Author: Tariq Arafa

What is pumped storage hydro?

What is pumped storage hydro?

Pumped storage hydro (PSH) is a large-scale method of storing energy that can be converted into hydroelectric power. The long-duration storage technology has been used for more than half a century to balance demand on Great Britain’s electricity grid and accounts for more than 99% of bulk energy storage capacity worldwide.

How does it work?

The principle is simple. Pumped storage facilities have two water reservoirs at different elevations on a steep slope. When there is excess power on the grid and demand for electricity is low, the power is used to pump water from the lower to the upper reservoir using reversible turbines. When demand is high, the water is released downhill into the lower reservoir, driving the turbines the other direction to generate electricity.

Pumped storage hydro plants can also provide ancillary services to help balance the power system, such as inertia from spinning turbines, which ensures the system runs at the right frequency and reduces the risk of power cuts.

Why is pumped storage hydro important for energy transition?

Governments around the world are shifting from fossil fuels to renewable energy sources to meet their climate goals. But critically important power technologies such as wind and solar pose challenges for power grid operators.

Being weather-dependent, the supply from these renewables is intermittent. For example, wind farms accounted for almost a quarter of the UK’s total electricity generation in 2020, but on some days, less than 10% of the country’s electricity needs were met by wind. Changing weather patterns and extreme weather events with prolonged periods of little wind or reduced daylight are a further the threat to grid stability.

When output from renewables falls, grid operators mostly turn to gas-fired power stations to plug the gap. But relying on fossil fuels such as natural gas in the long term to balance the grid will compromise efforts to reach net zero emissions by 2050.

Pumped storage hydro facilities act as vast ‘water batteries’. They are a flexible way of storing excess energy generated by renewables, cost-effectively and at scale.

How can pumped storage hydro capacity be increased?

As old thermal power plants are decommissioned and renewables provide an increasing share of the electricity supply, storage capacity will need to grow if climate goals are to be met. Over the next two to three decades, Great Britain’s energy storage capacity alone will need to increase tenfold, from 3 gigawatts (GW) to around 30 GW.

Pumped storage hydro power stations require very specific sites, with substantial bodies of water between different elevations. There are hundreds, if not thousands, of potential sites around the UK, including disused mines, quarries and underground caverns, but the cost of developing entirely new facilities is huge. A more cost-effective way to increase storage capacity is by expanding existing plants, such as the Cruachan Power Station in Scotland.

Pumped Storage Hydro fast facts

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Pumping power: pumped storage stations around the world

Loch Awe from Cruachan

Changing the world’s energy systems is a more complex task than just replacing coal power stations with wind farms. Moving to an energy system with more intermittent renewable sources like wind and solar will require greater levels of storage that can deliver electricity when it’s needed.

One of the long-established means of storing energy and using it to generate electricity when needed is through pumped hydropower storage. With upper and lower reservoirs of water, and turbines in between, these facilities act a bit like rechargeable batteries.

When there is excess electricity on the grid, the turbines are switched on to pump water from the lower to the higher reservoir (for example up a mountain or hill) where it’s stored. When electricity is needed, the water is released to flow from the higher reservoir toward the lower reservoir, passing through the turbines which generate electricity to send back to the grid.

Greater levels of intermittent renewables on energy systems around the world will make pumped storage all the more vital in helping to balance grids. Their mountainous locations also make pumped storage stations some of the most dramatic and interesting monuments in energy.

Here are some of the most interesting pumped hydro stations generating power and pumping water up mountains in the world:

1. The largest in the world (currently)

Bath County in Virginia, USA is dense with forests and mountain retreats, but below the scenery of the Allegheny Mountains lies the world’s biggest pumped hydro power station.

View of Appalachian mountains along Highway 220 in Warm Springs, Bath County, Virginia

The Bath County Pumped Storage Station has a maximum generation capacity of more than 3 gigawatts (GW) and total storage capacity of 24 gigawatt-hours (GWh), the equivalent to the total, yearly electricity use of about 6000 homes.

Construction began in March 1977 and upon completion in December 1985, the power station had a generating capacity of 2.1 GW. However, its six turbines were upgraded between 2004 and 2009 to over 500 MW per turbine. The power station’s upper reservoir can hold 14,000,000 cubic metres (m3) of water and its water level can drop by as much as 32 metres during operations.

