Bioenergy with carbon capture and storage (BECCS) is a process that uses plant material (biomass) to create energy. During this process, carbon dioxide (CO₂) that is released is captured and stored underground.

When plants are used for bioenergy, new plants can grow to replace them. These new plants absorb CO₂ from the air through photosynthesis. After the biomass is collected, energy is created in useful forms, such as electricity, heat, or biofuels, through methods like burning, fermentation, pyrolysis, or other processes. This energy use releases CO₂ into the air. In BECCS, some of this CO₂ is captured before it reaches the atmosphere and is stored underground using special technology. In some cases, BECCS can remove CO₂ from the air.

Studies suggest that BECCS could reduce carbon emissions by between 0 and 22 billion tons each year. As of 2024, three large-scale BECCS projects are operating globally. However, using BECCS widely is limited by the cost of the technology and the availability of biomass. Because growing biomass requires a lot of land, expanding BECCS may affect food production, harm biodiversity, and raise concerns about human rights.

Negative emission

The main benefit of BECCS is its ability to remove carbon dioxide (CO₂) from the atmosphere, creating negative emissions. This happens when carbon dioxide is captured from bioenergy sources, which are made from biomass—a renewable resource that absorbs CO₂ during its growth.

Carbon capture and storage (CCS) technology stops CO₂ from being released into the air when biofuels are burned. Instead, the CO₂ is stored in long-term locations, such as underground geological formations or in materials like concrete. This process results in a net reduction of CO₂ in the atmosphere. However, the overall effectiveness of this method can be reduced by emissions from transporting biomass, energy used during the process, and emissions from growing the biomass.

Not all BECCS systems capture CO₂ from combustion. Some systems also capture CO₂ from non-combustion sources, such as the kraft pulping process or during the production of biogas and ethanol.

BECCS technology stores CO₂ in geological formations for long-term safety. The length of time CO₂ remains stored depends on the method used. Natural reservoirs release about 10% of stored CO₂ each year, while depleted natural gas wells release about 10⁻¹⁰% annually. In 2005, the IPCC estimated that storing CO₂ underground through BECCS offers greater long-term safety compared to natural carbon sinks like oceans, trees, and soil. Natural sinks may risk worsening climate change if global temperatures rise.

Reducing CO₂ levels in the atmosphere using natural sinks like trees and soil alone may not be enough to meet low-emission goals. Even with ambitious efforts, significant additional emissions are expected this century. BECCS and Direct Air Carbon Capture are the only methods capable of creating negative emissions, which would lower the total amount of CO₂ in the atmosphere. This means emissions would not only stop but also reduce the existing CO₂ levels.

Cost

Cost estimates for BECCS can be between $60 and $250 for each ton of CO₂ removed.

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

Technology

The main technology for capturing CO₂ from biotic sources is similar to that used for capturing CO₂ from traditional fossil fuel sources. There are three main types of technologies: 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 promising method for carbon capture and storage (CCS). In oxy-fuel combustion, fuel is burned in a mixture of oxygen and recycled flue gas, unlike conventional air firing. Oxygen is produced by an air separation unit (ASU), which removes nitrogen from the air. Removing nitrogen before the process creates flue gas with high CO₂ and water vapor levels, eliminating the need for a post-combustion capture plant. Water vapor can be removed by condensation, leaving a high-purity CO₂ stream. This CO₂ can then be purified and sent to a geological storage site.

A key challenge in using oxy-combustion for BECCS is the combustion process. Biomass with high volatile content requires low mill temperatures to avoid fire or explosion risks. Additionally, the flame temperature is lower, so oxygen concentration must be increased to 27–30%.

"Pre-combustion carbon capture" refers to capturing CO₂ before energy is generated. This process involves five steps: oxygen generation, syngas production, CO₂ separation, CO₂ compression, and power generation. Fuel is first gasified using oxygen to create syngas, a mixture of carbon monoxide and hydrogen. Syngas then passes through a water-gas shift reactor to produce CO₂ and hydrogen. The CO₂ is captured, and hydrogen is used for energy production. This process is called Integrated Gasification Combined Cycle (IGCC). An air separation unit (ASU) can supply oxygen, but research shows that oxygen gasification is only slightly better than air gasification for coal. Both methods have similar thermal efficiency (about 70%). Therefore, using an ASU is not always necessary in pre-combustion capture.

Biomass is considered "sulfur-free" as a fuel for pre-combustion capture. However, other trace elements like potassium (K) and sodium (Na) in biomass can accumulate and damage equipment. Further improvements in separating these elements are needed. 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 water-gas shift process, reducing hydrogen production. Despite this, pre-combustion capture using biomass has a thermal efficiency similar to coal (about 62–100%). Research suggests that using a dry system instead of a biomass/water slurry is more efficient for biomass.

Post-combustion technology is another method for capturing CO₂ from biomass fuel. It separates CO₂ from flue gas after biomass is burned. Because it can be added to existing power plants like steam boilers or new power stations, post-combustion is often preferred over pre-combustion. According to a 2018 fact sheet, post-combustion technology has an efficiency of 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 parasitic energy consumption, where small unit designs lead to significant heat loss. Another challenge is handling flue gas mixtures from biomass, which contain high levels of alkali metals, halogens, acidic elements, and transition metals. These components can harm process efficiency. Therefore, selecting appropriate solvents and managing the solvent process is critical.

Biomass feedstocks

BECCS uses different types of biomass, such as leftover materials and waste from farming, trees, industry, and cities, as well as plants grown specifically to be used as fuel.

To make biomass-based carbon capture work and keep it carbon neutral, several challenges must be addressed. Biomass needs water and fertilizer, which are connected to environmental problems like using natural resources, conflicts over resources, and pollution from fertilizers. Another challenge is moving large amounts of biomass to places where carbon can be stored underground.

