Tag: carbon capture

An introduction to carbon accounting

Key takeaways:

  • Tracking, reporting, and calculating carbon emissions are a key part of progressing countries, industries, and companies towards net zero goals.
  • As a newly established discipline, carbon accounting still lacks standardisation and frameworks in how emissions are tracked, reduced, and mitigated.
  • The main carbon accounting standard used by businesses is the Greenhouse Gas (GHG) Protocol, which lays out three ‘Scopes’ businesses should report and act upon.
  • Carbon accounting evolves from reporting in the use of goals and timeframes in which targets are met.
  • Timeframes are crucial in the deployment of technologies like carbon capture, removals, and achieving net zero.

How can countries and companies find a route to net zero emissions? Many organisations, countries and industries have pledged to balance their emissions before mid-century. They intend to do this through a combination of cutting emissions and removing carbon from the atmosphere.

Tracking and quantifying emissions, understanding output, reducing them, and setting tangible targets that can be worked towards are all central to tackling climate change and reducing greenhouse gas emissions – especially when it comes to carbon dioxide (CO2). Emissions and energy consumption reporting is already common practice and compulsory for businesses over a certain size in the UK. However, carbon accounting takes this a step further.

“Carbon reporting is a statement of physical greenhouse gas emissions that occur over a given period,” explains Michael Goldsworthy, Head of Climate Change and Carbon Strategy at Drax. “Carbon accounting relates to how those emissions are then processed and counted towards specific targets. The methodologies for calculating emissions and determining contributions against targets may then have differing rules depending on which framework or standard is being reported against.”

Carbon accounting tools can help companies and counties understand their carbon footprint – how much carbon is being emitted as part of their operations, who is responsible for them, and how they can be effectively mitigated.

Like how financial accounting may seek to balance a company’s books and calculate potential profit, carbon accounting seeks to do the same with emissions, tracking what an entity emits, and what it reduces, removes, or mitigates. Carbon accounting is, therefore, crucial in understanding how countries and companies can contribute to reaching net zero.

A new space

How different organisations, countries and industries approach carbon accounting is still an evolving process.

“It’s as complex as financial accounting, but with financial accounting, there’s a long standing industry that relies on well-established practices and principles. Carbon accounting by contrast is such a new space,” explains Goldsworthy.

Regardless of its infancy, businesses and countries are already implementing standardised approaches to carbon accounting. Regulations such as emissions trading schemes and reporting systems, such as Streamlined Energy and Carbon Reporting (SECR) and the Taskforce on Climate Related Financial Disclosure (TCFD), are beginning to deliver some degree of consistency in businesses’ carbon reporting.

Other standards such as the GHG Protocol have sought to provide a standardised basis for corporate reporting and accounting. Elsewhere, voluntary carbon markets (e.g. carbon offsets) have also evolved to allow transferral of carbon reductions or removals between businesses, providing flexibility to companies in delivering their climate commitments.

The challenge is in aligning these frameworks so that they work together. For example, emissions within a corporate inventory or offset programme must be accounted for in a way that is consistent with a national inventory.

To date, these accounting systems have evolved independently with different rules and methodologies. Beginning to implement detailed carbon accounting, upon which emissions reductions and removals can be based, requires standardised understanding of what they are and where they come from.

Reporting and tackling Scope One, Two, and Three emissions

The main carbon accounting standard used by businesses is the Greenhouse Gas (GHG) Protocol. This voluntary carbon reporting standard can be used by countries and cities, as well as individual companies globally.

The GHG protocol categorises emissions in three different ‘scopes’, called Scope 1, Scope 2, and Scope 3. Understanding, measuring, and reporting these is a key factor in carbon accounting and can drive meaningful emissions reduction and mitigation.

Scope One – Direct emissions

Scope One emissions are those that come as a direct result of a company or country’s activities. These can include fuel combustion at a factory’s facilities, for example, or emissions from a fleet of vehicles.

Scope One emissions are the most straightforward for an organisation to measure and report, and easier for organisations to directly act on.

Scope Two – Indirect energy emissions

Scope Two emissions are those which come from the generation of energy an organisation uses. These can include emissions form electricity, steam, heating, and cooling.