While the amount of earth and rock moved during the construction of the dam and facilities would make a mountain more than 300 metres tall, the actual station occupies a relatively small amount of land to minimise its impact on the environment. The water from the upper reservoir has a use beyond power too – at times of drought it’s used to supplement river flow in the recreational area that surrounds the site.

2. The future largest in the world

Bath County will not be the world’s largest pumped hydro station for much longer. While China is already home to more of the top 10 largest pumped storage power stations than any other country, the Fengning Pumped Storage Power Plant in China’s Hebei Province will take the top position when completed in 2023, thanks to its 3.6 GW capacity.

Landscape of the Bashang grassland in Hebei, China

Construction first began on the monster project in June 2013 and is being developed in two 1.8 GW stages. The first stage is scheduled for completion in 2021, when six of the 12 planned 300 MW reversable pump turbine units roar into life.

The plant will serve Beijing-Tianjin-North Hebei electrical grid and highlights the rapid growth of renewables in the region. Fengning will act as a peaking plant to balance the expansive wind and solar parks in China’s northern Hebei and Inner Mongolia regions.

China has more installed pumped hydro storage capacity than any other country, thanks in large part to its extensive mountainous terrain (which can accommodate such facilities), as well as an increasing need to support growing intermittent renewable installations. The construction of Fengning, part of a pipeline of projects, will further the country’s capabilities, helping China reach as much as 40 GW of installed capacity in the coming years.

3. Most reversable turbines

Fengning will also take the record for the most individual turbine units in a pumped storage facility when it’s finished in 2023, a title that is currently jointly held by Huizhou Pumped Storage Power Station and Guangdong Pumped Storage Power Station. These two plants are the respective second and third largest pumped storage plants in the world today, each with eight reversable turbines.

Guangzhou City, Guangdong Province, China

While Guangdong Pumped Storage Power Station has a capacity of 2.4 GW, Huizhou has a slightly larger capacity of 2.448 GW. The increased number of turbines might mean more machinery to maintain and operate, but also offers the plants greater flexibility in how much electricity they absorb and generate.

4. Multiple dams and reservoirs

The Drakensberg Pumped Storage Scheme, located in the Drakensberg Mountains in the province of KwaZulu-Natal, South Africa, is a unique hydro facility thanks to its use of four dams. The Driekloof Dam, Sterkfontein Dam, Kilburn Dam and Woodstock Dam give the facility a generation capacity of 1 GW, and a total storage capacity of over 27 GWh. However, Drakensberg is not the largest facility in South Africa.

Drakensberg Mountains in South Africa

Drakensberg Mountains in South Africa

South Africa holds a total installed pumped storage capacity of nearly 3 GW from its four large facilities. The newest, and largest, is the Ingula Pumped Storage Scheme, which has a generation capacity of over 1.3 GW. Its name, ‘Ingula’, was inspired by the foamy river waters surrounding the facility and comes from the Zulu word for the creamy foam on the top of a milk vessel.

5. The oldest working pumped storage plant

Another country with the ideal terrain for pumped storage is Switzerland. The Alpine country’s landscape feeds water into Europe’s rivers such as the Rhine, making water a plentiful supply for the country’s energy. Hydropower as a whole accounts for around 57% of the country’s energy production and the country was one of the first to begin deploying pumped storage systems in the 1890s, although these were initially used for water management rather than supporting electricity generation.

Water dam and reservoir lake in Swiss Alps to produce hydropower

Switzerland is also home to the world’s oldest working pumped storage plant. The Engeweiher pumped storage facility was built in 1907 before reversable turbines were introduced in the 1930s. It was renewed in the early 1990s and is scheduled to continue operating until at least 2052.

6. The biggest in Europe

The Alps are also home to Europe’s biggest hydroelectric facility. In France, the Grand Maison hydroelectric power station operates in the Isère area of the Auvergne-Rhône-Alpes region, and has a capacity of 1.8 GW. During peak demand, it takes only three minutes for the station to supply its full 1.8 GW of power to the National Electricity Grid of France.

Grand Maison Hydroelectric Power Station

Sitting at an altitude of 1,698 metres the majority of the water that fills the upper reservoir, created by the Grand Maison Dam, comes from melted snow. This reservoir has a storage capacity of 140,000,000 m3 of water.

