BSA's Classroom "Plant Talking Points"

Imagine a world where the plants of the planet are harnessed to help its inhabitants find sustainable solutions for some of their most pressing needs – clothing, food, housing, jobs, clean air … clean water. Welcome to planet earth!


Clean air

carbon footprint

Plants are the air-purifiers for planet earth. They clean it, and in doing so produce the oxygen we, and all animals need to survive. This happens through one of the most amazing chemical reactions you can imagine, photosynthesis. More on this a bit further down, but as a lead in to the story we'll ask a question whose answer may astound you... Imagine the largest tree you've ever seen (even in a picture) - where does the matter come from that forms the mass of wood, branches and leaves?

The earth itself is a "closed system" in that it produces everything it needs to ensure the survival and development of its inhabitants. Within the system there is a delicate balance that must be maintained. In the page below we will explore one relationship within that balance, the air-purifying plants, man and Carbon Dioxide (CO2). We'll do so looking at things most of us use everyday as examples of mans part in this relationship (as a producer of CO2).

At present there is much debate about people's impact on the planet. This debate is most pronounced in the discussions around global warming and our responsibility for the continued increase in CO2 and other "greenhouse gases" released into, and consolidating in, the earth's atmosphere. Tying in directly to this problem are topics such as deforestation and the 1994 Kyoto protocols.

When you look around, it's a bit hard to comprehend we are really the newcomers on the planet. We've built so much and seem to be expanding everywhere. With our building and expansion, we use ever more fossil fuel to run our homes, our cars and the planes we fly in. Burning these fuels creates CO2 as one byproduct of the process. Even the batteries that run our cell phones, Ipods and other gadgets use electricity for charging, which in most instances creates more CO2.

As it turns out, CO2 is also a very important gas in the life processes. Plants use CO2 in the chemical process mentioned above, photosynthesis.

Photosynthesis is an extremely complex process. In its simplest form, this important reaction convert CO2 [carbon dioxide] and H2O [water] plus energy [sunlight] into O2 [oxygen] and (C6H12O6) [glucose]. The oxygen goes into the air you breathe.

6CO2 + 6H2O (+ light energy) -->-->-->--> C6H12O6 + 6O2
six molecules of carbon dioxide plus six molecules of water produce one molecule of glucose plus six molecules of oxygen

Taking the chemistry a bit further, we note that water supplies the oxygen atoms (indicated below as O.) required for the formation of molecular oxygen. We now write the equation as: 6CO2 + 12H2O. (+ light energy) -->-->-->--> C6H12O6 + 6O2. + 6H2O

And a wee bit further, photosynthesis produces carbohydrates other than glucose - cellulose and starch. They can be represented by (C6H10O5)n.

A better representation of our equation becomes 6nCO2 + 12nH2O. (+ light energy) -->-->-->--> (C6H12O6)n + 6nO2. + 7nH2O

Why is this important you ask? Cellulose (C6H10O5)n is a long-chain polymeric polysaccharide carbohydrate, of beta-glucose. What in the world is that you say... This forms the primary structural component of green plants. The green plants primary cell wall is made largely of cellulose and the secondary wall contains cellulose with variable amounts of lignin. Lignin and cellulose, considered together, are termed lignocellulose, which, in the form of wood, is the most common biopolymer on Earth. Now, once again, where does the matter come from that forms the mass of wood, branches and leaves?

Trees store carbon, sequestered from the air, as the wood and plant material that makes up their mass.

OK, so plants (most) use carbon in as a part of their life processes... Knowing this, how much CO2 is sequestered by an average tree? Well, it very much depends on type of tree. For our example we'll use a mature pine tree (Pinus radiata). An acre of pine trees (~120 trees) has the potential to sequester roughly 5 tons of CO2 per year.

Let's look at part of your "carbon imprint", your home, and make an estimate for the CO2 it might be producing each year. To do this estimate we'll make a few assumptions. Let's say your house is about 2,000 square feet, you have a heater, an air conditioner and a water heater. Check the boxes below for the items that fit your family situation.

