SOIL MICROBIAL FUEL CELLS
Scientists invent soil-fuelled power source that ‘lasts forever’
by Anthony Cuthbertson / 1.16/24
“Scientists have developed a new type of fuel cell that can provide endless power through electricity harvested from soil. A team from Northwestern University in the US say the book-sized unit could be used to power sensors used in farming, as well as remote devices in the Internet of Things (IoT). The technology works by generating electricity from naturally-occurring bacteria within the soil, offering a sustainable and renewable alternative to toxic and flammable batteries. “These microbes are ubiquitous; they already live in soil everywhere,” said George Wells, an associate professor of civil and environmental engineering at Northwestern University. “We can use very simple engineered systems to capture their electricity. We’re not going to power entire cities with this energy. But we can capture minute amounts of energy to fuel practical, low-power applications.”
The soil-based microbial fuel cell (MFC) is based on a 113-year-old technology first developed by British botanist Michael Cressé Potter, who was the first person to successfully generate electricity from microorganisms. It took until the 21st century for the first commercial applications to be proposed, with Foster’s Brewing using a prototype to convert the yeast in brewery wastewater into electricity. The latest fuel cell was tested in wet and dry conditions to power sensors measuring soil moisture and detecting touch, outlasting the power of similar technologies by 120 per cent. “The number of devices in the Internet of Things (IoT) is constantly growing. If we imagine a future with trillions of these devices, we cannot build every one of them out of lithium, heavy metals and toxins that are dangerous to the environment,” said Northwestern alumnus Bill Yen, who led the research. “We need to find alternatives that can provide low amounts of energy to power a decentralised network of devices… As long as there is organic carbon in the soil for the microbes to break down, the fuel cell can potentially last forever.”
The research was published in the journal Proceedings of the Association for Computing Machinery on Interactive, Mobile, Wearable and Ubiquitous Technologies on 12 January.
ELECTRICITY from WASTEWATER
Scientists Engineer E. Coli Bacteria to Generate Electricity
by Clare Watson / 13 September 2023
“Ever since 1911, when British mycologist Michael Cressé Potter noticed that brewer’s yeast generated electricity, scientists have been trying to harness the power of microbial fuel cells. But the efficiencies of tiny, budding ‘bioreactors’ have been too low for practical use. What’s more, it turns out microbes can be surprisingly picky in what substrates they digest to create electricity. Now, a team of researchers from the Swiss Federal Institute of Technology Lausanne (EPFL) has engineered one of the most common species of bacteria, Escherichia coli, to generate electricity from brewery wastewater – and it has surpassed the most recent bioengineered strains. “Though there are exotic microbes that naturally produce electricity, they can only do so in the presence of specific chemicals,” explains senior author and chemical engineer Ardemis Boghossian, from EPFL.
“E. coli can grow on a wide range of sources, which allowed us to produce electricity in a wide range of environments, including from wastewater.” To enhance E. coli’s ability to generate electricity, the researchers modified its genome to include instructions for protein complexes found in Shewanella oneidensis, one of the best-known bacterial electricity generators. S. oneidensis produces a flow of electrons when it reduces metals, an electrical signal that has been used, for example, to detect toxic metals such as arsenic in prototype systems. By incorporating all components of S. oneidensis’ electricity-generating pathway in E. coli, Mohammed Mouhib, the study’s lead author, Boghossian and colleagues ramped up its electroactivity two-fold compared to previously engineered strains (which only included part of the S. oneidensis pathway). However, those experiments were done in a single chamber under lab conditions. The real test for any potential technology is whether it can work in industrial settings.
Past research has explored using algae in brewery wastewater treatment. Breweries need to process the water they use to wash grains and flush out tanks before disposing of it because it contains a heady mix of sugars, starches, alcohols, and yeast that could trigger unwelcome microbial blooms if discharged untreated. So the team tested their E. coli system on a sample of wastewater collected from a local brewery in Lausanne, Switzerland, which the modified bacteria happily gobbled up over 50 hours. “Our bioengineered electric bacteria were able to flourish exponentially by feeding off this waste,” says Boghossian, whereas S. oneidensis, used as a comparator, wasn’t able to digest the mixed effluent. This makes the engineered E. coli far more suitable for treating industrial wastewater, even if its electricity-generating potential is still slower than S. oneidensis, the researchers say. E. coli’s appetite for different chemical substrates also means the engineered bacteria could possibly be adapted to other waste streams and feedstocks. In any case, the researchers will need to test whether their modified E. coli can process industrial volumes. If so, it could bring about some considerable energy savings. “Instead of putting energy into the system to process organic waste, we are producing electricity while processing organic waste at the same time – hitting two birds with one stone,” says Boghossian. The study has been published in Joule.
MICROBIAL FUEL CELLS
LOW COST ENERGY STORAGE
HOT SAND BATTERIES