7. The biggest in the UK

Across the Channel, the UK also boasts impressive hydropower and pumped storage credentials, having used water for electricity generation since 1879. The UK has a total hydropower capacity of over 4.7 GW, including 2.8 GW of pumped storage, with the wet, mountainous landscapes of Scottish Highlands and Welsh countryside particularly well suited to hydropower facilities.

Dinorwig hydroelectric power station

The largest of these is the Dinorwig Hydro Power Station which sits at the edge of Snowdonia National Park in north west Wales, although it’s hard to spot as most of the machinery is found underground. With a total capacity of over 1.7 GW, this pumped storage plant can power 2.5 million homes and is known by locals as ‘Electric Mountain’.

8. The station lying between the lochs

Surrounded by Loch Etive and Loch Nant, and perched on the north side of Loch Awe, Drax’s Cruachan Power Station was built between 1959 and 1965, 1 km inside of a hollowed-out mountain in Argyll and Bute, Scotland. Upon completion, the power station, also known as the ‘Hollow Mountain’, was opened by Queen Elizabeth II and can currently generate 440 MW of hydroelectric power in 30 seconds, helping to maintain stability on the electricity grid.

Cruachan Dam in Argyll and Bute

A proposed sister station, Cruachan 2, which would stand adjacent to the existing facility, could enable Cruachan to produce up to twice as much power, increasing its support of renewables coming onto the grid.

9. The world’s smallest

The Goudemand apartment building in the city of Arras, France is home to an extremely small pumped storage hydroelectricity system, with no mountain in sight. The residential building was transformed in 2012 to become grid-independent through the installation of solar panels, wind turbines, batteries and a 200 square metre (m2) open air water tank sitting on its roof. This tank, 30 metres above the ground, acts as an upper reservoir and is connected to five 10 m2 plastic water tanks in the basement, the lower reservoir.

Arras, France

While the 3.5 KWh (kilowatt-hours) capacity of the building’s micro facility is small, it provides useful knowledge to researchers, opening up the possibility of small, modular pumped storage systems to be developed and deployed at scale in the future.

Charge. Recharge. The evolution of batteries

From watches to toothbrushes, mobile phones to cars, batteries are a power source for many of our everyday belongings. And while their beginnings can be traced back to the 19th century, their innovation has transformed industries, technology use and society at large today.

Energy storage systems such as pumped-hydropower have long played an important role in balancing electricity systems, but as the UK and countries around the world seek to decarbonise industries and make greater use of intermittent, renewable sources, there is a need for greater levels of storage.

While pumped-hydro storage requires the right kind of terrain, batteries can theoretically be built wherever there is the space and investment. But what actually is a battery, and how does it work?

Turning chemicals to electrical flow

Batteries are comprised of one or more cells which store chemical energy, and are able to convert that energy into electricity. In most batteries, there are three main components: an anode, cathode and electrolyte.

The anode and cathode are terminals for the flow of energy and are typically made of metal. The electrolyte is a chemical medium that sits between the terminals allowing an electrical charge to pass through. This is often a liquid, but increasingly research points to the potential to use solids and create what are known as solid-state batteries.

How a lithium ion battery works

How a lithium ion battery works

It’s only when a battery is connected to a device that it completes a circuit and chemical reactions take place that allow the flow of electrical energy from the battery to the device. But how much electrical energy a battery can dispense has always been a hurdle to using them as a power source, making rechargeable batteries an important breakthrough.

The same reaction backwards

A key element in battery development was the exploration of rechargeable cells. These have long provided mobility and reliability in small scale outputs, but are now being looked to as a source of large-scale energy storage.

Invented by physician Gaston Planté in 1859, rechargeable batteries are possible because the chemical reactions that take place are reversible. Once the initial stored charge has been depleted via chemical reaction, these reactions occur again, but this time backwards, to store a new charge.

Battery charger with AA rechargeable batteries

Battery charger with AA rechargeable batteries

Using a lead-acid system, Planté’s composition was similar to that found in rechargeable batteries used in cars and motorbikes today, although the characteristics of these cells, such as their heavy weight, meant they were not convenient for many other uses.

As a result, a journey of continuous research and optimisation to decrease the size and weight of rechargeable batteries began. This includes investigation into the alternative chemical compositions found in batteries today – nickel-metal hydride and lithium-ion to name two.

Recharging in a low-carbon energy system

Just as we have seen the size and capacity of batteries bettered throughout history, the application and optimisation of modern-day lithium-ion cells looks to continue too, powering the world’s move towards a low carbon, renewable energy future.

