Kinkajou : I don’t think I would like to rely on aliens to supply us with technology. Humanity needs to look at its own environment and to work out its own solutions for its own specific problems. Why would you trust someone with unknown intentions?
Hydrogen Catalytic Process was developed by the "Species"
Kinkajou : In any case, the electrolytic conversion of water to hydrogen is not that hard and can be done quite efficiently using today’s technology.’ “What’s the big deal?
Erasmus :I think the main issues can be summarised as follows:
Hydrogen is very light. Consequently, it produces a lot energy per gram of stored fuel. A high energy/ mass ratio!
Hydrogen combines with oxygen to form water. Therefore if no carbon is used in the generation of the energy to produce the hydrogen, hydrogen does not have a carbon or greenhouse gas footprint.
- Burning carbon as fuel with oxygen generates 32.8 kJ per gram of carbon, with 3.7 g of CO2.
- Burning methane as fuel with oxygen generates 54.0 kJ per gram of methane, with 2.8 g of CO2.
- Burning diesel as fuel with oxygen generates 42.8 kJ per gram of diesel, with 3.1 g of CO2.
- Burning petrol or gasoline as fuel with oxygen generates 47.3 kJ per gram of petroleum, with 3.3 g of CO2.
Hydrogen is the outright winner. Burning hydrogen as fuel with oxygen generates 142 kJ per gram of hydrogen, with no CO2.
Kinkajou : Probably the most obvious fact here is that hydrogen is a very important fuel where weight considerations are critical. However, if one is to use hydrogen as a rocket fuel, oxygen needs to be carried as well, substantially limiting weight advantages derived from hydrogen being such a light fuel. (Oxygen is heavy).
Problems with Hydrogen
Erasmus :The main problems are related to:
- hydrogen is difficult to store due to its gaseous nature
- Hydrogen will combine explosively with oxygen, therefore can be a very unstable and dangerous chemical fuel.
- Hydrogen is stored cold, so energy is lost warming it to reaction temperature.
Kinkajou : Don’t forget about storing the gas at the time of generation, for later use. Hydrogen is a very small molecule. If the storage chamber has even a microscopic hole, the gas will escape. The slightest spark will make it explode. Storage technology needs to be perfect, but this sort of technology is well within current practice and capabilities.
Other Methods of Generating Hydrogen
Erasmus :Currently generating hydrogen is not cheap. We use fossilised fuels like coal or gas or oil sources as the main energy and fuel feedstocks for hydrogen generation in industry today. It is only when one considers the environment of the future that importance of hydrogen as a fuel becomes obvious. When petrochemicals are becoming expensive, and when technology gives us new options and new efficiencies, it will become necessary to generate and store fuel energy in different ways.
Kinkajou : Didn’t you generate hydrogen yourself, for balloons, when you were a child?
Erasmus :Yes .I used to make hydrogen to fill balloons as a child. Great fun. The formula was fairly simple. You combined aluminium foil strips with sodium hydroxide (caustic soda) and water in a bottle, on top of which a balloon was tied. The problem was more along the lines of slowing the chemical reaction down so that the reaction vessel, usually an old bottle, would not boil with the amount of exothermic heat generated. When the balloon had pressurised sufficiently you simply tied off the balloon with a piece of string, and hey presto a floating balloon was born.
Kinkajou : Is generating hydrogen really that easy?
Erasmus :Yes. Generally combining metals with water generates hydrogen gas and metal oxides. In the process I had above, I used the sodium hydroxide is a catalytic agent to accelerate the chemical reaction.
Erasmus :So I’ll summarize the main methods of generating hydrogen gas industrially today. Firstly it is possible to combine natural gas and water (steam) through various methods. Secondly carbon such as coal can be gassified and combined with water. Thirdly water electrolysis can be used. Lastly metals and water can be combined, as in our home hydrogen gas balloon example.
Industrially, bulk hydrogen is usually produced by the steam reforming of methane or natural gas. At high temperatures of the order of 700 to 1100°C , water (H2O) existing as steam ) reacts with methane or natural gas in an endothermic reaction to yield something called Syngas.
