Bioenergy with carbon capture and storage (BECCS) is a method 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. Energy from biomass is made by burning, fermenting, or using other methods. This process releases CO₂ into the air. In BECCS, some of this CO₂ is collected before it reaches the atmosphere and stored using special technology. In certain situations, BECCS can remove CO₂ from the air.
Studies suggest that BECCS could reduce up to 22 billion metric tons of CO₂ each year. As of 2024, three large BECCS projects are operating globally. However, using BECCS on a large scale is limited by the cost of the technology and the availability of biomass. Since growing biomass requires a lot of land, using it for BECCS might affect food production, human rights, and the survival of plants and animals.
Negative emission
BECCS is valuable because it can remove carbon dioxide (CO₂) from the atmosphere, leading to negative emissions. This happens when CO₂ is captured from bioenergy sources, which are made from biomass. Biomass is a renewable resource that absorbs CO₂ from the air as it grows.
Carbon capture and storage (CCS) technology stops CO₂ from being released when biofuels are burned and stores it in safe places, such as underground or in concrete. This process removes CO₂ from the atmosphere and stores it long-term. However, some CO₂ may still be released during the transportation of biomass, energy use in the process, or growing biomass.
Not all BECCS captures CO₂ from burning biofuels. Some BECCS captures CO₂ from other processes, like papermaking or when separating biogas and ethanol.
BECCS stores CO₂ in geological formations, such as underground rock layers, for a long time. The length of storage depends on the method used. CO₂ stored in natural reservoirs may slowly escape over time, while CO₂ stored in old natural gas wells escapes very little. In 2005, scientists estimated that storing CO₂ underground through BECCS would be more permanent than using natural carbon sinks like oceans, trees, or soil. Natural sinks carry risks, such as releasing more CO₂ if temperatures rise.
Reducing CO₂ in the atmosphere by relying only on natural sinks like trees and soil may not be enough to meet low-emission goals. Even with strong efforts to cut emissions, significant CO₂ will still be added to the atmosphere this century. BECCS and Direct Air Carbon Capture are the only methods that can create negative emissions, meaning they reduce the total amount of CO₂ in the atmosphere below current levels. This would not only stop emissions but also lower the overall CO₂ in the air.
Cost
Cost estimates for BECCS can be between $60 and $250 per ton of CO₂.
It was estimated that methods using electricity from non-fossil fuels to split salty water and react it with minerals could, on average, produce more energy and remove more CO₂ than BECCS by more than 50 times, at similar or lower costs. However, more research is needed to create these methods.
Technology
The main technology for capturing carbon dioxide (CO₂) from biotic sources, such as plants, often uses the same methods as those used for capturing CO₂ from fossil fuels like coal and natural gas. Three main types of technologies are used: post-combustion, pre-combustion, and oxy-fuel combustion.
Oxy-fuel combustion is a process already used in industries like glass, cement, and steel production. It is also a promising method for carbon capture and storage (CCS). In oxy-fuel combustion, fuel is burned in a mixture of oxygen (O₂) and recycled flue gas, instead of using air as in traditional methods. Oxygen is separated from air using a device called an air separation unit (ASU), which removes nitrogen (N₂). This process creates flue gas with high levels of CO₂ and water vapor. The water vapor can be removed by cooling, leaving mostly pure CO₂, which can then be purified and sent to storage sites underground.
A key challenge in using oxy-fuel combustion for biomass energy with carbon capture and storage (BECCS) is managing the combustion process. Biomass with high volatile content requires lower temperatures to avoid fire or explosion risks. Additionally, the flame temperature is lower, so oxygen levels must be increased to 27%–30% to maintain efficiency.
Pre-combustion carbon capture involves removing CO₂ before energy is generated. This process typically has five steps: oxygen production, syngas creation, CO₂ separation, CO₂ compression, and power generation. Fuel is first converted into syngas, a mixture of carbon monoxide (CO) and hydrogen (H₂), through a process called gasification. Syngas then passes through a reactor to form CO₂ and H₂. The CO₂ is captured, while the H₂ is used to generate energy. This combined process is called Integrated Gasification Combined Cycle (IGCC). Although an ASU can provide oxygen, studies show that using air instead of pure oxygen in gasification has similar efficiency for coal. Therefore, an ASU may not always be needed in pre-combustion methods.
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 equipment and damage mechanical parts. Further 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 CO to CO₂ in later steps, reducing hydrogen production. Despite this, the thermal efficiency of pre-combustion capture using biomass is similar to that of coal, ranging from 62% to 100%. Research suggests using a dry system instead of a biomass/water slurry can improve efficiency.
Post-combustion technology is another method for capturing CO₂ from biomass fuels. After burning biomass, CO₂ is separated from other gases in the flue gas. This method is often preferred because it can be added to existing power plants like steam boilers or used in new power stations. According to a 2018 fact sheet, post-combustion technology has an efficiency of 95%, while pre-combustion and oxy-fuel methods capture CO₂ at 85% and 87.5% efficiency, respectively.
Current post-combustion technologies face challenges. One issue is the high energy use required to capture CO₂, which can reduce overall efficiency. If the system is too small, heat loss may cause problems. Another challenge is handling the complex mix of substances in flue gas from biomass, such as alkali metals, halogens, acidic elements, and transition metals. These substances can harm the efficiency of the process. Therefore, selecting the right solvents and managing their use carefully is essential for successful CO₂ capture.
Biomass feedstocks
Biomass sources used in BECCS include leftover materials from farming and forests, waste from industries and cities, and plants grown especially for making energy.
