Smallholder farmers in poor economies like Ethiopia dominate the agriculture sector. Energy crop supply for biofuel processing will likely depend on the adoption behavior of farmers. The drivers of energy crop adoption at household level are predicted to include access related factors, assets and household characteristics. Using data from castor outgrower scheme in Ethiopia and applying a double-hirdle model, we analyze adoption as a two-step decision process. The results show that higher price of maize (a major staple crop) is strongly associated with lower size of land allocation to castor. Contrary to the widely accepted notion, access indicator variables such as distance from village centers (where most decentralized public service centers are located) and number of visits by public extension agents do not influence the decision to adopt. But interestingly, conditional on positive participation, farmers who live furthest from the village centers tend to allocate bigger proportion of their land to the energy crop.