Integrated Food Energy Systems (IFES) aim at addressing these issues by simultaneously producing food and energy as a way to address the energy component of sustainable crop intensification through an ecosystem approach, as defined in Box 1. This can be achieved in two ways: by combining the production of food and biomass for energy generation on the same plot; or by making multiple uses of each agricultural product and its residues. The concept of Integrated Food and Energy Systems (IFES) as such is not new. Simple integration of food and energy production at both small and large scales has shown many successful results. However, with the increasing complexity of the system, - and hence higher resource use efficiency, the number of successful cases diminishes. Concrete results on wide-scale implementation of more complex IFES are scarce. Few attempts have been made to assess the challenges that true resource-efficient IFES face (Sachs et al. 1991; Woods et al. 2006), and proper reports that evaluate research and pilot projects years after their implementation are hard to find. Given this situation, FAO held an international technical consultation in July 2010 on “How to make integrated food-energy systems work for both small-scale farmers1  and rural communities in a climate-friendly way”. This paper draws on an extensive review of literature and the findings of this technical consultation to identify what hinders IFES, in particular, and some key solutions that could help to realize their benefits on a wide scale. It starts by introducing the IFES concept and potential benefits, as well as some example of IFES in both developed and developing countries. It then briefly discusses the constraints related to IFES implementation, both at the farm level and beyond the farm, before venturing to suggest some possible solutions to overcome these constraints.