I admire Carl Benson’s quest for an environmentally responsible fuel to heat his greenhouse, but his praise for biodiesel may go too far. It is theoretically true that biodiesel is carbon neutral, but I don’t believe it has any effect on the problem of global warming. If I switch from fossil fuel to biodiesel I am still emitting roughly the same amount of CO2. The fact that I am burning used fry oil does not mean the crop from which the oil was derived absorved any more CO2 than if I had not burned it. Hence, using biodiesel instead of fossil fuel has no net effect on the amount of CO2 in the atmosphere, and therefore does not alleviate global warming. The only scenario I can see where biodiesel does not increase atmospheric carbon is if the oil crop from which it is derived is raised on land that was previously not absorbing much carbon…a desert.
    The carbon neutrality of biodiesel has a real effect on global warming only if we limit ourself to buring plant-based oil, and then only because the very limited supply of biodiesel would force a dramatic reduction in combustion. If all fossil fuels were replaced with biodiesel, it would take over a billion acres of oil crops to satisfy America’s appetite for combustion. Yet we have only 700 million acres of agricultural land available. In the unlikely event that we would be able to convert 200 million acres currently devoted to food and fiber production to oil crops, we would still have to decrease our fuel usage by over 80% to meet the supply of biodiesel. The real culprit in global warming is our addiction to combustion, not the type of fuel we use.

                    Jeff Falen
                    Persephone Farm
                    Lebanon, Oregon

Carl Benson replies:

    Jeff’s assertion that the most effective solution to the human contribution of excess atmospheric CO2 is to reduce combustion is valid.  Any combustion releases CO2 as a byproduct.
    However there is an important distinction between current plant based fuels and fossil fuels.  When we burn a vegetable oil based fuel to heat our greenhouses, CO2 is returned to the atmosphere.  Emphasis is on the word return here because when we burn a fuel that is plant based, such as wood or biodiesel, we are returning CO2 that was removed from the atmosphere in the recent past.  When we burn a petroleum- based fuel the CO2 that is released has been absent from the atmospheric carbon cycle for millions of years.  So my point is that we can choose to continually pile on additional carbon to the atmospheric load by burning fossil fuels, or simply return the carbon that is part of the current carbon cycle.
    Does using bio-diesel reduce CO2 already in the atmosphere? No. But it does not add to the problem, and burning fossil fuels does.  Clearly the choice comes down to:  If you are going to burn fuel, try do as little harm as you can.
    Additionally, I never advocated growing oil crops for fuel.  I am simply taking advantage of a waste product…used fry oil, that is already sitting at the kitchen door of our local diner.  Good growing!