Hydrogen Economy Now 10

CO2 + 2H2 is worth a try

Mohideen Ibramsha

1968 Alumni of Thiagarajar College of Engineering, Madurai, TN, India

1974 intellectual son of PhD guide Prof. V.Rajaraman & Mrs. Dharma Rajaramn, CS, EE, IIT, Kanpur, UP, India

1991 First HOD of CSE, CEC [now BSAU] Chennai, TN, India

Associate Professor (Retd), Computer Science, Framingham, MA, USA

Consultant R&D, M A M College of Engineering, Trichy, TN, India

Advisor, HyDIGIT Pte Ltd, Singapore

Email: ibramsha7@yahoo.com

Introduction: Electrochaea has a biocatalyst. The company has used Hydrogen to satisfy the equation CO2 + 4H2 → CH4 + 2H2O and has produced CH4 and discarded the excess water along with any microbe that grew during the reaction. Here we hope to persuade Electrochaea to at least run its bioreactor with Hydrogen to satisfy the equation CO2 + 2H2 → CH4 + O2 and if there is approximately equal amount of CH4 produced as when supplying Hydrogen to satisfy the CO2 + 4H2 → CH4 + 2H2O.

Place of evolution of microbe: We find that the microbes in the flooded paddy fields use the H2 produced by the decay of the straw of the last crop that was plowed back to consume the CO2 dissolved in the water and produce Methane. In a paddy field it is possible that H2 evolves from the buried straw continuously. Thus the microbes have more than required H2 at their disposal.

There are two processes to generate Hydrogen from CH4.

Partial oxidation: CH4 + 0.5 O2 → CO + 2H2 [1]

High temperature steam reforming equation

CH4 + H2O → CO + 3H2 [2]

The high temperature reaction is followed by the water shift reaction

CO + H2O → CO2 + H2 [3]

The steam methane reformation combines equations [2] and [3] and produces

CH4 + 2H2O → CO2 + 4H2 [4]

It is probable that the microbes follow the reverse of equation [4].

CO2 + 4H2 → CH4 + 2H2O [5]

The LHS of equation [4] has energy equal to 16 x 50 = 800 MJ per mol. The RHS of equation [4] has energy equal to 8 x 120 = 960 MJ for the eight mols of Hydrogen. Accepting these values as correct violates the Second Law(?) of Thermodynamics. We supply the ‘heat of reaction’ equal to 29% of the energy content of CH4 which works out to 232 MJ. Once we add the supplied ‘heat of reaction,’ the energy supplied becomes 1,032 MJ while the energy produced is just 960 MJ satisfying the Second Law(?) of Thermodynamics.

The LHS of equation [5] has 960 MJ of energy while the RHS has just 800 MJ of energy satisfying the Second Law(?) of Thermodynamics.

A number research articles on the Methane production by the CO2 consuming microbes use equation [5] and supply 80% H2 and 20% CO2 by volume in their experiments. In case the microbes had evolved in the digestive tracts and the flooded paddy fields, using equation [5] for the Methane production by the microbes might be justified.

Microbes evolved in oceans: We find the following in the literature.

https://www.nature.com/articles/s41598-017-01752-x

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Methanogenic archaea (methanogens) are ubiquitously present in anaerobic environments, such as digestive tracts, paddy fields, and aquatic sediments, and play an important role in anaerobic degradation of organic matter and the global cycle of carbon

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From the above quote, the microbes could have evolved in the ocean sediments, flooded paddy fields, or in the digestive tracts. However oceans are in existence for many many periods compared to the flooded paddy fields and the introduction the microbes to the digestive tracts through food. Thus we are compelled to agree that the microbes did not evolve in the flooded paddy fields or in the digestive tracts but reached them after evolution.

Assuming that the CO2 consuming microbes evolved in the aquatic sediments, would they produce Methane by

CO2 + 2H2 → CH4 + O2 [6]

Or by equation [5]?

We have already seen that equation [5] satisfies the Second Law(?) of Thermodynamics. What about equation [6]? The LHS of equation [6] has 480 MJ of energy while the RHS has 800 MJ of energy. It seems the microbes violate the Second Law(?) of Thermodynamics. Should nature, the microbes, obey the Second Law(?) of Thermodynamics?