CnHm + n/2 O2 → n CO + m/2 H2
Idealized examples for heating oil and coal, assuming compositions C12H24 and C24H12 respectively, are as follows:
C12H24 + 6 O2 → 12 CO + 12 H2
C24H12 + 12 O2 → 24 CO + 6 H2
When this reaction is carried out at more normal temperatures and pressures, using coal as the feedstock, the gaseous output product is more commonly known as town gas. Up till the recent technological drive to exploitation of natural gas derived from ground(mining) sources, town gas has been the main energy gas used in cities. Town gas is normally a composite of hydrogen gas, methane, carbon dioxide and hydrogen sulphide. The proportions depend on the type of chemical generation reaction chosen and the purity of the feedstocks.
Because a number of these methods use fossil fuel either as natural gas or as coal, the generation of hydrogen gas does give a greenhouse gas footprint. A number of methods have been proposed to cheat sums on greenhouse gas generation. For example combining carbon dioxide with magnesium or silica generates a family of chemicals that can be dumped deep within the earth. Unfortunately, there is a greenhouse gas cost in producing and extracting source feedstocks such as magnesium metal or suitable silicates to feed these sequestration reactions.
Kinkajou : I see! The plus with hydrogen is that it is the ultimate non-polluting chemical process. The waste product of the chemical process is water and heat. There are no strange chemicals and there is No pollution. This is the Holy Grail of clean green energy. Its structure and its nature lend itself to “on-site” production and usage in fuels cells, potentially of very microscopic size indeed.
The problems with hydrogen relate to its’ cost of production and storage.
Erasmus :I can see a few other problems. There are efficiency losses inherent in creating a chemical from electricity and using a heat or combustion process to recreate the electricity. There is also the need to look at the activation energy of the chemical reaction, ( a concept from thermodynamics). To bypass some of the problems associated with activation energy, most modern methods use some type of catalyst to increase or enhance the efficiency of the conversion process. Although there has been a lot of work done on metal catalysts with especially a focus on cheaper nickel composites as opposed to platinum-based catalysts, perhaps the greatest efficiency gains can occur with biological enzyme-catalysed reactions. Biological organisms are micro-factories tuned over many millennia to efficiently run a number of chemical processes.
I think if there is to be a breakthrough; it needs to be in the generation of chemical energy(hydrogen) from exothermic chemical reactions or the generation of chemical energy (hydrogen) from electricity. Biology may give us more options yet.
Kinkajou : Often the energy used to create the hydrogen has a solar source. So the conversion efficiency of solar energy finally being stored as hydrogen gas chemical energy is poor. To describe the process: solar energy arrives on the solar collector, is converted to electrical energy and then this is converted to chemical energy being stored as hydrogen gas.
Erasmus :There is another issue often forgotten, is that to make chemical reactions occur, we often have to add extra heat or pressure or voltage to drive the reaction at a speed where there is a commercially usable quantity of the gas generated in a realistic (commercial) time frame.
From thermodynamics, there needs to be a minimum of 237 kJ of energy to dissociate each mole of water(6x10E23 molecules), into its components. The minimum voltage from thermodynamic theory for the electrolytic conversion is 1.23 v. However as the chemical process runs very slowly at this voltage, even at higher temperatures, we have engineered our chemical processes to use higher voltages, currents and power to increase the yield of the conversion reaction. This extra energy is lost as heat and counts towards the reduction of the efficiency or yield of the chemical process.
Plants / Microbes and Hydrogen Production :
Tech : Cells vs Enzymes
Kinkajou : Hey! I just realised something. “Plants cheat.” They use enzyme-catalysed biological chemical processes to achieve the same purpose using individual units of energy to drive these reactions.
I get it,” says Erasmus.
Erasmus :Plants use highly evolved enzymatic processes to catalyse this reaction and thereby reduce the activation energy to a level where a commercially (or life viable) quantity of energy is stored in chemical systems. The energy of the hydrogen is traded off into acceptor compounds associated with carbon molecular skeletons, and the oxygen is dumped as waste. To be fair, a plant is essentially concentrated biological nanotech in a shell. It is not surprising that billions of years of evolution can do better than humans with a few bits of wire, some water and a few bowls. Our technology is at the caveman stage compared to the capabilities of nanotech machines built by evolutionary biology.
Electrolysis Cells and Hydrogen.
Kinkajou : So tell us about human cave tech : with a few bits of wire, some water and a few bowls. I think we call them electrolysis cells.
There are three main types of electrolysis cells.
