Beginning in the early 1970s with the Arab oil embargo and rapidly increasing energy costs, wood came to be viewed as a potential alternative source of renewable energy. Firewood and cogeneration technology, two already-developed uses of wood for energy, received new emphasis. With these new energy-oriented markets for wood, ranchers, forest owners, farmers, and owners of small rural properties began to come to the University of California's Cooperative Extension with questions about planting trees to produce wood energy crops, predominantly firewood. Interest in tree planting escalated when growers heard claims, often unsubstantiated, of extremely high growth rates, especially in eucalyptus.