In an aquatic sediment the water is available in plenty. Water dissolves CO2. Even the H2 released by the hydrocarbons in the sediment also dissolves in water. The excess Hydrogen, if any that is not dissolved in water could bubble up to the air above the water surface. Once the Hydrogen enters the atmosphere it continues to rise and eventually leave the atmosphere of earth. We should remember that in contrast to a flooded paddy field in which the straws that produce Hydrogen are replenished at least once an year, in ocean sediments the organic matter producing Hydrogen might not be replenished at all below the sediments in which the microbes live.

We find that at 20 C, 0.0016 g of H2 is dissolved in 1 Kg of water, while about 1.7 g of CO2 is dissolved in 1 Kg of water at the same temperature from https://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html .

One mol of H2 weighs 1 Kg whereas one mol of CO2 is 44 Kg. Thus the solubility of Hydrogen is 0.0016/1000 mol in 1 Kg of water. The solubility of CO2 is 1.7/44000 mol in 1 Kg of water. The solubility of Hydrogen is (0.0016/1000) / (17/44000) = 0.004141 = 0.4141% of the solubility of CO2 in water.

Do we then agree that evolution made the microbe take 8 atoms of Hydrogen and use 4 of them to produce CH4 and return 4 of them as water to make the availability of Hydrogen lower than what it was? Or do we say the microbe ejects two atoms of Oxygen after creating CH4 with just 4 atoms of Hydrogen? What happens to the two atoms of Oxygen?

Let us assume that the Oxygen atoms released by the microbe are negatively charged. If there are no other atom with more affinity to the electron, the electrons might be absorbed by the microbe leaving the two Oxygen atoms to join and form one molecule of the gas as O2. Is it not possible then that the single gaseous molecule of O2 bubbles up? When Oxygen bubbles up the bubbling causes more water to reach the environs of the microbe. The new water has dissolved Hydrogen and dissolved CO2 so that the microbe could eat the CO2 and grow.

If on the other hand when the microbe follows CO2 + 4H2 producing CH4 + 2H2O, the water gets further diluted and the availability of both dissolved CO2 and dissolved Hydrogen gets reduced. This makes further growth difficult.

Are we wrong to say that CO2 + 2H2 producing CH4 + O2 is better for the microbe than CO2 + 4H2 giving CH4 + 2H2O?

We think evolution favors CO2 + 2H2.

Is Electrochaea wasting Hydrogen?: Electrochaea bubbles 4H2 for CO2 possibly following the published literature in which it is very easy to find articles using the equation CO2 + 4H2 on the LHS.

What about the experiments performed when CO2 + 4H2 are bubbled through the water with the microbe? Why did we not get 2H2 + O2 as gases out of the reactor? Would 2H2 + 2O(-) result in the two negatively charged Oxygen atoms join together or they would drift away from each other as same charges repel? Would it be possible that H2 + O(-) react becoming H2O releasing the negative charge to be absorbed by the microbe? At this point in time, we don’t know, but it is more probable than two negatively charged Oxygen atoms joining to make one molecule of O2 ignoring the available gaseous Hydrogen.

Hydrogen limited Methane production: Let us consider a two decades old research paper that does describe experiments with Hydrogen less than the amount required by CO2 + 4H2 → CH4 + 2H2O.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.848.5160&rep=rep1&type=pdf

This August 19, 1997 paper dealing with Methanobacterium thermoautotrophicum ⃤H reports results of experiments conducted with different combinations of CO2, H2, and N2. The CO2 concentration was kept constant at 20%, while the H2 was varied with 5%, 10%, 20%, 40%, and 80% the remaining taken up by N2.

Quoting from the paper we have:

Methane-forming activity of whole cells. Inside the glove box, 2.5-ml portions of resuspended cells (OD578 5 1) were pipetted into a series of 55-ml serum bottles that were subsequently closed with black butyl rubber stoppers and aluminum crimp seals. Reaction mixtures in duplicate were pressured to 250 kPa with a gas mixture that contained 20% CO2, various concentrations of hydrogen (80, 40, 20, 10, or 5%, [vol/vol]), and additional nitrogen gas. After the gassing step, the serum flasks were placed in a water bath at 60°C. As soon as methane production started, the flasks were transferred to a shake incubator (250 rpm) at 60°C, and the (linear) rates of methane formation were monitored for approximately 1 h. Preliminary experiments showed that under the experimental conditions the rates of methane formation were not limited by hydrogen mass transfer. Methane was determined with ethane as an internal standard; 100-ml amounts of the headspace were analyzed on a Pye Unicam GCD-chromograph equipped with a Porapack Q 100-200 mesh column.

