[ExI] food crops for energy, was: RE: super soldier ants
spike66 at att.net
Tue Jan 10 18:05:50 UTC 2012
>... On Behalf Of Eugen Leitl
Subject: Re: [ExI] super soldier ants
On Tue, Jan 10, 2012 at 08:14:20AM -0800, spike wrote:
>> If anyone can figure out how to get an oilseed crop to prosper, it
> could be a minor contributor to the world's energy problem. Oilseed
> is used to make a light oil which can be used for fuel and could have
> industrial uses in addition to being a food crop.
>...Biodiesel EROEI is 3:1. This is below the energy cliff
>...Thin-film (CdTe) photovoltaics is already better than 40:1.
Good article on EROI, thanks Gene. I think EROI is a critically important
concept, which I also like because it tends to look good for my favorite
long term energy solutions: space based and ground based solar. Both of
these concepts are the engineer's playground.
That being said, I would caution against overuse of the EROI notion. For
instance, we can imagine some low EROI applications that are profitable in
the short run anyway. We already know that all food crops used as fuel are
low EROI, way worse than blanketing the same field with thin film PVs. But
we will not be blanketing those particular fields with PVs any time in the
immediately foreseeable. I don't have that kind of money, and power is
cheap in that area anyway: they have falling water nearby.
Consider the special case of oilseed. That is a crop that doesn't deplete
or contaminate the soil, doesn't require much labor to maintain if you don't
plant it repeatedly in the same field, doesn't require much on the way of
fertilizer, requires no irrigation and no weeding other than one application
of specialized herbicide. We planted about 80 acres of the stuff. Our guy
did it all in one day, so about two tanks of Diesel for that, and then he
went over it twice after that with machines, then harvest. So if you look
at just the fuel used to sow, herbicide once, fertilize once and harvest,
the EROI was excellent on that particular crop, however...
and there is always a however...
You can't do low-maintenance oilseed two years in a row in the same field
without aggressive slug control, which is expensive and labor intensive, so
the second year is almost not worth doing, especially if one has a
profitable alternative. The slugs are taken by surprise the first year by a
bounty far too abundant for all their offspring to devour, but the second
year, the rapidly growing and hungry slug families are ready and eager to
explode and devour everything in sight.
So my argument is that under certain special circumstances, some food crops
can be minor contributors to energy use, while fully acknowledging that they
do not compete in the long run against thin film PVs, and that they are over
the net energy cliff.
What is bothering me now is that we are seeing Solyndra and the other local
PV manufacturers go broke, while the cost of PVs even in the midst of this
production over-capacity environment is still way too high to use my Oregon
fields for solar electricity production.
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