Circular photosynthesis: Plant-based bioelectrical system hub for off-grid villages


More than 1 billion people – or 1 in 5 of the world’s population – still lack access to modern electricity. This figure is significant because energy is a central component of nearly every major challenge and opportunity the world faces today. Access to energy for all is essential for jobs, security, climate change, food production and increasing incomes. The United Nations Sustainable Development Goal (SDG) 7 has been designed in response to this issue and aims to ensure access to affordable, reliable, sustainable and modern energy for all.

A team at the University of Cambridge are promoting the development of ‘circular photosynthesis.’ Building on the ‘circular economy’ concept, in which we keep resources in use for as long as possible, extract the maximum value from them whilst in use, then recover and regenerate products and materials at the end of each service life, the team employ plant-based bio-electrochemical systems (plant-BES) to combat energy challenges in off-grid communities.

Bio-electrochemical systems (BES) are unique systems capable of converting chemical energy into electrical energy (and vice-versa) while employing microbes as catalysts. Photosynthetic microorganisms, as well as higher plants, are thus implemented to use solar energy for electricity generation. In addition to energy, plant-BES are capable of generating biomass and food, treating wastewater and promoting local jobs.

In a recent experimental study, the plant-BES prototype was able to generate contextually ~160 gram (dry weight) of grass per square meter per month and ~5000 mAh (milliamp hours). By comparison, a typical Ni-Cd battery carries ~300 mAh.

The plant-BES is most promising at latitudes between the equator and the tropics, with countries in this region located in Sub-Saharan Africa, South America, South Asia and South-East Asia. Suitable regions for plant-BES implementation have been identified, based on rainfall and available agricultural area per off-grid person. Based on these data, and applying the minimum regional conditions of 1000 mm/year rainfall and 1000 m2 per off-grid person, the plant-BES could potentially deliver electricity, biomass and wastewater treatment to about 857 million people.

An interactive computation sheet has been developed to determine the per-capita land requirements for plant microbial fuel cell implementation. The computation assumed that moderate power consumption for one individual living off-grid equated to ten hours of LED light usage, five cell phone calls and delivery of ten SMS. Based on these figures, it was shown that 2-3 squared metres of land is required to meet a person’s energy needs, using a plant-BES hub.

The challenge for the i-Team is to speak to a range of relevant experts about the electricity needs in the target areas to verify the theoretical feasibility of a Plant-BES hub for off-grid villages.

i-Teams website link:

Circular photosynthesis: Plant-based bioelectrical system hub for off-grid villages