How to generate electricity from the roots of living plants - Printable Version

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How to generate electricity from the roots of living plants - Henlus - 09-26-2021

Somewhere between three and four billion years ago, algae first appeared. This may not sound exciting, but it paved the way for life on earth and could ultimately point to part of the solution to today’s energy crisis.

Algae, along with other early organisms like cyaonobacteria, is photosynthetic. This means that it’s able to capture carbon and breath out oxygen in return. And we need oxygen to breathe. During the following billions of years, more photosynthetic organisms developed: plants.

The interesting thing about plants is that they convert CO2 into chemical energy - glucose - and produce water and oxygen. So basically plants do what we’re struggling to achieve, in a world threatened by climate change: they capture CO2, produce energy and keep our air clean and breathable. So why can’t we do the same thing? Well, we can’t “do” photosynthesis, but we can use it.

How it all started
At Wageningen University in the Netherlands, a crazy assistant professor, Bert Hamelers, thought that it should be possible to produce electricity from living plants, without harvesting them. He hired a Postdoc to do an experiment and he succeeded. They wrote a research proposal and hired a PhD-student to do more work on it: me.

I didn’t want to be in academia (who wants to be in a lab all day?) but not knowing what to do otherwise I ended up doing a PhD. Basically, my professor lured me into it by telling me that a spin-off company should be created from the research project, and he thought I would be fit to lead it. After just one month, I knew that I’d made the best decision of my life.

How it works

So how do you produce electricity with living plants? Simply by using the natural processes that already occur. In short: the plant produces organic matter via photosynthesis. Only part of this organic matter is then used for its own growth. The rest is excreted via the roots. Around the roots, bacteria feed on the organic matter and they release electrons. If you’re able to harvest the electrons into an electrode, you can couple the first electrode to a counter-electrode and build an electrical circuit, like in a battery. The electrons flow back into the natural system via the counter-electrode, so it’s completely circular.

Because we use the natural processes around the plant, nature is not harmed. It works day and night, summer and winter. It only stops when the plant and its surroundings completely dry up or freeze over. So wetlands would be the ultimate source of electricity. Probably the best thing about this technology is that it can be combined with existing applications for the same land. No more competing claims for food versus fuel: put both rice production and power on the same paddy
How we can use it
During my PhD, I worked on improving the power output from plants in the lab. At the same time I started a spin-off company, Plant-e, together with my colleague David Strik, to find applications for the technology. When I graduated in 2012 we launched the first product: a turning globe fuelled by the electricity from a plant. Unfortunately, at that time we couldn’t get the product produced so our first market entry failed. But we were able to attract some financing, so we hired some smart young people and worked on the next product.

In 2014 the first product was launched successfully: a modular system. Basically we sell planters with plants and wires that can be connected to LED lights, for example. This is not going to replace coal-fired power plants, but it’s a start. This is the first step towards using what nature has developed over billions of years, without interfering with nature.

The modular system can be used to set up small, self-powered sites in cities, but it is not scalable. So a new system is under development. This new system is a tube, which contains both electrodes and can be drilled horizontally in the root-zone of the plants. This way existing plants can be used to produce electricity and any wetland would ultimately be able to produce electricity.
The next energy revolution?

After wind, solar and hydropower, the full range of biomass sources are now ready for energy production. Our energy revolution has already started. We go from large scale to decentralized energy production, and we start to realize that no one individual source is going to save us.

It’s going to be the full range of alternative, renewable and sustainable technologies that are slowly replacing fossil fuels. I don’t think that one small company of five people in Wageningen, the Netherlands, is going to revolutionize our energy production. But I do want to be part of it.

Author: Marjolein Helder is the CEO of Plant-e, a World Economic Forum Technology Pioneer. She is participating in the World Economic Forum’s Annual Meeting in Davos.

RE: How to generate electricity from the roots of living plants - Henlus - 09-26-2021

Plants can generate electricity… and we may be able to use it
Plants can generate electricity… and we may be able to use it. If, as a child, you were lucky enough to build a clock powered by a potato , you may not be surprised to learn that plants generate electricity. Given the billions of years put into its development, photosynthesis is unsurprisingly much more efficient at generating energy from the sun than solar panels. Plants are nearly 100% efficient at converting photons from sunlight into electrons. New solar panels by comparison are being developed with a 30 to 36% efficiency, according to PV Magazine, which almost doubles the efficiency of current solar panels.

In 2013, the University of Georgia reported on research allowing scientists to tap into electricity created through photosynthesis before it’s used by the plant. The procedure basically takes electricity from the plant with nanotubes that are almost 50,000 times smaller than the thickness of a human hair. Thylakoids, the part of a plant where energy from the sun is stored, are disrupted and nanotubes conduct electricity away from the plant. The key is capturing electrons from the plants before the energy is stored as sugar. Once the electricity is siphoned off from the plant, the electricity can be used for any human application that electricity is usually used for. It’s been suggested that genetic engineering could be used in tandem with the technology to create plants specifically designed for electricity generation. The idea of creating usable electricity from plants only continues to grow.
Researchers from the University of Washington have conducted similar work on plants to generate electricity. There, electrical engineers designed a circuit that when attached to plants converts the plant’s natural energy into usable electricity. When attached to maple trees, the circuits were able to create 1.1 volts, less than a typical 1.5 volt battery such as the normal AA cell.