A business may buy electricity, for example, from an electricity supplier, which acquires power from a generator. If that generator is a fossil-fuelled power station the energy consumer’s Scope Two emissions will be greater than if it buys power from a renewable electricity supplier or generates its own renewable power.

The ability to change energy suppliers makes Scope Two relatively straightforward for organisations to act on, assuming renewable energy sources are available in the area.

Scope Three – All other indirect emissions

Scope Three is much broader. It covers upstream and downstream lifecycle emissions of products used or produced by a company, as well as other indirect emissions such as employee commuting and business travel emissions.

Identifying and reducing these emissions across supply and value chains can be difficult for businesses with complex supply lines and global distribution networks. They are also hard for companies to directly influence.

Add in factors like emissions mitigations or offsetting, and the carbon accounting can quickly become much more complex than simply reporting and reducing emissions that occur directly from a company’s activities. Nevertheless, these full-system overviews and whole-product lifecycle accounting are crucial to understanding the true impact of operations and organisations, and to reach climate goals.

Working to timelines

Setting goals with defined timelines and the development of rules that ensure consistent accounting is also crucial to implementing effective climate change mitigation frameworks throughout the global economy. Consider the UK’s aim to be net zero by 2050, or Drax’s ambition to be net negative by 2030, as goals with set timelines.

For many technologies, the time scales over which targets are set have added relevance. There are often upfront emissions to account for and operational emissions that may change over time. Take for example an electric vehicle: the climate benefit will be determined by emissions from construction and the carbon intensity of the electricity used to power it.

A timeline of BECCS at Drax [click to view/download]

Looking at a brief snapshot at the beginning of its life, say the first couple of years, might not show any climate benefit compared to a vehicle using an internal combustion engine. Over the lifetime of the vehicle, however, meaningful emissions savings may become clear – especially if the electricity powering the vehicle continues to decarbonise over time.

This provides a challenge when setting carbon emissions targets. Targets set too far in the future potentially risk inaction in the short term, while targets set over short periods risk disincentivising technologies that have substantial long-term mitigation potential. 

Delivering net zero

Some greenhouse gas emissions will be impossible to fully abate, such as methane and nitrous oxide emissions from agriculture, while other sectors, like aviation, will be incredibly difficult to fully decarbonise. This makes carbon removal technologies all the more critical to ensuring net zero is achieved.

Technologies such as bioenergy with carbon capture and storage (BECCS) – which combines low-carbon, biomass-fuelled renewable power generation with carbon capture and storage (CCS) to permanently remove emissions from the atmosphere – are already under development.

However, it is imperative that such technologies are accounted for using robust approaches to carbon accounting, ensuring all emission and removals flows across the value chain are accurately calculated in accordance with best scientific practice. In the case of BECCS, it’s vital that not only are emissions from processing and transporting biomass considered, but also its potential impact on the land sector.

Forests from which biomass is sourced will be managed for a variety of reasons, such as mitigating natural disturbance, delivering commercial returns, and preserving ecosystems. Accurate accounting of these impacts is therefore key to ensuring such technologies deliver meaningful reductions in atmospheric CO2within timeframes guided by science.

Accounting for net zero

While carbon accounting is crucial to reaching a true level of net zero in the UK and globally, where residual emissions are balanced against removals, the practice should not be used exclusively to deliver numerical carbon goals.

“To deliver net zero, it’s vital we have robust carbon accounting systems and targets in place, ensuring we reduce fossil emissions as far as possible while also incentivising carbon removal solutions,” says Goldsworthy.

“However, many removal solutions rely on the natural world and so it is critical that ecosystems are not only valued on a carbon basis but consider other environmental factors such as biodiversity as well.”

Why and how is carbon dioxide transported?

What is carbon transportation?

Carbon transportation is the movement of carbon from one place to another. In nature, carbon moves through the carbon cycle. In industries like energy, however, carbon transportation refers to the physical transfer of carbon dioxide (CO2) emissions from the point of capture to the point of usage or storage.

Why does carbon need to be transported?

Anthropogenic (man-made) CO2 released in processes like power generation leads to the direct increase of CO2 in the atmosphere and contributes to global warming.

However, these emissions can be captured as part of carbon capture and storage (CCS). The CO2 is then transported for safe and permanent storage in geological formations deep underground.

