Negative Emission Technology (NET)

Technological solutions to remove or reuse CO2 from the atmosphere

Nicholas Sievers

Photo by CHPerry from Forest Atlas

Image source: TheDigitalArtist from Pixabay

Greenhouse Gases and the Atmosphere

For over a hundred years, we have known that burning fossil fuels is causing the planet to warm. Svante Arrhenius, a Swedish scientist, postulated the connection of global average temperature to the concentration of greenhouse gasses (GHGs) in the atmosphere (Graham, 2000). GHGs are not inherently bad; for instance, water vapor (the most important GHG) is why the earth is temperate. To contextualize current CO2 concentrations, scientists have reliable estimates on what parts per million CO2 were during the early 1700s before coal and gasoline (Frumkin, 2016). In 2021, we sit around 412 ppm of CO2 in the atmosphere; the last time it was even close to this high was 350,000 years ago at about 300 ppm (Lindsay, 2020). A documentary by Al Gore, An Inconvenient Truth (2006), was one of the biggest media breakthroughs highlighting atmospheric CO2 concentrations as a growing problem. As it is sometimes referred to, the "hockey stick graph" provides a historical account of CO2 from a thousand years ago (Mann et al., 1999). Nevertheless, in 2021, climate change is still a polarizing topic, mainly because switching to a net-zero carbon dioxide (and Methane) economy is no easy task.

Historical Context

Climate change is caused by increased greenhouse gas (GHG) emissions in the atmosphere due to human activity.
Many proxies exist to discover ancient climate conditions.
CO2 from prehistoric times is largely stored underground.
Burning fuel releases CO2 into the air.

Burden of Disease and Health Effects

Climate change has a myriad of harmful health effects on ecosystems and living organisms.
People are affected by climate change worldwide.
The range, severity, and frequency of vector-borne diseases may be increased by climate change (Frumkin, 2016 and Beard et al., 2016).
People with respiratory problems are further at risk due to climate change (Beard et al., 2016).

Where is CO2 stored?

Carbon from fossil fuels, soil, organic matter, and plants are stored in carbon sinks. These can be found:

- - Ground
  - Oceans
  - Atmosphere

An Inconvenient Truth CO2 "Hockey Stick" Graph

A hockey stick graph represents 1000 years of atmospheric CO2 and shows a noticeable increase in CO2 around the industrial revolution.

An Inconvenient Truth (2006) on Youtube

Pollution and Public Health

Pollution is hazardous because of how particulate matter harms the lungs and exacerbates preexisting respiratory problems. Air pollutants of concern are particulate matter (PM), ground-level ozone, and other airborne particulates (Fann et al., 2016). Particulate matter (PM) comes from direct sources such as construction sites, fires, or general fuel combustion (US EPA, 2016).

Air Pollution

Air pollution is often associated with population size and manufacturing.
Pollution in China is inversely associated with wealth and education (Liu et al, 2016).
Social and geological context is closely tied to pollution. For example, New York City has a population twice as big as Los Angeles but has cleaner air. LA air quality is poor due to:
- - Population size
  - Meteorological factors (Littman and Magill, 1953)
  - Shipping docks and cars

Health Effects of Pollution

Immediate and sometimes long-term health impacts from pollution. Long-term exposure of PM2.5 is associated with higher risks of Ischemic Heart Disease and lung cancer (Jerrett et al., 2005)
PM smaller than ten micrometers are the most dangerous.
- PM can penetrate deep into your lungs or bloodstream.
- Small PM is associated with an irregular heartbeat, aggravated asthma, decreased lung capacity, respiratory problems, or even premature death (US EPA, 2016).
Pollution is carried by wind currents.
- Even if pollution occurs halfway across the world, it may be felt elsewhere.
- The health effects on at risk populations may be pernicious.

Image source: V.T Polywoda from Flickr

Image source: Wikimedia Commons

Environmental Justice

People of color, children, the disabled, homeless and the elderly are the most at risk from climate change and pollution (Banzhaf et al., 2019).
People of color and low income families are statistically more likely to live close to industrial activity and undesirable land uses (Frumkin, 2016).
Environmental Justice: everyone deserves a clean environment and no one should be affected disproportionately (Frumkin, 2016).

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Summary

The scientific consensus is stern about its findings: climate change is worsening, and we must act fast to avoid the worst (Lindsay, 2020 and Mann et al., 1999). Climate change and pollution disproportionately affect low-income individuals and people of color (Liu et al., 2016 and Banzhaf et al., 2019). Additionally, numerous health studies have demonstrated the heightened risk of respiratory disease and cancer from prolonged pollution exposure (Fann et al., 2016, Jerrett et al., 2005 and US EPA, 2016). As we move forward, the environment must be thought of as communal grounds and not be exploited. Though the future is uncertain and looking grim, we have a moral imperative to keep trying to reduce the burden of humans on earth. Rays of light, such as negative emission technology, exemplify the desire to reduce harmful environmental impacts. They should continue to be thought of as solutions.

