RE:
http://hnn.us/blogs/entries/49966.html
Greenhouses Are Actually Quite Efficient.
I don't know very much about organic farming, but I do know
something about thermodynamics, and I would like to deal with the
one specific issue of greenhouse agriculture versus imports..
Energy has both a quantity, and a quality, defined in
the negative as entropy. Hence you have the second and third
laws of thermodynamics. Transportation tends to require high
quality energy, such as electricity or kerosene. Depending on such
considerations as whether one could get a backhaul, a freighter
jet might, at a guess, wind up using a pound of
kerosene for every one or two pounds of green goods flown in
from Africa. The kinds of things which make attractive air freight
are the kinds of goods which don't weigh anything to
speak of, such as clothing.
Low-grade heating, such as heating a greenhouse to a modest
temperature, can be done with low-grade energy, and low-grade
energy is fairly ubiquitous. Britain is not a very cold climate,
and it is probably feasible to build solar greenhouses,
particularly if you use the kind of semi-active design
pioneered by Steve Baer of Zomeworks, in which insulated shutters
open and close at various times of the day, and create dead
air zones. The dominant mode of heat loss from greenhouse glass in
winter will be wind-driven convection. So the idea would be, in
the daytime, to continuously aim the shutters at the sun, so
as to minimize their interference with the sunlight, while
creating windbreaks over the greenhouse glass. At night, and in
adverse weather, the shutters would close. Glass would of
course be placed only where there was a southern exposure,
insulated frame-construction being used elsewhere.
[Sudha Shenoy objected that the British Climate is unsuited for
solar. To which I replied]
Solar heating has long
been popular in the Pacific Northwest, which has much the
same climate as Northwest Europe, but is very heavily "green." In
the Pacific Northwest, they do seem to be building solar
greenhouses. The difference is not one of climate, but one
of mind. It's Ken Kesey country. Britain may have a lot of
rain and clouds, but it is not very cold in winter. It all comes
out about even in the end. You might only need to keep the
greenhouse 10-20 deg-C above the outside. Space heating is the
easiest of solar applications, easier than water heating,
and much easier than solar electricity. There is a
relatively large margin for adverse circumstances.
[But then she complained that Briain is tood densely popolated to
allow greenhouse agriculture. To which I responded: ]
(05/10/2008 10:10 PM) I find that in 2000,
Britain was home to something like eleven million cattle,
six-and-a-half million hogs, forty million sheep, and a hundred
and fifty million chickens, perhaps three times as much livestock
per square mile as Argentina. To anyone but the most esoteric
gourmet, meat is none the worse for having been frozen, and it can
be readily shipped in that form at comparatively low expense. So
let's keep the greenhouses in perspective. Britain's population of
about one person per acre allows room for the odd
greenhouse. Interestingly, it seems that Britain
imports tomatoes from the Netherlands, which has
twice the population density. Tomatoes are very definitely a
high-value crop, yielding thousands of dollars worth
of crop per acre. Their very high yield in weight (35+
tons/acre) of course reflects the fact that they are mostly
water. Tomato paste, of course, like orange juice
concentrate, is an inexpensive product of rejected fruit. In
dehydrated form, it is likely to be inexpensively shipped
around the world. However, the value of a tomato tends to
increase, the closer it is to being fresh. That militates
against shipping tomatoes for long distances. Of course, with
the Channel Tunnel, Europe isn't really overseas from
Britain. Europe has an express train service with a
hub yard at Herne in the Ruhr, which does overnight
service for a twenty-ton European freight car, between any
two points in Western Europe. It runs at the same speeds as
traditional passenger express trains such as the Orient Express,
though not as fast as the new TGV-type trains.
An airport capable of handling jet freighters, cargo 747's, will
take up several square miles. For what it is worth, London's
Heathrow airport is approximately in the midst of what used
to be a market gardening belt, close enough in to allow daily
deliveries in the age of horse transportation. With the coming of
the railroads, market gardening districts moved further out, of
course. You treat transportation as if it were uniquely free.
Commercial aviation is in fact driven by air forces. It is not a
case of the invisible hand, but the very visible hands of men like
Sir Arthur "Bomber" Harris and Barnes Wallis. With the
increasing price of kerosene, the economics may very well have
shifted.
[But then, she insisted that flying produce aroundthe world was
cheaper than growing it locally. So, among other things, I
estimated how much kerosine air freight requires.]
