Biomass remains a key energy source for several billion people living in developing countries, and the production of liquid biofuels for transportation is growing rapidly. However, both traditional biomass energy and crop-based biofuels technologies have negative environmental and social impacts. The overall research challenge for bioenergy is to develop the technologies to produce useful products at low costs while minimizing the use of scarce resources such as arable land and water. This requires substantial advancements in modern biomass power generation and the success of liquid biofuel technologies that permit the use of lignocellulosic feedstocks or possibly algae. With such technologies, biomass resources could meet a significant fraction (over 10%) of global energy demand. Both improved policies and technologies are needed to ensure that bioenergy contributes significantly to economic, social, and environmental goals.