BERLIN, Germany (Reuters) -- A German inventor has angered animal rights activists with his answer to fighting the soaring cost of fuel -- dead cats.

Christian Koch, 55, from the eastern county of Saxony, told Bild newspaper that his organic diesel fuel -- a homemade blend of garbage, run-over cats and other ingredients -- is a proven alternative to normal consumer diesel.

"I drive my normal diesel-powered car with this mixture," Koch said. "I have gone 170,000 km (106,000 miles) without a problem."

The Web site of Koch's firm, "Alphakat GmbH", says his patented "KDV 500" machine can produce what he calls the "bio-diesel" fuel at about 23 euro cents (30 cents) a liter, which is about one-fifth the price at petrol stations now.

Koch said around 20 dead cats added into the mix could help produce enough fuel to fill up a 50-liter (11 gallon) tank.

But the president of the German Society for the Protection of Animals, Wolfgang Apel, said using dead cats for fuel was illegal.

"There's no danger for cats and dogs in Germany because this practice is outlawed in Germany," Apel told Bild on Wednesday in a story entitled "Can you really make fuel out of cats?"

"We're going to keep an eye on this case," Apel said.