Hydrogen is considered as the ‘energy for future’ since it is a clean energy source with high energy content as compared to hydrocarbon fuels. Hydrogen produced through green technology is referred to as biohydrogen; a fuel produced biologically, most commonly by bacteria. Biohydrogen is a potential biofuel obtainable from waste materials. Production of clean energy and utilization of waste materials make biological production of hydrogen a novel and promising approach to meet the increasing energy needs as a substitute for fossil fuels.
The demand for energy across the world has been increasing exponentially, the fossil fuel reserves have been decreasing, and the combustion of fossil fuels has serious negative effects on the environment due to carbon (IV) oxide [CO2] emissions. For these reasons, many researchers have been working on the exploration of new sustainable sources that could substitute fossil fuels. Hydrogen is considered as a viable alternative fuel and ‘energy carrier’ of future. Hydrogen gas is a clean fuel with no CO2 emissions and can be used in fuel cells to generate electricity. Also, hydrogen has a high yield of 122KJ/g which is 2.75 times greater than hydrocarbon fuels.
Hydrogen is a valuable gas and it is being increasingly demanded worldwide in recent years due to its uses;
as a clean source of energy;
as feedstock in the food industry for hydrogenation of fats and oils;
as feedstock in the chemical production industry;
as feedstock for the production of electronic devices;
as feedstock for steel processing; and
as feedstock in refineries for the desulfurization and re-formulation of gasoline.
It has been reported that 50 million tonnes of hydrogen are traded annually worldwide with a growth rate of nearly 10% per year. Based on the National Hydrogen program of the United States, the contribution of hydrogen to total energy market will be 8-10% by 2025. It was also reported by the US Department of Energy (US-DOE) that hydrogen power and transport systems will be available in all regions of the United States by 2040. I propose African nations should adopt this environment-conscious approach in their sustainability policy making.
Unlike fossil fuels, the major problem facing utilisation of hydrogen gas as a fuel is its non-existence in nature. Due to increasing need of hydrogen energy, development of cost-effective and efficient hydrogen production technologies has gained significant attention in recent years. The conventional and chemical hydrogen gas production methods including electrolysis of water, steam reforming of hydrocarbons and auto-thermal processes; all energy intensive and expensive. Biological hydrogen gas production is a viable alternative to the aforementioned processes. In accordance with sustainable development and waste minimisation issues, biohydrogen gas production from renewable sources, also known as “green technology” has received considerable attention in recent times.
If hydrogen by fermentation is to be introduced, the fermentation process will be dependent on organic acids (acetic acid, butyric acid and propionic acid) as substrates for photo-fermentation. These organic acids can be derived from any organic material source such as sewage wastewaters or agricultural wastes. The major criteria for the selection of waste materials to be used in bio-hydrogen production are the availability, cost, carbohydrate content and biodegradability. Major waste materials which can be used for hydrogen gas production include nitrogen deficient starch and cellulose containing agricultural or food industry wastes such as carbohydrate rich industrial wastewaters or effluent, waste sludge from wastewater treatment plants. Green technologies / bio-processes for hydrogen gas production include: bio-photolysis of water by algae, dark fermentation of organic materials, usually carbohydrates by bacteria (absence of light), photo-fermentation of organic waste materials by bacteria (in the presence of light). Another one is sequential dark and photo-fermentation process which is a rather new approach and has shown to be the most efficient method to produce hydrogen gas through fermentation because it allows the organic acids produced during dark fermentation of organic wastes to be used as substrate in the photo-fermentation process, thereby economically minimising the by-products of the fermentation process.
The two bacteria that have been identified for hydrogen production by fermentation are: Clostridium which is used in the dark fermentation; and Rhodobacter which is used in the photo-fermentation. The bacteria Clostridium could be improved for hydrogen production in the dark fermentation stage through metabolic engineering by disabling the oxygen uptake system. The photo-fermentation step with Rhodobacter is likely to gain the most from metabolic engineering. An option could be to disable the photosynthetic membrane system II (PS-II) or to decrease the expression of pigments which shields off the photo-system.
The low yields and rates of hydrogen formation by green technologies may be overcome by selecting and using more effective micro organisms or mixed cultures, developing more efficient processing schemes, optimizing the environmental conditions, improving the light utilisation efficiency and developing more efficient photo-bioreactors. Considerable research and development studies are needed to improve the state-of-the-art in bio-hydrogen production.
About Akinwande Akinsiku:
Akinwande Akinsiku is a young innovative and visionary green spiralist who hails from Ondo State in Nigeria. He is a graduate of Micro-Biology from Ladoke Akintola University of Technology, Ogbomoso. He is passionate about improving the global impact of man on the environment and is striving towards becoming a very successful entrepreneur in the environmental industry. His twitter handle is @AAkinsiku and can be contacted via firstname.lastname@example.org.