SPUDS: Self Powered Useful Devices – What We Need to Know to Make Them Useful, and Why Should We Care?

Some bacteria have the capacity to interact with solid surfaces, donating electrons to them to produce power (and clean water) in microbial fuel cells, or taking electrons from them to use for bioremediation of metals, or electrosynthesis in bioelectrical systems such as half-cells.  All of these useful properties are enabled by the ability of bacteria to move electrons between the cell interior and the external environment (referred to as extracellular electron transport, or EET), something thought to be impossible only a few years ago. 

Interestingly, the ability of EET-capable bacteria to produce electricity has, for the most part, obscured the real value of these organisms and the things they are capable of doing – almost all of which can be related to water, and various ways to improve water quality.  Perhaps they should never have been called microbial fuel cells, as their major impact(s) will almost certainly be felt with regard to what they do: cleaning and reclaiming wastewater, removing metal pollutants, etc., while generating enough energy to do their job without being connected to the power grid. 

Imagine how the world would change if water purification systems could be built and distributed in the developing nations of the world irrespective of a power grid – systems that could effectively dispose of human wastewater while producing ultra clean water (and some gray water) as products: and a little electricity to boot!  Designing systems like this for efficiency of useful purposes rather than maximum power production should be the goal of our program(s), and it is, in my opinion, an achievable goal.  Let’s call them SPUDs, and face up to the job of optimizing their usefulness!!

What do we need to know to do this properly?  The basics of electrochemistry are well in hand, and the design of bioelectrical devices, especially those compatible with EET-capable microbes has progressed remarkably well in the past 5 years.  What has not progressed at the same rate is the understanding of the “biological black box” – and how to interface this “black box” with the bioelectrical systems.  The microbial populations that lead to efficient waste and/or pollutant removal remain as “black boxes” because their complexities have not been elucidated.  This is in part because of the focus on power production as the goal of the research.  Here I plead for a focus on useful functions as the goal of the research.  How do we select microbes and/or populations for efficient reclamation of wastewater or removal of key pollutants?  How do we get these communities to function optimally in various types of SPUD designs?  How do we design the SPUDs for optimum performance of their environmental “jobs” rather than for maximum power output?  How do we scale systems up to sizes to fit different uses?  What are the microbial properties that lead to robust communities that function for many years?  How do we store microbial communities for population of new systems, and how do we teach the world to run this technology? These are all questions that can only be answered through the marriage of basic and applied science (electrochemistry, biochemistry, engineering, microbiology, etc), and a commitment to focus on the environmentally important jobs that can be done for world water by SPUDs.