Bioenergy with carbon capture and storage (BECCS) is a method that uses plants to create energy and then captures and stores the carbon dioxide (CO2) made during this process.

When plants are used for bioenergy, new plants can grow and take in CO2 from the air through photosynthesis. After the plants are collected, energy is made in forms like electricity, heat, or biofuels by burning, fermenting, or using other methods on the biomass. Using bioenergy releases CO2. In BECCS, some of this CO2 is caught before it goes into the air and stored deep underground. In certain situations, BECCS can take CO2 out of the air.

Experts say BECCS could remove between 0 and 22 billion metric tons of CO2 from the air each year. As of 2024, three large-scale BECCS projects are active globally. Expanding BECCS is limited by how much it costs and how much biomass is available. Because growing biomass needs a lot of land, using BECCS widely might harm food supplies, human rights, and wildlife.

Negative emission

The main benefit of BECCS is its ability to reduce carbon dioxide (CO₂) levels in the atmosphere to below what they were before human activity began. This happens because carbon dioxide is captured from bioenergy sources, which removes it from the air.

Bioenergy comes from biomass, a renewable resource that absorbs carbon dioxide from the atmosphere as it grows. Carbon capture and storage (CCS) technology stops CO₂ from being released when biofuels are burned and stores it in places like underground rock formations or concrete. This process removes more CO₂ from the air than is released during the process. However, the overall effectiveness of this removal can be reduced by emissions from transporting biomass, using energy during the process, and growing the biomass itself. Not all BECCS systems capture CO₂ from burning biomass. Some systems also capture CO₂ from non-burning sources, such as the kraft pulping process or during the production of biogas and ethanol.

BECCS technology stores carbon dioxide in underground geological formations for a long time, allowing biomass to continue absorbing CO₂ from the atmosphere. The length of time CO₂ stays stored depends on the method used. In natural reservoirs, about 10% of stored CO₂ may be released each year. In emptied natural gas wells, less than 10⁻¹⁰% is released yearly. In 2005, the IPCC estimated that storing CO₂ underground through BECCS provides more permanent storage compared to natural carbon sinks like oceans, trees, and soil. Natural sinks carry risks, such as increased climate change effects, if global temperatures rise.

Reducing CO₂ levels in the atmosphere by relying only on natural sinks like trees and soil will not be enough to meet low-emission goals. Even in the most ambitious plans to cut emissions, significant additional CO₂ will be released this century. BECCS and Direct Air Carbon Capture are the only methods that can create negative emissions, meaning they remove more CO₂ from the atmosphere than is released. This would not only stop emissions but also lower the total amount of CO₂ in the atmosphere.

Cost

Cost estimates for BECCS vary between $60 and $250 per ton of CO₂.

It was estimated that methods using electricity from non-fossil fuel sources to combine saline water electrolysis with mineral weathering could increase both energy production and CO₂ removal by more than 50 times compared to BECCS, at equivalent or lower cost. However, more research is needed to develop these methods.

Technology

The main technology for capturing CO₂ from biotic sources is similar to the technology used for capturing CO₂ from fossil fuels. Three main types of technologies are used: post-combustion, pre-combustion, and oxy-fuel combustion.

Oxy-fuel combustion is a common process in industries like glass, cement, and steel. It is also a method that shows potential for carbon capture and storage (CCS). In oxy-fuel combustion, fuel is burned in a mixture of oxygen and recycled flue gas, instead of using air. Oxygen is separated from air using an air separation unit (ASU), which removes nitrogen. This process creates flue gas with high levels of CO₂ and water vapor. The water vapor can be removed by cooling, leaving a stream of mostly pure CO₂. This CO₂ can then be purified and sent to a storage site underground.

A key challenge in using oxy-fuel combustion for Bioenergy with Carbon Capture and Storage (BECCS) is the combustion process. Biomass often has high volatile content, so the temperature during grinding must stay low to avoid fire or explosion risks. Also, the flame temperature is lower, so oxygen levels must be increased to 27–30% to maintain efficiency.

"Pre-combustion carbon capture" refers to capturing CO₂ before energy is produced. This process typically has five steps: oxygen generation, syngas generation, CO₂ separation, CO₂ compression, and power generation. Fuel is first converted into syngas, a gas made of carbon monoxide and hydrogen, through a process called gasification. Syngas then goes through a reactor to form CO₂ and hydrogen. The CO₂ is captured, and the hydrogen is used to generate energy. This combined process is called Integrated Gasification Combined Cycle (IGCC). An air separation unit (ASU) can provide oxygen, but research shows that using oxygen for gasification is only slightly better than using air. Both methods have similar thermal efficiency when using coal. Therefore, an ASU may not be necessary for pre-combustion capture.

