant cuts in CO2 emissions.
Chemicals
The production of chemicals is expected to continue to use fossil fuels as the building block of, for
example, fertilisers. The market for fertilisers is large and global, as they are essential to agriculture
practices in many countries. The production of fertilisers results in a high purity, high concentration
stream of CO2 as an off-gas. This CO2 off-gas, an unwanted by-product of the main process, can be
easily captured, as is the case at the Koch Nitrogen Company facility in Enid in the state of Oklahoma
in the USA.
Now, please use the global map of CCS below to locate the green flag in Oklahoma in the USA.
Hydrogen
We will discuss next the key role that hydrogen can play as a carbon free energy vector. Most of the
hydrogen produced today is used in oil refining and the chemical industries. In oil refining, it is used
to upgrade heavy oils into lighter petroleum products, which are widely used (without CCS for the
time being) across the economy. Hydrogen production is another process using fuels as a building
block and releasing a nearly pure stream of CO2.
Natural Gas Processing
Most of the CCS facilities in operation today are effectively used for the same application. It consists
of processing large quantities of natural gas and separating them from carbon dioxide. Certain types
of geological reservoirs of hydrocarbons contain both large quantities of natural gas and carbon
dioxide. The gases are separated immediately after extraction so that the natural gas can be
transported away.
Using the global map of CCS again, find and click on the green flag of the Sleipner facility. It is located
in the North Sea, off the coast of Norway, in Northern Europe. Sleipner was the first CCS facility in
Europe and the first to be located offshore.
List of Existing CCS Facilities
Here is the list of all the CCS facilities in operation worldwide, using information provided by
the Global CCS Institute. It is up to date as of September 2021. It shows the name and the location of
CCS facilities in operation, the annual volumes of CO2 they prevent from entering the atmosphere,
and when they started operation. The column on the right-hand side indicates the type of
applications or industries.
Get familiar with the type of industries that have CCS facilities in operation and the year they started
operation.
Sankey Diagrams
Sankey Diagrams
Energy systems rely on energy in three different forms, with two intermediate conversion steps.
Primary energy is converted to energy vectors. These energy vectors are then converted into useful
energy to provide an energy-based service to an end-user.
The flow of global energy, from primary energy to the billions of services to the end-user, results in
emissions of carbon dioxide into the atmosphere. To understand how we can decarbonise our
energy system, it is important to understand at which point in the cycle carbon dioxide is produced,
and how much is produced. To do so, we use what is called a ‘Sankey Diagram’.
A Sankey diagram is a typical flow diagram where the width of each line is proportional to the flow
quantity.
Let us look at an example, which reads from left to right. This is a Sankey diagram for the energy
flow across a filament lamp. 100 units of electrical energy enter the filament lamp, as shown on the
left-hand side. 10 units leave the filament lamp as light energy and 90 units are converted to and
leave as wasted heat energy.
Let’s look at a second example, where three friends each contribute €500 to a kitty for their holiday.
A kitty is a fund of money for communal use. This Sankey diagram shows the flow of money from
their individual contribution of €500 to their kitty of €1500, to the five categories of their final
expenses: airfare, accommodation, food, ground transportation and fun activities.
Sankey diagrams help us put a visual emphasis on the major transfers or flows within a
system and are helpful in locating dominant contributions to an overall flow.
The Flow of CO2 in Global Energy System
Let’s have a look at the Sankey Diagram of the flow of CO2 emissions throughout
the global energy system, based on data from the International Energy Agency.
Gigatonnes of CO2 contained in coal in red, natural gas in blue and
crude oil in yellow are shown on the left hand side.
On the right hand side, we have the emissions of CO2 to the atmosphere.
Note that the diagram focuses on energy and does not include a quarter
of global greenhouse gas emissions from agriculture, forestry and land use, and
it does not account for process emissions from industries,
such as the CO2 released from limestone in cement manufacturing.
Currently, the fossil fuels on the left hand side are converted into two type of
energy vectors: electricity, in the dark green node 'power generation',
and processed fuels, in the dark green node 'fuel transformation'.
CO2 emissions flow directly into these two nodes,
proportionally to the carbon content and the quantity of each fossil fuel used.
CO2 emissions eventually flow into four end-use sectors in light green,
namely industry, buildings, transport and other end use.
On the right hand side, emissions are collected as either direct emissions,
or indirect emissions.
So what does this mean?
Let’s have a look at direct emissions.
Processed fuels, such as the petrol to fuel our cars, contain carbon.
They are high carbon energy vectors.
When they are converted into useful energy by the end user,
it results in the emissions of CO2 to the atmosphere,
when you drive that car using petrol to fuel the engine.
The CO2 in these fuel-based energy vectors flows through the system and
is collected on the right hand side in black.
These downstream direct emissions
represents over half of the total emissions in the global energy system.
On the other hand, electricity is a carbon-free energy vector.
When it is used by the end user,
it does not result in the emission of CO2 to the atmosphere,
for example when you switch on a lamp or a computer in your home.
In the Sankey diagram, when electricity is used in buildings or
in industry, or when fossil fuels are converted to processed fuels,
the CO2 emissions associated with the production step of the energy vector,
upstream of the end user, flow into that sector.
These emissions are shown in grey as they flow through the Sankey diagram and
add up as the indirect emissions shown on the right hand side.
They account for
just under half of the total emissions in the global energy system.
The Sankey diagram also shows, that a fraction of the CO2 emissions
of mostly coal, but also natural gas, flows directly into the industry sector.
This could be pulverised coal used as fuel in steelworks.
Likewise, a fraction of the emissions of natural gas
flows directly into the buildings sector, for example in domestic gas boilers for
domestic heating, which are very common here in the UK.
We can reduce the amount of carbon dioxide emitted to the atmosphere by making
the energy system less carbon intensive, either by reducing the amount of fossil
fuels used to deliver the same quantity of energy vectors, and/or by reducing
the quantity of energy vectors to produce energy services into the end sectors.
That is energy efficiency.