There are companies like Plant-e already poised to capitalize on plant electricity generation. Plant-e explains that not all of the energy a plant creates is used for itself. Many plants actually improve soil content through the creation of ‘excess’ organic material that is secreted into soil and taken up by bacteria. The idea behind the ‘Plant Microbial Fuel Cell’ technology (P-MFC) is to collect and use electrons created by the breakdown of this organic material by soil bacteria for the generation of electricity.

So far, this type of electricity generation has only produced exceedingly small amounts of electricity. However, the technique has some obvious advantages. Unlike with the use of nanotubes and some other techniques, the plant itself isn’t disturbed. As with all schemes to use plants to generate electricity, the distribution of plants is more even globally than say fossil fuels. The method is also clean when compared to fossil fuels.

Land used for agriculture could also be used to produce electricity. The method typically requires use of plants that grow in waterlogged conditions, which would work with crops such as rice or cranberries but is also a limitation, especially in arid environments. Research and development are needed if the use of plants to generate electricity is to become practical in any real sense.

Another company, Voltree Power , holds the patent to this technology and was first to develop a tree-powered circuit. Voltree has tested using trees to power low voltage sensors to detect forest fires. Unfortunately, the sensors still require traditionally batteries. The trees merely extend the battery life of the sensors, making the system less than impressive.
Istituto Italiano di Tecnologia (ITT) in Pisa, Italy reported on new research to use plants for the generation of electricity. Researchers found that they can generate more than 150 volts of electricity from a single plant. The electricity generated is enough to power 100 of the highly efficient LED light bulbs. The researchers created a sort of cyborg tree made of natural and artificial leaves which generate electricity from wind. The research was headed by Barbara Mazzolai who previously created the world’s first ‘robot plant’ in 2012.

Structures in plant leaves are able to generate electricity from the leaf simply moving in the wind. This electricity is then transmitted through plant tissue. This new research aims to plug into the plant tissue and use this electricity, rather than electricity generated through photosynthesis as previous methods attempted.

Researchers used a nerium oleander tree in an experiment, by adding artificial leaves that touch the trees natural leaves. The research was published in October 2018, ushering in a new way to potentially generate electricity from plants.

There are still real obstacles to overcome before electricity can be widely generated by plants and it seems doubtful whether all our electrical usage could be supplied from plants, at least at current levels. It’s also unclear which method of electricity generation using plants will rise to the top as the most practical. Another problem less often looked at by scientists is one of ethics.

The ethical dilemma of genetically modifying organisms is one that is sometimes raised. Still widespread use of GMO technology in plants has gone forward without much of a broad public discussion. GMO crops are commonly grown now. According to the Center for Food Safety, currently 92% of US corn is genetically modified as is 94% of soybeans and 94% of cotton. The technology has vastly outpaced our ability to discuss its consequences rationally as a society or create laws to regulate it.

Whether using GMO technology or simply marrying electrical technology with natural plants, using plants to generate electricity represents engineering the natural. The act of using a plant to generate electricity is an act of modifying the life of intrinsic organism for our own purposes. It means changing another life without regard to that life’s ability or inability to give consent. This may seem trivial to some, as plants are not highly regarded. We still don’t have any idea of the consequences involved in modifying a plant in this way. We once had no idea of the consequences of burning fossil fuels to generate electricity. We’re clever at using the environment for short term gain but not so good at guessing at the long term consequences of our actions. With many simple but demanding solutions, humans have a knack for creating complex ways to solve our problems. Scientists also can’t ask a plant how it feels about being made part of an electrical generator.

By Zach Fitzner, Contributing Writer

RE: How to generate electricity from the roots of living plants - Henlus - 09-27-2021

Tiny Microbial Power Generator Runs On Spit - April 2014
Spit-powered, micro-sized microbial fuel cells produce enough energy to run on-chip applications, according to a paper in
Asia Materials .

Microbial fuel cells create energy when bacteria break down organic material producing a charge that is transferred to the anode. Bruce Logan, Professor Environmental Engineering at Penn State, has studied microbial fuel cells for more than ten years and usually looks to wastewater as a source for both the organic material and the bacteria to create either electricity or hydrogen, but says these tiny machines are a bit different.

One possible application would be a tiny ovulation predictor based on the conductivity of a woman's saliva, which changes five days before ovulation. The device would measure the conductivity of the saliva and then use the saliva for power to send the reading to a nearby cell phone.
Microbial fuel cell with saliva input ports. Credit: Bruce Logan, Penn State
Biomedical devices using micro-sized microbial fuel cells would be portable and have their energy source available anywhere. However, saliva does not have the type of bacteria necessary for the fuel cells, and manufacturers would need to inoculate the devices with bacteria from the natural environment.

