|Carbon dioxide concentration in the atmosphere as measured by the Mauna Loa Observatory on Hawaii.From NOAA, available at http://www.esrl.noaa.gov/gmd/ccgg/trends/. The sawtooth pattern of the graph likely reflects the absorption of carbon dioxide by vegetation throughout the year.|
We went through a fair amount of effort to determine how much carbon dioxide a giant sequoia can sequester. We will spare you the details of this calculation here, but please see our footnote for our sources and calculations.
The "General Sherman" sequoia tree in California is the largest living thing on Earth by volume. Its volume of 52,500 cubic feet, or about 1486 cubic meters, contains over one million kilograms (and over 2.2 million pounds) of stored carbon. This volume of stored carbon pulled over 1400 metric tons of carbon dioxide out of the atmosphere.
Americans, on average, produce 16.6 metric tons of carbon dioxide emissions per year (although this number has been decreasing recently due to efficiency gains). The General Sherman sequoia is so large that as a single tree it has stored about 86 years worth of a person's carbon emissions. In other words, one very large tree has been able to counteract over a lifetime of carbon emissions for the average American.
|The General Sherman Giant Sequoia Tree, from National Park Service, found at http://www.nps.gov/seki/learn/nature/sherman.htm, public domain|
These facts about the largest giant sequoia would be interesting but not particularly actionable if not for one simple fact. The giant sequoia can be grown in most of the United States - not just California. We ourselves are growing two giant sequoias in Indiana, both started with the Waterboxx PlantCocoon®. The sequoia's main requirement is sufficient water, and its water needs can be significant. However, the need for consistent water is most critical during the first few years of a sequoia's life outdoors. We have found that due to soil evaporation, we could not manually water sequoias enough for them to stay alive. Some other system was needed to prevent evaporation and ensure sufficient water available to the roots. It was our interest in planting sequoias in a better way that got us interested in the Groasis Waterboxx PlantCocoon®. One of our sequoias has now graduated from the Waterboxx PlantCocoon® - meaning the Waterboxx PlantCocoon® has been removed and used for other plants. The tree is doing well even though we haven't manually watered it, even once. It takes about 18-24 months to establish a small (6 inch) sequoia with the Waterboxx PlantCocoon® in our state. You can see our two sequoias in the pictures below. Neither of these trees has had any water from us or any sort of irrigation after initial planting and set up with the Waterboxx PlantCocoon®.
If you are interested in trying to grow a giant sequoia, our preferred source is Giant-Sequoia.com. To buy the Waterboxx, visit us at DewHarvest.com.
Footnote: Our Calculations and Sources
Note: we use American mathematical nomenclature here (commas to separate 1000s, periods to indicate decimals)
When calculating carbon dioxide sequestered by a sequoia, it is first necessary to have the density of sequoia wood. We were only able to find this information with great difficulty here after much searching. We did also receive a generous sample of sequoia wood from our friend Joe Welker at giant-sequoia.com (where we bought our sequoia trees). The measured density for a small piece of sequoia wood containing bark was approximately 0.48 grams/mL. We obtained this by measuring a small piece of sequoia wood (36 grams) on a very accurate postal scale. We then submerged this same piece in a graduated cylinder, which displaced 75 mL. 36/75 = .0.48g/mL which equals 0.48 g/cc as one milliliter is equal to one cubic centimeter, by convention.
This density of 0.48 g/cc is within the range of densities reported by Wolfgang Knigge in his scientific paper Giant Sequoia in Europe, http://www.fs.fed.us/psw/publications/documents/psw_gtr151/psw_gtr151_06_knigge.pdf) . His reported densities found average values of 0.345 g/cc in European giant sequoias and 0.369 g/cc in California giant sequoias. Our density of 0.48 g/cc converts to 480 kg//m^3 (the math for this conversion is 0.48g/cc x 1,000,000 cc/m^3. This result is then multiplied by 1 kg/1000 g, equaling 480 kg/m^3).
Next we need to calculate how much mass the largest living sequoia tree, General Sherman, contains. According to the National Park Service, the General Sherman sequoia has a volume of 1,486.6 cubic meters (http://www.nps.gov/seki/learn/nature/sherman.htm). To get total mass of this tree, we multiply 1486.6 m^3 by 480kg/m^3. This gives us a total mass of 713,568 kg for General Sherman.
This mass is of course not all carbon - much being oxygen, nitrogen, and other elements. Most trees are about 50% carbon by mass. However, as giant sequoias have more heartwood (more durable wood in the center of the trunk) than sapwood, and heartwood has a slightly higher carbon content, this value may be too low for sequoias. According to Sean Thomas in his Paper Carbon Content of Tree Tissues: A Synthesis (See section 4.1, available here: http://www.mdpi.com/1999-4907/3/2/332/htm), giant sequoias are approximately 55% carbon by mass. When we multiple our calculated mass for General Sherman of 713,568 kg x .55, we get a carbon mass of 392,462 kg.
We next need to convert the mass of carbon into metric tons, so we divide 392,462 kg by 1000 to get a value of 392.4 metric tons or carbon stored in General Sherman.
However, carbon is not the same as carbon dioxide. Carbon dioxide has one carbon atom and two oxygen atoms per molecule. Trees absorb the carbon when growing while (mostly) emitting the oxygen. The atomic weight of carbon is 12.001115, while the atomic weight of oxygen is 15.9994. So the total atomic weight of CO2 is 43.999915. With a little algebra, we see that since the ratio of carbon dioxide to carbon is 43.999915/12.001115 or 3.6663 units of carbon in the tree for every unit of carbon dioxide removed from the atmosphere. We obtained this information from the Broward County Florida Climate Change website (https://www.broward.org/NaturalResources/ClimateChange/Documents/Calculating%20CO2%20Sequestration%20by%20Trees.pdf) as well as contact with Richard Campbell from Save The Redwoods).
We can thus multiply our total mass of carbon, 392.4 tons by our conversion factor 3.6663 from above to get 1438.892 total tons of CO2 removed by the General Sherman giant sequoia.
Americans, on average, produced 16.6 metric tons (or tonnes) of carbon dioxide per year in 2013 (the most recent year available) according to the Netherlands Envirornmental Assessment Agency (Table A1.2, page 49 found at http://edgar.jrc.ec.europa.eu/news_docs/jrc-2014-trends-in-global-co2-emissions-2014-report-93171.pdf).
When we divide 1438.892 metric tons of carbon dioxide removed by General Sherman by 16.6 metric tons, we get 86.7 years of CO2. That is 86.7 years of carbon emissions sequestered in a single tree! We find this number so impressive that we checked our math several times.
Caveats: General Sherman is the largest sequoia now living, and any trees planted would be unlikely to get quite this large. We chose this tree as good data was available on its volume, and as a vivid example. Also, it likely took several hundred years to reach this size, with more carbon absorbed at larger sizes. So any sequoias planted are unlikely to absorb a whole person's carbon dioxide output for several decades. However, adults emit considerably more carbon dioxide than young children, so the growth and sequestration of a sequoia may roughly mirror a human's emissions.