It would reduce both upstream indirect and downstream direct CO2 emissions by
reducing the width of the lines on the diagram, but
it would not lead to close to zero emissions.
We can reduce upstream emissions in power generation in two further
ways: With nuclear and renewable electricity,
by reducing the flow of CO2 entering the power generation node, and
the upstream indirect emissions out to the four end sectors.
And with CCS, by diverting the flow of CO2, exiting the power generation node,
as indirect emissions into a new node for permanent geological storage.
We also need CCS to remove the direct emissions from industry and
collect them in the same new node corresponding to geological storage.
But the right hand side of the diagram shows well,
that this would only tackle half of the problem, and
that a different approach is needed to tackle downstream direct emissions.
We also need to eliminate the flow of CO2 into our buildings and
the transport sector, which result in a multitude of small and
dispersed sources of direct emissions, such as the exhaust of cars, and
the exhaust of boilers for domestic heating.
To do so is only possible if we can replace fossil fuels and
processed fuels by carbon-free energy vectors.
Let’s look at electricity.
That is one carbon-free energy vector that we use widely already.
We can electrify the way we heat our homes with devices called heat pumps,
by transferring heat from the air or
the ground into our home with the use of electricity.
It is, put in a simple way, a fridge in reverse.
We can electrify transport with electric vehicles to replace our
combustion-based cars.
Another carbon-free energy vector, with an important role to play, is hydrogen.
Hydrogen is a processed fuel made currently from fossil
fuels with CO2 emissions to the atmosphere,
although it could also be made using electricity and water.
Because hydrogen does not contain any carbon, its combustion is CO2-free.
It is another energy vector without downstream direct emissions at the point
of use.
We can use hydrogen in our homes in domestic boilers, and we can use hydrogen
for all sorts of vehicles using a technology called fuel cells.
Fuel cells can be embedded into vehicles to produce electricity using the chemical
reaction of hydrogen with air, without actually combusting the hydrogen.
Hydrogen is particularly suited for heavy vehicles, such as trucks,
as it offers a wider range than electric batteries.
Like electricity, the production of hydrogen, that is the conversion of
primary energy to that specific energy vector, needs to be low-carbon too.
Otherwise this would be simply transferring downstream direct emissions
to upstream indirect emissions.
I now invite you to have a look at the Sankey Diagrams we have prepared for you.
They show examples to decarbonise the global energy system.
To reach carbon neutrality, CO2 emissions in the global energy system must go down to zero. This
can only be achieved if we tackle direct emissions of end-use sectors, direct emissions from
industries, and the indirect emissions originating from the production of energy vectors.
We look next at four examples of options to reduce CO2 emissions in the global energy system and
examine the associated Sankey diagrams

Power Generation - energy efficiency and low-carbon electricity from renewables and
nuclear

The increased use of electricity and hydrogen in Transport and Buildings,

Hydrogen produced with CCS, as a fuel for 'Transport',

CCS in the 'Industry' and 'Power Generation' sector.
Before you move to the next section, please note that you can come back here to visualise the
Sankey diagram of the global flow of CO2 through the energy system (as of 2012 using data from the
International Energy Agency).
Efficiency and Renewables
Different Decarbonisation Strategies through Sankey Diagrams
Efficiency and Renewables
It is possible to reduce CO2 emissions from electricity in the global energy system with:

Renewable energy technologies, such as wind or solar power, and nuclear energy

Energy efficiency
The Sankey diagram below shows an illustration of how the flow of CO2 through the global energy
system might change.
With an increase in electricity production from low carbon energy (renewables and nuclear), there is
a direct reduction in the amount of fossil fuels burned in the node 'power generation' for producing
the same amount of electricity and delivering the same service to the end-user. This reduces the
flow of CO2 entering the system on the left-hand side, and is shown with the purple bar representing
the CO2 emissions of the unused fossil fuels. The flow of energy (not shown) actually remains the
same.
By increasing end-use efficiency, electricity users can realise the same electricity consuming
activities (i.e. lighting, watching TV, producing goods) by using less electricity. This reduces the size
of the 'power generation' node and has the indirect effect of reducing the amount of CO2 entering
the global energy system by leaving fossil fuels unused. Likewise, increasing the efficiency of the
conversion of fossil fuels into electricity has the same effect, and the flow of CO2 entering on the
left-hand side is indirectly reduced too. The emissions of the unused fossil fuels accumulate in the
purple bar on the left-hand side, and the flow of energy (not shown) is here reduced.
Overall, both energy efficiency and low-carbon electricity (renewables and nuclear) can reduce
indirect emissions significantly in the 'power generation' node, but they do not significantly reduce
the node 'Direct Emissions' on the right-hand side.
Decreasing carbon emissions in the electricity sector alone will not lead to the carbon reductions
necessary to achieve carbon neutrality.
Electrification and Hydrogen
Level 2 headings may be created by course providers in the future.
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Electrification and Hydrogen
Significantly increasing the use of electricity and hydrogen as energy vectors would modify the flow
of CO2 through the global energy system.
One example of changes to the end-user is electric vehicles, which could replace conventional
engines in the transport sector. Another example is the use of electric radiators and heat pumps in
homes and offices, in the buildings sector. Heat pumps are effectively refrigerators in reverse, well
suited for the temperature range of our homes. They use electricity to take heat from colder
ambient air or a local water source and return it at a higher temperature into the water of radiators.
The use of hydrogen by the end-user may involve domestic cars powered via a technology called fuel
cells. These cars have recently started entering the market. Hydrogen fuel cells also power local
networks of buses and are highly suitable for heavy goods trucks. In this block, we will look at how
hydrogen can be used in cities for cooking and heating homes.
The Sankey diagram below illustrates changes to CO2 flows in the four end-use sectors: Industry,
Buildings, Transport, Other End-use. It shows a possible pattern of emissions if strong efforts to
increase the use of electricity and hydrogen were deployed. Using carbon-free energy vectors allows
for the considerable reduction of direct emissions caused by the end-user, as illustrated by the much
smaller size of the bar in dark grey on the right-hand side.