Several challenges must be addressed to make biomass-based carbon capture work well and keep carbon levels neutral. Biomass needs water and fertilizer, which can cause environmental problems such as using too much water, causing pollution, or leading to fights over resources. Another challenge is moving heavy and hard-to-transport biomass to areas where carbon can be stored safely.
Projects and commercial plants
As of 2024, there are 3 large-scale BECCS projects in operation worldwide. All of these projects are ethanol plants. Between 1972 and 2017, plans were made to store 2.2 million tonnes of CO₂ each year using CCS technology 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 industrial-scale 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 saltwater layer. The IL-CCS 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. Monitoring continues for future use. The second phase began in November 2017, using the same storage area. This phase cost about $208 million, with $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. 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:
Challenges
Some environmental concerns and other issues about using BECCS on a large scale are similar to those of CCS. However, many people criticize CCS because it might increase reliance on non-renewable fossil fuels and harmful coal mining. This is not true for BECCS, as it uses renewable biomass instead. There are still 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 plant and animal life, competition with food production, and deforestation. It is important to use biomass in a way that helps the environment and reduces climate harm. Some plans for BECCS have been criticized because they would require a large amount of biomass.
To operate BECCS on an industrial scale, large areas of land would be needed. For example, removing 10 billion tonnes of CO₂ would require more than 300 million hectares of land—larger than the country of India. This could take land that is better used for growing food, especially in developing nations.
BECCS systems may also cause other problems. However, there is no need to expand biofuel use in energy or industry to support BECCS. Today, there are already many emissions from burning biomass that could be used for BECCS. In the future, if bioenergy systems grow larger, this might become an important issue.
The IPCC Sixth Assessment Report states: "Using BECCS and planting trees on a large scale would need more fresh water than previously used by plants, changing water cycles in certain areas (high confidence). This could affect water use, plant and animal life, and local climates, depending on the land’s previous use, climate conditions, and how much BECCS is used (high confidence)."
A challenge for BECCS, like other carbon capture systems, is finding good places to build power plants and store captured CO₂. If biomass is far from the power plant, moving it would release CO₂, reducing the benefits of BECCS. BECCS also has technical issues, such as the low efficiency of burning biomass. Biomass has less energy than coal, and converting it to energy is usually only 20-27% efficient, compared to about 37% for coal plants.
BECCS also raises a question about whether it is energy positive. Burning biomass uses little energy, and the process of capturing and storing CO₂ requires additional energy. This could reduce the overall energy output of the system.
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 globally. This large amount of biomass can be burned to create 26 exajoules of energy annually and remove 2.8 gigatons of carbon dioxide from the atmosphere through BECCS. Using this waste for carbon capture can help rural communities by providing social and economic benefits. Using crop and forestry waste helps avoid the challenges that come with BECCS.
Among forest bioenergy strategies, gasifying forest waste to make electricity is being supported by policies in many developing countries. This is because forest waste is plentiful and inexpensive, as it is a byproduct of regular forestry work. Unlike wind and solar energy, which are not always available, electricity from gasified forest waste can be produced continuously and adjusted to meet changing energy needs. Forest industries are well-suited to help expand forest bioenergy strategies to address energy and climate challenges. However, studies on forest bioenergy often do not clearly explain the costs of using forest waste for electricity or how this might affect traditional forestry work. Research on the financial benefits of producing both timber and electricity together could help explore these opportunities, especially in developing countries.
Although policies are increasing to use woody biomass for electricity, uncertainty about the financial costs and risks to investors is slowing progress, especially in developing countries where energy needs are greatest. This is because forest bioenergy projects face high financial risks, including expensive initial costs, operating expenses, and maintenance. These risks can discourage investors from supporting forest-based electricity projects.
Municipal solid waste includes organic materials like food, wood, and paper, so burning waste can produce some bioenergy. About 44% of global waste is food and green waste, and 17% is paper and cardboard. It is estimated that capturing carbon during waste incineration could reduce emissions by 700 kilograms of carbon dioxide per kilogram of waste, assuming 85% of carbon is captured. The specific types of waste do not greatly affect this result.
As of 2017, there were about 250 cofiring plants worldwide, including 40 in the United States. Burning biomass with coal is nearly as efficient as burning coal alone. Instead of cofiring, completely switching from coal to biomass in one or more parts of a power plant may be preferred.
Policy
Under the Kyoto Protocol agreement, carbon capture and storage (CCS) projects were not allowed as a way 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 on how to account for these methods were also completed.
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 government asked the Swedish Energy Agency 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 all aviation fuel by 2050. It also recommended that all aviation biofuels should be made using CCS once the technology is available.
In 2018, the U.S. Congress increased and extended the 45Q tax credit for sequestration of carbon oxides. This credit was raised to $50 per tonne of carbon dioxide for secure geological storage and to $35 per tonne of carbon dioxide used in enhanced oil recovery.
Public perception
Few studies have looked at how the public views BECCS. Most of these studies come from developed countries in the northern part of the world, which might not reflect opinions from all areas globally.
A 2018 study asked people online in the United Kingdom, United States, Australia, and New Zealand about BECCS. Most of them had not heard of BECCS before. People in these countries saw BECCS as having both good and bad qualities. In all four countries, 45% of people said they would support small tests of BECCS, while 21% said they would not. BECCS was somewhat preferred compared to other ways to remove carbon dioxide, such as direct air capture or enhanced weathering, and was much more preferred than methods like solar radiation management.
A 2019 study in Oxfordshire, UK, found that how people felt about BECCS depended on the policies used to support it. Most people agreed with taxes and rules to help BECCS, but they had different opinions about government money being used to support it.