The stove group had its work cut out for it. Currently, Salkantay residents burn llama dung in open pit fires over which pots of water are heated. Their diet consists mainly of soup and boiled potatoes.

The stove group introduced a more efficient combustion process using the llama dung and wood to increase the amount of heat provided per unit mass of fuel and to remove the hazardous products of combustion from the living quarters.

"Their stoves just fill up their homes with smoke," said Ben Richards, 24, of Kalispell, Mont., a junior majoring in mechanical engineering.

"Their ceilings are covered in soot," Richards said. "The children have respiratory problems from the smoke exposure."

The students built a prototype stove, with a flue, to reduce the smoke. The water heating mechanism developed by the efficiency group was also successfully tested with the improved stove.

The fuel group converted the llama dung into methane. The students created a reactor that would speed up the conversion rate. Exposing the reactor to direct sunlight increased the speed even more.

"We actually built the reactor on campus before we went to Peru. The students came up with the final design," said BYU chemical engineering professor Randy Lewis.

The reactor is surrounded by adobe walls painted black inside and topped with plastic, much like a greenhouse, he said.

Two spouses of engineering students paid their own way to go on the trip. They collected and delivered maternity, school and hygiene kits, along with clothing and hygiene coloring books to share with Salkantay residents.

"That had just as much effect on the people as did all the engineering projects," Richards said. "It was amazing to see the expressions on the women's and children's faces."

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E-mail: astewart@desnews.com