From electric vehicle batteries with a million mile lifespan to a 200 megawatt battery farm in South Africa, lithium-ion allows reasonably large-scale energy storage. It can also play a key role in power grid stabilisation over short durations of time such as a few hours.

Tesla gigafactory

Tesla gigafactory

For the UK to run on 100% renewable electricity sources, batteries would be imperative in complimenting other flexible renewables, such as biomass and hydropower. As a support technology, batteries can help ensure a continuous supply of electricity to homes and cities, even when cloud cover and low wind prevents other sources generating.

Conversely, charging and recharging batteries can also be used to absorb and store electricity when there is more sun and wind generation than needed, avoiding surges in electric current or wasted generation.

Changing charging

Woman charging smartphone using wireless charging pad

Alongside the advancements of battery capacity and composition, the way we use them to charge is also changing. Just as Bluetooth and Wi-Fi avoid the tethering required of wired connections, wireless charging can increase mobility and remove physical limitations.

Small-scale wireless charging is in use today. Many mobile phones, toothbrushes, smartwatches and earbuds now have wireless charging pads. These use near-field charging, meaning the device must be in close proximity to the charger to receive power.

However, efficient far-field charging is in development, with companies like Energous and Ossia developing over-the-air charging solutions for wearable tech, medical products, smart homes, and industrial equipment. This would mean devices could be powered and charged from many metres away.

The implications of this are vast, for example your devices could be charged just by entering your home or office. There could be less need for invasive surgery to change the batteries for pacemakers, neurotransmitters and other implanted medical equipment.

This type of technology could also provide passive charging for electric vehicles. The UK Department for Transport has announced a trial in Nottingham, where charging plates will be placed on parts of the town’s roads allowing electric taxis to charge while waiting briefly to pick up passengers. As charging technology and speed continues to increase, this might mean vehicles could charge wirelessly not only while parked, but when stopped at traffic lights.

3d rendered illustration of an elderly man with a pace maker

As the world shifts away from fossil fuels to renewable sources, batteries, with continued improvement in performance and capacity, will be crucial in supporting our connected lives, transport systems and electrical grids.

Committing to a net zero power system as part of COP26

Dear Prime Minister, Chancellor, COP26 President and Minister for Energy and Clean Growth,

We are a group of energy companies investing tens of billions in the coming decade, deploying the low carbon infrastructure the UK will need to get to net zero and drive a green recovery to the COVID-19 crisis.

We welcome the leadership shown on the Ten Point Plan for a Green Industrial Revolution, and the detailed work going on across government to deliver a net zero economy by 2050. We are writing to you to call on the Government to signal what this will mean for UK electricity decarbonisation by committing to a date for a net zero power system.

Head of BECCS inspects pilot plant within Drax Power Station's CCUS Incubation Unit

Head of BECCS Carl Clayton inspects pipes at the CCUS Incubation Area, Drax Power Station

The electricity sector will be the backbone of our net zero economy, and there will be ever increasing periods where Great Britain is powered by only zero carbon generation. To support this, the Electricity System Operator is putting in place the systems, products and services to enable periods of zero emissions electricity system operation by 2025.

Achieving a net zero power system will require government to continue its efforts in key policy areas such as carbon pricing, which has been central in delivering UK leadership in the move away from coal and has led to UK electricity emissions falling by over 63% between 2012 and 2019 alone.

It is thanks to successive governments’ commitment to robust carbon pricing that the UK is now using levels of coal in power generation last seen 250 years ago – before the birth of the steam locomotive. A consistent, robust carbon price has also unlocked long term investment low-carbon power generation such that power generated by renewables overtook fossil fuel power generation for the first time in British history in the first quarter of 2020.

Yet, even with the demise of coal and the progress in offshore wind, more needs to be done to drive the remaining emissions from electricity as its use is extended across the economy.

In the near-term, in combination with other policies, continued robust carbon pricing on electricity will incentivise the continued deployment of low carbon generation, market dispatch of upcoming gas-fired generation with Carbon Capture and Storage (CCS) projects and the blending of low carbon hydrogen with gas-fired generation. Further forward, a robust carbon price can incentivise 100% hydrogen use in gas-fired generation, and importantly drive negative emissions to facilitate the delivery of a net zero economy.