Yet, the flow of CO2 would shift from direct to indirect emissions, if no other measures are taken.
The emissions would occur instead in the 'Fuel transformation' and 'Power Generation' nodes. This is
shown on the diagram by the larger side of the pale grey flows, which travel through 'Transport' and
'Buildings' to accumulate in 'Indirect Emissions' on the right-hand side.
So, by simply shifting where emissions take place in the global energy system, the sum of indirect
and direct emissions on the right-hand side does not reduce.
In fact, total emissions would slightly increase. This is partly due to the fact that the transformation
of mostly crude oil and natural gas into hydrogen requires an additional energy step, which has
associated additional CO2 emissions. The other reason would be the electrification of heating since
electric radiators (unlike heat pumps) require considerably more energy than the combustion of
fossil fuels in the boilers or central heating of buildings. This would potentially lead to additional CO2
from fossil fuels entering the global energy system.
For electricity and hydrogen to contribute to reducing 'Indirect Emissions', additional steps to tackle
CO2 emissions in the 'Power Generation' node and the 'Fuel Transformation' node are therefore
necessary.
We shall next discuss the pattern of emissions when CCS is added to the global energy system.
Hydrogen with CCS
Hydrogen with CCS
'Direct Emissions' can be addressed by adding CCS to the production of Hydrogen, creating a carbonfree energy vector.
For the purpose of keeping the Sankey diagram easy to visualise, the use of Hydrogen only replaces a
fraction of fuels made from Crude Oil in the 'Transport' node. Hydrogen also has the potential to be
used as a carbon-free energy vector in 'Buildings', as previously discussed, and in the 'Industry' node,
but this is not shown here, for simplicity.
The Sankey diagram below includes a new node 'Geological Storage' in pink, as CO2 generated when
producing hydrogen from fossil fuels is captured, transported and permanently stored in geological
formations with CCS. The flow of CO2 stays within the global energy system, but is instead prevented
from entering the atmosphere.
This creates a carbon-free energy vector that reduces the 'Direct Emissions' passing through the
'Transport' node. The Sankey diagram also illustrates that Hydrogen is mostly produced from
Natural Gas, and would replace fuels made from Crude Oil. The flow of CO2 going to 'Fuel
Transformation' from Natural Gas in blue increases, and the flow of CO2 from Crude Oil gets smaller.
The Sankey diagram also shows 'Indirect Emissions' going from 'Fuel Transformation' to 'Transport'.
This is caused by the residual emissions of CCS in the production of hydrogen, which accounts here
for 10% of the total flow of CO2. In this example, Hydrogen produced with CCS significantly
decreases 'Direct Emissions' and slightly increases 'Indirect Emissions' in the 'Transport' sector'.
To achieve carbon neutrality of the global energy system, the use of Hydrogen made with CCS would
need to gradually increase to replace all transportation fuels made from Crude Oil. Residual
emissions from CCS facilities, associated with Indirect Emissions, would need to be brought down
close to zero, with the right incentive to do so.
CCS in Heavy Industries and Electricity
CCS in Heavy Industries and Electricity
Finally, using CCS in heavy industries and for electricity production, would change considerably the
flow pattern of CO2 through the global energy system.
Like the previous diagram, there is another additional node 'Geological Storage' in pink. CO2 is
collected with CCS from the nodes 'Industry' and 'Power Generation', and prevented from entering
the atmosphere.
In this scenario, CCS is applied to most large scale emitters. Utilising CCS in the power generation
sector and in industries takes away most of the direct and indirect emissions from these sources. We
assume here a small amount of residual emissions, which could possibly be brought down to zero, if
the fraction of CO2 captured were to increase.
Overall, CCS has the effect of dramatically reducing the flow of CO2 associated with the 'Indirect
Emissions' of 'Power Generation', which would otherwise pass through the nodes 'Industry' and
'Buildings' to accumulate on the right-hand side. CCS also achieves deep cuts in 'Direct Emissions'
from the 'Industry' node.
Net Zero Carbon in the Global Energy System
CCS has the potential to decarbonise two of the largest contributing sectors to CO2 emissions in the
global energy system.
To achieve net zero carbon emissions in the global energy system and tackle both Direct Emissions
and Indirect Emissions

CCS in 'Industry' and 'Power Generation' must be combined with efforts to reduce the
overall CO2 input with energy efficiency and renewable and nuclear electricity production.

Indirect emissions occurring in the 'Transport' and 'Buildings' must be tackled with the
extensive use of Electricity and Hydrogen, both carbon-free energy vectors. These two
vectors can be produced with a combination of renewable energy, nuclear energy and CCS.
Hydrogen: A Carbon Free Energy Vector
Level 2 headings may be created by course providers in the future.
We now look at how 95% of the world's Hydrogen is produced and how it inevitably results in the
production of CO2, making CCS unavoidable in that industry.
Start of transcript. Skip to the end.
Hydrogen (H2) is a convincing pathway to decarbonisation of the global
energy system.
It is a flexible energy vector, to replace process fuels and
address direct CO2 emissions from the energy end-user.
It is very similar to electricity in certain aspects: It requires production
and is clean at the point of use.
But unlike electricity, it can easily be stored at a range of volumes over weeks,
separating production from time of use, like with any other process fuels.
Hydrogen is not a new chemical though.
Global production is currently around 45 million tonnes per year, for
use in oil refining and chemical industries, such as fertilisers.
So let us try to make sense of that number.
It would provide about 4 times the total energy demand for heat in the UK,
a country with just under 1% of the global population.
So global production is already big, but it would need to get bigger,
by say 10 to 20 times to contribute to decarbonising the global energy system.
This is challenging, but certainly feasible across a 20 to 30 year horizon.
Yet, H2 is not new in the energy system.
Across the 19th century and a large part of the 20th century,
town gas was the dominant energy vector of the Industrial Revolution.
It was piped to many homes, industry and for street lighting.
It is still currently used at large scale in certain parts of the world, and
by millions of people.
Hong Kong, for example, uses town gas at an extensive scale.
