Large industrial plants frequently use biomass as a power source or raw material, resulting in the release of CO2 that contains carbon from the biomass. This type of CO2 is known as biogenic CO2 emissions. Unlike fossil fuel emissions that release carbon that’s been stored for millions of years, biogenic CO2 comes from recent carbon fixation and is considered part of the natural and short-term carbon cycle. As a result, there is an opportunity to capture and store this CO2, reducing overall greenhouse gas emissions. This is often called bio-CCS, or BECCS, depending on the context. Additionally, biogenic CO2 is of interest in the development of e-fuels that can replace conventional fuel types.
To identify opportunities for accessing large amounts of biogenic CO2, this article provides an overview of the six sectors that have the largest shares of biogenic emissions, as well as a bonus sector. For each sector, we draw on CaptureMap‘s great coverage of biogenic point sources of CO2 to identify sites and CO2 volumes.
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Why is biogenic CO2 important?
What’s so important about biogenic CO2? Afterall, CO2 is CO2, right? Well, not so fast. Carbon dioxide can come from different sources. Some belong to the slow domain of the carbon cycle, typically fossil fuels. Here, according to the Intergovernmental Panel on Climate Change (IPCC) we’re talking turnover times of more than 10 000 years. And some belong to the fast domain, typically from biomass, with turnover times less than 500 years.
In a carbon capture and storage perspective, capturing and storing the CO2 that comes from using biomass means removing carbon that was in the atmosphere in the first place. This gives a net negative effect on the total CO2 in the atmosphere, and is categorized under carbon dioxide removals (CDRs). The markets are typically willing to pay a premium for this biogenic CO2, hence the focus on the most suitable sectors.
1. Ethanol plants
Ethanol production plants have large amounts of biogenic CO2 emissions because they use natural biological processes to convert plant materials (such as corn, wheat, sugar beet or sugar cane) into ethanol fuel. During the production process, the plant materials are first fermented with yeast, which produces ethanol as a byproduct. The ethanol is then separated from the fermented mixture and purified for use as a fuel. The fermentation process also produces CO2 as a byproduct, which is released into the atmosphere as biogenic CO2 emissions.
As a rule of thumb, 1 kg of ethanol produced from corn gives 1 kg of biogenic CO2 from fermentation process and 0,5 kg of CO2 from the rest of production (could be a combination of fossil and biogenic, but is typically fossil). Therefore, ethanol plants often have CO2 emissions with ca. 70% biogenic CO2.
CaptureMap includes a total of 183 ethanol plants in Europe and North America. Most of these plants are located in the USA, with 168 facilities there. Due to GHG reporting requirements, CO2 from fermentation of plant materials is not reported, and the official data for CO2 emissions include mostly the fossil share of CO2. The 183 ethanol plants in our database reported a total of 21.8 million tonnes annually, mostly consisting of fossil CO2. Using the rule of thumb above, one can estimate the biogenic CO2 emissions to 44 million tonnes from these plants. The total is therefore likely closer to 65 million tonnes CO2 for both fossil and biogenic emissions.
In terms of CO2 concentration, biogenic CO2 from fermentation at ethanol production plants has the highest concentration, with ca. 80-90%. This makes it a very interesting source of CO2 to capture. The fossil part of emissions often comes from power generation on site, with a much lower concentration, typically 2-5% CO2.
The plants often have just a few stacks, with emissions from power generation separated from emissions from fermentation.
It is possible to capture most of the CO2 emissions from ethanol production plants, although the cost level for the biogenic part (high CO2 concentration from fermentation) will be much lower than the cost of capture for the power generation (mostly fossil emissions). Therefore many ethanol plants prioritize bio-CCS, through the capture of biogenic emissions when implementing carbon capture.
Many ethanol plants in the USA already have CO2 capture in place, including the South Bend Ethanol plant pictured to the left. At least two large projects for pipelines collecting CO2 from ethanol plants are ongoing in the USA: Navigator CO2 Heartland Greenway and Summit Carbon Solution.
Interested in knowing more about carbon capture on ethanol production? Check our article about it.
2. Biomass power plants
Biomass power plants use various types of bio-based fuels as input to produce power and/or heat. Many of these plants were originally designed and built to use biomass, while some other are converted from other fuels, typically coal. Some plants also use a mix of various fuel types, including both biomass and fossil fuels, therefore the share of biogenic CO2 at power plants can vary greatly, anywhere from 0 to 100%.
