“Be kind, for everyone you meet is fighting a hard battle” - Often attributed to Plato but likely from Ian McLaren (pseudonym of Reverend John Watson)

Tuesday, June 26, 2007

Turning resources to refuse

I read somewhere, I don't remember where, something to the effect that "an economy is a system for turning natural resources into refuse." Obviously, that's hyperbole, but it's not completely without basis. A couple of posts back I looked at national and global energy consumption, comparing time frames and comparing countries and the world. I thought that I could pursue that a little further and see what the energy requirements are to "turn natural resources into refuse."

As I stated in the post linked above, in 2006 the United States consumed 100.41*10^15 btu, or 1.059*10^20 joules of energy. In that time, we produced 245 million tons, or 222*10^9 kilograms of "MSW," municipal solid waste. I can't find an authoritative source for total air pollution in 2006, but in 2005 the total was 141 million tons. Now, that number is on a strong downward trend, it was 188 million in 1995 and 160 million in 2000. Bearing this in mind, I'll use 136 million tons or 123*10^9 kilograms in 2006. I can't find good numbers for water pollution and liquid waste, so I'll blithely assume it's negligible. With that in mind, I'll say we produced 345*10^9 kilograms of waste. So for a start, we used 307 million joules of energy per kilogram of waste. Now, 307 million joules is the amount of energy in about 6.5 kilograms or 2.5 gallons of gasoline.

So our economy used the energy available in 6.5 kilograms of gasoline to produce a kilogram of waste. Let's be optimistic and assume that the combined efficiency of all the energy conversion processes we use is 40%. That would mean that we really needed 16.25 kilograms of gasoline or equivalent to produce a kilogram of waste. Now what does that mean? Good question. From one point of view, if our energy to waste ratio were high, it could mean we didn't waste much, that that energy went into useful things. On the other hand, if our energy to waste ratio were low, it could mean we were efficient, since it wouldn't have taken much energy to produce our byproducts. But I suspect a big number is what we'd like to see.

The complexity of the situation comes from the fact that, taken independently, we'd like to produce small amounts of waste, and we'd like to consume small amounts of energy. I think the way to get a handle on this would be to find out how much energy in joules is contained in an "average" kilogram of manufactured product. In the end, what we want is as little of our consumed energy as possible to go into things that are discarded.

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