A history of bioenergy

The biological fuel cell (bio battery)

Hydrogen - The (new) kid on the block - bears the burden of every bearer of hope. All projections for rapid progress and completion of the energy transition (industry, mobility, heating) seem to lie on it. It should not only complete the energy turnaround, but also become the foundation of a new economic system. Michael Jordan among the elements, which should give a shaky economic system support, a new spirit, a new energy: clean, renewable, hydrogen. Lots of burden on number one on the periodic table. And (biogenic) hydrogen has the potential to fulfill this difficult role. A hydrogen technology that could be for our civilization in 100 years what the internal combustion engine is currently is the fuel cell (a statement for which there are passionate critics!). A variant of the fuel cell that biological Fuel cell or bio-battery, I would like to introduce you today.

The oldest power source known to man: the galvanic cell

The basic principle of the fuel cell is the galvanic cell. Named after the Italian Luigi Galvani, it can convert chemical energy into electrical energy, the same form of energy conversion as a gas turbine with an attached generator. Or a cyclist who drives along the sea with an ice cream under a full moon and receives the electricity for playing his playlist via a dynamo.

The oldest apparatus discovered to date for the use of electrical energy is probably the Baghdad battery (250 AD - Electricity in ancient times?). There are even notes and pounds which are the first Copper-zinc-copper sulfate-based batteries (similar to the Baghdad battery) in ancient India 4.000 years ago demonstrate. Wherever the root of the electric battery lies, just like modern fuel cells, these are based on the galvanic principle.

A distinction is made between three types of galvanic cells, the first two corresponding to the known batteries and the third variant being the fuel cell.

Galvanic cell type 1: standard battery
Galvanic cell type 2: Rechargeable battery (accumulator)
Galvanic cell type 3: fuel cell

Fuel cells are rocket science!

Fuel cells (Grubb-Niederach) are originally a NASA spin-off technology and therefore in the truest sense of the word Rocket Science (Gemini Space Program, 1965 + 1966). As soon as the hydrogen has been obtained, for example by using excess electrical energy (electrolysis), it can be converted back into electricity at any point in time. The classic way is to convert hydrogen, like any other high-calorific gas (e.g. natural gas / methane, propane or butane), into electrical and thermal energy in a modern combustion engine (turbine), i.e. to generate electricity and heat. This has advantages, but also disadvantages, which will be explained in more detail later in the article. Another way is the energetic conversion of the hydrogen in one cold and not in a hot combustion: combustion in a fuel cell.

The most important components of every fuel cell are the two electrodes and the electrolyte in which the electrodes are immersed. One electrode, the anode, acts as a positive pole and removes the electrons from the fuel, which has to be constantly added to the connecting electrolyte solution of the fuel cell. In the case of hydrogen, splitting this fuel produces two positively charged protons in addition to two electrons. The electrons flow from the anode directly to the cathode via a conductor, creating the desired current flow. With modern Fuel cell types (e.g. PEMFC) the charged H + ion migrates through a semi-permeable membrane, which is stretched between the anode and cathode in the electrolyte, and combines with the supplied oxygen on the other side (cathode) to form water. The following video from Simpleclub provides a visual explanation of the fuel cell.

The search for the optimal fuel for a fuel cell

As already mentioned, a fuel cell also has a Cold burn spoken. The reason is that when the fuel or fuels are burned, only electrical energy (electricity) and no thermal energy (heat) is generated. The fuel cell can be operated with different fuels. What is needed is a chemical element or a compound which, under certain conditions, releases an electron and breaks down into its ions (anion, cation). In chemistry, one speaks of reducing agent, which functions as an electron donor and thus provides the base currency for every flow of electricity. On the other side of the fuel cell (redox reaction), a second fuel is required that takes up the electron: the oxidizing agent, which is reduced itself. In theory, a wide range of elements or molecules can be used as fuels.

In practice and when upscaling a fuel cell, questions such as the availability and cost of fuels play a major role and are taken into account when selecting the reducing and oxidizing agents. The effort (costs!) For generating the physical framework conditions for releasing the electron must also be taken into account. In economic application, these boundary conditions mean that currently above all Hydrogen-oxygen fuel cells can be built using hydrogen as a reducing agent, oxygen as an oxidizing agent and, for example, potassium hydroxide as an electrolyte. The future among the Fuel cell types should belong to the liquid fuels (eg methanol), which are simpler in construction and more stable in operation because of the liquid-to-gas instead of gas-to-gas transition.