Next year, the world’s attention will focus on Glasgow and negotiations crucial to achieving our climate change targets, with important commitments already made by China, the EU, Japan and South Korea amongst others. An ambitious 2030 target from the UK will help kickstart the Sprint to Glasgow ahead of the UK-UN Climate Summit on 12 December.

Electricity cables and pylon snaking around a mountain near Cruachan Power Station in the Highlands

Electricity cables and pylon snaking around a mountain near Cruachan Power Station, Drax’s flexible pumped storage facility in the Highlands

2030 ambition is clearly needed, but to deliver on net zero, deep decarbonisation will be required. Previous commitments from the UK on its coal phase out and being the first major economy to adopt a net zero target continue to encourage similar international actions. To build on these and continue UK leadership on electricity sector decarbonisation, we call on the UK to commit to a date for a net zero power system ahead of COP26, to match the commitment of the US President-elect’s Clean Energy Plan. To ensure the maximum benefit at lowest cost, the chosen date should be informed by analysis and consider broad stakeholder input.

Alongside near-term stability as the UK’s carbon pricing future is determined, to meet this commitment Government should launch a consultation on a date for a net zero power system by the Budget next year, with a target date to be confirmed in the UK’s upcoming Net Zero Strategy. This commitment would send a signal to the rest of the world that the UK intends to maintain its leadership position on climate and to build a greener, more resilient economy.

To:

  • Rt Hon Boris Johnson MP, Prime Minister of the United Kingdom
  • Rt Hon Rishi Sunak MP, Chancellor of the Exchequer
  • Rt Hon Alok Sharma MP, Secretary of State for Business, Energy and Industrial Strategy and UNFCCC COP26 President
  • Rt Hon Kwasi Kwarteng MP, Minister for Business, Energy and Clean Growth

Signatories:

BP, Drax, National Grid ESO, Sembcorp, Shell and SSE

View/download letter in PDF format

 

COP26: Will countries with the boldest climate policies reach their targets?

To tackle the climate crisis, global unity and collaboration are needed. This was in part the thinking behind the Paris Agreement. It set a clear, collective target negotiated at the 2015 United Nations Climate Change Conference and signed the following year: to keep the increase in global average temperatures to well below 2 degrees Celsius above pre-industrial levels.

In November 2021, COP26 will see many of the countries who first signed the Paris Agreement come together in Glasgow for the first ‘global stocktake’ of their environmental progress since its creation.

COP26 will take place at the SEC in Glasgow

Already delayed for a year as a result of the pandemic, COVID-19 and its effects on emissions is likely to be a key talking point. So too will progress towards not just the Paris Agreement goals but those of individual countries. Known as ‘National Determined Contributions’ (NDCs), these sit under the umbrella of the Paris Agreement goals and set out individual targets for individual countries.

With many countries still reeling from the effects of COVID-19, the question is: which countries are actually on track to meet them?

What are the goals?

The NDCs of each country represent its efforts and goals to reduce national emissions and adapt to the impacts of climate change. These incorporate various targets, from decarbonisation and forestry to coastal preservation and financial aims.

While all countries need to reduce emissions to meet the Paris Agreement targets, not all have an equally sized task. The principle of differentiated responsibility acknowledges that countries have varying levels of emissions, capabilities and economic conditions.

The Universal Ecological Fund outlined the emissions breakdown of the top four emitters, showing that combined, they account for 56% of global greenhouse gas emissions. China is the largest emitter, responsible for 26.8%, followed by the US which contributes 13.1%. The European Union and its 28 member states account for nine per cent, while India is responsible for seven per cent of all emissions.

These nations have ambitious emissions goals, but are they on track to meet them?

China

Traffic jams in the rush hour in Shanghai Downtown, contribute to high emissions in China.

By 2030, China pledged to reach peak carbon dioxide (CO2), increase its non-fossil fuel share of energy supply to 20% and reduce the carbon intensity – the ratio between emissions of CO2 to the output of the economy – by 60% to 65% below 2005 levels.

COVID-19 has increased the uncertainty of the course of China’s emissions. Some projections show that emissions are likely to grow in the short term, before peaking and levelling out sometime between 2021 and 2025. However, according to the Climate Action Tracker it is also possible that China’s emissions have already peaked – specifically in 2019. China is expected to meet its non-fossil energy supply and carbon intensity pledges.

