0.7 pounds of CO2 per passenger mile when flying. (from www.Travelmatters.org) I prefer to use the rounded up estimate of one pound per passenger-mile because the estimate used by TravelMatters.org is an average, and I want to recommend an ?above average? estimation of carbon emissions. We want to make a global cooling estimate, not just carbon neutrality.

One Pound of CO2 per mile of car driving

A gallon of gasoline (6 pounds in weight) turns into about 20 lbs of carbon dioxide gas when burned.

A car that gets 20 miles per gallon means a pound of CO2 per mile.

The largest estimate is that there are XXX tons of CO2 produced directly and indirectly in the USA each year. Dived that number by 300 million inhabitants and we get about 20 tons of CO2 per person in the USA.

How many trees does it take to absorb 20 tons of CO2?

I have a fairly liberal view in this matter. For my personal use, I like to plant trees that will absorb the 20 tons within 30 years. When I want a lower number (if a client wants to spread out the absorption over 40 or 50 years, then fewer trees are recommended for planting).

The estimates are cautious if we assume that the trees, when reaching maturity, will generate additional trees. If we assume that a fraction of the trees will not reach maturity, then we have an estimate that is over stretching. The value of tree planting is found in having an expansive view of how much carbon a tree will absorb and what impact that tree will have on global warming. The first answer is ?about a ton? of CO2 will be absorbed over the life of a typical Leucaena (this number is based on 50 pounds of CO2 per year for 40 years). The second answer is ?who knows? Perhaps 10 tons per tree? because a single tree could generate at least 100 seedlings that might compete. Perhaps ten of these trees could reach maturity, so that over 100 years, one tree and its descendents could account for 10 tons of carbon storage.

That said, I like to give people a near-term answer.

Here are my assumptions

TABLE 1

Years

0 to 5 less than 100 pounds

6 5

7 7

8 9

9 11

10 15

11 20

12 25

13 30 122

14-25 50 x 12 600

After 25 years, about 722 pounds

After another 10 years (35 years) 722 +500 = 1222 pounds.

Call it 1200 pounds over 35 years. Or about 0.6 tons per tree.

IN other words, 10 trees will offset 6 tons

30 trees will offset 18 tons

So about 35 trees will offset 20 tons.

At 20 cents per tree, $7 a year will plant 35 trees and offset 20 tons of CO2, the per capita amount of carbon emission that each person on average is responsible for. People who travel more should sponsor at least one tree every 2000 miles of additional travel.

If one wants to use a shorter win, perhaps 10 years to count the carbon storage, many more trees will be needed. As shown in my cautious tree model, the first ten years are ignored and the years between 6 and 10 account for only 47 pounds, not 1200 pounds. Using round numbers, 50 pounds per tree x 24 trees will equal what I assume one tree can reasonably store. 24 trees for 1200 pounds, meaning 40 trees for 2000 pounds means that a robust global cooling program would require people to sponsor 800 trees to offset the 20 tons that they produce indirectly. That's a rather stiff burden and the estimate doesn't capture the offspring of the planted trees.

My feeling is that any additional planting is a good thing and with the proper assumptions, we can show that any tree planting program leads to global cooling. One tree per person is inadequate for demonstrating care for the environment, but 800 trees per person per year is overkill. That's why I've settled on 35 to 40 trees per person per year as a moderate ?global cooling person? standard.

Best wishes.

Steve McCrea

www.freeenglishlessons.com

I even calculate a number for my students so that they are carbon neutral or global cooling when they are in my class.

Notes

The following notes are adapted from www.TravelMatters.org

http://www.travelmatters.org/calculator/individual/methodology

Pounds of CO2 per Passenger Mile Traveled

More than CO2 is considered in the table. Other greenhouse gases are produced by the combustion of transportation fuels. Nitrous oxide (N2O) and methane (CH4) are stronger because they remain in the atmosphere longer and absorb and reflect more radiation than carbon dioxide.

This travelmatters.org calculator calculates carbon dioxide equivalents so that the global warming potential of gases other than CO2 are accounted for in the emissions estimate. This means that we can estimate the amount of greenhouse gases produced for each mile traveled by each passenger on a train or bus. The pounds of emission per mile is multiplied by the number of miles reported, to result in the pounds of emissions produced for all of the miles traveled on each mode.

Average Emissions per Mile

Type lbs co2/mile

Vanpool 0.27

Subway or Elevated Rail 0.35

Commuter Rail 0.41

Amtrak 0.46

Streetcar or Trolley 0.46

Trolleybus 0.54

Bus 0.90

Demand Response 2.09

Monorail or Cable Car 2.39

Ferry Boat 2.68

Moped 0.2

Scooter 0.3

Motorcycle 0.4

Motor home 2.7

Carpool 1.1

Taxi 1.1

Rental Car 1.2

Airplane 0.64

For the carpool category, divide by the number of passengers reported.

Data for calculating Personal vehicle emissions were based on fuel efficiency records for each make, model and year of car.

Assumed: a gallon of gasoline, when burned, produces 24.116 pounds of CO2 equivalents.

Steve McCrea

Carbon Sequestration Consultant

www.RoadLovers.com reader and editor