Capturing and storing CO2 prevents it from entering the atmosphere and contributing to global warming. Processes that can deliver negative emissions – such as bioenergy with carbon capture and storage (BECCS) and direct air capture and storage (DACS) – aim to permanently remove CO2 from the atmosphere through CCS.

In CCS, carbon must be transported from the site where it’s captured to a site where it can be permanently stored. This means it needs to travel from a power station or factory to a geological formation like a saline aquifer or depleted oil and gas reservoirs.

As of September 2021, there were 27 operational CCS facilities around the world, with the combined capacity to capture around 40 million tonnes per annum (Mtpa) of CO2. It’s estimated that the UK alone has 70 billion tonnes of potential CO2 storage space in sandstone rock formations under the North Sea.

How is carbon transported?

CO2 can be transported via trucks or ships, but the most common and efficient method is by pipeline. Moving gases of any kind through pipelines is based on pressure. Gases travel from areas of high pressure to areas of low pressure. Compressing gas to a high pressure allows it to flow to other locations.

Gas pipelines are common all around the world, including those transporting CO2. In the US there are, for instance, more than 50 CO2 pipelines – covering around 6,500 km and transporting approximately 68 million tonnes of CO2 a year.

Gas takes up less volume when it’s compressed, and even less when it is liquefied, solidified, or hydrated. Therefore, before being transported, captured CO2 is often compressed and liquefied until it becomes a supercritical fluid.

In a supercritical state, CO2 has the density of a liquid but the viscosity (thickness) of a gas and is, therefore, easier to transport through pipelines. It’s also 50-80% less dense than water, with a viscosity that is 100 times lower than liquid.

This means it can be loaded onto ships in greater quantities and that there is less friction when it’s moving through pipes and, subsequently, into geological storage sites.

How safe is it to transport carbon?

It’s no riskier to transport CO2 via pipeline or ship than it is to transport oil and natural gas, and existing oil and natural gas pipelines can be repurposed to transport CO2.

To enable the safe use of CO2 pipelines, CCS projects must ensure captured CO2 complies with strict purity and temperature specifications, as well as making sure CO2 is dry and free from impurities that could impact pipelines’ operations.

Whilst there are a growing number of CCS transport systems around the world, CCS is still is a relatively new field but research is underway to identify best practises, materials and technologies to optimise the process. This includes research around potential risks and techniques for leak mitigation and remediation.

In the UK, the Health and Safety Executive regulates health, safety, and integrity issues for all natural gas pipelines, which are covered by legislation. The legislation ensures the safety of pipelines, pressure systems and offshore installations and can serve as a strong foundation for CO2 transport regulation.

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What is the carbon cycle?

What is the carbon cycle?

All living things contain carbon and the carbon cycle is the process through which the element continuously moves from one place in nature to another. Most carbon is stored in rock and sediment, but it’s also found in soil, oceans, and the atmosphere, and is produced by all living organisms – including plants, animals, and humans.

Carbon atoms move between the atmosphere and various storage locations, also known as reservoirs, on Earth. They do this through mechanisms such as photosynthesis, the decomposition and respiration of living organisms, and the eruption of volcanoes.

As our planet is a closed system, the overall amount of carbon doesn’t change. However, the level of carbon stored in a particular reservoir, including the atmosphere, can and does change, as does the speed at which carbon moves from one reservoir to another.

What is the role of photosynthesis in the carbon cycle?

Carbon exists in many different forms, including the colourless and odourless gas that is carbon dioxide (CO2). During photosynthesis, plants absorb light energy from the sun, water through their roots, and CO2 from the air – converting them into oxygen and glucose.

The oxygen is then released back into the air, while the carbon is stored in glucose, and used for energy by the plant to feed its stem, branches, leaves, and roots. Plants also release CO2 into the atmosphere through respiration.

Animals – including humans – who consume plants similarly digest the glucose for energy purposes. The cells in the human body then break down the glucose, with CO2 emitted as a waste product as we exhale.

CO2 is also produced when plants and animals die and are broken down by organisms such as fungi and bacteria during decomposition.

What is the fast carbon cycle?

