Letters to the Editor
Chernobyl Kid
Published Letters: 67 Editor's Choice: 13
-
A square of farmland 4700 kilometers on a side.
[Read the article: Bring on the biofuels]
[Read more letters about this article: Here]Andrew's article overlooks the real issue in the biofuels debate. Few serious people would deny that under the right circumstances, biofuels CAN yield more energy than they take to produce. To suggest otherwise is a bit of a straw man. (In any case, only four of the six studies cited suggest that they do.) The question is, can biofuels replace in any serious way our fossil fuel consumption?
And, from this model, the answer is pretty clearly no. Even the four positive-yield studies still produce results like (at best) 1.5 net energy ratio. (That is, 1.5 joules of ethanol and other fuels coming out for every joule of energy inputs.) For comparison, Alaska oil in 1996 is given at around 11.1 net energy ratio. (That's Odum 1996, which incidentally gave corn and sugarcane biofuels as 1.10 and 1.14 respectively, suggesting comparable system boundaries to the papers reviewed by ERG.) Figures for Texas oil from 1940's discoveries (from other studies and, admittedly, perhaps different system boundaries) give net energy ratios on the order of 28 to 100+! Tout court, our lifestyle is built around energy that's a hell of a lot easier to get at than biofuels. Replacing them with ethanol is gonna involve some serious compromises.
I won't get into the details of the individual models, because that's a bit outside of my competence. I'm just an urban planner. But I notice that the most optimistic study (Shapouri's, with the 1.5 net) shows a bunch of suspicious zeroes in the biorefinery phase. ("NR" means "not reported.") Perhaps I have missed something; perhaps all the energy comes from "primary energy" (i.e. solar) but I doubt it.
I also notice that none of the models include the energy cost of moving the products to market. How much will be used to move that ethanol from Iowa or Brazil or wherever to the gas tank in suburban Los Mengeles?
Finally--for the real reality check--how many hectares of farmland would have to be dedicated to producing fuels to meet our current needs? Shapouri (again the most optimistic of the papers) shows 73,424 net megajoules' yield per hectare. (Cell B49, Shapouri-adjusted) Currently, global petroleum use alone amounts to 30 billion barrels per year at about 6100 megajoules per barrel. That's 183 trillion megajoules of petroleum per year, of which something something on the order of one-tenth goes into producing more petroleum. So, call it 165 trillion megajoules' per year net petroleum energy. (I'm not even getting into the natural gas and coal here, right? I'm just talking about oil, which provides about 40% of traded energy worldwide.)
That works out to 2.25 billion hectares dedicated to biofuels to match our petroleum consumption. Or, a square of farmland 4700 kilometers on a side.
-
If you're not against him, you're with him.
[Read the article: Impeach Bush]
[Read more letters about this article: Here]At a certain point, failure to impeach, despite mountains of evidence, equals complicity.
Another reason for NOW NOW NOW is that at some point, Al-Quaeda or whoever might issue a call to have Bush removed. And when that happens, Democrats will not be able to impeach without being accused of caving in to terrorists.
-
Very well, so there's enough gross energy coming in.
[Read the article: Exajoules of hope]
[Read more letters about this article: Here]Okay, so we've established that at 7,500 exajoules of technically-exploitable renewable energy per year, there's enough to replace current energy use by a couple of orders of magnitude.
This is really the first and simplest hurdle, but having cleared it, we can talk intelligently about the rest of them. Questions would include:
How much of that energy is exploitable at $60 per barrel-of-oil-equivalent? How much at $70? How much at $200? How much at $10,000?
Of each of the energy alternatives listed, to what extent are they constrained by other limitations?
For instance, a square metre of solar panel requires a certain amount of exotic metals. How much of those metals exist? Recoverable at what cost? Any area of solar panels will involve transmitting the energy a certain distance to the end user. How much of the energy will be lost in the transmission?
Biodiesel is constrained by the area of land that can be used to grow plants--and on whether that land area can do so year after year, without succumbing to the erosion typical of large-scale agriculture. The recent discussion of Alex Farrell's paper on biomass, I did a rough calculation and figured out that to replace current oil consumption, you'd need a square of land 4,700 kilometers on a side. Is there enough water? How much fossil-fuel input will be required in the form of fertilizers?
When thinking of the potential of renewable energy to allow us to keep doing what we do, consider the following: For over thirty years (since the OPEC embargo of 1973-1974) we have known that our (the West's) oil supplies are finite. We've been dependent on foreign regimes located in politically-unstable parts of the world. We've had to spend larger and larger sums to pacify those areas enough to keep the oil coming. We've had growing warnings of global climate change. During this entire time, the principles and basic technology of hydrogen, fuel cells, solar panels, wind turbines, nuclear reactors, biomass and geothermal have been known at least since the 1960's. We have had the largest cohort of working-age population (the Baby Boomers) with the most wealth and the most access to education in a period of sustained world peace and the absence of any major disrupting events.
In other words, under thirty years of the best conditions for doing Stuff Other Than Immediate Crisis Management, coupled with a clear need for such long-term innovation, we have not come up with something that could replace our current energy regime--not even close. This, to me, suggests either that such replacements are not practically feasible, and/or we do not have what it takes to figure them out under even the best conditions.
In a more general sense, it may be that civilizations can only get so big and complex before they become incapable of focusing on goals that will allow them to continue.