Biomass as an energy source – that’s a phrase which everyone reading this post has read at least once in a life. For those who hasn’t, we can imagine biomass as everything living, doesn’t matter if it’s a cow or algae under the sea. By using it as an energy source we mean the various ways of conversion, some we’ve known throughout the centuries (like burning wood) some are more advanced and sophisticated. And that’s the topic of this post, well not entirely, because more than on the means (which I will also mention) I’m focusing on the product. The product is BIOHYDROGEN.
Biohydrogen as the name suggests is hydrogen gas made by renewable means which are mostly fermentation processes. There are also thermochemical ways of generating hydrogen but they are more energy demanding and we’re focusing on using waste as a feedstock. Waste, either domestic, industrial or wastewater from water treatment plants is considered a second generation biomass resource. The definition of second generation biofuels is following: ‘The resource base for the production of second-generation biofuel are non-edible lignocellulosic biomass resources (such as leaves, stem and husk) which do not compete with food resources.’ [1] The other principle to turn biomass into H2 is based on biochemical processes. There are two main ways, which are only differentiated by the type of bacteria and by conditions they need to do their ‘work’. Those two are called dark fermentation and photofermentation[2]. Like the names suggest those two processes need either sunlight or darkness. In both of those the bacteria consume various complicated carbohydrates and turns them into alcohols, acetone and small amounts of H2 and CO2 [3].
The dark fermentation is mainly anaerobic (conditions where no oxygen is present) process. The advantage of this process is as you think that it doesn’t rely on sunlight so it can work in day or night. The restrictions of this process are that the bacteria is highly dependent on the acidity of its surroundings and also on the fact that hydrogen pressure can’t build up too much as it lowers additional production [3].
If the dark fermentation bacteria are night owls then photofermentation bacteria are early birds, because only sunlight gives them energy to get up and work (quite literally!). Other then that they need some organic acids, some water and voilà there is H2 (also with some CO2 we can’t escape that really). The efficiency is better the with dark fermentation but there are a few drawbacks. The bacteria need a pre-treatment because the waste waters may contain toxic compounds also the need organic acids for them to work which can be a difficulty which we’re facing when utilizing this process [3]
Now when we’ve described main biochemical means of biohydrogen production there is an important question: Why all this? Can biohydrogen save us all from global warming, can it solve all our energy demand issues? Well, probably not. What hydrogen can offer that other fuels don’t and why should we care? It is undoubtedly a good question. For the most part it has highest energy density of any fuel! And when burned or used in fuel cells it only produces water vapour and no CO2 like other fuels [3]. Also the worldwide demand for hydrogen was 73,9 Mt worldwide and about three quarters of it were made from natural gas and only small fraction of it was made renewable way according to IEA [4]. The vital step to ensure sustainability is to move away from the utilization of fossil fuels even in this field and getting rid of our waste in doing so offer all the benefits. The main drawbacks are still it’s costs which can’t compete with generation of hydrogen the unsustainable way. If we look away from hydrogen that is currently mostly used in industry there are concepts of whole hydrogen ecosystem where the hydrogen is proposed to be used as energy carrier for electricity storage, because as we know the problem with renewable energy is mostly that we can’t efficiently store electrical energy for longer periods of time. Until long term storage technologies are developed our economies will still have to rely on fossil fuels and hydrogen could be the one that changes the path we’re currently on.
References:
[1] KAMAL, Talha Akbar. Resource Base for Second-Generation Biofuels [online]. 14.2.2020 [cit. 2020-09-15]. Available from: https://www.bioenergyconsult.com/second-generation-biofuels/
[2] Biohydrogen. Etip Bioenergy [online]. [cit. 2020-09-15]. Available from: https://www.etipbioenergy.eu/value-chains/products-end-use/products/biohydrogen
[3] NIKOLAIDIS, Pavlos a Andreas POULLIKKAS. A comparative overview
of hydrogen production processes. Renewable and Sustainable Energy Reviews
[online]. 2017, 67, 597-611 [cit. 2019-02-01]. DOI: 10.1016/j.rser.2016.09.044.
