RegGuheert
Well-known member
Thanks for those numbers! Please provide a reference for them.WetEV said:Not quite that bad. However, when biofuels were the source of energy for farming, the EROEI was about 3. That's based on farming by mule/horse/oxen, of course. The farms could feed the farmers, their farm animals, and about twice as many town and/or city people. EROEI from sugar cane to ethanol is around 8. Firewood is around 30. A combination biofuel and electric farm looks to me to have an EROEI of around 10, and a biological EROEI of around 20.
Some thoughts:
- Farmers in cold climates burned wood to heat their homes. In many cases, the bioenergy was already there when they took over the land. However, beyond a certain population density, the trees all get used up. This is what happened in England in the 16th century to hasten the transition to coal, in spite of coal being a much dirtier fuel. To suppose that they could now move back from coal to wood is extremely unlikely, even with modern practices.
- Firewood that is harvested on one continent and shipped to another continent likely has a very low EROEI. Also, I suspect that 30:1 only counts the harvesting of the firewood and assumes it grew their naturally. Any type of sustainable forestry likely has much larger energy inputs including all of the energy used for nurseries, planting, etc.
- Sugar cane appears like it might have sufficiently-high EROEI, although some question whether the denominator is being properly counted.
Agreed. In addition, the clearing of land to provide for biofuel production is destroying many habitats around the world. Unfortunately, this is being done at an alarming rate.WetEV said:Of course, there are lots of complicating factors. The soil is being eroded, on the average, faster than the geologic rate of replacement, so crops and/or methods of farming need to change. Mining soil for fuel is just as short sighted as mining fossil fuels.