There were 11 growth conditions applied in the chemostats. The parameters of the growth conditions are listed in Table 1. For 6 growth conditions the Hydrogen-dependent Methane production by resting cells operated under different H2-CO2 gassing regimes were reported in Figure 2. The figure was exported to the ‘Paint’ program and the pixel coordinates were measured using the ‘pencil.’

The coordinates for origin corresponding to zero Methane production rate and zero percentage Hydrogen were found to be (94,528). The coordinates of 80% H2 concentration were (509, 528). The coordinates for the Methane production rate of 1.5 micro mol per minute per milligram dry weight of the microbe were (94,6). The

coordinates for the 80% H2 concentration for the environment MCR I corresponding to its Methane production rate were (509,64).

The number of pixels for 1.5 micro mol per minute per milligram dry weight of microbe is 528 - 6 = 522. One vertical pixel corresponds to 1.5/522 = 3/(522 x 2) = 3/1044 = 1/348 micro mol per minute per milligram dry weight of microbe. The vertical pixels for MCR I for 80% H2 are 528 - 64 = 464. The Methane production rate for 80% H2 is 464/348 = 1.333 micro mol per minute per milligram dry weight of microbe. The Methane production rate for all other conditions of Figure 2 are calculated likewise and reported in the table below.

No Environment 5% H2 10% H2 20% H2 40% H2 80% H2 41 to 80 in %

1 MCR II 0.147 0.227 0.279 0.3678 0.3736 1.5769

2 II 0.218 0.282 0.399 0.4282 0.4310 0.6539

3 I 0.261 0.302 0.399 0.4511 0.4569 1.2857

4 IV 0.580 0.592 0.621 0.6695 0.6724 0.4332

5 MCR I 0.612 0.914 1.115 1,3218 1.3333 0.8700

6 III 0.690 0.856 1.210 1.2586 1.2730 1.1441

When we use 80% H2 with 20% CO2, we spend 100% more H2 compared to 40% H2 with 20% CO2. However from the above table we find that the increase in the CH4 yield is a meagre 1.5769% or less.

From a commercial point of view, wasting 40% H2 to have a gain of 1.5769% or less gain in CH4 would at the minimum reduce the profit if not lead to loss. Hence we suggest using 40% H2 with 20% CO2 and 40% N2 as experimented earlier. The output from the bioreactor would have N2, CH4, and residual CO2 and residual H2. The gases could be separated and the N2, CO2, and H2 recovered could be recycled in the bioreactor.

The reason for the miniscule increase in the production of CH4 when the gas input is changed from 20% CO2, 40% H2, and 40% N2 to 20% CO2 and 80% H2 is possibly for

future research. We hypothesize that the crowding near the ports of the microbe through which CO2 and H2 enter the microbe might be a cause. Instead of aggravating the crowding by the use of 40% N2, we might try using CO2 and H2 only increasing their percentages to reach 100% for the total.

Instead of 20% CO2, 5% H2, and 75% N2, we might try 80% CO2 and 20% H2. In the table above, we find that under environment III the Methane production is 0.69 micro mol per minute per gram dry weight of the microbe. In case we get a Methane production rate of 2.76 micro mol per minute per gram dry weight of the microbe or an amount close by, we could use the 80% CO2 and 20% H2 and recycle the unused CO2 and H2. From the above table we see that the maximum rate of Methane production of 1.2586 micro mol per minute per gram dry weight of the microbe achieved under environment III with 20% CO2, 40% H2 and 40% N2 is less than 50% of the expected rate of 2.76 micro mol per minute per gram dry weight of the microbe.

Conclusion: When excess H2 is supplied along with CO2, we hypothesize that the negatively charged Oxygen atoms that are ejected by the microbe combine with the available Hydrogen gas and produce H2O molecules. If the bioreactor is operated under Hydrogen limited conditions, it is possible that even though some of the ejected negatively charged atoms combine with the gaseous Hydrogen, more CH4 would be produced than now. By capturing the gas leaving the bioreactor, Electrochaea could separate the produced CH4 and recycle the residual CO2 and H2.

