Why Is It Essential to Calculate Biogenic Carbon Emissions?

Circular economy is becoming a MUST to help mitigate climate change. Bioenergy (energy made from biomass) plays an important role in the concept of circular economy providing circularity and low emissions compared to fossil energy.

Countries’ net zero targets and growing demand for electricity require more bioenergy which could lead to deforestation and biodiversity loss (Kraxner et al., 2013). This makes it quintessential to also calculate the biogenic carbon emissions along with other emissions for a fair comparison with the ones stemming from fossil energy.

What is the carbon neutrality concept of biomass?

Biomass refers to all materials of organic origin that are not of fossil origin, for example: naturally occurring Phyto- and Zoo- mass, residuals (animal waste) and organic household waste etc. (Kaltschmitt et al., 2016).

Biomass is assumed to be a carbon neutral energy source because of the global biogenic carbon cycle in the environment, which means carbon released from burning biomass will be captured again during the biomass growth through photosynthesis as shown in the figure below (Ragauskas et al., 2006; Zeman and Keith, 2008). Unlike biogenic carbon, fossil carbon follows a linear approach rather than a cyclical one, as it releases considerable amounts of carbon that was stocked underground into the biosphere and destabilize the natural greenhouse gas emissions-capture balance (figure 1).

Carbon neutrality of biomass still leads to a biased comparison of emissions from bioenergy to fossil energy, since complete removal of these emissions through photosynthesis might take a long time depending on the regrowth rate of plants.

What are Carbon pools?

When biogenic CO2 is sequestered, it is stored in different types of so-called “carbon-pools” which are commonly known as:

1. living biomass: living biomass above ground such as stem, stump, branches etc., and below ground such as fine roots;

2. dead organic matter: dead wood, leaves and organic matter;

3. soil organic matter: organic carbon in mineral and organic soil.

Why is calculating biogenic emissions so important?

As pointed out previously, biogenic emissions are part of the natural greenhouse gas emission-capture cycle. They could therefore be perceived as “carbon neutral”. Yet, the timeframe and conditions at which they are recaptured can greatly differ according to the state and type of the ecosystem, particularly as it is modified by human activity through e.g. deforestation, anthropogenic emissions etc. That is why it is crucial to specifically look at biogenic emissions and calculate them to obtain a clearer and more accurate picture of the studied emissions.

How do we calculate biogenic carbon emission for bioproducts/bioenergy?

Biogenic carbon emissions are net emissions/removals of biogenic carbon to/from the environment expressed in carbon dioxide equivalents (meaning that all relevant greenhouse gases expressed in CO2 for the purpose of comparison and simplicity, which is also abbreviated as “CO2e”). Biogenic emissions are expressed as a positive value as they increase carbon in the atmosphere (negative impact) and removals as a negative value as they decrease carbon in the atmosphere (positive impact) according to PAS 2050:2011 BSI guidelines (British Standards Institution, 2011). To measure the effect of biogenic emissions on climate change, a variety of methods and metrics have been proposed (Miner and Gaudreault, 2020). The most often used metric is GWPbio (Cherubini et al., 2011; Gmünder et al.,  2020).

What is GWPbio?  

GWPbio is the global warming potential factor for biogenic carbon for 100 years. It is based on CO2 decay rate in the atmosphere and regrowth of biomass and is greatly influenced by type of climate, the management strategies used and the type of biomass (Liu et al., 2017). The GWPbio varies from -1 to 1. A bioproduct or bioenergy that has a GWPbio value of 0 is considered carbon neutral. Higher GWPbio values result in higher emissions, which may be equal to or higher than emissions from fossil fuels for example, GWPbio value 1 shows the global warming potential of biogenic CO2 is same as of fossil CO2.  Bioproducts that store carbon for 100 years has a GWPbio value of -1. Fast growing plants known as short rotation crops (eucalyptus, hybrid poplar, willow etc.) typically have a low value(close to 0) of GWPbio  (Cherubini et al., 2011; Guest et al., 2012).

Can CO2e emissions from bioenergy be larger than the fossil ones?

Some studies (Scherer and Pfister, 2016; Van Fan et al., 2021) showed that bioenergy can be worse in terms of total CO2e emissions when compared to fossil energy. For example, Van Fan et al. (2021) claimed that if the GWPbio for corn stover and switchgrass to produce bioelectricity is higher than 0.33 and 0.34 respectively, the CO2e from bioelectricity generated from corn stover and switchgrass would be higher than of natural gas, which is relatively efficient in terms of electricity production in relation to CO2e emissions.