In the past, the smallest fuel cells have been two-chambered, but this micro version uses a single chamber with a graphene- rather than platinum-coated carbon cloth anode and an air cathode. Air cathodes have not been used before because if oxygen can get to the bacteria, they can breath oxygen and do not produce electricity.

"By producing nearly 1 microwatt in power, this saliva-powered, micro-sized MFC already generates enough power to be directly used as an energy harvester in microelectronic applications," the authors write.

Logan credits the idea to fellow researcher Justine E. Mink. "The idea was Justine's because she was thinking about sensors for such things as glucose monitoring for diabetics and she wondered if a mini microbial fuel cell could be used," Logan said. "There is a lot of organic stuff in saliva."

"We have previously avoided using air cathodes in these systems to avoid oxygen contamination with closely spaced electrodes," said Logan. "However, these micro cells operate at micron distances between the electrodes. We don't fully understand why, but bottom line, they worked."

The anode is actually composed of carbon nanomaterial graphene. Other microbial fuel cells used graphene oxide, but the researchers showed that pure multi-layered graphene can serve as a suitable anode material.

While the researchers tested this mini microbial fuel cell using acetate and human saliva, it can use any liquid with sufficient organic material.

RE: How to generate electricity from the roots of living plants - Henlus - 09-27-2021

Brush Anode And Tubular Cathode Scale Up Microbial Fuel Cells - March 20th 2007

Generating electricity from renewable sources will soon become as easy as putting a brush and a tube in a tub of wastewater.

A carbon fiber, bottle-brush anode developed by Penn State researchers will provide more than enough surface for bacteria to colonize, for the first time making it possible to use microbial fuel cells for large scale electricity production. In addition, a membrane-tube air cathode, adapted from existing wastewater treatment equipment, will complete the circuit.
"The carbon fiber brushes are electrically conducting, very inexpensive to produce and supply large surface area for the bacterial biofilm attachment," says Bruce E. Logan, the Kappe Professor of Environmental Engineering.

"These anodes can be made by any existing brush manufacturer in any size or shape desired."

Microbial fuel cells work through the action of bacteria, which can pass electrons to an anode of a fuel cell. The electrons flow from the anode through a wire to the cathode, producing an electric current. In the process, the bacteria consume organic matter in the wastewater and clean the water. The Penn State approach uses the bacteria that naturally occur in wastewater, requiring no special bacterial strains or unusual environmental demands.

Previously, Logan and his team showed that small, rectangular fuel cells that used a carbon fiber paper as anode and a carbon fiber paper with platinum catalyst as cathode could produce electricity and clean water from wastewater. However, commercial scale-up for carbon fiber paper cells was not practical.
Using brush anodes, which have 300 to 1,500 times more surface area than the previously used carbon paper anode, the fuel cells created more than twice the power produced by the fuel cells two years ago. A fuel cell using a small brush about 1 inch in diameter and 1 inch long produced the equivalent of 2.4 watts for every 260gallons of water using the carbon paper cathode, the researchers reported in today's (Mar 21) online edition of Environmental Science and Technology.
"The anode is no longer a limiting factor in power production for these cells," says Logan.
Other carbon anodes were problematic because the pores or spaces became clogged with the biofilm and lost efficiency, but because the brush contains very fine fibers with plenty of circulation room around them, dead bacteria do not clog the brush.

With the anode no longer limiting scale up or bacterial growth, the researchers turned to the cathode. " "We needed a new type of cathode that could produce much more surface area," says Logan. "Many systems use platinum catalysts, but platinum is too expensive
While the brush anode can be submerged in the wastewater, the cathode must have one side exposed to the oxygen in the air to work. The researchers looked at membrane tubes currently used in wastewater treatment applications for an answer. Commercially available in a variety of sizes ranging up to 6 to 8 foot tall, these membrane tubes are not electrically conductive.

"We painted the tubes with conducting graphite paint and added a cobalt-based catalyst," says Logan.

The painted tubes did work to produce power, but not as much as the carbon paper doped with platinum.

"We showed a proof of concept with these tubes, but now we have to improve the efficiency and reduce costs," says Logan.
The researchers tested two cathode configurations, one with the catalyst on the outside of the tubes and one with the catalyst on the inside of the tube.

In the best test case, the researchers used a carbon fiber brush anode and two tubular cathodes of about .6 inches in diameter doped with a cobalt catalyst on the inside, the fuel cell produced 18 watts per 260 gallons of water and achieved a charge efficiency of more than 70 percent.

The newly configured anodes and cathodes also allow for a variety of configurations of the fuel cell. "With these new anodes and cathodes the design of a wastewater treatment reactor could be as simple as a large tank with the brushes and tubular cathodes inserted into the same tank," says Logan

An additional benefit to the microbial fuel cell is that while it generates electricity, it cleans up the wastewater, something that usually requires the consumption of energy.

Working on the anode research were Logan, Shaoan Cheng, research associate and Valerie Watson, graduate student, civil and environmental engineering, and Garett Estadt, recent graduate, chemical engineering.
Working on the cathode research were Logan; Cheng; and Yi Zuo and Doug Call, graduate students, civil and environmental engineering.