Negative Emission Technologies (NET)

Negative Emission Technologies (NET) are any technology designed to remove greenhouse gasses from the atmosphere or capture them directly. These are typically facilities designed to sequester CO2 in a solid form for reuse, but they also use plant biology to capture the gas. Scientists are thinking of plant CO2 removal properties as long-term storage for CO2 (sequestration). We can undo some damage to the planet's climate by sequestering CO2 in the earth as well as reuse the CO2.

Carbon Capture and Storage

Carbon Capture and Storage (also known as CCS) is the overall process of "the capture of carbon dioxide (CO2) from fuel combustion or industrial processes, the transport of this CO2 via ship or pipeline, and either its use as a resource to create valuable products or services or its permanent storage deep underground in geological formations" (IEA, 2021). Many CCS facilities retrofit natural gas, coal, or power plants that simultaneously produce power and capture CO2 emissions. Reuse of the captured CO2 varies by facility. Some store it underground in deep aquifers, while others use it for oil recovery, which unfortunately is utilized in the fossil fuel industry for greater extraction.

If anything is clear, we have not yet separated ourselves from fossil fuel reliance. Oil Recovery is the process of displacing oil in reservoirs with heat, captured CO2 gas, or sometimes chemicals (US DOE, n.d.). Oil recovery efforts do not necessarily increase the harm of oil extraction but rather maximize extraction by reusing gas that would otherwise go into the atmosphere. Oil recovery is by no means a long-term solution to the problem. However, the current energy infrastructure poses a predicament that we cannot ignore in good faith.

One practical use of CCS (that does not need machinery) is storing CO2 in soil and in plants. According to Ontl and Schulte (2012), the ground used to be a much larger reservoir for CO2 before the industrial revolution. Though plants release CO2 when they decompose, not all organic matter decomposes at the same rate. By strategically using plants to absorb CO2, more gas is stored than released at any given time. One caveat is that reforestation and large-scale replanting temporarily sequesters carbon into the soil to slow climate change and that CO2 may be released from the earth later on.

Image Credits: Wikimedia Commons

Geoengineering: technological solutions to climate change to achieve a specific goal (Boyd, 2021). For example, a net-zero emissions economy needs geoengineering

Practical Uses

Oil recovery increases extraction efficiency.
Carbon Capture and Storage (CCS)
- Capture atmospheric CO2
- Store it or reuse it
- Solid, liquid, or gas (stored or under a pressure gradient.)
Reforestation and growing plants to store CO2.
Mitigation and adaptation to address climate change.

Examples:

Global Thermostat CCS technology
Quest by Shell CCS technology

Image Credits: Wikimedia commons

Examples:

- HoSt Bioenergy Systems in Vancouver, WA
- Bioenergy Washington in Renton, WA

Bioenergy

Bioenergy is not a new technology by any means, but the nature of how it fits in the larger CCS sphere is why it is relevant. Bioenergy is a renewable energy source made from raw materials and other organic waste (USDA NIFA, n.d.). With the 2 degree climate change coal in mind, Reid et al (2020) argues that Bioenergy is simply an intermediary step in our goal of transitioning to a 100% renewable energy economy because of the following reasons: cost of alternative energy will be competitive with (or less expensive) than Bioenergy, it requires too much land, and because there are simply better options long term.

Practical Uses

Can replace fuel in vehicles and some petroleum byproducts in many products (US DOE, n.d.)
3 ways to convert to fuel (US DOE, n.d.) include combustion, bacterial decay, and state conversion (liquid or gas)
We could produce up to 1 billion tons of biofuel by 2040 and be able to meet other demands (US Dept of Energy, n.d.)

Biochar

Biochar is "black carbon produced from biomass sources [i.e., wood chips, plant residues, manure or other agricultural waste products] for the purpose of transforming the biomass carbon into a more stable form (carbon sequestration)" (USDA, 2020). Biochar is created by processing plants through burning (pyrolysis), which produces biofuel in an anoxic environment (USDA ARS, 2021). While some CO2 is released during pyrolysis, it is not the same as combustion due to the lack of oxygen. The plant matter thermally decomposes and turns into bio-oil and biochar (Renner, 2007). Some gasses are released into the air during this process, but more gasses are ultimately sequestered inside the biofuel and biochar, so the process is ultimately carbon-negative. Biochar can be harmful when inhaled (Brewer and Brown, 2012), but it still is a practical storage method for CO2.

