Monday, July 29, 2002

Horsepower, or is there work after death?

There's no point in beating a dead horse, but that doesn't mean you can't get any more work out of him.

In animated cartoons, the way to make a horse run faster was always to give him a whiff of some glue. I learned that as a little kid, but I didn't know what it meant. And if I didn't know right now, that would be alright too, because it's not the most pleasant topic. Yes, I'm talking about rendering plants, where dead animals and other waste get recycled into glue, gelatin, food supplements, pet food, bone meal, cosmetics and others.

This tells more about them and their processes than you might care to know, including the possible connection with mad-cow disease.

So why do I bring this up? Actually I was looking for waste-to-energy information, and I figured that rendering plants might be good candidates for this. They use a fair amount of energy to cook their ingredients, and their byproducts would include fats that could be turned into biofuels. These can be used to drive a diesel generator, which can provide power to run pumps, conveyors and lighting loads.

But we're not through yet. The engine heat can be used to preheat the water used for processing, and the exhaust heat might be usable too if only for a turbocharger. Using the energy in this way is called cogeneration, and by using it your energy input will give you more output horsepower.

If you want to do it you'll have to pony up some money though - this increases capital costs significantly. The heating and electrical power output of the diesels might not match the requirements of the rest of your process, and you might need special auxiliaries either for startup or for backup. Personnel will need more training, maintenance people will have to learn new tricks and the viability of the whole works depends strongly on the cost of alternatives like electric power and diesel fuel.

But you don't know until you analyze it. Given that a successful implementation could lower costs substantially, it might be that anyone using a cogen system in this application considers it a trade secret and won't talk about it.

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