Bioenergy with carbon capture and storage

• 1. Introduction

  ›

  Bioenergy with carbon capture and storage, known as BECCS, is one of only two methods scientists have identified that can actually pull carbon dioxide out of the atmosphere. Not merely stop adding to it. Pull it back out. The other method is direct air capture. Every other proposed climate tool reduces future emissions. Only these two can, under the right conditions, make the absolute amount of CO2 in the atmosphere go down.

  How does that work? The basic logic runs through the natural cycle of plants and trees. When vegetation is harvested and burned for energy, it releases CO2. But new vegetation can grow in its place, drawing that same CO2 back from the air through photosynthesis. If you intercept the carbon before it ever re-enters the atmosphere and lock it underground, you have not just broken even. You have removed carbon that was already there.

  The potential scale is enormous. Estimates put the range of negative emissions from BECCS at zero to 22 billion tonnes of CO2 per year. But as of 2024, only three large-scale BECCS projects are operating anywhere on Earth. The gap between that potential and that reality raises questions that go to the heart of how humanity plans to address a warming planet.

• 2. How the Carbon Loop Closes

  ›

  Biomass grows by pulling CO2 from the air. That is not unique to BECCS. What is unique is what happens after the biomass is burned. In a conventional bioenergy plant, combustion releases CO2 and it enters the atmosphere. BECCS intercepts that stream.

  The CO2 is captured and then routed to geological storage, typically deep saline formations or depleted natural gas wells. Storage in natural reservoirs has a release fraction on the order of ten to the minus seven per year, meaning the gas stays down for an extraordinarily long time. In 2005, the IPCC concluded that geological storage offers better permanence than conventional carbon sinks like oceans, trees, or soil, which can themselves release carbon when temperatures rise.

  CO2 does not have to come only from burning. BECCS can also capture carbon from fermentation during ethanol production, from the kraft pulping process in paper mills, and from the upgrading of biogas. In each case, biogenic carbon that would otherwise reach the air is redirected into the ground.

  In practice, the net effect is reduced by emissions from transporting bulky biomass to combustion sites and from the energy consumed by the capture and compression equipment itself. These real-world losses mean the carbon math is not automatic. They are precisely why monitoring projects like the one in Decatur, Illinois track outcomes rather than assuming them.

• 3. Three Ways to Catch Carbon

  ›

  Post-combustion capture is considered the most flexible of the three main BECCS technologies. It is retrofittable to existing steam boilers, and a U.S. Department of Energy fact sheet from March 2018 put its expected efficiency at 95%, higher than either of the other two approaches.

  Oxy-fuel combustion works differently. The fuel burns in a mix of pure oxygen and recycled flue gas rather than ordinary air. Removing the atmospheric nitrogen from the process produces a flue gas stream rich in CO2 and water vapor. The water condenses out, leaving a relatively pure CO2 stream ready for compression and storage. For biomass with a high volatile content, the process requires careful temperature control to prevent fire and explosion, and the oxygen concentration needs to reach 27-30%. Its efficiency lands at 87.5%.

  Pre-combustion capture turns the fuel into a gas before any burning takes place. The biomass is gasified with oxygen to produce syngas, a mixture of carbon monoxide and hydrogen. A water-gas shift reactor then converts the CO and steam into CO2 and hydrogen. The CO2 is captured, and the hydrogen, a clean fuel, is used to generate electricity. This approach, called Integrated Gasification Combined Cycle, achieves thermal efficiency of roughly 62-100% with biomass. One notable quirk: biomass is considered sulfur-free, but it carries trace elements including potassium and sodium that can accumulate in the system and degrade mechanical components over time. That requires separate management of those trace compounds.

• 4. The Decatur Experiment

  ›

  Decatur, Illinois is home to the Illinois Industrial Carbon Capture and Storage project, the first industrial-scale BECCS operation in the world. Carbon dioxide from the Archer Daniels Midland ethanol plant there is captured and injected into the Mount Simon Sandstone, a deep saline formation underground.