Consisting of 50% H2 by volume, 25% by energy content and
is produced from fossil fuels.
In order to decarbonise heat in buildings and transport,
a long term strategic plan is needed to deliver zero carbon hydrogen.
The main concerns for a large scale use are currently: Costs and
the deliverability of a decarbonised production method.
Natural gas is used to produce over 95% of hydrogen today, and
is expected to continue to dominate production.
Hydrogen made from natural gas is currently cheaper than the alternatives,
for example using electricity to split water into hydrogen and oxygen,
a process called electrolysis, although cost reductions are expected for
both methods as production increases.
But producing hydrogen from natural gas, or any other fossil fuels, and
using hydrogen as the energy vector, increases the overall production of CO2,
so CCS will therefore be essential to enable large scale use of hydrogen.
Likewise, the availability of zero carbon electricity is critical for
electrolysis methods using electricity.
To make hydrogen a zero carbon vector, volatile emissions of natural gas to
the atmosphere during extraction and transport will need to be addressed.
And so will the residual emissions from its production from natural gas with CCS,
by increasing capture levels as close as possible to 100%.
Let’s take a look at how 95% of hydrogen is produced today.
We will go through some basic chemistry to do so.
If you have never done any chemistry, or you can’t simply remember it,
the main message is that carbon dioxide is inevitably produced.
It then needs to be separated from the hydrogen and
prevented from entering the atmosphere using CCS.
So the dominant method for producing hydrogen from fuels,
such as natural gas, is called Steam Methane Reforming.
It takes place in a large pressurised vessel, called a reformer,
where steam is used to produce hydrogen from methane, which accounts for
95% of natural gas by volume.
So let’s take a look at the chemical reaction.
Methane is a gas composed of one atom of carbon attached to four
atoms of hydrogen, CH4.
It is this atom of carbon,
which eventually results in the production of CO2.
Steam, shown here as a molecule of water, H2O,
is injected at high temperature from 700ºC to 1000ºC.
The chemical reaction takes place and both methane and steam recomposes as
carbon monoxide, consisting of a molecule with an atom of carbon,C, and
an atom of oxygen, O, and hydrogen in its gaseous form, shown here as H2.
Note that the reaction is reversible, so
that the resulting gas leaving the reformer is a mixture of methane,
CH4, steam, H2O, carbon monoxide, CO, and hydrogen, H2.
In order to recover additional hydrogen, a second chemical reaction takes
place at a lower temperature where the addition of an excess of steam, H2O,
converts carbon monoxide, CO, into carbon dioxide and more hydrogen,
by shifting the equilibrium of the reaction towards more hydrogen.
So the production of carbon dioxide is inevitable,
since the atom of carbon comes directly from the feedstock: methane,
which- remember- accounts for 95% of natural gas.
The final step consists of the separation of carbon dioxide and
other impurities, leaving essentially pure hydrogen.
Instead of being vented to the atmosphere, as is current practice, the carbon dioxide
needs to be separated and prevented from entering the atmosphere using CCS.
If we are going to ramp up the use of hydrogen to create another carbon-free
vector to use in transport and in buildings,
the availability of CCS is therefore critical for that industry too.
To find out about what is happening with hydrogen and CCS,
please have a look at the information provided in the next section to find out
about the very first CCS project in the sector.
When molecules of natural gas (CH4) are converted to Hydrogen (H2), Carbon Dioxide (CO2) is
inevitably produced and can be separated using CCS.
But what actually makes Hydrogen a carbon-free energy vector? It can burn with Oxygen (O2) to
release energy in the form of heat, without carbon dioxide emissions.
H2 + O2 -> H2O
Hydrogen can also be reacted with Oxygen in a fuel cell to produce electricity, instead of heat. Fuel
cells rely on electron transfer to produce energy from a fuel, for example, hydrogen or natural
gas, without combustion.
Decarbonising Heating with Hydrogen
Decarbonising Heating with Hydrogen
To deploy hydrogen into a widely used carbon-free energy vector in the economy, the infrastructure
to transport hydrogen to the end-user is critical.
Repurposing the existing natural gas infrastructure could possibly be more cost-effective and less
disruptive than an electrification route, or heating networks using water, both of which would
require extensive works to build or upgrade the networks. In order to find out which option is more
cost-effective and more practical, specific studies must be carried out a national and regional level.
In the UK, the gas distribution network has been upgraded over the last 15 years and will continue to
be upgraded for the next 15 years. This 30-year effort aims at replacing most intermediate pressure
and low-pressure distribution pipes with polyethylene pipes. These new plastic pipes began to be
installed throughout the country 15 years ago for safety reasons, to reduce risks of leakage and pipe
failure.
This replacement programme is taking place irrespective of any consideration for carbon emission
reduction, yet this means that the gas distribution network following that upgrade will be capable of
delivering hydrogen when the old infrastructure was not. It offers a great opportunity to bring
hydrogen into UK cities to offer a refuelling service for hydrogen vehicles, similar to the service we
are familiar with liquid, and it brings hydrogen into UK cities for space heating and water heating.
This is an example, which could be emulated in the low-carbon cities of the future.
The next video shows how this could be implemented at the scale of a medium-sized city, taking the
example of the city of Leeds in the United Kingdom. Leeds has a population of 0.7-0.8 million people.
The hydrogen transport network could then be gradually extended at a national level over the next
10-20 years. The video is made available courtesy of Northern Gas Networks, a gas utility company
based in the United Kingdom, on behalf of the Leeds H21 City Gate project. The video in full (18min)
is available by clicking here.
Start of transcript. Skip to the end.
With hydrogen recognised as a low carbon alternative to natural gas,
the H21 Leeds City Gate project was created to determine,
whether the existing gas grid of a large UK city could be converted to hydrogen,
using technology already available today.
H21 asked a series of key questions,
to establish the feasibility, and method for converting Leeds.
What was the energy demand of the city?
Could supply be achieved to match this demand?
Could the network be converted to carry hydrogen and how much would all this cost?
Leeds was chosen as the perfect city for the project, because of its size and
its location.
