According to the California Department of Forestry and Fire Protection’s Fire and Resource Assessment Program (CDF FRAP 2005) there are over 340 million bone dry tons (BDT) of nonmerchantable, technical (potentially available) forest biomass, and slightly over 62 million BDT of shrubland biomass, that could be used for energy production in California. However, these CDF estimates did not account for a variety of administrative and ecological constraints that may limit where or how much biomass can actually be removed, due for example to concerns about impacts to ecologically sensitive lands or areas of high conservation value. We therefore evaluated to what degree additional ecological and administrative constraints might reduce the CDF estimates of technical forest and shrubland biomass for energy production. This coarse evaluation is meant more to illustrate the nature and extent of the constraints these issues may present to biomass use, rather than provide a comprehensive and precise quantification of the issues.