Drop internal combustion: go for steam!

It is possible, according to this article.

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“Internal combustion is dirty and complicated,” Schoell says. Steam engines, on the other hand, are simpler and more efficient and can use a variety of fuels. Unlike a regular internal combustion engine, which explodes a mixture of fuel and air hundreds of times a second inside its cylinders to drive the pistons, steam engines burn fuel continuously in a different chamber. And since this combustion is separate from the engine’s moving parts, any fuel that gets steam hot enough to drive the engine’s pistons will do.
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Schoell’s company, Cyclone Power Technologies, has recently signed a deal to develop a Cyclone for lawn mowers and other garden equipment. And unlike most garage tinkerers, Schoell has even won the respect of the pros: In 2006, he won the Distinguished Automotive Engineering Award from the Society of Automotive Engineers for the Cyclone’s design.
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More details about the Cyclone Engine here.

Video.