Image Credits: Wikimedia commons

Examples:

Backwoods Biochar in Vancouver, WA
Walking Point Farms LLC in Tigard, OR

Practical Uses

Good for agriculture
Longterm CO2 storage solution
Reuse option for organic waste

References

Banzhaf, S., Ma, L., & Timmins, C. (2019). Environmental Justice: The Economics of Race, Place, and Pollution. Journal of Economic Perspectives, 33(1), 185–208. https://doi.org/10.1257/jep.33.1.185

Beard, C. B., Eisen, R. J., Barker, C. M., Garofalo, J. F., Hahn, M., Hayden, M., Monaghan, A. J., Ogden, N. H., & Schramm, P. J. (2016). Ch. 5: Vectorborne Diseases. The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. U.S. Global Change Research Program. https://doi.org/10.7930/J0765C7V

Boyd, P. (2021). Geoengineering. Brittanica. https://www.britannica.com/science/geoengineering

Brewer, C. E., & Brown, R. C. (2012). Biochar. In A. Sayigh (Ed.), Comprehensive Renewable Energy (pp. 357–384). Elsevier. https://doi.org/10.1016/B978-0-08-087872-0.00524-2

Fann, N., Brennan, T., Dolwick, P., Gamble, J. L., Ilacqua, V., Kolb, L., Nolte, C. G., Spero, T. L., & Ziska, L. (2016). Ch. 3: Air Quality Impacts. The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. U.S. Global Change Research Program. https://doi.org/10.7930/J0GQ6VP6

Frumkin, H. (Ed.). (2016). Environmental Health: From Global to Local (3rd ed.). Jossey-Bass.

Graham, S. (2000, January 18). Svante Arrhenius [Text.Article]. NASA Earth Observatory. https://earthobservatory.nasa.gov/features/Arrhenius

IEA. (2021). Carbon Capture, Utilization and Storage. International Energy Association. https://www.iea.org/fuels-and-technologies/carbon-capture-utilisation-and-storage

Jerrett, M., Burnett, R. T., Ma, R., Pope, C. A., Krewski, D., Newbold, K. B., Thurston, G., Shi, Y., Finkelstein, N., Calle, E. E., & Thun, M. J. (2005). Spatial Analysis of Air Pollution and Mortality in Los Angeles: Epidemiology, 16(6), 727–736. https://doi.org/10.1097/01.ede.0000181630.15826.7d

Lindsay, R. (2020). Climate Change: Atmospheric Carbon Dioxide. https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide

Littman, F. E., & Magill, P. L. (1953). Some Unique Aspects of Air Pollution in Los Angeles. Air Repair, 3(1), 29–34. https://doi.org/10.1080/00966665.1953.10467586

Liu, W., Xu, Z., & Yang, T. (2018). Health Effects of Air Pollution in China. International Journal of Environmental Research and Public Health, 15(7), 1471. https://doi.org/10.3390/ijerph15071471

Mann, M. E., Bradley, R. S., & Hughes, M. K. (1999). Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophysical Research Letters, 26(6), 759–762. https://doi.org/10.1029/1999GL900070

Ontl, T., & Schulte, L. (2012). Soil Carbon Storage. Nature Education. https://www.researchgate.net/profile/Todd-Ontl/publication/313189912_Soil_carbon_storage/links/59482764aca272f02e0aecc3/Soil-carbon-storage.pdf

Reid, W. V., Ali, M. K., & Field, C. B. (2020). The future of bioenergy. Global Change Biology, 26(1), 274–286. https://doi.org/10.1111/gcb.14883

Renner, R. (2007, September 2). Rethinking biochar. Environmental Science & Technology, 2.

US Dept of Energy. (n.d.). Bioenergy Basics. Energy.Gov. Retrieved December 7, 2021, from https://www.energy.gov/eere/bioenergy/bioenergy-basics

US Dept of Energy. (n.d.). Enhanced Oil Recovery. Energy.Gov. Retrieved November 18, 2021, from https://www.energy.gov/fecm/science-innovation/oil-gas-research/enhanced-oil-recovery

US EPA. (2016, April 19). Particulate Matter (PM) Basics [Overviews and Factsheets]. https://www.epa.gov/pm-pollution/particulate-matter-pm-basics

USDA. (2020). Biochar. US Department of Agriculture. https://www.ars.usda.gov/midwest-area/stpaul/swmr/people/kurt-spokas/biochar/

USDA ARS. (2021). What is Pyrolysis? : USDA ARS. Agricultural Research Service (USDA). https://www.ars.usda.gov/northeast-area/wyndmoor-pa/eastern-regional-research-center/docs/biomass-pyrolysis-research-1/what-is-pyrolysis/

USDA NIFA. (n.d.). Bioenergy | National Institute of Food and Agriculture. Retrieved November 18, 2021, from https://nifa.usda.gov/topic/bioenergy

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