Counting All the Carbon: A Waxman-Markey Wart

by Bill Chameides | July 2nd, 2009
posted by Erica Rowell (Editor)

Permalink | 12 comments

When lands are changed from one use to another to grow biofuel crops, the change tends to lead to greater emissions of carbon dioxide into the atmosphere. So assessing the climate impact of biofuels should take that fact into account. (NREL)

To love something means accepting it, “warts and all.” Well, here’s one Waxman-Markey wart I don’t even like: its failure to count all the carbon.

In theory bioenergy is climate neutral (see figure). The carbon dioxide (CO2) that is emitted when biomass is burned comes from carbon that the plant took in from the atmosphere during photosynthesis. That carbon is part of a circle going nowhere: plants take CO2 out of the atmosphere in photosynthesis, and CO2 goes into the atmosphere when the biomass is burned. No net CO2 emissions and no net climate effect.

Unfortunately, it is not that simple. You have to count all the carbon.

Embedded CO2 Emissions: Bioenergy Is Rarely Climate Neutral

Producing biofuels such as ethanol often requires energy from fossil fuels and thus CO2 emissions from those fossil fuels. These “embedded emissions” must be counted when assessing the climate impact of bioenergy, and as a result, bioenergy is rarely climate neutral.


Simple, idealized life cycle for climate-neutral biofuel.

Nevertheless, the embedded emissions of biofuels on a gallon to gallon basis are usually smaller than the embedded emissions associated with fossil fuel production, and thus bioenergy is often a good climate bet from this point of view.

Land-Use Changes

A far less straightforward issue relates to changes in land use. To explain this, let’s return to the concept of bioenergy and climate neutrality but reverse the order of things — instead of CO2 out and CO2 in, let’s analyze it as CO2 in and CO2 out.

CO2 into the atmosphere: We start by harvesting biomass, for example, in the form of corn or timber. We burn the biomass to make energy and in the process we emit CO2. These emissions of a greenhouse gas warm the atmosphere even though they came from biomass. No climate neutrality there.

CO2 out of the atmosphere: But normally, whatever crop we harvest and burn would be planted again for more fuel. As that replacement crop grows, it removes the CO2 that was emitted in the first step.

© State of New South Wales through the Department of Water and Energy

So there’s our circle going nowhere again, this time CO2 out and CO2 in. No climate impact, right? Not necessarily.

This scenario envisions a steady state in land use. For example, once a cornfield, always a cornfield, season after season. But what happens if an old-growth forest with an enormous store of sequestered carbon in its trees and soil is cut down and planted with, say, corn, which is then harvested and burned and then replanted in, say, soybeans this time?

The carbon released from the conversion of the old-growth forest is never removed, and this represents a net flow of CO2 into the atmosphere. In this scenario the carbon emissions are from a direct land-use change.

Indirect Land-Use Change — The Wrench in the Bioenergy Works

Far more complicated and contentious are emissions from indirect land-use change.

Suppose a U.S. farmer who’d been selling corn for food decides to sell that corn for bioenergy instead. That would produce an imbalance between supply and demand for corn for food that will induce another farmer somewhere to fill that food-corn gap. If that other farmer, perhaps living in South America or Africa, does so by converting an old-growth forest to cornfields, that change will lead to a net emission of CO2.

Now, these emissions come from an indirect land-use change since the change does not occur on the same farm. But beware of the word indirect: the CO2 that ends up in the atmosphere is just as real as CO2 from burning fossil fuels or direct land-use changes.

So is indirect land-use change an issue? It looks like it. A couple of papers in Science last year (see here and here) concluded that indirect land-use changes, occurring primarily in Brazil to compensate for the use of American corn for ethanol, make corn ethanol a larger net emitter of CO2 than gasoline — forget climate neutral.

In a more recent Science paper, Marshall Wise of the University of Maryland and colleagues projected that any climate-mitigation strategy that ignored land-use changes when assessing emissions from bioenergy would:

  • lead to the conversion of almost all of the world’s unmanaged forests and pastures to farms for bioenergy crops,
  • cause a huge jump in corn prices, and
  • because of the excess CO2 emissions, require a “negative” emission rate of fossil fuel CO2 to stabilize atmospheric concentrations at 450 ppm.

Ag-Food Fight With EPA

EPA took these findings seriously: it included indirect land-use changes in its assessment of corn ethanol emissions and concluded that corn ethanol did not qualify as a “renewable fuel.” That decision pissed off Representative Collin Peterson (D-MN), who represents a corn-growing district. In the run-up to the vote on the climate bill, Peterson threatened to take his marbles and his House ag-friends home and not vote for Waxman-Markey.

