Farmer David Jimenez Zamora barely flinched when gas and electricity prices in Spain soared with the energy crisis. He kept heating the covered pool in the 18th century farmhouse he rents to tourists and the hot water running for as many as 26 guests at once without getting the terrifying energy bills hammering fellow Spaniards. His secret? Olive stones. "We use olive pits from our trees to heat the swimming pool, the underfloor heating system and get hot water," said the 48-year-old. "This is normally used from September onwards," he said, standing by a store holding 5,000 kilos of stones overlooking a sea of olive trees in the province of Granada, in the southern Andalusia region. Olive stones also power the machines producing Spain's famed "liquid gold" olive oil at two agricultural cooperatives he's part of. Solar panels cover the rest of their energy needs. The use of pits to fuel boilers in homes and small enterprises, mills and even flights in Spain's olive-growing heartland shows the role the industry