Biomass is considered a "sulfur-free" fuel for pre-combustion capture. However, other elements like potassium (K) and sodium (Na) in biomass can build up in the system and damage equipment. More research is needed to improve methods for removing these elements. After gasification, CO₂ makes up 13–15.3% of syngas from biomass, compared to 1.7–4.4% from coal. This higher CO₂ level limits the conversion of carbon monoxide to CO₂ in the reactor and reduces hydrogen production. However, the thermal efficiency of pre-combustion capture using biomass is similar to that of coal, around 62–100%. Some studies suggest using a dry system instead of a biomass/water slurry is more efficient for biomass.

Post-combustion technology is another method used to capture CO₂ from biomass fuels. After burning biomass, CO₂ is separated from other gases in the flue gas. This method is considered better than pre-combustion because it can be added to existing power plants, like steam boilers, or new ones. According to a 2018 report, post-combustion technology has an efficiency of about 95%, while pre-combustion and oxy-fuel capture CO₂ at 85% and 87.5% efficiency, respectively.

Current post-combustion technologies face challenges. One major issue is the high energy use required for the process. If the system is too small, heat loss can cause problems. Another challenge is managing the mixture of gases in flue gas from biomass. These gases include alkali metals, halogens, acidic elements, and transition metals, which can reduce process efficiency. Careful selection of solvents and proper management of the solvent process are needed to address these issues.

Biomass feedstocks

Biomass sources used in BECCS include materials such as leftover parts from farming, leftover parts from cutting down trees, waste from industries and cities, and plants grown specifically to be used as fuel.

Several challenges must be addressed to make biomass-based carbon capture possible and ensure it does not add carbon to the environment. Biomass needs water and fertilizer, which are connected to environmental problems like using resources in ways that harm the environment, conflicts over resources, and fertilizer runoff. Another major challenge is transportation: large amounts of biomass must be moved to areas where carbon can be stored safely.

Projects and commercial plants

As of 2024, there are 3 large-scale BECCS projects operating worldwide. All of these projects are ethanol plants. Between 1972 and 2017, plans were made to store 2.2 million tonnes of carbon dioxide (CO₂) each year using carbon capture and storage (CCS) in biomass and waste power plants. None of these plans had started by 2022.

The Illinois Industrial Carbon Capture and Storage (IL-CCS) project, started in the early 2000s, is the first large-scale Bioenergy with Carbon Capture and Storage (BECCS) project. Located in Decatur, Illinois, USA, IL-CCS captures CO₂ from the Archer Daniels Midland (ADM) ethanol plant and stores it in the Mount Simon Sandstone, a deep underground rock layer. The project has two phases. The first phase, from November 2011 to November 2014, cost about $84 million. During this time, the project captured and stored 1 million tonnes of CO₂ without any CO₂ escaping from the storage area. Scientists continue to monitor the site for future use. The second phase began in November 2017, using the same storage area. This phase cost about $208 million, including $141 million from the Department of Energy. This phase can capture three times more CO₂ than the first phase, allowing IL-CCS to store over 1 million tonnes of CO₂ each year. As of 2019, IL-CCS was the largest BECCS project in the world.

In addition to IL-CCS, other projects capture CO₂ from ethanol plants on a smaller scale. Examples include:

• Arkalon in Kansas, USA: 0.18–0.29 million tonnes of CO₂ per year
• OCAP in the Netherlands: 0.1–0.3 million tonnes of CO₂ per year
• Husky Energy in Canada: 0.09–0.1 million tonnes of CO₂ per year

Challenges

Some environmental concerns and other issues about using BECCS on a large scale are similar to those of CCS. However, one major criticism of CCS is that it might increase reliance on limited fossil fuels and harmful coal mining. This is not the case with BECCS, as it uses renewable plant material instead. There are other concerns about BECCS, such as the possible increase in biofuel use. Producing biomass can face challenges, including limited farmland and fresh water, loss of wildlife habitats, competition with food crops, and deforestation. It is important to use biomass in ways that provide the most energy and climate benefits. Some BECCS plans have been criticized for requiring very large amounts of biomass.

To remove 10 billion tonnes of CO₂, BECCS would need over 300 million hectares of land, an area larger than India. This could take land that is better used for growing food, especially in developing countries.

These systems may also have other negative effects. However, there is no need to expand biofuel use for BECCS today, as there is already a lot of CO₂ from biomass sources that could be used. In the future, if bioenergy systems grow larger, this might become an important issue.