Projects and commercial plants

As of 2024, there are 3 large BECCS projects in the world. 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 been completed by 2022.

The Illinois Industrial Carbon Capture and Storage (IL-CCS) project, started in the early 2000s, is the first large-scale BECCS project. It is 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 leaks 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 has three times the capture ability of the first phase, allowing IL-CCS to store over 1 million tonnes of CO₂ each year. By 2019, IL-CCS was the largest BECCS project in the world.

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

Challenges

Some environmental concerns and other issues about using BECCS on a large scale are similar to those of CCS. However, one common 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 biomass. There are other concerns about BECCS, such as the possible increased use of biofuels. Producing biomass can lead to several sustainability issues, such as limited arable land and fresh water, loss of plant and animal life, competition with food production, and deforestation. It is important to use biomass in a way that provides the most energy and climate benefits. Some BECCS plans have been criticized for requiring very large amounts of biomass.

To operate BECCS on an industrial scale, large areas of land would be needed. For example, removing 10 billion tons of CO₂ would require more than 300 million hectares of land (larger than India). This could use land that is better suited for farming and food production, especially in developing countries.

These systems may also have other negative effects. However, there is no need to increase biofuel use in energy or industry to support BECCS. Today, there are already many emissions from biomass sources that could be used for BECCS. In future plans for expanding bioenergy, this might become an important issue.

The IPCC Sixth Assessment Report states: "Widespread use of BECCS and planting more trees would need more fresh water than previously used by plants, changing how water moves in certain areas (high confidence). This could affect water use, plant and animal life, and local climates, depending on the land and climate conditions (high confidence)."

A challenge for BECCS, like other CCS systems, is finding good places to build power plants and store captured CO₂. If biomass is far from the power plant, transporting it releases CO₂, which can reduce the benefits of BECCS. BECCS also has technical issues, such as the low efficiency of burning biomass. Biomass generally has a lower energy value than coal. Converting biomass into energy is usually about 20-27% efficient, while coal plants are about 37% efficient.

BECCS also raises questions about whether the process is energy positive. The low efficiency of converting biomass into energy, the energy needed to grow and transport biomass, and the energy used for capturing and storing CO₂ can reduce the overall energy output of the system. This might lead to less power being produced.

Alternative biomass sources

Every year, 14 gigatons of forestry waste and 4.4 gigatons of crop waste (such as barley, wheat, corn, sugarcane, and rice) are produced worldwide. This large amount of organic material can be burned to create 26 exajoules of energy annually and remove 2.8 gigatons of carbon dioxide through a process called BECCS. Using this waste for carbon capture can help rural areas by providing economic and social benefits. Using crop and forest waste helps avoid problems that might happen with BECCS.

Among ways to use forest materials for energy, turning forest waste into electricity through gasification is being supported by policies in many developing countries. This is because forests have plenty of organic material, and it is affordable since it is a byproduct of regular forestry work. Unlike wind and solar energy, which are not always available, forest waste gasification can provide continuous electricity and can be adjusted to meet changing energy needs. Forest industries are well-suited to help expand these energy strategies to address energy and climate challenges. However, many studies do not clearly explain the costs of using forest waste for electricity or how this might affect traditional forestry work. Research into whether producing both timber and electricity together is financially possible could help in developing countries.

Even though policies are pushing for electricity made from wood, uncertainty about costs and risks keeps investors from moving forward, especially in developing countries where demand is highest. This is because forest energy projects face high financial risks, including expensive equipment, operating costs, and maintenance. These costs and risks can discourage people from investing in forest-based electricity projects.

Municipal solid waste includes materials from living things, like food, wood, and paper. Burning this waste can produce some energy. About 44% of global waste is food and green waste, and 17% is paper and cardboard. If carbon capture is used, burning waste could reduce carbon emissions by 700 kilograms of carbon dioxide per kilogram of waste, assuming 85% of carbon is captured. The exact mix of waste does not greatly affect this result.

In 2017, there were about 250 plants worldwide that mix biomass with coal for energy, including 40 in the United States. Burning biomass with coal is as efficient as burning coal alone. Sometimes, completely switching from coal to biomass in a power plant might be better than mixing the two.

Policy

Based on the Kyoto Protocol agreement, carbon capture and storage (CCS) projects were not allowed as a method to reduce emissions for Clean Development Mechanism (CDM) or Joint Implementation (JI) projects. By 2006, there was increasing support to include fossil CCS and BECCS in the Kyoto Protocol and the Paris Agreement. Studies were conducted to explain how this could be done, including the use of BECCS.

Policies were created to encourage the use of bioenergy, such as the Renewable Energy Directive (RED) and Fuel Quality Directive (FQD). These policies required 20% of total energy consumption to 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 be made using CCS as soon as the technology becomes available.

In 2018, the U.S. Congress increased and extended the section 45Q tax credit for capturing and storing carbon oxides. This tax credit was raised 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 views BECCS. Most of these studies were done in developed countries in the northern hemisphere, which may not reflect opinions from all parts of the world.

A 2018 study asked people in the United Kingdom, United States, Australia, and New Zealand about BECCS. Most participants had little knowledge of BECCS before the study. The study found that people thought BECCS had both positive and negative qualities. In the four countries, 45% of people said they would support small tests of BECCS, while 21% said they would not. Compared to other ways of removing carbon dioxide, like direct air capture or enhanced weathering, BECCS was somewhat preferred. It was much more preferred than methods that manage solar radiation.

A 2019 study in Oxfordshire, UK, found that people’s views on BECCS were affected by the policies used to support it. Most participants approved of taxes and rules to support BECCS, but they had mixed opinions about government funding for the practice.