Alas, compromise is the name of the game in Washington, and Peterson got what he wanted before the bill passed in the House. Indirect land-use changes will not be included in the bioenergy accounting ledger for at least five years while the National Academy of Sciences (NAS) studies the issue. Then the agriculture department, energy department, and EPA will all have to approve the NAS study, and, assuming they do, Congress will have to decide what to do when folks like Peterson and his friends can once again threaten a hissy fit.

Maybe the Senate will get it right.

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  1. Mary Serreze
    Jul 3, 2009

    I am a journalist in Western Massachusetts, where 4 biomass plants, equaling 175 MW, are proposed. I am trying to understand some of the rhetoric. “Biomass plants are carbon-neutral,” say proponents. This comes across as an artful turn-of-phrase. What does this mean? I am not a scientist–but still, it doesn’t seem right. Will the carbon dioxide emitted by an incinerator be sequestered at the same rate that the forest was harvested to produce fuelstock? The blogger at this link: quotes from the IPCC guidelines for carbon accounting: “Within the energy module biomass consumption is assumed to equal its regrowth…Any departures from this hypothesis are counted within the Land Use Change and Forestry module,” and reports that “The reason biomass is not reported as an emission in the energy section of the reporting is because it would be double-counting to do so, as this emission has been accounted for already under forests.” If his analysis is correct, then wood-burning biomass plants are not carbon-neutral–the carbon emissions are simply accounted for elsewhere.

    • Crush
      Jul 6, 2009

      Carbon emitted when you burn grass, for instance, would be equal to the amount of carbon absorbed by the grass when it regrows the following year. The difference is that the carbon emitted from fossil fuels took billions of years to form underground and has been pulled up and put into the atmosphere in less than 100 years. Burning biomass produces no net increase in the amount of carbon in the cycle. Burning fossil fuel does because it was sequestered billions of years ago and can’t be replaced for another billion years. That said, it takes far longer for a tree to grow and recoup the carbon that is emitted by burning it, so that would be much less sustainable than grass. However, I doubt the facilities you refer to are proposing to get their biomass by cutting down the forest. I expect they plan to use waste wood (used pallets, demolition waste, forest thinning, diseased or infested trees cut down by the Parks Department, etc.). In that case, it would be even better than using a dedicated energy crop, since the wood would have simply been thrown away to decay or burned if not for its use as power.

      • Mary Serreze
        Jul 7, 2009

        There is nowhere near enough waste wood to feed another 190 megawatts of production in Western Massachusetts. (Plants planned for Greenfield, Russell, Springfield, Pittsfield, Fitchburg.) Logging rates would need to triple on all Massachusetts forests, public and private, in order to provide a continuous supply of wood for the biomass plants. At least 2.4 million tons of wood per year would be required. Half a million tons of waste wood is there–so we are looking at about 1.8 million tons of new trees. (DCR records show current annual State forest land logging rates at 0.05 million tons of wood, and annual private land logging of 0.57 million tons.) State forest lands are being targeted for biomass fuelstock: a proposed management plan issued by the state for the four western Massachusetts districts call for a 400% increase in state forest logging, which have historically been minimal. The Russell Biomass plant, by its own estimates, would emit 1.5 times as much carbon dioxide per unit of energy generated as the worst carbon dioxide emitting power plant in the entire Northeast region. Woody biomass can only be deemed carbon-neutral if full and proper carbon accounting is done on the forestry side. Massachusetts has not taken this step to date. (Forestry activities, even if severe, do not, according to the state, amount to a permanent land use change, thus fall through a crack in the carbon accounting.) The big prob is of course the inclusion of woody biomass in the state’s Renewable Porfolio Standard. The Mass “Green Communities Act” calls for utilities to purchase 15% of their electricity from “renewables” by 2020. The state of Massachusetts is fast-tracking these projects, requiring minimal environmental review. Woody biomass, as proposed in Western Massachusetts, is *not* carbon neutral. And this is not a good, time, historically, to be cutting down our forests.

      • Mary S. Booth
        Jul 7, 2009

        I’m writing from Massachusetts, too, on behalf of the Massachusetts Environmental Energy Alliance. Large-scale woody biomass-to-electricity plants may be the most egregious example of “green” energy touted as carbon neutral, when in fact it is not. Scientists tell us we need to reduce greenhouse gas emissions immediately – we can’t afford to wait to re-sequester the carbon that’s released by burning forests. A 50-MW woody biomass plant burns about 650,000 tons of wood per year, or over a ton a minute. At a thinning rate of 15 tons per acre, the plants that are proposed in Massachusetts would require logging about 120,000 acres per year to supply wood or about 100 times the current annual acreage! Not only is all this carbon sent into the air, the ability of the forest to sequester carbon is impaired (in fact, recently logged forests act as net carbon sources, not sinks). Saying that biomass is carbon neutral without doing the math and looking at the actual regrowth rate of forests (and taking into account the important carbon sequestration function that the relatively young and vigorous forests of the Northeast provide) is irresponsible. Unfortunately, there are a lot of policy-makers who like the sound of an inexhaustible supply of “carbon-free” energy who don’t care to examine the numbers closely.

