Carbon

Pop vocabulary is full of 2 types of buzzwords right now. It's either Obama_____ (as in Obama-mama, Obama-mania, Obama-nation, Obam-ination) or Carbon_________ (carbon-footprint, carbon-balance, carbon-impact).

There's a [gold]rush to minimize one's carbon-footprint by buying carbon-offsets. The way it works is that 1-you fly to Spain 2-Booking online, you see a popup add telling you (gasp) how many carbon-units you're releasing into the atmosphere on the flight as a per person basis 3-The ad suggests you buy carbon-offsets, in the form of trees planted in the Amazon Rainforest to soak up the carbon you just released. 4-You do, and receive a warm feelgood that your trip is carbon-neutral.

That all seems fine and good, but here's the rub.
1--The newly planted trees will indeed be soaking up atmospheric carbon. You can think of it as "Yours", but its more likely offsetting the carbon released by the slash and burn activity going on deeper in the forest to make way for cattle pasture. There will still be a net release of carbon to the atmosphere during your flight.
2--The Amazon Rainforest's natural state is, in fact, forest. By that I mean that after the land has been spent on pasture and abandoned, it will eventually return to forest. This process will take a while--the soil will have been depleted, and it takes time for trees to grow, but eventually the forest will return. (Over the last 100 years, New England has reforested from the slash and burn practices of the colonists. New England was >95% forest at one time, the settlers had converted it to >90% pasture by 1800, and in 1990, it was >75% forest again--numbers are approximate. The forests returned without the efforts of Peace Corp volunteers with shovels. Similarly, the Western US is now being irrigated so that the deserts will blossom like the rose. It's a temporary situation. If the people of Salt Lake were to abandon their lush lawns, the sagebrush would return.)
3--The trees you've paid to have planted may upset the balance of the forest. How? It's likely that the trees that are planted (if they are actually planting trees, and not just scamming Al Gore and the American tourists) will likely be of just a few species. They were probably selected based on one or two traits. Perhaps they were chosen because those species have marketable qualities--exotic furniture lumber, useful for paper, straight for building material, who knows--maybe they're just easily propogated. Worst case is that the trees you are paying to have planted as a carbon offset are actually becoming a giant agricultural project, subsidizing the corporatization of the Amazon. At best, the trees were nursery grown and are all seeds from a small number of mature trees, so they have limited genetic variability. A natural forest is made up of a tremendous variety of species. The seeds may be blown in on the wind or carried in by bird droppings. However they arrive, they'll possess a great deal of genetic variability which will contribute to the general health and vigor of the forest.

I want to replace the concept of carbon-footprint with a more practical concept. Let's call it the carbon-1/2 life. That is the time it takes for 50% of the CO2 released into the atmosphere to be absorbed back into the earth. So, if an activity has a carbon-1/2 life of 10 years, and 100 grams of CO2 are released, in a decade, 50 grams of CO2 will still remain in the atmosphere. After 20 years 25 grams will remain, after 50 years 6 grams will remain. It will take 80 years for 99% of the released carbon to leave the atmosphere.

Here's an example. I live in the temperate forest of New England. My heating sources are 1-solar gain through the windows, 2-Onsite and sustainably harvested wood, 3-propane.

The heat from the sun really is carbon-neutral, or to be more accurate carbon-free. No carbon is released or exchanged, so the carbon-1/2 life = zero days. I neglected the energy used to fabricate, ship, and install my windows, but you get the idea.

The heat from the wood is also carbon-neutral. By that I mean that as trees are cut, they are replaced by seedlings. It's a natural process, and eventually, the seedlings will absorb enough atmospheric CO2 to offset the cut trees. Therefore heat from the wood is carbon-neutral, but its not carbon free. In fact, the CO2 released into the atmosphere through combustion will persist for approximately 50 years, until the seedlings grow to the size of the trees that were cut down. Perhaps it takes 5 years for the young trees that sprout in what had been shaded by the cut trees to reach 1/2 the size of the trees that were cut, so the carbon-1/2 life is 25 years, and it will take 200 years for 99% of the carbon to be removed from the atmosphere. This is simplified a bit--I ignored the gas it took to power the chainsaw, but its a fair approximation.

The heat from the propane will have a very long carbon-1/2 life, millenia. There is no easy way to remove it from the atmosphere. A partial list of suggested approaches follows:
1-store the carbon deep in the ocean waters. This is a natural process, but it too is a delicate balance. Storing excess carbon in the seas will acidify the waters and have repercussions that I won't detail here. 2-Store the carbon in the earth, possibly using it to fill the voids created by drilling for oil. Maybe, but this is a very expensive process. 3-Plant trees--see my above comments.

Realistically, the only way to remove the carbon released by burning fossil fuels is to grow large amounts of biomass, bury it deep in the ground where the products of decay won't release the CO2 into the atmosphere negating your efforts. Wait for the heat and pressure of the pile to restore the fossil fuels. Keep in mind that there is limited cropland available for growing the biomass (you could create more by slashing and burning some rainforest, but I again direct you to the above comments), it will take a large amount of biomass to resorb the amount of CO2 resultant from the use of fossil fuels, and there is not a convenient place to store the biomass while waiting for gas and oil to form.

You still have to keep an eye on so-called carbon-free options. Solar and wind are carbon free excluding the energy used to manufacture equipment, ship it, install, and maintenance of the solar collectors or turbines. The carbon-1/2 life of such energy sources is very low, but its still not zero. Corn based ethanol has a higher carbon-1/2 life when you include the energy required to process corn into ethanol. By some calculations, it takes more energy to produce a gallon of ethanol than is available in the ethanol. The carbon-1/2 life of nuclear energy doesn't fare much better when you consider the enormous cost of building a nuclear powerplant and consider the environment impact of the cooling tower: fish killed during water intake (carbon-1/2 life equals decades), fish/plankton/seaweed killed from heated water released from plant (carbon-1/2 life equals decades) energy used operating and guarding the nuclear plant (carbon-1/2 life equals millenia).

Bottom line--no matter who makes a buck from your desire to reduce your carbon impact, fossil fuel consumption is going to adversely impact the atmospheric CO2 balance. Renewable combustion also has an impact on the atmospheric CO2 balance, but a gallon of vegetable option has a much lower carbon-1/2 life than a gallon of gasoline. Some renewables like solar and wind power are relatively carbon-free, with a carbon-1/2 life close to zero.

The term carbon-1/2 life gives a much more rigorous comparison of our energy options than carbon footprint. It's also a catchy phrase for everyday conversation.