SubscribeDavid Pimentel, an expert on food and energy at Cornell University, has estimated that if all of the world ate the way the United States eats, humanity would exhaust all known
global fossil-fuel reserves in just
over seven years. Pimentel has his detractors. Some have accused him of being off on other calculations by as much as 30 percent. Fine. Make it ten years.
Although about 50% of all the solar energy captured by photosynthesis worldwide is used by humans, it is still inadequate to meet all of the planet's needs for food worldwide (Pimentel and Pimentel, 1996). To make up for this shortfall, about 345 quads of fossil energy (oil, gas, and coal) are utilized worldwide each year (International Energy Annual, 1995). Of this, 81 quads are utilized in the United States (DOE, 1995a,b). The U.S. population consumes 40% more fossil energy than all the solar energy captured by harvested U.S. crops, forest products, and other vegetation each year (Pimentel and Pimentel, 1996) ... The world supply of oil is projected to last approximately 50 years at current production rates (BP, 1994; Ivanhoe, 1995; Campbell, 1997; Duncan, 1997; Youngquist, 1997). Worldwide, the natural gas supply is adequate for about 50 years and coal for about 100 years (BP, 1994; Bartlett and Ristinen, 1995; Youngquist, 1997). These estimates, however, are based on current consumption rates and current population numbers. If all people in the world enjoyed a standard of living and energy consumption rate similar to that of the average American, and the world population continued to grow at a rate of 1.5%, the world's fossil fuel reserves would last about 15 years (Campbell, 1997; Youngquist, 1997).
... there are two different types of energy analysis for determining energy efficiency. ... For example, producing biodiesel from transesterification has a life cycle energy efficiency of around 82% or so (can't remember exactly). In this analysis, ALL energy input is included, including solar energy input. It's essentially a means of analyzing the efficiency of the process. The analysis tells us that the energy in the fuel is 82% of the sum of ALL of the energies that are input into producing it - but, it includes solar energy (into photosynthesis), which we don't put in. It includes it by counting the energy in the vegetable oil as an energy input, even though we don't produce that energy.[emphasis added]
But, the fossil fuel energy efficiency of producing biodiesel (from soy) is 320% - the energy in the product (biodiesel) is 320% of the fossil energy put in (or the energy that WE as humans put in, since the energy doesn't have to come from fossil sources - i.e. , running tractors on biodiesel, electricity for running the plant coming from renewables, etc.). A fossil fuel efficiency greater than 100% means it's a renewable fuel - but, the life cycle energy efficiency CAN NOT be >100%, since it includes ALL energy input, even that that we're not responsible for.
As fossil fuel stores are depleted, modern solar resources are likely to supply an increasing fraction of societal energy demands. Fortunately, these resources are more efficient than fossil fuels in terms of solar energy capture (Table III).I hardly see this as a damnation of biomass. Furthermore, while it is true that ethanol has been a debacle, ethanol is not biodiesel or those fuels that might be generated by thermal depolymerization (which, admittedly, still has to prove itself worthwhile to do).
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BTW, I just noticed that this made the Drudge Report frontpage today...
posted by samelborp at 12:37 PM on February 24, 2004