ABSTRACT
Major constraints on production of bioenergy are land resource and productivity and water availability and quality. The sustainability of bioenergy or in another sense, a constraint on bioenergy depends on the productivity of the land use change, both direct and indirect. Net positive energetics should be set for the different types or categories of bioenergy. A most important factor or constraint is water, by precipitation and irrigation. Water may be a constraint for producing biomass for bioenergy, although some second-generation biomass crops need less water and can be grown on marginal land. Due to the constraint of low energy density and large bulk, biomass needs to be consumed within the local region where it is produced, thus minimizing transportation costs. Food security, environmental, social, and economic costs and benefits have to be considered, and in most cases they are intertwined. Although national strategies and/or policies for bioenergy primarily focus on energy production they also consider the constraints.