United States

The forecast for the second largest emitter, the US, has also been affected by the pandemic. Economic firm Rhodium Group has predicted that the US could see its emissions drop between 20% and 27% by 2025, meeting its target of reducing emissions by 26% to 28% below 2005 levels.

However, President Trump’s rolling back of Obama-era climate policies and regulations, his support of fossil fuels and withdrawal from the Paris Agreement (effective from as early as 4 November 2020), suggest any achievement may not be long-lasting.

The United States’ Coronavirus Aid, Relief, and Economic Security Act, known as the CARES Act, does not include any direct support to clean energy development – something that could also change in 2021.

European Union

CCUS Incubation Unit, Drax Power Station

Carl Clayton, Head of BECCS at Drax, inspects pipework in the CCUS area of Drax Power Station

The European Union and its member states, then including the UK, pledged to reduce emissions by at least 40% below 1990 levels by 2030 – a target the Climate Action Tracker estimates will be achieved. In fact, the EU is on track to cut emissions by 58% by 2030.

This progress is in part a result of a large package of measures adopted in 2018. These accelerated the emissions reductions, including national coal phase-out plans, increasing renewable energy and energy efficiency. The package also introduced legally binding annual emission limits for each member state within which they can set individual targets to meet the common goal.

The UK has not yet released an updated, independent NDC. However, it has announced a £350 million package designed to cut emissions in heavy industry and drive economic recovery from COVID-19. This includes £139 million earmarked to scale up hydrogen production, as well as carbon capture and storage (CCS) technology, such as bioenergy with carbon capture (BECCS) – essential technologies in achieving net zero emissions by 2050 and protecting industrial regions.

India

India, the fourth largest global emitter, is set to meet its pledge to reduce its emissions intensity by 33% to 35% below 2005 levels and increase the non-fossil share of power generation to 40% by 2030. What’s more, the Central Electricity Agency has reported that 64% of India’s power could come from non-fossil fuel sources by 2030.

Wind turbines in Jaisalmer, Rajasthan, India

Along with increasingly renewable generation, the implementation of India’s National Smart Grid Mission aims to modernise and improve the efficiency of the country’s energy system.

It is promising that the world’s four largest emitters have plans in place and are making progress towards their decarbonisation goals. However, tackling climate change requires action from around the entire globe. In addition to NDCs, many countries have committed to, or have submitted statements of intent, to achieve net zero carbon emissions in the coming years.

Net zero target

CountryTarget Date Status
Bhutan 🇧🇹Currently carbon negative (and aiming for carbon neutrality as it develops; pledged towards the Paris Agreement)
Suriname 🇸🇷Currently carbon negative
Denmark 🇩🇰2050In law
France 🇫🇷2050In law
Germany 🇩🇪2050In law
Hungary 🇭🇺2050In law
New Zealand 🇳🇿2050In law
Scotland 🏴󠁧󠁢󠁳󠁣󠁴󠁿2045In law
Sweden 🇸🇪2045In law
United Kingdom 🇬🇧2050In law
Bulgaria 🇧🇬2050Policy Position
Canada 🇨🇦2050Policy Position
Chile 🇨🇱2050In policy
China 🇨🇳2060Statement of intent
Costa Rica 🇨🇷2050Submitted to the UN
EU 🇪🇺2050Submitted to the UN
Fiji 🇫🇯2050Submitted to the UN
Finland 🇫🇮2035Coalition agreement
Iceland 🇮🇸2040Policy Position
Ireland 🇮🇪2050Coalition Agreement
Japan 🇯🇵2050Policy Position
Marshall Islands 🇲🇭2050Pledged towards the Paris Agreement
Netherlands 🇳🇱2050Policy Position
Norway 🇳🇴2050 in law, 2030 signal of intent
Portugal 🇵🇹2050Policy Position
Singapore 🇸🇬As soon as viable in the second half of the centurySubmitted to the UN
Slovakia 🇸🇰2050Policy Position
South Africa 🇿🇦2050Policy Position
South Korea 🇰🇷2050Policy Position
Spain 🇪🇸2050Draft Law
Switzerland 🇨🇭2050Policy Position
Uruguay 🇺🇾2030Contribution to the Paris Agreement

While the COVID-19 pandemic has disrupted short-term plans, many see it as an opportunity to rejuvenate economies with sustainability in mind. COP26, as well as the global climate summit planned for December of this year, will likely see many countries lay out decarbonisation goals that benefit both people’s lives and the planet.