An optimal fuel for a fuel cell is therefore inexpensive, easy and safe to handle and efficient with regard to a high voltage gradient (Cell voltage).

The evolution of the biological fuel cell (bio-battery)

What is it now Biological fuel cell, short Bio fuel cell, Microbiological fuel cell or or sometimes Bio battery?

The History of the biological fuel cell begins 100 years ago with the discovery (1911) by Professor MCPotter of the University of Durham that bacteria (E. Coli) produce electrical energy under certain circumstances. A generation of scientists later, bacteriologist Barnet Cohen from Yale University was able to interconnect several bio-batteries in such a way that a voltage drop of 35 volts and a current strength of 2 milliamps could be achieved. Another generation later, in the 1960s, a bacterium (Clostridium butyricum) was used for the first time to ferment sugar to produce hydrogen as a reducing agent for the anode. The test results were made in 1963 by Delduca of the Society for Industrial Microbiology released. Unfortunately, the production of hydrogen by microorganisms was still unstable. The problem of Instability of the biological fuel cell was solved by the Japanese research team around Shuichi Suzuki in the late seventies. In the XNUMXs it was researchers at King's College, UK, who carried the torch on to the biological fuel cell. At the beginning of the nineties, MJ Allen and H. Peter Bennetto presented their work on the extraction of electrical energy from carbohydrates through the use of bio batteries. In the mid-XNUMXs, three scientists from the Department of Chemistry at Harvard University in Cambridge published an influential paper on the improvement of microbiological fuel cells (Eng .: Microbial Fuel Cell = MFC). Microbial and Enzymatic Biofuel Cells by G. Tayhas R. Palmore and George M. Whitesides summarizes the current knowledge (1994) about the influence of enzymes as catalysts for biological fuel cells.

Current research on bio fuel cells / bio batteries

Since 1994 a new generation of scientists and engineers has been working to further develop the understanding of the fundamentals and the use of the bio-fuel cell. Several research teams have caused a stir in the MFC community over the past decade. For one thing, that's the one Logan Research Group the environmental engineer Bruce. E. Logan of the Department of Civil & Environmental Engineering at Penn State University. In the following video he presents some research results. The group focuses on improving the design of the microbiological fuel cell with a focus on the design of the electrodes and reducing the costs of the bio-battery.

One of the leading research groups dedicated to understanding the bio-fuel cell is also based in Germany. At the TU Braunschweig, at the Institute for Ecological and Sustainable Chemistry, the team around Professor Uwe Schröder is researching the Basics and the further development of the biological fuel cell. One focus of the chair for bioelectrochemistry is electron transport within BES (bioelectrochemical systems).

Another active team are the scientists led by Ioannis A. Ieropoulos, Professor of Bioenergy at the Bristol Robotics Laboratory at the University of the West of England. The team contributes with regular publications to improve the Performance and efficiency (current and voltage) of the bio-fuel cell at.

Difference between classic and bio fuel cells

The term Fuel cell (English Fuel Cell) has something organic about it. While classic, metal-based fuel cells have this designation because of their closed reaction space with the polar construction principle, the designation of a “cell” takes on an additional meaning for biological fuel cells.

The special thing about a biological fuel cell is that it can combine electrolysis to produce the required hydrogen with the subsequent conversion into electricity using the principle of the galvanic cell. That is a very important difference. By merging the two processes in one device (bio-battery), the complex preparation of the anode fuel is no longer necessary. The storage and transportation of the fuel by the Cooling of hydrogen close to absolute zero (-253 ° C) or pressure storage at 700 to 1.200 bar are not very helpful from the point of view of energy efficiency.

Thus, not only chemical hydrogen storage or hydrogen carriers (LOHC) such as methanol come into question as hydrogen carriers, but can also be extended to a wide range of hydrocarbons, which can be used as a food source for microorganisms. This includes a variety of simple sugars, multiple sugars (carbohydrates) and under certain conditions (hydrophobic cell wall, biosurfactants) also fats, which can be broken down by bacteria to produce energy. The most promising application of the bio fuel cell is based on this ability of the microorganisms - but more on that later. In spite of all positive forecasts, it is still advisable to stay on the ground, because it is precisely this recourse to microorganisms and communities of MO (biocenoses) that makes understanding and operating a microbiological fuel cell quite complex.

