Thursday, June 11, 2009

Coal vs. Coke

One of the people who put some time into reading Grain Into Gold criticized our use of coal in the home. While I still feel that there would be some cultures that would use coal to heat their immediate living area negligent of the health risks (though somewhat mitigated by good ventilation), I have come to believe that what many people call coal is not coal. In many historic references to coal, I believe they actually mean coke. (No - not the beverage) Coke is to coal what charcoal is to wood. You burn it without air and all the junk burns off leaving a nearly pure carbon behind. Coke is far less likely to kill you from breathing its fumes.
In order to recognize this change of strategy, I’m planning to write up coke as a fuel alternative in Coins of the Realm. Since this book is not expected to be immediately available, let’s give you some of the ideas now:
First off, Grain Into Gold assumed that people were deep mining coal. On Fletnern, I typically assume they are strip mining it. This means that instead of 500lbs per day, the unskilled workers can mine and load about a ton a day. This drops the “at location” cost of a ton of house heating coal to 10sc (from 15 - sure it seems like it should be only 7sc for a miner’s daily wage, but what about the wagon drivers and the foreman and the other support staff?). I assume that the coke ovens are relatively close to the coal strip mine, since there are no trains. You move the coal, likely down the side of the hill and pour it into a coke oven. Three Fletnern days later (about 60ish hours) it has been burned down from coal to coke. Trying to get yield rates prior to 1900, the best source I saw said 65%, so if you fill an oven with 3,500lbs of coal, you get 2,300lbs of coke (rounded). Each coke burner can usually handle six ovens or loading and unloading two a day. Having spent some of my youth shoveling gravel and asphalt, I think a man working himself harder than his body wants to work could have accomplished this if the production lines were intelligently handled. The historic references seem to imply they did quite a bit more, but they did have some help from coal cars and train tracks. So anyway, assume that a 9sc a day burner supported by the equivalent of another 9sc guy (this is the foreman, wagon drivers, brick deliverers, etc.) burns two ovens a day effectively. 17.5sc worth of coal went in. 9sc worth of labor applied, and our 2,300lbs of coke is valued at 26.5 or roughly 23sc per ton of coke.
OK - so, the at location price of coal is now 10sc per ton and the at location cost of coke is 23sc per ton. If the burners did everything perfect, then about 1,300lbs of coke should provide the same fuel as a ton of coal. Let’s estimate that where a ton of coal heats a small home for six to eight weeks, a ton of coke would likely last eight to ten weeks. Using more modern information, it is likely that as equivalent fuels coke is about 75% of the weight of coal.
For transport, I’m going to have 15 ton wagons pulled by teams of 10 oxen driven by two men with no guards that move about 18-20 miles a day on a very good road. The city of Forsbury is 115 miles from the coal mines, so a ton of coke in Forsbury would run about 29sc.
OK - lots of numbers, lots of math. In case you haven’t bought Grain Into Gold yet, this is why you want to. We’ve done the research on historic products and how they were produced. We then back everything into the full economic system, beginning with what the cost of a loaf of bread is. By the way - a loaf of bread (16oz) costs one silver coin. That wasn’t a coincidence!

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