On Sep 9, 12:26 pm, Michael Tobis <[email protected]> wrote:
> I have several doubts.
I do as well, but mostly about the optimistic
asssumptions for water requirements.
>
> Chief among them is this: it is important to understand that even if a
> biofuel plan is sustainable, it is not necessarily a sustainable
> carbon sink.
When steady state is reached, begin burying compressed biochar
(essentially high grade coal) deep underground (like coal).
> ...
> Secondly, if we expend the capital to irrigate, say, Australia, is
> biofuel the best use of that massive endeavor?
No. Both the Outback and the Sahara have plenty of sun. As both
reverse osmosis and pumping have interruptable power requirements,
solar thermal will do. Sell the biofuels to compete against fossil
fuels.
>Fuels, for all their
> importance are cheap.
Petroleum based fuels won't be in decades to come.
> Indeed, they are mostly important because they
> are cheap.
I disagree. People need transportation, electricity and heat at
current and projected population densities.
>
> Thirdly, I'm not sure that the coupling between land surface and
> rainfall is one of the more robust model results, so I don't think we
> ought to bet the farm on it.
I'm not sure I understand, but the authors are far too
optimistic about the ability to carefully control water so
that none is wasted. For the Sahara, gum trees are
probably the wrong choice; I suggest beginning with acacia
and sand willow. The Chinese find sand willow around the
Gobi works well to help control desertification.
By starting one would discover the amount of water required. That
requirement, even if larger than the authors state, does not make the
plan impossible; the difficulties are raising the capital and also
political.
>
> I'm all for instrumental solutions if they actually work.
I am as well. I actually think that, near sea coasts,
making biomethane from algae in tanks can compete against
natural gas. The further inland one goes the higher the
transportation costs, not so much for water or gas, but
for removing biochar, for example. Biochar uneconomic to
transport could be sequestered underground.
So it may well be that the enitre project cannot pay its
own way. It would lower the use of fossil carbon, those
requirements being met by biological carbon. It would continue to
store large amounts of carbon above ground every year for about a
century. Thereafter one sequesters more compressed biochar deep
underground.
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