Depending on the point at which the two phases of the redox reaction take place direct and indirectly Differentiated bio fuel cells. As the name suggests, the fuels (e.g. hydrogen and oxygen) can be burned (oxidized) directly at the electrode or indirectly in the electrolyte solution. Depending on which type of fuel cell is used, the electron can flow directly from the anode to the cathode or has to be via a mechanism or transporter (Mediator) are transported from the location of the electron separation through the electrolyte solution to the anode.

Crucial for profitability
every fuel cell is the catalyst

One of the reasons why fuel cells did not make a breakthrough for a long time was the high cost of platinum, which was the most effective catalyst in the 70s and 80s Activity, selectivity and stability of all other catalysts for fuel cells overshadowed. At the beginning of the 21st century, this high cost threshold could be continuously reduced (by around 80 percent) because it was new Catalysts found for the use of hydrogen (e.g. molybdenum-phosphorus, MoP) and the durability of the membrane (PEM) could be extended. In addition, carbon is often used to increase the surface area for applying the actual catalyst. The catalyst used also forms one of the major differences between the various types of fuel cells and is essential to wrest the electrons from the fuel for the current flow under mild conditions (room temperature, atmospheric pressure, neutral pH value), or to oxidize the fuel.

While the catalyst in classic fuel cells is usually an active carrier material (e.g. platinum, ruthenium or palladium), microbiological fuel cells rely on organic and renewable catalysts. With the organic catalysts of MFC there are further differences in the preparation of the catalyst. So use the direct biological fuel cell an enzyme as a catalyst (e.g. triose phosphate isomerase or superoxide dismutase / SOD) and the indirectly Bio-fuel cells fall back on an active, living organism (microorganism → mostly a bacterium), which enables or accelerates the redox reaction.

First promising field of application for the microbiological fuel cell

Okay okay, the historical development, the theoretical feasibility, the vision, a lot makes sense with the fuel cell. But apart from that, what about the practical application of this type of electricity generation in the here and now # Germany2020? After all, the microbiological fuel cell or bio-battery is still in its infancy and still has a few miles to go before it can run alone or is marketable.

Be careful, there is a business case that connects two social goals so elegantly that, thanks to the synergies that are released, viable use of microbiological fuel cells is already possible today. And that without, but especially when setting up funding programs. What is meant is the combination of energy generation (electricity) and wastewater treatment. As with the (hot) combustion of sewage gas in a combined heat and power plant, it can also be converted into electricity directly with the help of a microbiological fuel cell. In other words, using the flowing wastewater as a source of food for microorganisms. Integrated into a bio-battery, the bacteria not only clean the wastewater (biochemical oxygen demand, BOD), but also promote the targeted flow of electrons (electricity).

This combined process can theoretically be used in 10.000 sewage treatment plants in Germany alone. For many municipalities around the world, sewage treatment plants are the facilities with the highest energy consumption and are sustainable according to estimates by Nature Sewage systems are responsible for around 3 percent of global electricity consumption. Accordingly, they alone need German sewage treatment plants around 4.4 terawatt hours of electricity every year, which corresponds to an electricity consumption of around 3 million citizens (Umweltbundesamt, 2009). This means that wastewater treatment alone contributes around 3 million tons of CO2 to Germany's annual climate balance. Microbiological fuel cells are not rainbow-farting unicorns either, but their widespread use in sewage treatment plants can help stabilize our living conditions on this planet on many levels.

The vision that wastewater treatment will be driven even more strongly in the future through the targeted use of electrochemical processes in microorganisms is shared by energy. and water managers worldwide. A selection of the economic and scientific players:

Summary and Conclusion
to the technology of biological fuel cells

The fuel cell is the reverse of electrolysis. It doesn't need electricity, it produces electricity. To do this, it does not produce hydrogen, but needs hydrogen. The biological fuel cell is special in that it is the only one that can combine hydrogen and electricity production. This requires an elegant cooperation between humans and microorganisms, in which biomass is broken down and the natural flow of bioenergy is used for electricity production.