Here is a Patent Application of interest filed with the US Patent Office. Patent Application 20100233775 was filed on September 16, 2010. The application has 155 claims when accessed on September 9, 2018. We quote some of the claims here.

1. A system for using methanogenic archea for the creation of useful products comprising: a culture of methanogenic archea for converting an input material into an output material; a reactor vessel for housing at least a portion of the culture of methanogenic archea; an input material stream, said input material stream being directed into said reactor vessel to facilitate contact between said input material stream and said methanogenic archea; and an output material stream created at least in part by the culture of methanogenic archea.

2. The system of claim 1, wherein said reactor vessel further comprises: an input material stream port for operationally coupling said reactor vessel to a source of said input material stream; and an output material stream port for facilitating removal of said output material stream.

3. The system of claim 1, wherein said reactor vessel further comprises an agitation system, said agitation system being at least partially positioned within said reactor vessel, said agitation system enhancing contact between said input material stream and said culture of methanogenic archea.

4. The system of claim 1, wherein said reactor vessel further comprises a recirculation system, said recirculation system enhancing contact between said input material stream and said culture of methanogenic archea.

5. The system of claim 1, wherein said reactor vessel further comprises a pH adjustment system, said pH adjustment system facilitating the maintenance of a pH of the methanogenic archea combined with a mixture of said input material stream and said output material stream.

6. The system of claim 2, further comprising a condenser environmentally coupled to said output material stream port, said condenser allowing a gaseous portion of said output material stream to be separated from a non-gaseous portion of said output material stream.

7. The system of claim 1, further comprising an input material stream flow control whereby the flow of the input material stream into said reactor vessel may be controlled.

8. The System of claim 1, further comprising an atmospheric pressure adjustment system, said atmospheric pressure adjustment system facilitating the control and maintenance of atmospheric pressure within said reactor vessel.

9. The system of claim 1, further comprising an oxidation reduction potential

adjustment system, said oxidation reduction potential adjustment system facilitating the maintenance of an oxidation reduction potential of the methanogenic archea combined with a mixture of said input material stream and said output material stream.

10. The system of claim 1, further comprising: said input material stream comprises approximately 2 parts hydrogen to one part carbon dioxide; said input material stream is routed into said reactor vessel at a rate of 0.5 to 4.0 scfm per 5 cubic feet of reactor vessel volume; wherein approximately 5 to 15% of the carbon dioxide is converted to biomass through contact with the culture of methanogenic archea; said output material stream is generated at a rate of between 10 and 150 VVD; and wherein said output material stream comprises approximately 50 to 85% CH4.

We hope our suggestions to Electrochaea are not impacted by the above patent application. We believe Electrochaea would be exempt from these claims as it uses a patented microbe. If necessary, Electrochaea could enter into agreement with the innovators of this patent application in view of the immense benefit that awaits them if they implement CO2 + 2H2 → CH4 + O2.

The preceding post is at

https://mohideenibramsha7.wixsite.com/website/single-post/2018/08/24/Hydrogen-Economy-Now-9

The earlier posts in this series are:

https://mohideenibramsha7.wixsite.com/website/single-post/2018/07/25/Hydrogen-Economy-Now-1
https://mohideenibramsha7.wixsite.com/website/single-post/2018/08/02/Hydrogen-Economy-2
https://mohideenibramsha7.wixsite.com/website/single-post/2018/08/06/Hydrogen-Economy-Now-3
https://mohideenibramsha7.wixsite.com/website/single-post/2018/08/07/Hydrogen-Economy-Now-4
https://mohideenibramsha7.wixsite.com/website/single-post/2018/08/07/Hydrogen-Economy-Now-5
https://mohideenibramsha7.wixsite.com/website/single-post/2018/08/08/Hydrogen-Economy-Now-6
https://mohideenibramsha7.wixsite.com/website/single-post/2018/08/09/Hydrogen-Economy-Now-7
https://mohideenibramsha7.wixsite.com/website/single-post/2018/08/09/Hydrogen-Economy-Now-8