What is carbon dioxide?

What is CO2?

Carbon dioxide (or CO2) is a colourless and odourless naturally occurring gas in the earth’s atmosphere which is made up of one carbon atom and two oxygen atoms.  As a greenhouse gas (GHG), it traps heat, making sure the planet isn’t uninhabitably cold. However, fast rising levels of CO2 and other long-lasting GHGs in the atmosphere are currently causing global warming to occur at an alarmingly rapid rate.

What is the carbon cycle?

Carbon is the basis of all life on earth – it is a key ingredient in almost everything on the planet. As the earth has a closed atmosphere, there has always been the same amount of carbon on the earth, but it is in a constant state of change, transitioning from gas to solid to liquid and moving between the atmosphere and the earth. This process is called the carbon cycle, and it is key to ensuring the earth is capable of sustaining life. CO2 forms one part of this process and makes up the largest available source of carbon on earth.

How is CO2 made?

Carbon is stored in oceans, soil, and living things and is released from this storage into the atmosphere in the form of CO2. CO2 is created when one carbon atom meets two oxygen atoms, which join together through a number of processes, including the decay of organic matter, the combustion of materials such as wood, coal and natural gas, through the breathing of humans and animals, and from events such as volcanic eruptions.

How does CO2 affect the planet?

An abundance of CO2 in the earth’s atmosphere means more heat gets trapped, which in turn contributes to a rise in global temperatures and climate change. This acceleration in carbon entering the atmosphere began during the Industrial Revolution around the 1800s, when fossil fuels were mined and burned to create energy, which released long-stored carbon into the atmosphere in the form of CO2.

From the beginning of the Industrial Revolution until today, the amount of carbon in the atmosphere has increased from 280 parts per million, to 387 parts per million, which constitutes a 39% increase. Today, CO2 levels are the highest they’ve been in 800,000 years.

CO2 is created when one carbon atom meets two oxygen atoms, which join together when organic materials containing carbon are burned: wood, coal, and natural gas.

How can countries reduce CO2 in the atmosphere?

According to the Paris Climate Agreement, nations must work to limit warming of the globe to be well under two degrees Celsius above pre-industrial levels. In the first half of 2015, the earth registered a one degree Celsius rise in global temperatures above pre-industrial levels, which means drastic and meaningful action must be taken to decarbonise within the next few years.

There are many ways to reduce the earth’s carbon footprint, including reforestation and using alternative ways to generate energy that don’t rely on fossil fuels. For example, wind, solar, biomass and hydro can all provide sustainable, carbon-neutral and low carbon sources of electricity.

Technology such as carbon capture and storage (CCS) can capture carbon permanently storing CO2 from industries in which some CO2 emissions remain. By combining CCUS with biomass energy (bioenergy with carbon capture and storage, or BECCS) it is even possible to generate negative emissions, where more CO2 is removed from the atmosphere than is emitted.

CO2 fast facts

  • In the 1960s, the growth of CO2 occurred at 0.6 parts per million per year. In the last 10 years, the rate has been 2.3 parts per million per year
  • The average human breathes out 93 kilograms of CO2 per year – however, our breathing only contributes 0.65 billion tonnes of carbon returned to the atmosphere, which is 0.01% of the amount released by fossil fuels each year
  • Trees absorb CO2 in the atmosphere and release it in the form of oxygen, making them vitally important in the world’s fight against climate change. In the US alone, forests absorb 13% of the nation’s carbon output

There are many ways to reduce the earth’s carbon footprint, including using alternative ways to generate power.

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Turning waste into watts

Fields being ploughed by tractor

Think of carbon emissions and the image that comes to mind is often of industrial sites or power generation – not of what we eat and what we throw away. But food waste is a major contributor of greenhouse gas emissions.

Globally, food loss and waste from across the food chain generates the equivalent of 4.4 gigatonnes of carbon dioxide (CO2) a year, or about 8% of total greenhouse gas emissions.

But what if there was a way to reduce those emissions and generate power by using discarded food and other organic waste like grass cuttings or nut shells? A technology known as anaerobic digestion is increasingly making this idea a reality.

How anaerobic digestion works

All organic waste products have energy in them, but it’s tied up in the form of calories. When food and vegetation rots, microorganisms break down those calories into gases and other products.

