One of the reasons governments have been pushing biomass burning is the notion that it would displace fossil fuels and thereby reduce CO2 emissions. Biomass is renewable and displaces fossil fuels. But would it reduce CO2 emissions?
Fossil Fuels: Ancient Storage
In Batteries from the Carboniferous, I noted that fossil fuels are Nature’s ancient method of storing solar and photosynthetic energy in the ground. Inadvertently, fossil fuels have served as a multimillion year old storage battery, which sat in the ground because no species had learned to use it efficiently until human beings figured out how in recent centuries.
Because using it releases a number of pollutants, however, fossil fuels are a somewhat imperfect battery. These pollutants are: particulate matter, sulfur dioxide, nitrogen oxides, various hydrocarbons and carbon monoxide (the latter two if combustion is less than 100% efficient). [Note: CO2 is not in my list of pollutants. It is the stuff of life, rather than a pollutant. You, dear reader, are 18% carbon, virtually all of which originates in CO2 in the atmosphere. Don’t try to go without carbon!]
In order to figure out whether burning biomass rather than fossil fuels would reduce atmospheric CO2 emission, consider the following analogy.
Whether you pay your electricity bill out of your savings account (analogous to carbon in fossil fuels) or your checking account (analogous to carbon in newer biomass), your total wealth (checking + savings, analogous to total carbon in fossil fuels and newer biomass) is the same assuming the bill is paid out with equal efficiency, i.e., all fees are equal, whichever account you use.
From the electrical company’s point of view, its revenues are also the same.
Although paying it from your checking account makes your savings account larger, you are no better or worse off, on net. So, it makes no difference which account you use, either to your net wealth or the electrical company.
What willmake a difference is being able to decrease your electricity bill or increasing the amount you bring in to your checking account. But if the total bill is the same, it makes no difference which account you use.
Similarly, what carbon is no longer tied up in fossil fuels and in newer biomass ends up in the atmosphere (minus what is dissolved in the oceans and re-used in photosynthesis). Thus, it makes little or no difference to the atmosphere whether one uses new biomass or old biomass (aka fossil fuels).
That using biomass is any more sustainable than using coal, for instance, is based on compartmentalization (between checking and savings accounts). What is more “sustainable” (or “sustainable” for a longer time) — note the quotes, I use the word advisedly, but that’s another story — is either to reduce the use of energy or to generate biomass more rapidly (without displacing something else that would generate equal or more biomass).
Finally, note that for the combustion phase, it is possible to burn fossil fuels more efficiently than biomass. Hence, the former ought to reduce CO2 emissions overall. But a more sophisticated analysis ought to consider life-cycle consequences (including CO2 released in extraction, preparation, transportation, etc., of the two forms of biomass).
Biomass may be renewable, politically correct, and fossil-fuel displacing. But it is unlikely to reduce atmospheric CO2 concentrations much, if at all.