We chose Leeds because it's one of the biggest cities in the UK.
It's got a complex gas grid.
It's got a very high demand,
which makes it efficient to start looking at the initial conversion.
So you've got one and
a quarter percent of the UK population being served by this one project,
that means you've got good stepping stones to do the same for any other city.
The first challenge for the project team was to establish the actual demand for
the Leeds area.
The city generates an annual energy demand for heat of 6 Terawatt-hours.
Having established demand the team needed to identify how
to supply this volume of hydrogen.
The most viable solution, noting the amount of energy we need in the gas sector
for heat, is to use what's called steam methane reforming.
A steam methane reformer is a process of generating high
purity hydrogen on an economical large scale.
We take natural gas and then we react that natural gas with steam over a nickel
catalyst to generate crude hydrogen gas.
Almost all the hydrogen made in the world today comes from steam methane reformers.
Tens of millions of tons a year.
So the easy thing to do is to do more of the same.
Steam Methane Reformers, or SMRs, are an established method of producing
hydrogen at scale, already in operation in the UK like this plant at Teesside.
In the United States, SMRs are already being used alongside established
carbon capture technology to capture the separated carbon,
which can be used for enhanced oil recovery or stored safely.
The H21 project team established,
that in order to meet the annual energy demand for Leeds of 6 Terawatt-hours,
a secure continuous hydrogen supply of 1025 MW will be required.
This will be generated by four SMRs, which will be located in Teesside,
due to the already large chemical production infrastructure and
potential for carbon capture and storage.
Here in the Tees Valley we are well used to developing large
scale industrial projects and processes.
We are probably one of the largest concentration of engineers here in the UK,
all of them have experience in making hydrogen.
We've got a population who are used to this kind of development.
Who have seen the benefits that it has brought to the region over the decades and
we think this is the right place to do it.
In order to manage the high demand in winter and low demand in summer,
the hydrogen production facilities need to be supported by a combination
of daily storage at Teesside and inter-seasonal storage in the Humber area.
This will be provided in the form of salt caverns.
A salt cavern is a mined void in a geological formation of salt, or halite.
It's like a big laboratory flask.
It's very big and it's a long way down.
Salt caverns act as reservoirs, providing a store of gas that
allows the network to cope with intra-day and inter-seasonal swings in demand.
You need stores alongside, so that the steam methane reformers can operate at
that optimum, which is continuously, and when the gas demand in the city does
not need the hydrogen it can be diverted to the stores to refill them.
It's the same methodology as we use for gas storage in the U.K. already.
The north of England is a great place for salt caverns and hydrogen production.
The gas is available, the salt is available,
a good place to start doing this.
To transport the hydrogen from the site of production and storage to Leeds,
a hydrogen transmission pipeline will be built connecting the city's gas grid
to Teesside and Hull.
A hydrogen transmission pipeline is the same as a natural gas transmission
pipeline.
The pressures is a bit lower, but they look the same,
i.e you can't see them at all.
To determine if the existing gas network was the right size,
Northern Gas Networks, the gas utility for Leeds, used their network design software,
adapted to show the results when running hydrogen through the system.
We run the model and analysed: is the network the right capacity to
convert from methane to hydrogen?
And it is.
Modelling showed,
that the majority of the network is appropriately sized for hydrogen.
At the extremities, some reinforcement will be required in order to ensure
that suppliers maintain their peak demands.
With demand and associated supply resolved, and the network established as
the right size, the biggest challenge is to create a conversion strategy for
the city, which has minimal impact on customers.
In order to define a credible conversion strategy, the team was able to draw on
the lessons from the relatively recent towns gas to natural gas conversion, and
adopt these to the gas grids of today.
The gas for the first 150 years was called towns gas and
it was called that because the gas was manufactured locally in every town.
Following the discovery of the North Sea gas fields,
the UK converted from towns gas, which contained 50% hydrogen,
to natural gas in a major nationwide operation.
Between 1966 and 1977 the UK undertook a towns gas to natural gas conversion,
which was a conversion that happened over ten years.
And at peak in 71-72 the UK were converting 2.3
million appliances per annum.
We had an extensive look at how we did the original conversion,
and what you have to do is be able to compartmentalise the city into small
enough chunks, that you can convert in a way that's acceptable to the customers,
whilst maintaining methane supply to the rest of the city.
Converting a city the size of Leeds is expected to take three years and
would only be undertaken during the summer months, when demand for heating is low.
The city would be compartmentalised into distinct areas, and
each summer one third would be converted.
This would ensure minimal disruption for customers and
security of supply in winter.
Leeds would be divided up into a number of geographical areas, and
those would be each converted in a matter of few days, and
during that period gas appliances would be changed over.
We would need to develop a new range of hydrogen appliances and hydrogen burners,
so we could go into properties and we could upgrade the appliances.
Using hydrogen to fuel appliances is not a technical challenge.
There are already examples around the world like this hydrogen cooker.
As far as the customer is concerned, it is probably the least disruptive change you
would have to move to a clean carbon economy,
because you would be changing equipment within the house, but
you wouldn't be having to change the whole infrastructure within the house.
So, minimal disruption in highways and in the homes as well.
The final part of the project is to establish how much the conversion
will cost.
The total costs for the project have been estimated at just over 2 billion pounds,
split approximately 50/50 between appliance upgrades across the city and
the building of hydrogen production, storage and pipeline infrastructure.
Additionally, around 140 million pounds in initial annual costs,
will be required for hydrogen production and carbon capture,
reducing significantly over time, with economies of scale as more cities convert.
Funding the project through a regulatory business plan would allow cost
to be socialized across the UK, as was done for
the original towns gas to natural gas conversion.
This would result in a minimal impact on UK customers' gas bills.
The H21 Leeds City Gate project has established that converting a city
like Leeds is both technically possible and financially viable.
Before conversion can begin, a series of enabling projects must be undertaken
to ensure every aspect of the process has been thoroughly tested and planned.
In addition key policy decisions will be required,
about whether to proceed with hydrogen conversion and
with the associated Carbon Capture and Storage programmes.