        • Crush
          Jul 10, 2009

          This is why electric cars aren’t the answer. The ramp-up in needed electricity capacity will require dirty power plants. There’s just no way to get the wind and solar industries at a large scale in time, and you’re not going to convince new coal plants to go up temporarily until clean technology takes hold. That would be an economic fiasco.

      • Mary Serreze
        Jul 7, 2009

        One last thing. Here’s what the Massachusetts Sierra Club has to say about the “carbon-neutrality” of electricity plants, such as Russell Biomass, which will burn whole trees…

        • Crush
          Jul 7, 2009

          Yeah, I don’t think trees count as an energy crop. “Biomass plants are carbon-neutral,” is a little too broad in this case. I see signs that electric cars will get the media hammer for the rapid increase in electic capacity needed to make them viable.

  2. Crush
    Jul 2, 2009

    The science is shaky on land use change. There’s a lot of idled cropland in the world that could just as easily be used for any expansion, and US exports for soy and corn haven’t fallen as ethanol has risen. Neither has corn carryover. European Union decided not to use the theory in its climate rules because they determined the science isn’t solid enough for policy yet.

    • Bill Chameides
      Jul 2, 2009

      Crush, Valid point, although I think “shaky” is an overstatement of the uncertainty of this effect. There may be lots of idle cropland, but that does not mean that forests won’t be cut down to grow food crops. And there is a good deal of data to indicate that forests are cut down. More importantly: when it comes to an emissions cap, it is imperative that the integrity of the cap be protected. Even if the science on land use change is ‘shaky,’ it cannot be ignored. Better to err on the side of safety than to allow the use of bioenergy without accounting for land-use change which turns out to be a huge source of CO2. The alternative could be the scenario projected by Wise et al.

      • Crush
        Jul 2, 2009

        It also seems wrong to hit ethanol twice for emissions: first for the corn in the U.S., and second for the corn or soybeans in Brazil raised for food. The argument seems to state that the U.S. acres would normally be used for food, therefore new land in Brazil or the Ukraine must be farmed to replace that. Doesn’t that mean that with or without ethanol, those U.S. acres would produce the same emissions, only as food production? In that scenario, it seems to me that ethanol should be penalized for the foreign acres, but not the U.S. acres. Thank you for the civil discourse on this. This is a very interesting topic. I am, obviously, an ethanol supporter, so we are coming from different perspectives. As someone who believes the benefits of ethanol, I see a promising fuel being threatened by a theory whose authors admit is extremely difficult to nail down from a policy perspective. That gets me a little emotional. Your level-headed response kept me from getting too fired up.

        • Dan K.
          Jul 6, 2009

          As someone originally from Eastern Europe, I can tell you that from a policy, regulatory and any other perspective really, counting such a thing in places like the Ukraine is going to be very difficult. It’s hard to convince a part of the world that is not really conscious of environmental issues to begin with. On the point of ethanol, as many other biofuels, discussions tend to get heated (i.e. personally, I don’t see much promise at this point in biofuels unless algae technology has a breakthrough – my thinking on this topic is that if you’re shooting for some level of a cure-all, might as well go for broke). Also, I’m a fan of biodiesel after studying in my coursework if it comes from oil that will be discarded, such as from restaurants. Probably the most promise is for airlines, especially since their emissions are generated higher up in the atmosphere and thus more damaging. See related articles to that below. As for ethanol itself, a great study was done by a Stanford professor recently that took a very LCA (life-cycle analysis) look at different renewables and potential fuels as found that ethanol (corn and cellulosic) perform the worst. This is also the trend in the research. The study goes into many factors, but if one is talking about corn ethanol (I do not know which, Crush, which you favor), I think that I’d rather feed people than my car (which, by the way, would have a shorter range, all else equal, on ethanol, since it has innately less BTUs/gallon than gasoline or diesel). Links to the Stanford study: And let’s face it – not that our Ag policies are the most productive [for the world], furthering ethanol from corn is just another federal farm subsidy. People I work with indicate that farmers hate this – while they’ll fight you tooth-and-nail to keep their lifeline, they consider it like welfare. But that’s another matter! Cheers, Dan

        • Dan K.
          Jul 6, 2009

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