1.Solid oxide electrolysis cells typically operate at high temperatures around 800°C. At these temperatures ,the significant amounts of the energy required for the electrolysis chemical reaction can be provided as thermal energy or heat
2.Polymer electrolyte membrane cells typically operate below 100°C are fairly simple and can be designed to accept a range of voltage inputs making them much more suitable for use with sources of renewable energy such as solar photovoltaic or wind energy.
3.Alkaline electrolysis cells optimally operate at high concentrations of electrolyte for example KOH or potassium carbonate and at temperatures often near 200°C.
There have been some proposals for using chemical fuel substrates such as carbon within electrolysis cells to burn the oxygen and hence reduce the required amount of electrical energy to feed into the hydrogen generating chemical reaction. The issue here is again efficiency and in particular energy mass ratios.
Kinkajou : Still let’s go back to the chemical “cell” or battery. This is the frontline of human tech in power generation via hydrogen gas.
Erasmus :The chemical reactions occurring in the cell are as follow:
Reduction at cathode: 4 H+ (aq:) + 4e− → 2H2 (g)
Anode (oxidation): 2 H2O (l) → O2 (g) + 4 H+ (aq:) + 4e−`
These equations are balanced as written.
For a well-designed cell the largest loss occurs due to the need to generate over-potential for the electron oxidation of water to oxygen at the anode. Electrocatalysts to reduce the activation energy for this chemical reaction have had only limited success. Researchers have used
- Platinum alloys ( probably the most common solution
- Cobalt and phosphate Combinations
- Carbon-based catalysts.
Other solutions to the problem of developing more effective or efficient electric catalysts to reduce the reaction over potential for the four electron oxidation of water to oxygen at the anode include the use of molybdenum sulphide, graphite micro dots or carbon nanotubes, the use of perovskite which is a titanium calcium oxide mineral, and nickel nickel oxide combinations.
The anode chemical reaction is the more difficult. The reactive oxygen intermediates need to have an overvoltage situation to drive the chemical reaction with a reasonable yield in a short time frame.
The simpler cathode reaction to produce hydrogen can be electrocatalyzed with almost thermodynamic optimum efficiency by platinum. Theoretically, a hydrogenase enzyme could also be used to facilitate the reaction. If other, less effective, materials are used for the cathode then another large efficiency loss occurs from the need for overvoltage to drive the chemical reaction.
The energy efficiency of this electrocatalytic reaction is probably of the order of about 30%. . But then don’t forget once you make the hydrogen gas, you need to convert it back onto electricity again. So the true exigency of the entire process may be much less. I.e. 30% * 30% >> this is a dreadful yield for then energy involved. It only works where the input energy is free as in sunlight or solar power systems
Kinkajou : Or else, where size matters, such as miniature fuel cells or batteries.
Kinkajou : There is an obvious application here for the need for storage technologies. If the hydrogen can be generated and stored on-site, the electrolytic cell has now become a fuel cell.
It is now technology for the storage and transport not just the generation of energy. These extra uses would increase the applicability of the technology to a number of industrial situations. The most obvious example is the generation of fuel in cars. Solar voltaic energy can only produce energy at a specific rate, based on the amount of available solar radiation. If a car parked in the open can generate hydrogen gas and store hydrogen gas all day, this becomes a substantial additive energy source to battery stored electrical energy. Potential advantages include increased range, increased speed, and increased efficiency.
Erasmus : Increasingly I am seeing the issue of “horses for courses”. There is no one technological solution for everybody. There are many different niches for which different technological solutions may be appropriate. For example if you park your car in a shaded car park all day, solar voltaic energy generation is essentially useless. If your car is left on a street location all day, extra hydrogen generated through the day could well significantly reduce the need for refuelling or re-energising. The solution you need depends on who you are, where you are, and are what you do.
Bio-Hydrogen : Enzyme Catalysed vs Electrolysis Cells
Kinkajou : What else can you tell us about biologically enzyme-catalysed reactions for the production of hydrogen?
Erasmus :Biohydrogen can be produced from fermentative reactions using organic substrates. While this technology is probably not relevant to you driving your car, it can be extremely relevant as a by-product of recycling techniques. Gram positive bacteria of the Clostridium genius have a high natural hydrogen production rate. Clostridia produce hydrogen via a reversible hydrogenase enzyme. Because this reaction is reversible, the partial pressure of hydrogen produced acts to reduce the efficiency of the conversion process. Hydrogen must be extracted continuously to allow the chemical reaction to progress efficiently.