In Europe, there are a total of 111 facilities whose emissions are made up of over 50% biogenic CO2, and they emit a total of 46 million tonnes of biogenic CO2 annually. Similarly, in the USA, 26 biomass power and heat plants emit 6.8 million tonnes of biogenic CO2 each year.
The concentration of CO2 in biomass power and heat plants varies between 5 and 15%, depending on the type of fuel used and the combustion process employed. Most of these plants have one or a few stacks, depending on the number of power generation units.
In theory, it is possible to capture around 90% of the emitted CO2, depending on the capture process used. Significant amounts of biogenic CO2 could therefore be captured from biomass power plants around the world, giving it a great potential for BECCS.
Several biomass power plants have BECCS project underway, including: the Ørsted Avedøre (pictured above) and Asnæs power stations (Denmark), the Drax power station (UK), ENSO and Carburos Metálicos (Spain).
3. Waste to energy plants
Waste-to-energy plants (WtE) burn waste to produce heat and electricity. It is often municipal waste with a mix of various fractions, including plastics, food, paper, and other types of materials. On average, about half of the waste contains carbon of biological origin (e.g. from food and paper), and therefore about half of the CO2 emitted from the WtE plants is biogenic CO2. Based on reporting data from 112 different WtE plants in Europe and USA, the average biogenic share in their CO2 emissions is 59%, with variations from facility to facility.
A total of 52 million tonnes biogenic CO2 is emitted from 601 WtE plants in Europe and North America. Many of these plants are located in Europe, where waste incineration is more prevalent, while the East Coast of USA and Canada also has a few plants. It is interesting to note that new plants are being built in Canada and in the UK, making them interesting countries for integrating carbon capture plants in design instead of retrofitting existing plants.
The CO2 concentration in the WtE plants’ flue gas typically varies from 5 to 15%, and most plants have one to a few stacks in the vicinity of one another, simplifying the capture. Waste heat may be available on site, although it is often used for district heating and/or electricity production.
Capture projects on WtE plants has shown that capture rates of 90%, or more, are achievable, providing great opportunities for capturing large amounts of biogenic CO2 and developing BECCS projects.
WtE plants with BECCS projects underway include Twence Hengelo (Netherlands, picture to the left), Hafslund Oslo Celsio Klemetsrud (Norway, project on hold at the time of this writing), KVA Linth (Switzerland) and Viridor Runcore (UK), among others.
Curious to read more about carbon capture on WtE plants? Check our dedicated article.
4. Cement plants
It often comes as a surprise that cement plants emit biogenic CO2. After all, ca. 60% of the cement emissions come from the production process, which involves limestone, a substance literally made of fossils. These process emissions are generated during the chemical reaction that occurs when limestone and other materials are heated in the cement kiln to create clinker, the main ingredient in cement. This reaction releases CO2 as a byproduct.
Energy-related emissions, on the other hand, are primarily generated by the combustion of fuels in the cement kiln to provide the high temperatures needed for the chemical reaction. Cement plants notoriously make use of many different types of fuels, mostly of fossil origin, but also sewage sludge, wood waste, animal waste and many other types of biomass-based fuels. As a result, the CO2 emissions from many plants contain 5 to 15% biogenic emissions, in particular in Europe.
A total of 5.4 million tonnes biogenic CO2 is emitted from 93 cement plants in Europe, based on the data available in CaptureMap. In the USA, the total biogenic CO2 from cement plants is 0,8 million tonnes from 21 plants.
The CO2 concentration in the exhaust fumes varies from 15 to 30%, depending on the fuel used and the share of emissions from process. Each facility may have one to multiple emission points, depending on the design of the plan (e.g. number of pre-calciners and rotary kilns).
Some cement plants have waste heat available, which can help reduce the capture costs. As a result, capture rates of up to 70 to 90% of the CO2 are achievable, although some plants may choose to capture a lower share of their CO2.
Several cement plants have capture projects in the making, with some share of bio-CCS, including Norcem Brevik (Norway, picture to the right), CBR Antoing (Belgium), Lehigh Redding (USA), Cementa Slite (Sweden), and Holcim Obourg (Belgium), among others.
Interested in reading more about CO2 emissions from cement? Check our article about this industry.
5. Pulp and paper
Pulp and paper production involves the processing of wood or other plant-based materials to produce paper, cardboard, and other paper products. Biogenic CO2 emissions occur during the pulping process, which is the process of breaking down the plant material to extract the cellulose fibers that will be used to make paper. In addition to the pulping process, other steps in the paper production process can also contribute to biogenic CO2 emissions. For example, the energy used to power the production process may come from the burning of biomass or other organic fuels, which can also release biogenic CO2.