The natural process of plants and animals releasing CO2 into the atmosphere through respiration and decomposition and plants absorbing it via photosynthesis is known as the biogenic carbon cycle. Biogenic refers to something that is produced by or originates from a living organism. This cycle also incorporates CO2 absorbed and released by the world’s oceans.

The biogenic carbon cycle is also called the “fast” carbon cycle, as the carbon that circulates through it does so comparatively quickly. There are nevertheless substantial variations within this faster cycle. Reservoir turnover times – a measure of how long the carbon remains in one location – range from years for the atmosphere to decades through to millennia for major carbon sinks on land and in the ocean.

What is the slow carbon cycle?

In some circumstances, plant and animal remains can become fossilised. This process, which takes millions of years, eventually leads to the formation of fossil fuels. Coal comes from the remains of plants that have been transformed into sedimentary rock. And we get crude oil and natural gas from plankton that once fell to the ocean floor and was, over time, buried by sediment.

The rocks and sedimentary layers where coal, crude oil, and natural gas are found form part of what is known as the geological or slow carbon cycle. From this cycle, carbon is returned to the atmosphere through, for example, volcanic eruptions and the weathering of rocks. In the slow carbon cycle, reservoir turnover times exceed 10,000 years and can stretch to millions of years.

How do humans impact the carbon cycle?

Left to its own devices, Earth can keep CO2 levels balanced, with similar amounts of CO2 released into and absorbed from the air. Carbon stored in rocks and sediment would slowly be emitted over a long period of time. However, human activity has upset this natural equilibrium.

Burning fossil fuel releases carbon that’s been sequestered in geological formations for millions of years, transferring it from the slow to the fast (biogenic) carbon cycle. This influx of fossil carbon leads to excessive levels of atmospheric CO2, that the biogenic carbon cycle can’t cope with.

As a greenhouse gas that traps heat from the sun between the Earth and its atmosphere, CO2 is essential to human existence. Without CO2 and other greenhouse gases, the planet could become too cold to sustain life.

However, the drastic increase in atmospheric CO2 due to human activity means that too much heat is now retained between Earth and the atmosphere. This has led to a continued rise in the average global temperature, a development that is part of climate change.

Where does biomass fit into the carbon cycle?

One way to help reduce fossil carbon is to replace fossil fuels with renewable energy, including sustainably sourced biomass. Feedstock for biomass energy includes plant material, wood, and forest residue – organic matter that absorbs CO2 as part of the biogenic carbon cycle. When the biomass is combusted in energy or electricity generation, the biogenic carbon stored in the organic matter is released back into the atmosphere as CO2.

This is distinctly different from the fossil carbon released by oil, gas, and coal. The addition of carbon capture and storage to bioenergy – creating BECCS – means the biogenic carbon absorbed by the organic matter is captured and sequestered, permanently removing it from the atmosphere. By capturing CO2 and transporting it to geological formations – such as porous rocks – for permanent storage, BECCS moves CO2 from the fast to the slow carbon cycle.

This is the opposite of burning fossil fuels, which takes carbon out of geological formations (the slow carbon cycle) and emits it into the atmosphere (the fast carbon cycle). Because BECCS removes more carbon than it emits, it delivers negative emissions.

Fast facts

  • According to a 2019 study, human activity including the burning of fossil fuels releases between 40 and 100 times more carbon every year than all volcanic eruptions around the world.
  • In March 2021, the Mauna Loa Observatory in Hawaii reported that average CO2 in the atmosphere for that month was 14 parts per million. This was 50% higher than at the time of the Industrial Revolution (1750-1800).
  • There is an estimated 85 billion gigatonne (Gt) of carbon stored below the surface of the Earth. In comparison, just 43,500 Gt is stored on land, in oceans, and in the atmosphere.
  • Forests around the world are vital carbon sinks, absorbing around 7.6 million tonnes of CO2 every year.

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How is carbon stored?

Carbon storage is the process of capturing and trapping that CO2. This can occur naturally in the form of carbon sinks like forests, oceans, and soils that store carbon. However, it can also be manually carried out through technology.   

One of the most well-established ways of storing carbon through the use of technology is by injecting CO2 into naturally occurring geological formations that can lock in or sequester the molecule on a permanent basis. Carbon storage is the final phase of the carbon capture, usage, and storage (CCUS) process.