Methane or Ammonium molecules. Science concept. 3D rendered illustration.

Methane or Ammonium molecules.

Exactly what these ‘other products’ are depends on whether there is any oxygen present. With oxygen, the products are water, CO2 and ammonia, but remove oxygen from the equation and a very valuable gas is produced: methane (CH4). The lack of oxygen is also what gives anaerobic digestion its name – when oxygen is present it becomes aerobic digestion.

During the anaerobic digestion process, bacteria and other microorganisms break down organic matter, gradually deteriorating complex polymers like glucose or starch into progressively simpler elements, such as alcohol, ammonia, CO2 and, ultimately, CH4, a biogas with huge potential as a fuel for other processes.

Anaerobic power in practice

The CH4 produced in anaerobic digestion is incredibly useful as a fuel – turn on a gas hob or stovetop and it’s predominantly methane that provides the fuel for the flame. The chemical compound is also the main component in the natural gas that makes up much of Great Britain’s electricity supply.

This means using anaerobic digestion to create CH4 out of waste products turns that waste into a valuable power source. But it’s not as simple as putting a bag over a rubbish tip and hoping for the best.

Instead, anaerobic digestion is carried out in large tanks called digesters. These are filled with feedstocks from biological substances that can include anything from food scraps, to alcohol and distillery waste, to manure. Under the right conditions microorganisms and bacteria begin to digest and breakdown these substances into their basic elements.

The air quantity and temperature of the digesters is carefully regulated to ensure the microorganisms have the best possible environment to carry out the digestion of the feedstock, with different types of feedstock and microorganisms operating best in different conditions.

The biogas created as a result of this digestion is then captured, ready to be turned into something useful.

biogas plant

Making use of biogas

Three different things can happen to the biogas produced during the course of the digestion. Locally, it can be combusted on-site to provide further heat to regulate the temperature of the anaerobic digestion units.

Or, it can be combusted in a combined heat and power (CHP) generator, where it can generate electricity to be used on site — for example to power a farm — or sold through energy suppliers such as Opus Energy onto wider regional or national electricity networks. This biogas electricity is an important element of Great Britain’s energy supply, accounting for 6,600 GWh or 7.3% of all power generated by solid and gaseous fuels in 2017.

Some of the biogas can even be cleaned to remove CO2, leaving behind pure methane that can be pumped onto natural gas grids and used to provide heat and power to households. Government research estimates a fully utilised biogas sector could provide up to 30% of the UK’s household gas demands.

After the digestion process has been completed and the biogas has been removed, what is left behind in the digester is a mass of solid matter called digestate. This is extremely rich in nutrients and mineral, such as potassium and nitrogen, making it an excellent soil enhancer.

Where anaerobic digestion is being used today

Today, much of anaerobic digestion power is generated on farms – unsurprisingly, given the ready access to biological waste material to use as feedstock. As well as a potential source of electricity and heat, it also gives farmers access to a new revenue stream, by selling electricity or biogas, as well as reducing utility and fertiliser costs.

While many of these installations are smaller scale, some can get quite big. Linstock Castle Farm in North Cumbria, for example, has a biogas facility with a 1.1 megawatt(MW) operating capacity, enough to power as many as 2,000 homes at a time. It was originally installed by the farmers as a more cost-effective way of growing their business than buying more dairy cows.

Biogas plant on a farm processing cow dung as a secondary business activity

There is, however, potential for anaerobic digestion to operate on an even larger scale. In the US, the city of Philadelphia is developing a system that will link all newly built households together into a network where food waste is automatically collected and transported to a biogas generating facility.

Closer to home, Northumbrian Water uses 100% of its sludge, the waste produced from purifying water, to produce renewable power via anaerobic digestion. It’s estimated to have reduced the carbon footprint of the facility’s operations by around 20%, and saved millions of pounds in savings on operating costs.

There have also been experiments with using biogas to power vehicles. The ‘Bio-Bus’ was the first bus in the UK to be powered by biomethane made from food, sewage and commercial liquid waste, and ran between Bath and Bristol Airport.

But anaerobic digestion power is not a magic bullet. It will be right in certain situations, but not all. If utilised effectively, anaerobic digestion and biogas could fill a vital role in national electricity and gas networks, while at the same time helping dispose of waste products in an environmentally-friendly and cost-effective way.