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carbon offsets

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).
  • Carbonfund.org — 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.

Filed in Environmental issues

Comments on this entry are closed.

  • Rob Miller August 2, 2006, 2:54 pm

    Interesting article. I have struggled with this same issue. My personal belief is that, similar to our energy portfolio, no one item will provide the whole solution. Even if we could replant the entire planet in trees, it will not stop global warming, if we cover it in windmills, it might but at what cost? I agree with you that we first must reduce. I then believe that offseting the remaining use is worthwhile, if only to drive the market and interest. Use the offset to cover your base consumption as you continue to conserve. I would also like to see the offsets fund a broader portfolio which I believe is required.
    On the bird issue, an interesting point from Idaho. Two wildfires have been caused this year by raptors being electrocuted by powerlines and then starting a grass fire. Windmills, while a threat to birds, might not be the largest threat.

  • sciencewoman August 2, 2006, 5:03 pm

    Hmmm…once again you've done the careful research to confirm what I suspected. (That's a compliment by the way). As a carbon offset buyer, I never really viewed my gas consumption as a neutral activity. In fact, I have just as much guilt now as I ever did. But it did seem like a good way to allocate some of my charitable giving for the year in a way that would have some net benefit.

  • John August 2, 2006, 8:12 pm

    I have been suspicious of carbon offsets as well. What bothers me the most is that the pollution is still entering the atmosphere and still causing harm regardless of offset purchases. Buying credits from a wind energy company seems like a bad-aid at best. What really needs to be done is a combination of making alternative energy mainstream instead of a niche and conservation.

    Planting trees around one's own community might be a more worthy endeavor than paying someone to do it somewhere else.

  • Nuthatch August 2, 2006, 8:18 pm

    I'd like to reiterate that I hope nobody sees me as poo-pooing the idea of wind energy, reforestation, or the intent behind offsets. The point is that carbon offsets are not as simple nor cause-and-effect as they appear to be. If you choose to offset your emissions, it will take some time and effort to determine if what you are supporting is not ineffective or harmful. And the best solution begins at home.

  • Roger B. August 3, 2006, 8:21 am

    Thanks for this well researched and reasoned post. It confirmed my own 'gut feeling' about these schemes. We have to face up to the fact that reducing our personal energy consumption is by far the most effective action we can take to cut carbon emissions.

    By the way, there used to be a group here in the UK called "Conservationists Against Tree Planting".

  • Daniel Collins August 3, 2006, 9:35 am

    Good stuff. One point though – windpower is not an offset. Offsets must have negative carbon footprints. Windfarms just have smaller, positive ones, as do CFLs.

  • Nuthatch August 3, 2006, 11:46 am

    Daniel, since financial support of wind projects are used as offsets, I would hope that the carbon use of the project itself is factored in somehow. But this illustrates the problem with calculating a monetary value that is the equivalent of some tonnage of carbon. The inexactness of these calculations are another criticism I've seen leveled at offset schemes. I don't think one can take them too literally, you just have to feel like you are making a contribution to a renewable energy project, and not consider it an "offset" to some amount of your own carbon footprint.

    I've added a new link to the post to a Salon article on carbon offsets.

  • Alan Gregory August 3, 2006, 9:03 pm

    There is a fourth recommendation on where NOT to place a wind farm: In the middle of a roadless area. In Pennsylvania, where highways, power line cuts and other linear disturbances mar the landscape left and right, only the ridgetop forests remain extant. To develop a wind farm atop an Allegheny ridge means fragmenting the landscape. Studies after studies after studies have pinpointed the various harms that follow such fragmentation: Reduced nesting productivity by forest-interior songbirds, increased predation by smallish predators (racoons, opossums, chipmunks), increased nest parasitism by cowbirds, invasive species, etc. I see very little coverage of this important issue in mainstream media accounts of wind farm plans. And about the same level of coverage in the more scientific press.

  • Laura August 7, 2006, 11:07 am

    Wayne at Niches has posted a rough calculation of the size of forest that would have to be planted annually if we were to rely solely on carbon sequestration as an offset. A very lively rant.

  • Nuthatch August 7, 2006, 12:29 pm

    Indeed, I've read that there isn't enough land on earth to plant adequate sequestering forests. Bravo to Wayne for going through all those numbers!

  • Timothy Colman August 12, 2006, 3:12 am

    Conservation of energy would take us a long way to carbon restricted diet. Rocky Mtn Institute has been working on shift to this kind of thinking for years.

    I think people would respond to a book on low carbon diet.
    Could help educate people about the changes we need to make quickly.

    Unfortunately– British Petroleum is the only company pushing this idea consistently in the media.

    I am playing around with chapter titles — ideas on content welcome.

  • kris August 19, 2006, 8:24 am

    This is very interesting. I am definitely not as "green" as I should be. I don't know why I sort of fell asleep on energy issues several years back only to wake up and wonder why we built this house as we did. The first thing we need to do–my spouse and I–is to figure out how to cut our energy use and how to begin to install some alternative energy sources.

    My spouse gets a company car to drive, a different one every two or three months (they keep changing the time span). He gets no choice as to what he'll be driving. Imagine our horror and shame when he was given the keys to a Hummer!! That thing is a gas hog, it's enormous, ugly, and just wrong. Shudder.

  • Nuthatch August 19, 2006, 8:48 am

    Over the last few years, husband and I have replaced all light bulbs in the house with compacts fluorescents, replaced our hot water heater with a tankless type, gotten a high-efficiency furnace and front-loading washer, added insulation, and we drive a hybrid and low emissions vehicles. But he works for an auto supplier, and sometimes needs to drive a test vehicle — usually a huge truck. I feel sort of embarrassed!