Carbon Capture and Storage is pretty critical, in my understanding,
to any decarbonisation pathway.
But certainly for the opportunity to decarbonise the gas grid,
Carbon Capture and Storage is essential.
To demonstrate the potential impact of H21,
the project team has also provided a vision of what a UK wide incremental
roll-out of a hydrogen economy could look like.
Because conversion is incremental, it can be fast or
slow as required to meet UK carbon reduction targets.
As well as heat, H21 can support decarbonisation, above transport and
electricity generation, with hydrogen refuelling stations and
micro combined heat and power appliances in the home.
In terms of a nationwide roll-out of hydrogen,
we are well placed with the amount of the natural gas we can bring into the country,
we're well placed with the experience we have with these kind of chemical
processes, we have the sites around the country.
The potential is huge.
Ultimately, H21 could position the UK as a world leading hydrogen economy,
and establish a global market, similar to the liquid natural gas market of today.
Providing a long lasting sustainable solution to energy decarbonisation.
Hydrogen could be transported directly into our homes, at an acceptable economic cost. One of the
remaining factors for the use of hydrogen in our homes is to ensure that hydrogen is used safely for
cooking and heating.
Robust understanding of safety is here essential, supported by meaningful regulation. Piping 100%
hydrogen into homes requires an understanding of how we, the individual end-user, might interact
on a daily basis.
Studies in the UK have compared, within the boundary of a domestic property, intentional leaks of
hydrogen and natural gas, which is already used routinely for cooking and heating:

Since Hydrogen is a molecule much lighter than air, it rises above air. This has a positive
effect on safety.

Hydrogen also disperses within air much faster than natural gas, so that, in the practical
experiments conducted, the hydrogen leak did not reach the energy content of a leak of
natural gas.
The studies concluded that the risks associated with a hydrogen leak and the impacts of any
explosion, or fire, are broadly similar to natural gas. By learning from our experience of safely
handling natural gas in millions of homes, and with meaningful regulation, it is possible to ensure the
safe use of hydrogen in our daily life.
Conclusion
The extent to which hydrogen is used will be determined by the developments of a suitable
transport infrastructure, of large-scale storage interim facilities and, most importantly, by addressing
the environmental impacts of providing the primary energy for the production of hydrogen and by
addressing the social impacts of using hydrogen in our cities and our homes.
A holistic approach looking at the whole energy system is necessary to take into account primary
energy supply, energy security and decarbonisation, and the use of CCS is critical for that industry
too.
Zero-Carbon Hydrogen
‘Blue' and ‘Green' Hydrogen
You might have come across the terms ‘blue hydrogen’ and ‘green hydrogen’ previously. The colours
are used - arbitrarily - in relation to hydrogen production methods. Hydrogen molecules occur
naturally, and they are neither green nor blue.
Hydrogen produced with CCS is commonly referred to as ‘blue hydrogen’.
'Green hydrogen' is used to refer to hydrogen produced via 'electrolysis' - an electric current is used
to break molecules of water (H2O), forming hydrogen (H2) and oxygen - provided that
renewable electricity is used.
Independently of colour, both production methods are expected to play a role in the future.
How to do 'Blue Hydrogen' properly for a Net-Zero Target
We may have, or will, come across common misconceptions about hydrogen production with CCS.
One of them is that emissions of natural gas occurring upstream of hydrogen production, so-called
fugitive emissions, raise questions about the effective climate impact of blue hydrogen.
These fugitive emissions occur when natural gas escapes during the drilling, extraction, and
transportation process. They are a problem because methane - the main constituent of natural gas is a potent greenhouse gas, approximately 25 times more powerful than carbon dioxide over a 100year timescale.
A balanced perspective on the impacts associated with blue hydrogen must recognise that high
levels of fugitive emissions, if left unregulated, may seriously harm climate efforts.
To achieve net-zero blue hydrogen, the industry needs to use appropriate technologies and
regulating standards, so that no organisation or country is inclined to take shortcuts.
A properly designed net zero hydrogen system based on natural gas would require two things:

Reduce upstream methane leakage emissions as much as possible: responsible oil and gas
companies are targeting a major reduction in methane emissions from current levels down
to one quarter of a percent. This is equivalent to the emissions of around 2.5% of the CO2
formed when the gas is converted to hydrogen, and the technology is there to sniff out
accidental and systematic offenders.

Take note of the residual emissions and offset them using bio-energy with CCS or direct air
capture and storage: with fairly high estimates for direct air capture of 500 $/tCO2, this
translates to an additional 0.6 $ per kg of hydrogen produced. If we compare this to the
production costs of non-net-zero blue hydrogen in the US of around $2 per kg of hydrogen,
the increase seems to be minor in comparison to the means of mitigating climate change.
The climate does not care at all what colour hydrogen we use – it just cares about CO2 emissions
and these will need to be net-zero for all hydrogen sources.
For more information on net-zero blue hydrogen, click here for a recent, open-access research
article.
The Limits of 100% Renewable Energy
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Electricity is the other carbon-free energy vector with a key role to play to decarbonise the global
energy system.
Nearly two-thirds of electricity is generated from fossil fuels, according to the International Energy
Agency. The sector is, however, undergoing a radical shift, with the acceleration of the deployment
of electricity generated from renewable sources, and new drilling technologies allowing for the
extraction of natural gas. In particular, the installed capacity of wind turbines and solar panels is
increasing rapidly, whilst, in North America, natural gas is rapidly replacing coal for thermal power
generation. But, even though the addition of renewable generation capacity is at a record high, fossil
fuel-based generation and associated emissions are still rising along with electricity demand.
We now discuss the prospects of 100% of renewable energy in electricity generation, and, by
extension, in the global energy system, before we look at the significant increase in costs if we
choose to decarbonise electricity without using CCS.
The idea of an energy system powered by 100% renewable energy is
actively being promoted by some organisations.
We will now discuss the fundamentals reasons as to why it
is unlikely to be practical or cost-effective.
