OLD GROWTH TREES
At the University of Michigan
University of Michigan
Greenhouse Gas Emissions
Our Background Research & Calculations:
Here is our incredibly rough estimate land area needed to offset the University's current emissions to meet the 2025 goal. The goal is to reduce their greenhouse gas emissions by 25% below 2006 levels by 2025
2006 emissions times .75:
679,869 mtCO2 x 0.75 = 509,902 mtCO2, here is the target of yearly emissions to achieve.
Necessary yearly sequestration rate for the forest (2013's emissions rate minus target yearly emissions rate):
709,982 mtCO2 – 509,902 mtCO2 = 200,080 mtCO2
Translating this to the percentage reduction of current GHG emission rate needed to achieve 2025 goal:
200,080 mtCO2/709,982 mtCO2= 28.2% = ~28% reduction
Forest Layout:
1 acre = 43,560 ft2
Canopy sequoias will be spaced in 40 ft. increments from each other, which means they will be centered in a 40 X 40 square in a layout grid:
40 ft. x 40 ft. = 1,600 sq. ft.
1 sequoia can fit in a 1,600 ft2 area (in the way we have designed our system, as many companion plants will be present as well):
43,560 ft2/1,600 ft2 = 27.225
Determining how much carbon an acre of sequoias and companion plants sequester:
CO2 Sequestration Rate of a Forest (data obtained from Dr. Bruno D.V. Marino, CEO & Founder of Planetary Emissions Management, Inc.): the rest of the forest will sequester ~18.4 mtCO2/acre/year. Young sequoias sequester CO2 at the same rate as the average young tree in a forest.
Using carbon sequestration data obtained from the USDA Forest Service, we averaged the carbon sequestration rate of six common trees species found in the Northern Lake States of the United States to get an estimate for how much CO2 a young sequoia tree will sequester at different points in its lifetime (we were unable to find data on sequoias specifically).
When converted to mtCO2/acre/year, the average NLS tree species sequesters 6.6 mtCO2/acre/year by age 5 and 18.0 mtCO2/acre/year by age 15
Rate of mtCO2/acre/year increase as a function of time:
From age 0-5 years:
(6.6 mtCO2/5 years) = 1.3 mtCO2/acre/year
From age 5-15 years:
(18.0 mtCO2 - 6.6 mtCO2)/10 years = 1.1 mtCO2/acre/year
Soil sequestration rate:
14 tons of carbon/hectare/year = 18.9 mtCO2/acre/year
This is the rate for a dryland ecosystem, which are generally less productive ecosystems than forest ecosystems. This means that our estimate of carbon sequestration is probably low. We scoured peer-reviewed literature looking for a proper rate of soil sequestration but to no avail. This, once again, shows the need for more research in this area.
Calculating the number of acres needed:
A single acre with trees adds 1.3x mtCO2/acre/year (where X is the number of trees in the acre) for the first 5 years of growth and 1.1x mtCO2/acre/year for the next four years of growth.
At year nine, an acre will be sequestering, from sequoias alone:5(1.3x mtCO2/acre/year) + 4(1.1x mtCO2/acre/year) = 10.9x mtCO2/acre/year
In addition to the sequoia sequestering rate, we must add the sequestering rate of all the other plants in our system and the sequestering rate of the soil.
Rate of Soil: 18.9 mtCO2/acre/year
Rate of Rest of Forest: 18.4 mtCO2/acre/year
Total Rate of Sequestration at Age Nine:
18.9 mtCO2/acre/year + 18.4 mtCO2/acre/year + 10.9 mtCO2/acre/year = 48.2 mtCO2/acre/year
200,080 mtCO2/year is how much the University emits beyond their goal. This is what needs to be offset.
(200,080 mtCO2/year) / (48.2 mtCO2/acre/year) = 4,151 acres of our forest if you want it to offset for the 2025 goal by 2025
Total Rate of Sequestration at Age Fifteen 18.9 mtCO2/acre/year + 18.4 mtCO2/acre/year + 18.0 mtCO2/acre/year = 55.3 mtCO2/acre/year
200,080 mtCO2/year is how much the University emits beyond their goal. This is what needs to be offset.
(200,080 mtCO2/year) / (55.3 mtCO2/acre/year) = 3,618 acres of our forest if you want it to offset for the 2025 goal by 2031
Things to remember:
This estimate gives the acreage needed to offset the target carbon emissions as if the University will do nothing else to combat their carbon emissions. Still, to put 4,000 acres into perspective, the average farm in the US is now around 1,000 acres. Basically, the University would need to fund about 5 farms to switch to our permaculture forest in order to offset its emissions.
Also, the sequoia's rate of sequestration will only increase. As a mature tree, estimates put the rate of sequestration close to 30 times that of their juvenile selves.
