Bioenergy systems are an essential part of a renewable energy portfolio, particularly as only liquid biofuels can replace petroleum in key applications. Unlike fossil energy systems, bioenergy systems can potentially be sustainable, that is, able to operate indefinitely into the future. Based on our work and the work of others who have examined various sustainability aspects of bioenergy systems, we believe it is possible to operate these systems so that they are sustainably profitable, improve the welfare of local populations, and provide environmental benefits for local and global ecosystems. However achieving greater sustainability by deploying bioenergy systems will not occur without careful thought and consideration. Therefore we propose and apply a set of sustainability objectives for bioenergy systems that span the economic, environmental, and social aspects of sustainability.