So the concept of a 100% renewable energy society would require, that we electrify
all of our energy vectors – a considerable challenge by itself – and
that 100% of electricity is made from renewable sources.
The sources of renewable electricity with the most potential for
growth are wind and solar power.
Their production comes and
goes on their own schedule, depending on sunlight and wind speeds.
They cannot be dispatched on demand.
In other words, they cannot be turned on and off as needed by the end-user.
To balance that variations in sun and wind, and meet carbon targets,
both short-term and long-term, the electricity grid needs dispatchable,
that is available on demand at any time,
low carbon electricity to meet the demand of end-users.
So deep decarbonisation of the electricity sector presents two challenges: First,
rapidly increasing the amount of low carbon electricity in the system,
and second, ramping up low carbon dispatchable resources to balance
the variable energy from wind and solar.
Two large sources of dispatchable low carbon power are nuclear and
thermal plants burning fossil fuels, or biomass with CCS.
Is it possible to decarbonise without these technologies?
Most models of future energy systems find that deep decarbonisation
is more cost effective with dispatchable power plants.
That is particularly true above 60 to 80% of decarbonisation,
when the costs of renewables-only options rise sharply.
There are two main reasons for this increase in cost.
At very high levels of renewable use,
the installation of new capacity is likely to directly compete with
existing renewable electricity production, instead of replacing high carbon sources.
Since the output of solar energy is correlated to sunlight,
solar power facilities will reach their maximum output at the same time, and
likewise for their minimum output.
Wind speeds, on the other hand, are greatly affected by weather patterns.
Even with geographical dispersion of wind turbines at the scale of a country, there
is an element of correlation of their output, or lack of output in this case.
So it has been suggested to massively oversize the installed capacity of wind
and solar, and then build electricity transmission lines across countries.
After all, the wind is always blowing somewhere, some argue.
Because this would be extremely capital intensive, it is highly unlikely to be
cost-effective due to the low utilisation of the transmission infrastructure.
The second reason to rule out renewables-only options
comes from the limitations of energy storage.
Energy storage is the principle of storing energy at a time of excess production.
In this case high wind speeds or sunlight.
And returning it to the energy system at a time of low production- low wind
speeds and/or sunlight.
A large amount of progress must be made to achieve short-term energy storage
at the scale of the electricity grid of a country, from where we are now.
With existing energy storage technologies, and by extrapolating on the cost
curves of emerging technologies, it may be possible to achieve some level
of significant short-term energy storage, for a few hours, perhaps up to a few days.
Yet, there are monthly, seasonal and even decadal variations in weather patterns.
The wind is always blowing somewhere I said earlier.
Except that it is not.
Let’s take the example of anticyclonic weather conditions
resulting in several weeks of cold, windless winter across a country.
This is a likely event over the course of a decade,
which we cannot ignore in the planning of future energy infrastructure.
This would result in both high energy demand and
close to zero production from wind turbines,
while levels of solar energy production would be consistently low.
It would require to be able to continuously release
several weeks of energy storage.
Except for the very few countries with a mountain dominated geography and
where electricity is essentially based on hydro-power.
We do not have any other credible,
cost-effective way of storing the total energy need at the scale of a country, and
then return it for such a long period of time.
Now, that is the main limitation of 100% renewable energy systems
relying on large scale energy storage.
If we were to massively oversize renewable energy capacity, and were able to build
large scale short-term energy storage, we would have to build nuclear and/or
thermal power plants burning fossil fuels with CCS anyway, to handle these rare but
likely weather events and ensure the energy security of our societies.
We would build possibly twice as much electricity capacity as needed,
with half of it staying idle for most of time, except for a few weeks every year.
The consequences in terms of costs would be enormous.
The Intergovernmental Panel on Climate Change estimates that,
if CCS were not to be available as a technology,
the cost of reaching 2ºC of global warming would likely increase by 50 to 200%.
In the UK, independent studies using whole energy system models,
show that the cost of meeting CO2 emission targets without CCS
would increase by up to 1% point of GDP every year until 2050.
100% renewable targets are unlikely to be ever met.
Yet, they captivate the imagination, galvanise efforts and
provide reassurance to the public about long-term climate targets.
But not every target is helpful.
In a way, they make solving climate change deceptively easy,
without recognising practical concerns.
And most importantly, 100% renewable targets confuse the means with the end.
The priority for
the climate is to stop emissions of carbon dioxide from entering the atmosphere.
Replacing the use of fossil fuels with renewables has obvious benefits, such
as increasing energy security or reducing the impacts of fossil fuel extraction, but
too much emphasis on renewable energy diverts attention from the end game,
carbon emissions, and from investments in more effective and
more balanced carbon reduction pathways, with significant levels of CCS.
If the end game is global warming, then the focus of our efforts must be CO2 emissions, not
renewable energy.
The limitations to 100% renewable energy come from the lack of a low-cost, large-scale, long term
method to store energy at the scale of the energy system of a country, with the exception of
hydropower and fossil fuels. A small number of countries with a favourable geography have
considerably decarbonised their electricity production with hydro-power, nuclear energy or a
combination of both.
But, for many other countries, this is not an option. They will continue to rely on their conventional
power stations and the low-cost, large scale, long term, high carbon energy storage contained in coal
piles, as shown in the image below, and the low-cost, large scale, long term, high carbon energy
storage of the large volumes of oil and natural gas pipelines. These countries must eventually use
CCS extensively to achieve carbon neutrality in electricity production.
Electricity: A Carbon Free Energy Vector
We now look at the specificities of electricity as a commodity, and of the electricity system, and then
discuss the role of CCS in decarbonising this sector of the economy.
Start of transcript. Skip to the end.
Electricity is a carbon free energy vector,
that we use widely in our daily lives.
In a way, electricity has become synonymous, in many countries,
with economic development and social progress.
It has become so central to everything we do
that we cannot imagine living without it for any long periods.
The last unexpected power cut you have experienced has probably left you
completely exposed.
Yet, electricity is far from being carbon-free at the point of production.
It accounts for 40% of global energy related CO2 emissions in 2014,
according to the International Energy Agency.