(05/11/2008 07:22 PM) Of course, obviously,
the Dutch were long famous for market gardening, and indeed,
until the industrial revolution changed the rules, they were
famous for almost any kind of production which required
exemplary skill. In large sections of Northern Europe, as far east
as Moscow, it was axiomatic that the way to upgrade one's economy
was to get some Dutchmen to immigrate. The Dutch did not
have any special geographical advantages, unless you call being
under water a geographical advantage. There is such a thing
as the "Hans Brinker mentality," and no doubt a Braudelian
historian would be inclined to account for this in terms of the
need to keep back the sea.
Consulting a land-use map of Britain, circa 1980, I find that
there were significant market gardening districts outside of
Belfast, Dublin, Edinburgh, Dundee, Leeds, Birmingham, and
Bristol, apart from the districts around London, and along the
south coast. Glasgow, Newcastle, Liverpool-Manchester, and Cardiff
were striking in not having such districts, and this could not
really be accounted for in climatic terms. What these latter
areas did seem to have in common was a single-minded fixation on
mining and manufacturing. There is no obvious reason why
greenhouse districts could not be established in economically
depressed areas, along main rail lines leading south, only a few
hours from the markets. The north of England is not the Yukon,
after all. I consulted a table of representative world climates,
and was impressed by the mildness of the Scottish climate, which
is not to be compared with that of the Ohio country.
I gather that a tomato is ancestrally a jungle vine, presumably
adapted to growing up the sides of trees, living in the filtered
light below the jungle canopy. A maximum supply of direct sunlight
for photosynthesis does not seem to be critical per se, or may
even be disadvantageous, provided the plant is kept sufficiently
warm and moist. These conditions can be met in a greenhouse
better than in any open-air climate, save for the microclimate
created by a tropical rain forest. It turns out that the
Kenyans are resorting to greenhouses, for want of the right kind
of climate in their own country. Among other virtues, a greenhouse
keeps insect pests out, and increases the crop yield. At this
level, the Kenyans' comparative advantage, such as it is,
boils down to little more than cheap labor.
A greenhouse is durable, and might, with ordinary good management,
last for twenty or forty years. The pro rata cost of using it is
not all that great. Given that we are talking about a very
simple form of construction, two dollars per square
foot ought to be achievable. Assuming thirty-five tons
of crop per acre per year, and a long-term five percent interest
rate, I come up with a figure of about six cents per pound of
tomato for the cost of using the greenhouse.
By contrast, the cost of flying a Boeing 747 is something
like five or six thousand dollars per hour, plus three or four
thousand gallons of fuel per hour, whatever that costs at
the moment. That works out to somewhere in the vicinity of a
dollar or two per pound of cargo at present oil prices, depending
on the details of a particular shipment. The airplane is not
durable in the sense that an automobile is durable, and it is
always needing replacement parts of one kind or another, and vast
numbers of mechanics to install those new parts. Land
vehicles can be designed to be rugged, to go for years
with minimal maintenance, but an airplane so designed
would be too heavy to get off the ground. So around the
margins, air freight becomes an exercise in using expensive labor
to get access to cheap labor. If that is not a losing game,
it is at least a precarious one. The same high-grade labor
which is used to maintain the jet airplanes could alternatively be
employed in inventing ways to reduce the labor requirements of
producing common articles of consumption. At present, mechanical
harvesting seems only to be feasible for green tomatoes,
which have a lower value. Possibly, better harvesting machines
could be designed.
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Sources:
Here are some links for solar heating in Britain.
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A solar housing development in Shropshire
http://www.treehugger.com/files/2008/02/the_wintles_bri.php
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A firm in Wiltshire supplying solar heating products.
http://www.soltrac.co.uk/whysolar.htm
http://www.soltrac.co.uk/suitability.htm
Money quote: "We cannot install solar [water] heating onto a
thatched roof. With temperatures up to 250°C not unheard of in
summer – and in a test one of our systems reached 149°C in
November in southern England – we think this would be tempting
fate."
Their best solar collector is designed on the thermos-bottle
principle, with a transparent outer tube, using a vacuum for
insulation. Convection cannot take place in a vacuum, and
the other two modes of heat transfer, conduction and radiation are
not terribly effective at such, um, modest temperatures
(radiation really comes into its own at thousands of degrees). One
could in principle construct a window pane with vacuum insulation.