Do you have a TV? (a regular TV uses about 120 kwh of electricity thus producing ~196 lbs. of CO2)
Do you have a washing machine? (regular washer uses about 120 kwh of electricity thus producing ~196 lbs. of CO2)
How about a dryer? (a dryer uses about 1,079 kwh of electricity thus producing ~1,770 lbs. of CO2)
Do you use a dishwasher? (a dishwasher uses about 512 kwh of electricity thus producing ~840 lbs. of CO2)
What about a stove? (a stove may use about 975 kwh of electricity thus producing ~1,600 lbs. of CO2)
A microwave? (a microwave uses about 209 kwh of electricity thus producing ~343 lbs. of CO2)
How about your refrigerator? (a refrigerator uses about 1,079 kwh of electricity thus producing ~1,770 lbs. of CO2)
Do you have a computer at home? (a computer uses about 262 kwh of electricity thus producing ~430 lbs. of CO2)
What about a printer? (on average, running a printer uses about 45 kwh of electricity thus producing ~74 lbs. of CO2)
OK, how about a cell phone? (charging your cell phone uses about 9 kwh of electricity thus producing ~15 lbs. of CO2)
What about air-conditioning? (an average air-conditioner uses about 2,800 kwh of electricity thus producing ~4,592 lbs. of CO2)
And your water heater? (an average water heater uses about 2,800 kwh of electricity thus producing ~4,592 lbs. of CO2)
And we're pretty sure you have electric lights, right? (an average home's lights use about 1,400 kwh of electricity thus producing ~2,296 lbs. of CO2)
Heating, do you use electric or gas heating? (gas uses about 50,000 cubic meters of gas or ~ 6,053 lbs. of CO2, electric heating uses about 2,800 kwh of electricity thus producing ~4,592 lbs. of CO2) To make things simple and consistent, we'll assume you use electricity.

Check the box to complete your calculations.

Wow...., based on the information you supplied, your home uses approximately KW hours of electricity, which creates about pounds of CO2 (1.64 x your KWH), or tons of CO2 (your pounds/2,000). Now for the interesting part!!!

You do the math. One acre of Pinus radiata processes and stores roughly 5 tons of CO2. As shown, our home produces approximately tons of CO2. How many acres of trees are needed to offset your home? How many individual trees?

Click here to check your answer!

 

 

 

 

 

Yes, it takes roughly acres or trees to offset the CO2 used in running your home. Now.... another component of your carbon imprint... what about your transportation needs...... Every gallon of gas you burn running your car creates roughly 20 lbs. of CO2. So if my car gets 20 miles per gallon and I do 20,000 miles per year..... yikes, that's another 10 tons of CO2 (you do the math for your car(s)!). Hmmmm...... that's another 2.0 acres or another 240 trees.

Think about this problem for a moment. This problem is one small component in a much larger issue. Trees have a limited life span and also create CO2 when the die and decay or are burned in a fire. And where do the aquatic plants fit in? Did you know the ocean plants are estimated to take in as much or more CO2 each year than the land plants? It is thought that CO2 sequestered in plants on the oceans surface that die and descend to oceans depths may be released back into the atmosphere over a much longer timeframe than that stored in trees. Have you ever consider this as a reason for keeping the oceans clean and ensuring a thriving environment for plants? How important is this?

Interesting "Plant Talking Point" isn't it. How far can you stretch the point? We'd love to hear your thoughts on the subject and share them with others. If you'd like, please send your class discussion to: PlantingScience@botany.org. Remember, solutions are all around us. Talking about and considering options helps us develop and build on new ideas. No matter how hard it seems, think long term. What kind of world do you want for your grandchildren’s children?

Thanks for stopping by!!

The information contained in this "Plant Talking Point" was supplied by Bill Dahl of the BSA Staff Team.


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