ISSN 13640321. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1364032116305366
[4] The Future of Hydrogen [online]. 7.2019n. l. [cit. 2020-09-15]. Available from: https://www.iea.org/reports/the-future-of-hydrogen
The Environmentalization 
Hello Radomír,
Interesting blog post on a subject that I’m not that familiar with (luckily I found this, seems to been posted in the wrong category. Maybe on one if the moderators can put it in the right category). Good that you mention two different procedures to produce biohydrogen and the differences between these two. Really good for someone who haven’t heard much about the subject before, like me, to hear about the benefits along with the draw backs.
Good job!
Sincerely,
Markus
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Thank you! I tried to fix the confusion with messed up categories. It should be alright by now:-)
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Hi Radomir, interesting, new knowledge for me. Another way to create rocket fuel H2 is by electrolysis split water into hydrogen and oxygen, how about use the energy from a power plant that uses biomass as source. Will this be more effective and better for the enviroment?
BR Fredrik
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Hey Fredrik,
well that would be kind of problematic, using waste is kind of a go-to regarding these technologies because you basically get rid of it and at the same time you create other energy carrier that can then be utilized. Like killing two birds with one stone. With using something as a steam cycle it’s problematic because essentially you create ‘higher’ energy (electricity) through thermochemical conversion from woody biomass and then to create H2 it has to go through electrolysis that has efficiency of its own. If i put it in figures (just ca.) steam cycle has efficiency of 30% and electrolysis about 50%, 0.3*0.5 = 0,15, so the efficiency of this would be about 15%. If you had a kilo of wood with LHV of 18 MJ/kg, you would end up with 2.7 MJ of energy after the whole process. Maybe using other renewables (like solar and wind) would be wiser because the input (unlike wood) doesn’t really cost us anything. Hope I answered your question.
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Hej Radomír,
I just read your blog about biohydrogen and enjoyed it, because I already learned the basics of biochemical conversion during a lecture, but your described conversion methods of dark fermentation and photofermentation were new for me.
As you know, I have selected woody biomass in my blog which can also be converted to hydrogen by thermochemical conversion and therefore I also see a great potential in the production of hydrogen.
Thanks for your blog!
Best regards,
Nico
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Hi Radomìr, Thank you for your interesting article! I did not know that it was possible to produce hydrogen biologically, or at least on an industrial scale. What I knew though was that, along with the high energy consumptions, the use of hydrogen posed concerns in terms of safety, is it correct? Maybe it would be interesting to research weather this aspect can be influenced by this new technique.
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Well, it’s not completely true, hydrogen as a fuel is flammable as many other fuels, it’s true that it is flammable in a quite wide range of its oxygen-fuel mixture percentages but it also has very small and light molecule (have a look at a periodic table of elements;-)) and it usually just escapes into atmosphere and it doesn’t accumulate. See the picture (https://www.hytep.cz/images/stories/clanky/safety/bezpecnost.jpg)
Sorry for the quality (hydrogen car on the left on the right gasoline car)
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Hi Radomir,
It really is a problem that we must solve. The production costs of many alternatives to fossil fuels, Biohydrogen, biodiesel, biogas, etc., is the biggest drawback to curbing the consumption of fossil fuels.
However, I think that we have a great advantage and it is that sustainability has become a fundamental value for today’s society and that it will increase in future generations. If the majority want to change, the next step is the settlement of these renewable energies.
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Hej Radomir! Thanks for an interesting post! I wrote about biogas production from sewage waste so now I’m wondering what exactly the difference in the production of methane vs hydrogen are. Methane is produced under similar conditions so I wonder if hydrogen has such a high energy content why it is not more common to find. Especially for air pollution inside cities hydrogen would be a great solution!
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