That is 13 gigatonnes of CO2 per year, nearly two tonnes for every person on
the planet, and more than twice the emissions of transport in absolute value.
Only very few countries have low carbon electricity production.
In Europe, for example, Norway uses close to 100% hydro-power,
France mostly nuclear and Sweden a combination of both.
Renewable sources of electricity have had high growth rates in recent years.
The share of renewable power, in the addition of new electricity capacity
globally, is now close to 50%, mostly solar and wind.
This high growth is expected to continue for many years, possibly decades.
Yet, if one excludes hydro-power,
renewable sources represents 8% of today’s global electricity production.
So much more is still to be done, but
renewables are on a steep upward trajectory.
Previously, we have explained that 100% renewable electricity,
let alone energy, is unlikely to be practical, or cost effective,
due to the limitations of large scale long-term energy storage.
So we need other ways to decarbonise.
This is where CCS can play a major role in future electricity systems.
The electricity system- that is the electricity gridis a formidable piece of invention and engineering, built over decades.
And because electricity is so essential,
it is regulated to guarantee rights of access, unlike many other commodities.
So electricity is different.
The electricity system works today on the basis of a dense,
interconnected network going in one direction from generators of electricity,
our power stations, to the final consumers.
Transmission and distribution is extremely efficient and
the system is, in most parts of the world, extremely reliable.
Because there is currently very limited storage,
supply must match demand at all times.
And most of that demand is unresponsive.
It does not respond to price signals.
This is us, the domestic customers.
So the system works on the basis of forecasting demand,
building the generators and the transmission to meet that demand, and
then match that demand in real time.
Yet, it is changing to accommodate renewable electricity to make demand more
responsive, and will continue to change as we electrify more and
more end-use energy services in transport and in heating.
It also needs to change to include CCS.
Currently, coal and
gas-fired power stations handle the variability of electricity demand and
the variability of renewable electricity by adjusting flexibly their production.
These power stations are critical to fill the gaps during the many hours
throughout the year, when the wind is not blowing and the sun is not shining.
It is critical that we ensure that their emissions do not enter the atmosphere.
These coal and gas fired power stations, fitted with CCS,
will compete in the future with nuclear power, and with energy storage.
But they will also play another very fundamental role.
Oscillations in the electricity system are bad,
they can potentially break the system.
It is a very dynamic system where demand constantly changes across various time
scales, from milliseconds to hours, and supply has to adapt in real time.
This makes it hard to control, hence why there is a lot of inertia built in
the system to constantly absorb and respond to these oscillations.
So coal and gas-fired power stations, and also nuclear,
ensure that the frequency of the electricity gird stay within safe limits.
They dampen the oscillations, protect the system and protect all of our appliances.
Because these plants are continuing to play that role in our electricity systems,
they need CCS to prevent the CO2 they generate from accumulating into
the atmosphere.
And the third reason to deploy CCS in electricity is
related to a concept called 'total electricity system costs’.
Total electricity system costs matter, because they
represent the total expenditure paid by a country for its electricity.
The lower they are, the lower the end-user pays.
Adding variable renewable electricity production
is currently a cost effective way to lower ‘total electricity system costs’ and
lower CO2 emissions at the same time.
But because wind and solar cannot be dispatched on demand,
that is turned on and off as needed by the end-user,
their cost-effectiveness gradually reduces, the more capacity is installed.
As our electricity systems move towards zero carbon intensity of
electricity production, and because of the correlation of the output of solar and
wind, due to weather patterns and sunlight, higher levels of variable
renewable electricity would result in low carbon electricity competing with low
carbon electricity, instead of replacing carbon intensive electricity production.
This is where it is more cost effective to use other means, such as CCS, to reduce
‘total electricity system costs’, to chase the emissions of the power stations
filling the gaps between peaks of wind and solar electricity production.
So unlike other sectors, there are alternatives to Carbon Capture and
Storage in the electricity industry.
But because of the importance of coal and gas-fired power stations in our current
electricity systems, and because of the crucial role they will continue to play
when fitted with CCS in future electricity systems,
the International Energy Agency estimates that more than 2000 CCS power stations
would be installed in a scenario for 2◦C of climate change.
Because coal and gas-fired power stations play a critical role in ensuring the reliability of our
electricity grids and are expected to continue to do so, CCS may prove to be crucial to address their
CO2 emissions. Currently, there are cheaper ways to decarbonise than CCS, although none of these
options would achieve carbon neutrality at an acceptable cost to society:

Countries with access to relatively cheap supplies of natural gas can avoid emissions at least
cost by switching from coal to gas-fired generation, but would lock themselves into a lower
but still significant source of CO2 emissions that will need to be addressed in the medium to
long term, with CCS.

Adding variable, renewable electricity from wind and solar is currently a cost-effective way
to avoid emissions from fossil fuel electricity because they are being added to electricity
grids with low levels of renewable energy. Electricity from wind and solar power plants can
replace a large fraction of the energy produced from coal and gas-fired power stations. Yet,
the unavailability of large scale, cost-effective, long term energy storage prevents the
closure of these coal and gas-fired power stations: They must stay open to provide energy and generate CO2 in their combustion gases - during recurring periods of low availability of
wind and solar electricity.
In practice, it is likely that the optimal mix of low emissions technologies in the power
sector will include a combination of these technologies.
Start of transcript. Skip to the end.
We have explored the manufacturing industries where CCS
can address emissions of carbon dioxide to the atmosphere, and
in particular the steel and the cement industries.
We have discussed how increasing the use of existing carbon-free energy vectors
can address direct emissions by the end-users of energy services, for
example from the multitude of dispersed sources in vehicles and in our buildings.
And we have explained the critical role of CCS in the low-carbon electricity systems.
In the next block, we will examine the key technologies to capture carbon dioxide in
manufacturing process, in power stations and in the production of hydrogen.
We will then discuss how we can currently use carbon dioxide and
how we could use it as a feedstock to create new products.
And finally, we will look in more details at technologies to
capture carbon dioxide directly from the air.