Depending on the process of metabolism, we speak of fermentation when the electron uptake happens inside the microorganism and of breathing when the electron uptake takes place outside the microorganism. In the special fermentation case of anaerobic / anoxic fermentation, biogas is produced, the methane content of which can be converted into heat in the hot combustion (CHP) and this can then be converted into electricity. In the case of breathing, the generation of electrical energy takes place more directly. Living biomass (microorganisms) decompose dead biomass (organic matter in wastewater), whereby the formation of ions can be accelerated and the flow of electrons can be achieved through the introduction of electrodes (including catalysts). Since little or no heat is generated, we speak of cold combustion.

A stable running bio-battery, which takes over the hydrogen production as well as the electricity production under economical conditions, is an energy technology of the future that has earned this name. Clean energy which is produced 24/7, approaching the ideal of the circular economy, cleaning wastewater and producing electricity. As a civilization, we are still developing this technology, but on a laboratory scale the process is already working beautifully. The next step is upscale and thus the economic use of the biological fuel cell. Investors, companies and government funding programs are in demand to help the technology reach the market.

Finally, a short summary or an outlook on the next steps in dealing with the technology. According to the seminal book by Tayas, Palmore and Whitesides (Harvard University, Cambridge) on the status of the biological fuel cell, we face the following opportunities and challenges:

Diversity of new input materials

Biological fuel cells can use biomass between waste paper and glucose, which conventional fuel cells cannot process.
Environmentally compatible framework conditions

Biological fuel cells are naturally environmentally friendly and their enzymes work at low temperatures and neutral water (pH 7).
Enzymes are inexpensive and renewable

Organic catalysts (enzymes) are renewable and can be produced more cheaply by fermentation than the finite metal catalysts such as platinum, palladium or rhodium.
Higher turnover rate needed

In order to outperform platinum-powered fuel cells in terms of turnover rate, enzymes or enzyme complexes must be found or developed that achieve a specific activity (enzyme unit) of greater than 103 U / mg.
Compatibility with human body

The organic basic principle of bio-batteries opens the door to innovative fields of application. In theory, these can be implanted in humans and, for example, provide the energy for implanted prostheses.

Questions, feedback, ideas?

So much for the idea of the fuel cell, which is based on the activity of the smallest living beings (microorganisms). Do you have any questions or suggestions about biological fuel cell technology? Here you have the opportunity to add them. Many thanks.

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Ron Kirchner

Ron works as a consultant on energy & climate issues. As an environmental engineer, he advises decision-makers on the design or implementation of their concepts. He prepares studies, market analyzes and reports for state governments, companies and associations.

A history of bioenergy

The biological fuel cell (bio battery)

The oldest power source known to man: the galvanic cell

Fuel cells are rocket science!

The search for the optimal fuel for a fuel cell

The evolution of the biological fuel cell (bio-battery)

Current research on bio fuel cells / bio batteries

Difference between classic and bio fuel cells

Crucial for profitability
every fuel cell is the catalyst

First promising field of application for the microbiological fuel cell

Summary and Conclusion
to the technology of biological fuel cells

Diversity of new input materials

Environmentally compatible framework conditions

Enzymes are inexpensive and renewable

Higher turnover rate needed

Compatibility with human body

Questions, feedback, ideas?

Ron Kirchner

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Post a comment Cancel comment

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The oldest power source known to man: the galvanic cell

Fuel cells are rocket science!

The search for the optimal fuel for a fuel cell

The evolution of the biological fuel cell (bio-battery)

Current research on bio fuel cells / bio batteries

Difference between classic and bio fuel cells

Crucial for profitability every fuel cell is the catalyst

First promising field of application for the microbiological fuel cell

Summary and Conclusion to the technology of biological fuel cells

Diversity of new input materials

Environmentally compatible framework conditions

Enzymes are inexpensive and renewable

Higher turnover rate needed

Compatibility with human body

Questions, feedback, ideas?

Ron Kirchner

Share post with someone:

Post a comment Cancel comment

Crucial for profitability
every fuel cell is the catalyst

Summary and Conclusion
to the technology of biological fuel cells