Biohydrogen can be produced by a number of bacteria using enzyme systems designed to work in anaerobic environments. The ability of mixed bacterial species to operate together allows the degradation of a variety organic waste materials into hydrogen. This chemical reaction also produces a number of organic acids. These could be a significant by-product of this process, if able to be extracted.
Enteric bacteria such as Escherichia coli and Enterobacter aerogenes are also capable of bio- hydrogen fermentation processes. Unlike the Clostridium, these enteric bacteria produce hydrogen by the by the cleavage of formic acid (a one Carbon acid). Formic acid cleavage is an irreversible reaction hence hydrogen production by this method is not sensitive to the build-up of partial pressure of hydrogen produced.
The advantage of using facultative anaerobes like E. coli in hydrogen production is that these germs can be grown quickly in high oxygen environment and then used to produce hydrogen at a high rate when the oxygen is removed. These germs are tolerant of anaerobic environments, hence the term facultative and anaerobe.
Kinkajou : Sounds Easy!
Erasmus :There are other important considerations in using bacteria as organic fermentative factories. Enteric bacteria and Clostridium have an optimum operational temperature of around 30°C, as do many common microorganisms and environment. This means that to prevent contamination from other organisms affecting the fermentation reaction, the substrate feedstock for the chemical reaction needs to be sterilised.
Alternate bacteria which function better at high temperatures such as 70°C , restricting the growth of common contaminative micro-organisms may be more useful. Examples are bacteria such as Hyperthermophilic archaea such as Thermotoga neapolitana .
Similarly fermentation reactions produce organic chemicals which are often toxic to the bacteria synthesizing them. High concentrations can affect the efficiency of the fermentation process, and can trigger adaptive mechanisms in the bacteria such as sporulation to allow them to survive hostile environments. To stop this occurring, organic fermentative by-products need to be removed from the substrate media. Common methods include, for example, photo fermentation methods.
Biohydrogen can also be produced by light dependent reactions in either aerobic or anaerobic environments depending on the biological agent used. For example:
Chlamydomonas reinherdtii or Chlamydomonas moewusii , (both being species of green algae), if deprived of sulphur in their culture medium will switch from oxygen based photosynthesis to an enzyme mediated (hydrogenase) reaction. Cyanobacteria are commonly considered for hydrogen production by oxygenic photosynthesis.
Purple non-sulphur (PNS) bacteria such as bacteria of the genus Rhodobacter have also been considered as being useful for the production of hydrogen by an oxygenic photosynthesis and photo fermentation. Rhodobacter sphaeroides has been shown to produce hydrogen while feeding on organic acids, consuming to 98% of the organic acids in the substrate during the photo fermentative process.
Photo fermentative bacteria can use light between 400 to 1000 nm in wavelength which covers visible and infrared spectra. Algae and cyanobacteria in contrast use light in the 400 to 700 nm wavelengths which span the visible light spectrum. This suggests some ability to tailor environmental factors in controlling chemical reactions.
Shading and proper light distribution becomes a significant problem in photo fermentative production of bio hydrogen. Use of LED lighting with energy being generated from renewable sources may represent an acceptable method of altering the outputs of photo fermentative processes.
Erasmus :There is significant potential for improving hydrogen yield from a number of these organisms through metabolic genetic engineering. Alterations of the hydrogenase or nitrogenase enzyme systems are obvious targets. Alterations in pigment expression another obvious target, in that they shield the photo fermentative micro-organisms from controlling effects derived from input light.
The combination of dark and photo fermentation systems has been considered as a method of altering the efficiency of hydrogen organic acid production .For the production of bio hydrogen by fermentation processes, waste by-products of the fermentation process need to be minimized. Combined fermentation techniques allow the reuse of otherwise waste chemicals and organic by-products through photosynthetic fermentation processes.
The high concentrations of excess nitrogenous compounds and ammonia in the waste materials tends to inhibit the nitrogenase enzyme systems of wild-type photo fermentative bacteria, resulting in a reduction hydrogen production. While the presence of such nitrogenous compounds is a problem for chemical reactions synthesizing hydrogen, it is a potential advantage for agricultural applications via the production of nitrogenous fertilizers.
