How much energy do you have to put in to plant, grow, harvest and process the plant material to produce the bio-diesel or alcohol end product compared to the energy content of the end product itself. Oil has a very high EPR. The figures I've seen range from 100 to 1 for oil obtained from a new oil field down to 10 to 1 for oil obtained from mature fields. That is, for every joule of energy you invest to produce conventional oil, you get out anywhere from 10 to 100 joules of energy at the other end. Our economy is therefore based on using a fuel with a high EPR.
....Oil used to have an EPR of 100 to 1. It only took one barrel of oil to extract 100 barrels of oil. This was such a fantastic ratio that oil was practically free energy. In fact, at one point in Texas, water cost more than oil! Oil's EPR is now down to 10 to 1, which is still pretty good. If a proposed alternative energy source doesn't have an EPR comparable to oil, the amount of good it does us is very limited. Keep these questions in mind as we examine the shortcomings of the oil alternatives in the following questions. www.hknet.org.nz/Oil-in-crisis.htm
My guess is that bio-diesel obtained by growing and processing plant material will not come close to the EPR that conventional oil provides and in the case of ethanol we know the EPR using current methods of production is actually negative.
Biofuels and the Ethanol Myth
Oil derived from plants is sometimes promoted as a fuel source to replace petroleum. However, a comprehensive study by Giampietro and others (1997) concludes: "Large-scale biofuel production is not an alternative to the current use of oil and is not even an advisable option to cover a significant fraction of it." The facts and experience with ethanol are an example. The Post-Petroleum Paradigm – and PopulationWhether producing bio-diesel will be more efficient than producing ethanol or whether its better to get bio-diesel from hemp rather than from soybeans, isn't the really important issue. The issue for our western style developed economies will be, how does producing bio-diesel or ethanol compare to producing gasoline/conventional diesel in energy efficiency.
Also another point we have to consider is how much land will be taken up to grow the diesel-oil or alcohol crops to meet transportation needs and will that leave us enough arable land to meet our food requirements (especially if population growth continues). Our factory farming methods are already very damaging to the soil and unsustainable in the long term.
FOOD, LAND, POPULATION and the U.S. ECONOMY
by David Pimental, Cornell University & Mario Giampietro Istituto of Nazionale della Nutrizione, Rome
KEY FINDINGS
At the present growth rate of 1.1% per year, the U.S. population will double to more than half a billion people within the next 60 years. It is estimated that approximately one acre of land is lost due to urbanization and highway construction alone for every person added to the U.S. population.
This means that only 0.6 acres of farmland would be available to grow food for each American in 2050, as opposed to the 1.8 acres per capita available today.At least 1.2 acres per person is required in order to maintain current American dietary standards. Food prices are projected to increase 3 to 5-fold within this period.
If present population growth, domestic food consumption and topsoil loss trends continue, the U.S. will most likely cease to be a food exporter by approximately 2025 because food grown in the U.S. will be needed for domestic purposes.
Since food exports earn $40 billion for the U.S. annually, the loss of this income source would result in an even greater increase in America's trade deficit.
Considering that America is the world's largest food exporter, the future survival of millions of people around the world may also come into question if food exports from the U.S. were to cease. FOOD, LAND, POPULATION, AND THE U.S. ECONOMYSo will the land actually support the amount of plant material we are going to require if we want to convert a large proportion of our present fossil fuel consumption to bio fuels and still maintain our current energy intensive economies?
I can see that bio-diesel etc. might help as a bridging fuel to help ease us into a new type of less energy intensive economy, but my concern is too many people expect that the scientist in the lab coats will pull a rabbit from the hat by coming up with some magic fuel elixir which will allow us to magically replace petroleum and still maintain our energy intensive consumer culture on ad infinitum.