ROSARIO IZAPA, Mexico (Reuters) - All his life elderly Mexican farmer Gonzalo Cardenas has planted a stalky weed that grows wild in southern Mexico to form a sturdy live fence around his tropical fruit trees.
Now it turns out the weed, jatropha, could be used to fuel jet planes and the Mexican government wants farmers to grow entire fields of it to turn into biodiesel.
Known locally as "pinon," jatropha is a hearty shrub that grows with no special care. Its oil-rich seeds are being eyed as an attractive feed stock for biofuel since the poisonous plant does not compete with food crops.
"I always had pinon around my corrals, just because it helped keep people off my land," said Cardenas, 78 and exhausted after helping one of his cows give birth at his farm in the balmy village of Rosario Izapa in southern Mexico.
Jatropha is native to Mexico and Central America but was likely transported to India and Africa in the 1500s by Portuguese sailors convinced it had medicinal uses.
Now India is planting the bush en masse, converting it into a green energy source used to power trains and buses with less pollution than crude oil. Mexico hopes to follow suit.
President Felipe Calderon signed an agreement with the president of Colombia in January to build a 14.5 million peso ($936,000) experimental biodiesel plant in southern Mexico with a production capacity of 12,000 liters (3,170 gallons) of biofuel a day.
Mexico passed a law last year to push developing biofuels that don't threaten food security and the agriculture ministry has since identified some 2.6 million hectares (6.4 million acres) of land with a high potential to produce jatropha.
"If I had more land I would plant it because they say it's good business," Cardenas said, surrounded by rare rambutan and mangosteen fruit trees.
Demand for the eco-friendly fuel could grow now that U.S. President Barack Obama has promised to invest $150 billion over 10 years in renewable energy infrastructure.
Continental Airlines ran a two-hour test flight in January of a Boeing 737 passenger plane powered with a mix of jatropha and algae-based biodiesel, following the lead of Japanese and New Zealand airline companies.
"The biofuel mix actually ran more efficiently and burned less fuel in total than the conventional (jet-fuel powered) engine," Steve Lott, a spokesman for the International Air Transport Association, or IATA, said.
The airline industry will consume 67 billion gallons of fuel this year, or 6 percent of the world's oil, a concern for environmentalists as well as airline budgets, especially after the spike in gas prices last year, Lott said.
The IATA wants all its members to use 10 percent renewable fuels by 2017. The challenge will be to ramp up output of green fuels at a rate fast enough to meet growing demand.
Mexico is running tests to find jatropha varieties that produce the most oil with the least care. Some 300 different types are being monitored at a government research center in Rosario Izapa, near Mexico's border with Guatemala.
In Guatemala, entrepreneur Ricardo Asturias has been promoting jatropha for the past eight years and now has his own plantations and biodiesel factory. He says the region's genetic diversity will give it an edge over competitors in Asia.
"This plant is native to Mesoamerica. In our nurseries we have 57 different varieties and we're not finished yet," he said. "In India there are only three recognized varieties."
Once Mexican investigators find the optimal jatropha strain, they will distribute seeds to interested farmers who like the fact the shrub is low maintenance.
"You sow it and it grows. It's not like corn," said Rafael de Leon, 39, his land ringed by bushy jatropha that can grow taller than he is. "If there's money in it, we'll plant it."
(Additional reporting by Brendan Kolbay in Guatemala City; editing by Jim Marshall)