There was something about fifteen years ago which was very
similar, a flat vacuum tube, a cathode ray tube, which, for a
time, looked as if it might be a cheap flat-screen display for
computers. The designers used large numbers of little
spacer blocks between two sheets of glass to hold the
glass sheets apart. Now, for conventional household use, it might
not be very popular to have a window with an internal grating of
rubber-clad steel, but for greenhouses, that need not
be a problem.
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Another solar energy firm in Devon.
http://www.eco-exmoor.co.uk/sol_water_faq.php
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http://www.cleanerenergy.co.uk/solarenergy.html
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A short "foundation pamphlet," about solar water heating. Quotes a
figure of 1000 KWh of raw sunlight per square meter of
rooftop, per year, in Britain, though not specifying which
season. That would be 114 watts, continuous, or about half of
typical American figures.
http://cms.ises.org/uploads2/SSF/pictures/materials/308/Swh.pdf
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A small commercial solar greenhouse in New England, in
a much harsher climate than Britain.
ANNE RAVER, CUTTINGS; What a Little Chicken Breath Can Do,
Published: March 7, 1993
http://query.nytimes.com/gst/fullpage.html?res=9F0CE4DB103EF934A35750C0A965958260&sec=&spon=&pagewanted=all
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Something from the last energy crisis... Plus ca change, or
whatever it is the Frenchman says?
GARY ADKINS, "SOLAR ENERGY," _Illinois Issues_ (University of
Illinois at Springfield), April 1981
http://www.lib.niu.edu/1981/ii810412.html
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SCRAP
http://en.wikipedia.org/wiki/Steve_Baer
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"Living the eco-life in Cornwall"
http://www.independent.co.uk/environment/living-the-ecolife-in-cornwall-470591.html
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http://www.newscientist.com/article/mg12917544.200-green-technology-comes-of-age-the-ecoboom-of-the-past-fewyears-has-transformed-the-fortunes-of-a-community-of-alternativetechnologists-living-and-working-in-the-welsh-hills-the-public-can-nowbuya-stake-in-the-centres-future--and-help-to-finance-construction-of-amodern-waterpowered-railway-.html
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http://www.domegreenhouse.com/
http://en.wikipedia.org/wiki/Tomato
http://www.kdcomm.net/~tomato/
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Agriculture college reports from California. Cite typical
yields for tomatoes of 35 tons/acre or more. This is for
plants grown in the open field.
http://www.sarep.ucdavis.edu/ccrop/ccres/1999/3.htm
http://calag.ucop.edu/0304OND/pdfs/Tomato_Irrig.pdf
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Report on wholesale tomato prices in Florida in 2005,
suggests that normal prices would be on the order of 20-40
cents/lb. This would imply a wholesale crop value of
$15,000-$30,000 per acre, not allowing for rejects. A more
realistic figure would probably be $5000-$10,000.
http://www.freshplaza.com/2005/08dec/2_us_tomatoprice.htm
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Report on the spread of greenhouse tomato growing in
North America. The Canadians often have the advantage,
despite their famously awful climate, because of their
comparatively enthusiastic adoption of Dutch technique. The
greenhouses enable them to produce comparatively high-value
vine-ripened tomatoes in winter, whereas the field growers have to
pick tomatoes green in summer, store them in refrigerated
warehouses, and then chemically ripen them with ethylene.
http://www.agecon.ucdavis.edu/extension/update/articles/v5n3_2.pdf
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http://en.wikibooks.org/wiki/A_Wikimanual_of_Gardening/Tomato
http://www.msu.edu/~sindijul/Tomatoes%20in%20Kenya.htm
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Advantages of greenhouses for tomato growing in Kenya. Kenya is
basically a country of savannas and deserts, not of jungles, so
they find greenhouses useful.
http://www.freshplaza.com/news_detail.asp?id=8859
http://africanagriculture.blogspot.com/2007/10/kenya-to-test-greenhouse-tomato.html
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EDUARDO PORTER, "In Florida Groves, Cheap Labor Means
Machines," New York Times, March 22, 2004
http://query.nytimes.com/gst/fullpage.html?res=9C02E5DA1F31F931A15750C0A9629C8B63&sec=&spon=&pagewanted=all
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History of the tomato harvesting machine.
http://www.age.uiuc.edu/classes/tsm311/Mechanizing%20Miracle.pdf
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