Lawrence B. Crowell
I am having a bit of an argument with some in the Green party on hemp energy. I am not against this as such, but the claims are outrageous. They claim that only 6% of farmland could be used to produce our current consumption requirements of oil. The problem is that the hemp coalition ideology and the rest is the basis for a “pan hemp” energy platform. I see this as a complete illusion. Below are some of my arguments to counter this:
The problem is that the energy incident on the surface of the Earth is integrated from a maximum power irradiance of around 1200watts/m^2. There is no miracle plant that somehow can photosynthetically store orders of magnitude more energy than another plant. Hemp might store more energy than corn, but it is highly unlikely that it stores ten times that amount. In effect the bioenergy of plants are all within a few times of each other.
Even if hemp has several times the energy capacity of corn, then since the EROEI for corn based ethanol is 1/2 (more energy in than out) the EROEI for hemp might then be about 2. Maybe better than break-even, but no bonanza either. Consider that the EROEI for Mideast oil is around 26-30. Also do the numbers! I think that realistically these agriculturally based fuel sources at best will be used to only run farm machinery. Even if hemp can produce 1000 gallons of ethanol per acre per year that amounts to 2.7 gallons per day on average, or .05 barrels. This means that 493,480,000 (about 1/2 billion) acres of land would have to be devoted to hemp production to produce as much fuel as currently required. That is a lot of real estate!
As the United States encompasses approximately 3.8 billion acres of land, and about half of it or 1.9 billion acres of land is arable land, then my estimate, based on energetics and some simple math, that it would require 1 billion acres to produce oil from hemp to completely recover 25 million barrels/day, then it appears to me that it would require we devote over 50% of arable land to hemp growth. Now given efficiencies and conservation efforts that might be reduced to 20%. That is considerably more than the 6% quoted.
Further given that the Energy Returned On Energy Investments (EROEI) for corn based ethanol is about 1/2, the energy input is twice the energy output, then even if hemp based ethanol got 4 times what corn does the EROEI for hemp is around 2. Consider that “elephant” oil fields, such as those in the middle east, have an EROEI of 25-29. Even the declining oil fields in the US have an EROEI of around 10. This means that of the fuel produced by hemp about half of it is cycled back into the process to produce it. So then with this meager EROEI for hemp, you would then require that nearly a billion acres of land would have to be devoted to produce fuel at current rates.
The price for energy as a rule tracks the EROEI. The cost is further not entirely a linear function of EROEI either. The cost for a gallon of fuel from hemp would be somewhere between $20-$50 a gallon. That is not an attractive price at the pump!
Malthus predicted that by the mid 19th century that the human race and in particular Europe would face a population crash from a peak of 1 billion. Frankly the world operated completely on bioenergy. What prevented that is we that by 1800 the world was shifting to coal energy where railroads and other machinery averted this disaster. Another analogous crisis occurred in the 1880s where a protein crisis emerged. What averted a further population crash was the Haber process of nitrogen fixing, which requires natural gas of light fuels. In effect the human race has been shifting away from bioenergy for 200 years simply because our populations are simply too large to be sustained that way.
Now one can easily point to various negative feedback processes that have occurred from this process of using nonbioenergy sources. However, do we really honest think that as we reached a bioenergy crisis in 1800 with a population of 1 billion that we can seriously return to that basis with a population of 6+ billion?
Again I stand by my conclusion. Agriculturally based production of fuel is just never going to be any major source of energy! Ethanol production for fuel is already a horrid waste of agricultural land, and is an energy sink. On a very local basis it can produce some amount of energy for immediate requirements, but on the large scale I doubt it can ever be more a very small percentage of total energy production.