In Europe and North America, a total of 181 million tonnes biogenic CO2 are emitted from 286 pulp and paper plants, based on data in CaptureMap. North America alone has 156 pulp and paper plants, emitting 101 million tonnes biogenic CO2. Europe has 130 plants emitting 80 million tonnes biogenic CO2.
The CO2 concentration at pulp and paper plants varies depending on the source of the CO2. Recovery boilers often account for two thirds of the CO2 emissions and the flue gases include 10 to 15 % CO2. The power boilers are typically responsible for 20% of the emissions, and there the flue gases also contain 10 to 15 % CO2. The remaining emissions come from lime production on site, which has a CO2 concentration of about 15-30 % in the flue gases.
Depending on the cost level, ca. 70 to 90% of the total CO2 emissions are capturable on pulp and paper plants, giving the opportunity to capture large amounts of biogenic CO2 for bio-CCS projects.
The Tanjungenim Lestari Pulp & Paper mill (Indonesia, pictured to the left) is an example of a CCS project at a pulp and paper mill.
Interested in knowing more? Read about post-combustion CO2 capture from the pulp and paper industry in this post from Aker Carbon Capture’s head of Research and Innovation.
6. Food: alcohol and sugar production
Food-grade alcohol and sugar production have a lot in common with ethanol production, so it is not surprising that they also have large amounts of biogenic CO2.
In alcohol production, biogenic CO2 is released through the fermentation of organic materials, such as corn, barley, and sugarcane. During the fermentation process, yeast is added to the organic material to convert the sugars into alcohol. This process releases CO2 as a byproduct, which is a biogenic source of carbon dioxide emissions. In addition to the fermentation process, other steps in the production of food-grade alcohol can also contribute to biogenic CO2 emissions. For example, the energy used to power the production process may come from the burning of biomass or other organic fuels, which can also release CO2.
Biomass is also used as an energy source in the sugar industry, leading to biogenic CO2 emissions. In addition some fermentation may occur during sugar production (depending on the process), leading to biogenic CO2 emissions.
CaptureMap contains 47 alcohol and sugar plants, emitting a total of 4.5 million tonnes biogenic CO2 per year in Europe and North-America. Note that the emissions may be underestimated if CO2 from fermentation is not reported (see also details on ethanol).
For both alcohol and sugar production, the CO2 emissions come mainly from power generation or from fermentation. Power generation at these plants typically has a CO2 concentration between 2 and 5 %. The CO2 concentration from fermentation is much higher and can reach up to 80-90 %. Some sugar production plants also have a lime kiln on site, which will contribute to ca. 10 to 20 % of the emissions, with a CO2 concentration of about 15-30 % in the flue gases.
It is possible to capture up to 90 % of the CO2 emissions from alcohol and sugar plants, although the costs may be much lower if only CO2 from fermentation is captured. In that case, a lower capture rate will be achieved.
An example of an alcohol production site capturing CO2 with bio-CCUS, albeit at small scale, is the Austin Beerworks brewery, read more about it here.
Bonus. Biogas plants
Biogas, also referred to as “renewable natural gas” in North America, is produced through the fermentation of food waste and other biomass-based resources into methane. This methane is an excellent renewable energy source, utilized for power and transportation, among other sectors.
The output from the fermentation process typically consists of 65% methane and 35% CO2. However, for most production plants, only the methane fraction is commercially valuable, leading to the separation and on-site venting of the CO2. This CO2 stream has a high concentration, typically over 98% CO2, making it an attractive opportunity for collecting biogenic CO2 at low cost.
A downside is that most biogas production plants release limited amounts of CO2, ranging from 10 000 tonnes per year for medium-sized plants to 40 000 tonnes per year or more for larger ones. Additionally, CO2 emissions are often not publicly reported in most countries, making it challenging to monitor the availability of biogenic CO2 volumes from biogas production plants. Instead, we use a rule of thumb of 100 tonnes biogenic CO2 per GWh biogas production.
Rule of thumb for biogas emissions: 100 tonnes biogenic CO2 per GWh production
Several biogas plants in Europe already market their biogenic CO2, although mostly for utilisation. Typical uses include: food grade CO2 (e.g. for beverages), greenhouses (for enhancing growth), and dry ice production. To read more about CO2 emissions from biogas plants, and the potential to capture, use or store this CO2, check this report from the European Biogas Association.