All in all, bioenergy is becoming more and more relevant for industries and countries to achieve their net zero targets. Accounting all emissions associated with bioenergy is therefore crucial, as it helps make more accurate and complete GHG inventories.

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As data experts and fervent innovators, we are currently working on increasing the depth of information of our datapoints to give more information on the different  kinds of emissions and their values.

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References

British Standards Institution. (2011). The guide to PAS 2050:2011 : how to carbon footprint your products, identify hotspots and reduce emissions in your supply chain. Bsi. Access: PAS-2050_00_prelims.qxd (bsigroup.com)

Cherubini, F., Peters, G. P., Bernsten, T., Strømman, A. H., & Hertwich, E. (2011). CO2 emissions from biomass combustion for bioenergy: atmospheric decay and contribution to global warming. GCB Bioenergy, 3(5), 413–426. https://doi.org/10.1111/j.1757-1707.2011.01102.x

Fan, Y. V., Klemeš, J. J., & Ko, C. H. (2020). Bioenergy carbon emissions footprint considering the biogenic carbon and secondary effects. International Journal of Energy Research, 45(1), 283–296. https://doi.org/10.1002/er.5409  

Gmünder, S., Zollinger, M., Dettling, J., Spitzer, M., Stevenson, M., & Wwf. (2020). Biogenic carbon footprint calculator for harvested wood products data & calculations 2 Methodology Report -Biogenic Carbon Footprint Calculator. Access: https://files.worldwildlife.org/wwfcmsprod/files/Publication/file/8ac6an0ydo_Biogenic_Carbon_Footprint_Calculator_Methodological_Report_July2020_Quantis.pdf?_ga=2.74061522.1939894528.1665092898-27544469.1664528933

Guest, G., Cherubini, F., & Strømman, A. H. (2012). Global Warming Potential of Carbon Dioxide Emissions from Biomass Stored in the Anthroposphere and Used for Bioenergy at End of Life. Journal of Industrial Ecology, 17(1), 20–30. https://doi.org/10.1111/j.1530-9290.2012.00507.x  

Kaltschmitt, M., Hartmann, H., & Hofbauer, H. (2016). Energie aus Biomasse (M. Kaltschmitt, H. Hartmann, & H. Hofbauer, Eds.). Springer Berlin Heidelberg. https://doi.org/10.1007/978-3-662-47438-9  

Kraxner, F., Nordström, E.-M., Havlík, P., Gusti, M., Mosnier, A., Frank, S., Valin, H., Fritz, S., Fuss, S., Kindermann, G., McCallum, I., Khabarov, N., Böttcher, H., See, L., Aoki, K., Schmid, E., Máthé, L., & Obersteiner, M. (2013). Global bioenergy scenarios – Future forest development, land-use implications, and trade-offs. Biomass and Bioenergy, 57, 86–96. https://doi.org/10.1016/j.biombioe.2013.02.003  

Liu, W., Zhang, Z., Xie, X., Yu, Z., von Gadow, K., Xu, J., Zhao, S., & Yang, Y. (2017). Analysis of the Global Warming Potential of Biogenic CO2 Emission in Life Cycle Assessments. Scientific Reports, 7(1). https://doi.org/10.1038/srep39857  

Miner, R., & Gaudreault, C. (2020). An analysis of GWP bio and the effects of scale. Access: https://www.ncasi.org/wp-content/uploads/2020/07/WP-20-07_GWPBio_July2020.pdf

Ragauskas, A. J., Williams, C. K., Davison, B. H., Britovsek, G., Cairney, J., Eckert, C. A., Frederick, W. J., Hallett, J. P., Leak, D. J., Liotta, C. L., Mielenz, J. R., Murphy, R., Templer, R., & Tschaplinski, T. (2006). The Path Forward for Biofuels and Biomaterials. Science, 311(5760), 484–489. https://doi.org/10.1126/science.1114736  

Scherer, L., & Pfister, S. (2016). Hydropower’s Biogenic Carbon Footprint. PLOS ONE, 11(9), e0161947. https://doi.org/10.1371/journal.pone.0161947  

Zeman, F. S., & Keith, D. W. (2008). Carbon neutral hydrocarbons. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 366(1882), 3901–3918. https://doi.org/10.1098/rsta.2008.0143  

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