  The pilot phase ran from November 2011 to November 2014, at a capital cost of approximately 84 million dollars. During those three years, the project captured and stored 1 million tonnes of CO2 without any detected leakage from the injection zone. Monitoring continues.

  Phase 2 began in November 2017, using the same injection zone. Its capital cost was about 208 million dollars, of which 141 million came from the U.S. Department of Energy. The second phase has a capture capacity three times larger than the pilot, allowing the facility to capture over 1 million tonnes of CO2 annually. By 2019, it was the largest BECCS project in the world.

  Smaller operations exist elsewhere. The Arkalon plant in Kansas captures between 0.18 and 0.29 million tonnes of CO2 per year. OCAP in the Netherlands handles between 0.1 and 0.3 million tonnes. Husky Energy in Canada runs at 0.09 to 0.1 million tonnes. All of them, like the Decatur project, draw their carbon from ethanol production, which is also why all three of the large-scale BECCS projects currently operating in the world are ethanol plants.

• 5. The Land Problem

  ›

  Removing 10 billion tonnes of CO2 per year would require upwards of 300 million hectares of land. That is a larger area than India. The land needed to grow biomass at that scale sits at the center of the most serious objections to large-scale BECCS deployment.

  Biomass crops compete directly with food production. In developing countries, where agricultural land is already under pressure, redirecting large areas to energy crops poses documented risks to food security, water access, biodiversity, and human rights. Biomass cultivation also needs fertilizer inputs, and fertilizer runoff is its own environmental problem.

  The IPCC Sixth Assessment Report stated with high confidence that extensive BECCS deployment, alongside afforestation, would require more freshwater than the vegetation it replaces, altering regional water cycles with potential consequences for biodiversity, downstream water users, and local climate.

  There is a partial way around the worst of this. Globally, 14 billion tonnes of forestry residue and 4.4 billion tonnes of residue from crop production, mainly barley, wheat, corn, sugarcane, and rice, are generated every year. Using that existing waste rather than planting new energy crops could yield 26 exajoules of energy per year and achieve 2.8 billion tonnes of negative CO2 emissions through BECCS, without displacing food or forest. The challenge is that forest residue gasification projects face high capital, operation, and maintenance costs that discourage investors, particularly in developing countries where forest biomass is most abundant.

• 6. Cost, Policy, and Public Opinion

  ›

  Cost estimates for BECCS range from 60 to 250 dollars per tonne of CO2, a wide band that reflects how much the figure depends on location, biomass source, and technology choice. Research into electrogeochemical methods, which combine saline water electrolysis with mineral weathering powered by non-fossil electricity, suggests those approaches could increase both energy generation and CO2 removal by more than 50 times relative to BECCS at equivalent or lower cost, though further development is needed.

  On the policy side, carbon capture and storage projects were excluded from the Kyoto Protocol's Clean Development Mechanism and Joint Implementation provisions. By 2006, support was growing to include both fossil CCS and BECCS in international climate agreements. In 2018, the U.S. Congress increased and extended the Section 45Q tax credit, raising it from 25.70 to 50 dollars per tonne of CO2 for geological storage, and from 15.30 to 35 dollars per tonne for CO2 used in enhanced oil recovery. In the same year, the UK's Committee on Climate Change recommended that aviation biofuels provide up to 10% of aviation fuel by 2050, with CCS applied to all aviation biofuels as soon as the technology is ready.

  Public awareness of BECCS has been limited. A 2018 study involving online respondents from the United Kingdom, United States, Australia, and New Zealand found that participants had little prior knowledge of the technology. Despite that, 45% said they would support small-scale trials of BECCS, while only 21% were opposed. Respondents in the study preferred BECCS moderately over direct air capture or enhanced weathering, and strongly preferred it over solar radiation management. A 2019 study in Oxfordshire found that public approval shifted noticeably based on which policy tools were used to support BECCS: taxes and standards drew general approval, while government funding support generated mixed reactions.