The conversion of biomass into energy is perhaps more challenging to the technologist than energy from fossil fuels.  Water, dissolved organic and inorganic compounds, and solid particulates of various size can be present in biomass processes.  It is perhaps the development of microbial fuel cells where the philosophical thinking of process miniaturization will play a wider role.  Distribution of knowledge, in a fashionable, intriguing style through miniaturized devices, can be substantially enhanced (accelerated) by low power consuming devices (such as smart phones).  A rethinking of "what is a powerplant?" can create enormous innovations, given recent advances in membrane materials of construction, immobilized whole cell methodologies, metabolic engineering, and nanotechnology.
The challenges of microbial fuel cells relate mainly to finding lower cost manufacturing methods, materials of construction, and systems design.  [http://www.engr.psu.edu/ce/enve/logan/journal_publications.htm Bruce Logan] from the Penn State University has described in several research articles and reviews these challenges.
However, even with existing designs which generate low power, there are applications in [http://www.technologyreview.com/business/21332/page1/ distribution of electrical recharging] systems to remote areas of Africa, where smart phone, can enable access to the vast information of the internet, and to provide lighting.  These systems can run on agricultural, animal and human waste streams using naturally occurring bacteria.