Friday, January 27, 2017

Tandoor Bread Ovens, Part II



Bread ovens
Multi-fuel capability of tandoor ovens is one of their most endearing features. The burner tray can be fueled with natural gas, LP, producer gas, stove wood, charcoal, coke, buffalo chips, jets of atomized petroleum oil...you name it.

Pizza ovens and the ovens used to make submarine sandwiches are heated with natural gas or electricity.  Period.

Tandoor ovens also appear to offer reasonable energy efficiency, a feature you would expect in a technology that evolved in a region that is chronically short of firewood.  Your barbecue grill might work as a bread oven in a pinch but it is neither flexible regarding fuel nor is it particularly energy efficient.
Supplying a medium sized metropolitan area would require about 500, 60", four feet deep shells.
Another factor that favors tandoor ovens is the availability of shells or housings for those ovens.  Literature suggests that concrete can survive 750 degrees Fahrenheit provided thermal shocks (gradients) are avoided and free water is carefully baked out at the first heating.  Above 750 F the concrete loses water of hydration and rapidly degrades.
Ready availability usually means economical prices.  This price schedule supplied by Northern Concrete Products.
An approximation for the bread production of a 60" diameter, tandoor oven is 1.5-to-2 loaves a minute provided it can be kept fueled.  Running around-the-clock that gives a top end production somewhere north of 2000 loaves a day....enough for 4000 people.

Why the fixation on bread ovens?
Logistics.

A cubic foot of baked bread (four, 20 oz loaves) delivers about 5500 Calories, requires special dunnage (racks) to transport and has a shelf life of about a week.

A cubic foot of bread flour (35 pounds) delivers about 70,000 Calories, does not require special dunnage and has a shelf life of about six months.

If you were the National Guard, would you rather drop off 20,000 pounds of bread flour once a month or would you rather deliver 1000 loaves of bread every day for a month?  Maybe delivering 1000 loaves every day does not sound like a big deal...but there is more to consider.

Keep in mind that a large disaster will shrink the number of foods being supplied so each food that is supplied will be eaten in larger quantities.  In normal times loaf of bread might last four days in your house.  In times of emergency that loaf of bread might supply half your daily calories and that one loaf will disappear very quickly.

Consider Columbus, Ohio is a medium sized metropolitan area with 2,000,000 people.  That noodles out to about 1,000,000 loaves of bread a day (a thousand deliveries) vs. thirty-three deliveries of flour.

Far fewer emergency workers will be pinned down delivering flour vs. bread.  They will be exposed to less hazard.  It will drive resilience, industry and "agency" down to the local level.

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