Why do we need to store carbon?

Global bodies like the UN’s Intergovernmental Panel on Climate Change (IPCC), as well as the UK’s own Climate Change Committee, emphasise carbon capture and storage as crucial to achieving net zero emissions and meeting the Paris Agreement’s goal of limiting temperature rises to within 1.5oC.

This includes supporting forest growth through afforestation and reforestation, and other nature-based solutions to store carbon, alongside CCUS technology.

The European Commission also highlights CCUS’s role in balancing increased energy demand and continued fossil fuel use in the future, with the need to reduce greenhouse gas emissions and prevent them entering the atmosphere.

How is carbon captured and transported to storage?

In naturally occurring examples, forests and ocean fauna absorb carbon through photosynthesis. When the vegetation eventually decomposes the carbon is sequestered into soil and seabeds.

Carbon can also be captured from emissions sources such as factories or power plants. The carbon is captured either pre-combustion, where it is removed from the fuel source, or post-combustion, where it is removed from exhaust fumes in the form of CO2.

The CO2 is then converted into a supercritical state where it has the viscosity of a gas but the density of a liquid, meaning it can travel more easily through pipelines. It can also be transported via trucks and ships, but pipelines are the most efficient.

Where can carbon be stored?

Natural carbon sinks differ all over the world, from peatlands in Scotland to Pacific coral reefs to the massive forests that cover countries like Russia, Canada, and Brazil. Wooden buildings also act as carbon storage as they maintain the carbon within the wood for long time periods.

The CO2 captured by manmade technologies can also be stored in different types of geological formation: unused natural gas reserves, saline aquifers, and un-minable coal mines.

The North Sea, with its expansive layers of porous sandstone, also offers the UK alone an estimated 70 billion tonnes of potential CO2 storage space.

If negative emissions technologies (which actively remove emissions from the atmosphere) were to capture and store the equivalent amount of CO2 as the 258 million tonnes expected to remain in the UK economy in 2050, it would take up just 0.36% of the available storage space.

Years of research by the oil and gas industries mean many such geological structures have been mapped and are well understood all around the world.

Carbon storage fast facts

How is the carbon kept in place?

In nature-based carbon sinks the carbon does not always remain in one location. In a forest, for example, trees and plants will hold carbon until the end of their lifetime after which they decompose, releasing some CO2 into the atmosphere while some is sequestered into soil.

When CO2 captured through CCUS is stored several things can happen to it in a geological storage site. It can be caught in the minute intervening spaces within the rock through capillary action, or trapped by a layer of impermeable cap-rock, which prevents it from moving upwards.

CO2 may also dissolve in the water and then sinks as it is heavier than normal water. The carbonated water reacts with basaltic rocks which cover most of the ocean floor. The reaction releases elements like calcium, magnesium, and iron into the water stream. Over time, these elements combine with the dissolved CO2 to form stable carbonate minerals that permanently fill pores within the rock.

How does CO2 enter the storage sites?

The CO2 is injected into the porous rocks of depleted or unused natural gas or oil reserves, as well as saline aquifers – geologic strata, filled with brine or saline water. Porous rock is filled with holes and gaps between the grains that make up the rock. When CO2 is injected into these structures, the CO2 floods the pores, displacing the brine or remnants of oil and gas. It then spreads out and is trapped in the dome-like structures of the rock strata called anticlines.

How long can CO2 be stored?

Appropriately selected and maintained geological reservoirs are “very likely” to retain 99% of sequestered carbon for more than 100 years and are “likely” to retain 99% of sequestered carbon for more than 1,000 years, according to the 2005 Special Report on CCS by the IPCC. Another study by Nature found that more than 98% of injected CO2 will remain stored for over 10,000 years.

In natural carbon sinks, the length of time that carbon is stored varies and depends on environments being preserved. Peatland, for example, builds up over thousands of years storing carbon. However, as peatlands degrade from attempts to drain them to create arable land, as well as peat extraction for fuel, they begin to emit CO2. The lifecycle of a tree by contrast is relatively short before it decomposes and releases some CO2 back into the atmosphere.

The ability for geological storage to contain CO2 for millennia means it can truly remove and permanently store emissions.

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