Erasmus :A few final and novel ways of generating hydrogen need to be mentioned. The use of photocatalysts using solar energy to generate hydrogen directly from water is generating some interest. There has been some work done on bio-hydrogen generation using a novel enzyme pathway and carbohydrate feedstocks. The key technology involves cell-free synthetic enzymes .
The reaction is: C6H10O5 + 7 H2O → 12 H2 + 6 CO2
Some work has been done using enzyme driven processes to convert xylose to hydrogen using a range of enzymes especially polyphosphatexylulokinase.
Finally besides dark fermentation, electro-hydrogenesis which utilizes microbes for electrolysis is another proposed pathway . It has been proposed to use microbial “fuel cells “to generate hydrogen from waste water from other industrial processes. In microbial fuel cells, a range of reactions generate the hydrogen. In biological hydrogen production as with for example algae, chemical processes within the algae generate the hydrogen instantly.
Hydrogen in Nature
Kinkajou : Does nature Produce hydrogen naturally ?
Erasmus :There are other alternatives for the generation of hydrogen. For example water will spontaneously dissociate around 2 ½ thousand degrees Celsius. The problem of course is that at these temperatures metal containment vessels and metal pipes melt.
Kinkajou : Perhaps in the long run if we solve the problem of containment vessels for nuclear fusion reactions, we can use the same containment technology the generation of hydrogen gas from water at high temperature. Currently our containment technology runs along the lines of utilising electrostatic forces to hold charged atoms within the containment field. However, if we are able to generate gravity this gives a totally new containment technique, complimentary to utilising electrostatic forces and probably well-suited to the thermal splitting of water into hydrogen and oxygen.
Erasmus :An outstanding insight!
Kinkajou : Again if we use catalysts to reduce the activation energy for these processes, it becomes obvious that lower temperatures may be able to be used to generate hydrogen from water. This forms the basis of chemical processes based on: sulphur and Iodine chemical cycles OR copper chlorine chemical cycles .
Kinkajou : So what have you learned Goo?
Goo :I think the generation of hydrogen is a worthwhile goal for the human race. But I think it will be a long road before we utilise hydrogen to its full potential.
A serious long-term problem human race faces is the non-sustainability of its fuel and substrate feed stocks, which are currently derived from the mining of petrochemicals. Humans need to change how they think about energy. In the long-term, commercial necessity will drive innovation.
Humans have a lot to learn about the operation of fuel cells utilising hydrogen. There are issues with catalyzing anode and cathode reactions, and storing generated gas. Much research will be needed to understand how altering molecular structures of metal composites can alter the ability of molecular metal composite in catalyzing chemical reactions.
The frontier of biology perhaps provides the most enticing solutions. Enzyme-catalysed reactions for the production of hydrogen, for the for the generation of organic intermediates, for the production of hydrogenated storage molecules such as hydrocarbons, and for the performance of other molecular tasks such as recycling, all beckon .
Strangely nature has provided many of the solutions in the frontier of biology already. Humans really need to be able to engineer combinations of solutions for a particular molecular process rather than to actually engineer each step of a new process. If DNA is doing it already, humans just need to recycle those bits of DNA and to combine them in sequences that humans control and that enable their biological nano factories to do the tasks humans require of them.
Unfortunately humans do not have the tools, knowledge or the wisdom at this point in time, to work with DNA in control sequences and in protein engineering.
I can see a few problems that we haven’t even talked about. Generally to succeed we must plan to succeed. The structure of our governments is such that patent law is may not allow us to undertake the long-term learning process that is required to enable us to work with DNA. If you cannot generate a return every step of the way, there is nothing to drive the process of innovation forward. Governments are short-sighted. Patent laws are complex and short-term and I’m sure you’re rapidly reaching the point where they restrict long-term planning innovation.
Dr Xxxxx :Yes! One needs only to look at the collapse of the pharmaceutical industry due to short timeframes allowed by patents to recover investment, very high research development and marketing costs, and the propensity of governments as customers in avoiding payment for research and development.
Yes you can save a lot of money in how you pay for new molecules. But if there’s not a lot of money, there won’t be a lot of new molecules.
Dr AXxxxx : Yes! Can you trust these people in government or in industry to reach for our future? Can they understand how their actions impact on the progress of the human race?