carbon offsets

August 2, 2006

in Environmental issues

What does it mean to be “carbon neutral”?
There is a lot of talk lately about going “carbon neutral” by purchasing carbon offsets.  You calculate (via various formulas available online) how many tons of carbon you are responsible for, based on your consumption of electicity, gasoline, etc. Then you make a contribution to offset those emissions — a contribution that invests in some sort of renewable energy or a reforestation project, for example.  The cost for each metric ton of CO2 you offset is between about US$6 – $30. The goal is to neutralize one’s impact on global climate change.

This is an intuitively appealing idea.  Does it hold up under analysis?

Is wind power the most ecologically-friendly offset?
Wind farms are bar far the most frequent projects supported by carbon offset marketers.  Wind energy is a great, clean, renewable resource. However, it is not without environmental consequences, namely disturbance or mortality to wildlife, especially birds.

Properly sited wind farms are of little risk to birds, as far as we know at this time. The March 2006 issue of Ibis, the journal of the British Ornithological Union,  was devoted to papers on renewable energy and birds. One excellent paper [1] provided an overview of the four main risks to birds: collision, displacement due to disturbance, barrier effects and habitat loss.  The authors made three recommendations on where NOT to place wind farms:

1) Where there is a high density of wintering or migratory waterfowl.
2) Where there is a high level of raptor activity.
3) Where there are breeding, wintering, or migratory populations of less abundant species or those of conservation concern.

The paper also notes that not enough research has really been done about some of the less obvious impacts of wind turbines on birds (no pun intended), evaluation methods have not been refined and take at least a full year to provide a complete picture, but that there are ways to mitigate effects, including emerging technology.

Therefore I wondered if, in the rush to build these farms in the U.S., how many and which ones were wildlife-friendly.  I started to look for and examine the environmental impact statements of individual projects offered as offsets by various marketers.  I was not encouraged by what I saw, and obviously this was a very tedious process.  So I decided to look at other ways to offset my carbon emissions.

What about reforestation?
What person who is striving towards a green lifestyle doesn’t like the idea of planting trees?  In the carbon-neutral scheme, carbon is sequestered in trees, which act as sinks, because about 50% of the dry biomass of a tree is carbon.

This seems straightfoward enough. Except that initially, carbon sequestration is very slow in a young tree.  It gains as the tree matures, but most trees do not reach maturity for 40 to 80 years. Different tree species sequester carbon at different rates, depending on how fast they grow, with trees in the tropics growing faster, and temperate and boreal species growing slower.  And of course, the whole effect is only temporary — one the tree dies or is burned, the carbon is released into the atmosphere.  Many experts do not see forest carbon sinks as viable offsets, for these and a host of other reasons (more resources below the fold).

Does buying carbon offsets really make sense?
I began to get a little discouraged.  I realized that “additionality” was one of the most important aspects of carbon offsets overall — that the project supported would not otherwise have happened.  This was not always easy to determine.  I found that there was also criticism of  the trading in carbon credits on the Chicago Climate Exchange.  Then I came across a piece by economist Charles Komanoff on Gristmill :

“When you stop and think about it, the whole idea of driving a car, paying money into a green kitty to offset the CO2 from burning the gas, and then calling the car trip carbon-neutral, is ludicrous.”

Crediting me…with climate neutrality for financing green energy, while the actual implementer — a wind developer here, an insulation installer or a mass transit builder there — also takes credit, is double-counting. But it’s worse than padding the books. Carbon offsets are disturbingly redolent of the sale of indulgences in the Middle Ages, by which the wealthy could expiate their sins without prayer or good works by greasing the palms of the Church hierarchy.”

Supporting the implementation of renewable energy projects or the restoration of forests is a great idea, and I encourage it.  But it is not the solution to curbing global climate change, and shouldn’t be used as an excuse to drive a Hummer.  What we should be spending our $30 on — rather than buying a ton or two of carbon emissions — is compact fluorescent lightbulbs.  Or better home insulation.  Or any number of other means by which we can reduce our own carbon emissions.

Below the fold, resources on going “low carb” and reducing your carbon footprint, carbon offset marketers that offer solar and renewable energy projects, and other resources.

Update: In Jan 2007, Enviroblog summed up a UK Independent article on whether or not carbon offsetting really works. A few days later, the New York Times published a piece noting that recent research indicates that planting trees outside of the tropics does little to help global warming, and may instead contribute to it. All are worth reading.

Going low carb

Some carbon offset marketers with projects other than wind or reforestation:

  • NativeEnergy — Mostly wind projects, but you can also choose to offset via ReMooable energy (methane generators in the Mid-Atlantic states).
  • — allows you to choose between renewable energy projects (8 projects: 4 wind, 2 solar, 1 biomass digester, 1 methane processor).

Resources on carbon sinks, sequestration, and reforestation offset projects:

  • Sinkswatch – initiative of the World Rainforest Movement, tracks carbon sequestration projects highlighting their threats to forests and other ecosystems, to forest peoples as well as to the climate.
  • The carbon shop: planting new problems — World Rainforest Movement.


[1] Drewitt, A. L. and R. H. W. Langston,  2006. Assessing the impacts of wind farms on birds. Ibis 148: 29-42.


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