The IPCC Sixth Assessment Report states that using BECCS and planting more trees on a large scale could use more fresh water than previous vegetation, changing water movement in certain areas. This could affect water use, wildlife, and local climates, depending on the land and climate conditions.

A challenge for BECCS, like other carbon capture systems, is finding good places to build power plants and store CO₂. If biomass is far from the power plant, transporting it can release CO₂, reducing the benefits of BECCS. BECCS also has technical issues, such as the low efficiency of burning biomass. Biomass generally has less energy than coal, with thermal conversion efficiency around 20-27%, compared to about 37% for coal plants.

BECCS also raises questions about whether the process uses more energy than it produces. The low energy efficiency of biomass, the energy needed to grow and transport it, and the energy required for CO₂ capture and storage can reduce the overall energy output of the system.

Alternative biomass sources

Every year, about 14 billion tonnes of forestry waste and 4.4 billion tonnes of crop waste (mostly from barley, wheat, corn, sugarcane, and rice) are produced worldwide. This large amount of plant material can be burned to create 26 exajoules of energy each year and reduce carbon dioxide emissions by 2.8 billion tonnes through a process called BECCS, which captures carbon from the air. Using this waste for energy can help communities in rural areas by providing economic and social benefits. Using crop and forest waste avoids some problems that might happen if BECCS is used in other ways.

In many developing countries, turning forest waste into electricity through a process called gasification is becoming more supported by policies. This is because forest waste is plentiful and cheap, as it is a leftover product from normal forestry work. Unlike wind and solar energy, which depend on weather, forest waste gasification can provide electricity continuously and can be adjusted to meet changing energy needs. Forest industries are well suited to help expand these energy strategies to address energy shortages and climate change. However, studies often do not look closely at the costs of using forest waste for electricity or how this might affect traditional forestry jobs. Research that examines whether producing both timber and electricity together could be financially practical would help in developing countries.

Even though governments are encouraging the use of wood waste to make electricity, uncertainty about the financial risks and costs still makes it hard for investors to support this energy source, especially in developing countries where energy demand is highest. This is because forest bioenergy projects face high costs for building, running, and maintaining gasification plants, which can discourage investment.

Municipal solid waste includes materials from living things, such as food, wood, and paper. About 44% of global waste is food and green waste, and 17% is paper and cardboard. Using carbon capture during waste incineration could reduce emissions by 700 kg of CO2 for every kg of waste burned, assuming 85% of carbon is captured. The types of waste in the mix do not greatly affect this result.

As of 2017, there were about 250 plants worldwide that burn biomass along with coal, including 40 in the United States. Burning biomass with coal is as efficient as burning coal alone. However, some plants may choose to completely switch from coal to biomass instead of using both together.

Policy

Under the Kyoto Protocol agreement, carbon capture and storage (CCS) projects were not allowed as tools to reduce emissions for the Clean Development Mechanism (CDM) or Joint Implementation (JI) projects. By 2006, there was increasing support to include fossil CCS and bioenergy with carbon capture and storage (BECCS) in the Kyoto Protocol and the Paris Agreement. Studies were done to explore how these methods, including BECCS, could be used.

Policies such as the Renewable Energy Directive (RED) and Fuel Quality Directive (FQD) encouraged the use of bioenergy. These policies required that 20% of total energy consumption come from biomass, bioliquids, and biogas by 2020.

The Swedish Energy Agency was asked by the Swedish government to create a support system for BECCS to be used by 2022.

In 2018, the Committee on Climate Change suggested that aviation biofuels should supply up to 10% of total aviation fuel demand by 2050. It also recommended that all aviation biofuels should use CCS as soon as the technology becomes available.

In 2018, the U.S. Congress raised and extended the section 45Q tax credit for storing carbon dioxide. This credit was increased from $25.70 to $50 per tonne of CO₂ for secure geological storage and from $15.30 to $35 per tonne of CO₂ used in enhanced oil recovery.

Public perception

Few studies have looked at how the public feels about BECCS. Most of these studies come from developed countries in the northern hemisphere, so they might not show what people worldwide think.

A 2018 study asked people online in the United Kingdom, United States, Australia, and New Zealand about BECCS. Most of them had little knowledge of BECCS before the study. How people felt about BECCS included both positive and negative ideas. In the four countries, 45% of people said they would support small tests of BECCS, while 21% said they would not. People liked BECCS more than some other ways to remove carbon dioxide, such as direct air capture or enhanced weathering, but they liked it much more than methods like solar radiation management.

A 2019 study in Oxfordshire, UK, found that how people viewed BECCS was greatly affected by the rules and support used for it. Most people approved of taxes and standards, but they had different opinions about the government giving money to support BECCS.