The production of biohydrogen can take place with a number of different types of microorganisms, whether they be algae or bacteria. Biohydrogen production can be phototrophic or hetereotrophic, meaning one can produce hydrogen using sunlight or instead use dark fermentation, which is hetereotrophic cultivation. The method of dark fermentation for hydrogen production using microbes can use a wide variety of carbon based feedstocks, therefore much research has already been done with food processing, lignocellulosic, manure or food wastes for hydrogen production. There are a large number of industries where these types of wastes are generated. The wastes from the above mentioned sources are also considered renewable resources. Renewable wastes used for hydrogen production can come from such food processing sources such as the potato, sugar, wheat, soybean, olive and dairy industries [ 1. Ozgur et al 2010 ]. The more effective types of waste sources include those which have high sugar or carbohydrate content which is typical of crops such as sugar beets, sweet sorghum, sugarcane, wheat and potatoes. Other useful sources for dark fermentation would include many of the same wastes that would be used for producing compost, this includes food, cellulosic and manure wastes. Fruit wastes such as cranberry or apple processing types can be utilized towards compost material or converted into useful health supplements or neutraceuticals. Compost and biohydrogen would share similar waste resources due to the high carbon to nitrogen (C to N) ratio, this would include mostly carbohydrate and lipid sources. Food wastes are a great source for compost and biohydrogen but could also be used to make chemicals like lactic acid or also used to produce bioenergy [ 2. Chong et al 2009 ]. Sources such biodiesel glycerine waste are also legitimate sources that could be used for biohydrogen. Again, like other renewable waste resources, biodiesel glycerine should find a large number of uses, for fermentation purposes alone. Another area where renewable waste is utilized frequently is animal feed. The same crop or food processing wastes could be used for either animal feed or biohydrogen production, similar to the previous comparison above with compost. For example, potato processing makes food stuffs such as french fries and potato chips but also leaves a lot of waste material in the form of peels and pulp which can be used as animal feed. It can be ensilaged and processed like corn stover to make the animal food. However, as also mentioned above, potato processing waste is high in carbohydrates which makes it a prefferable fermentation source for biohydrogen.
In addition, many types of food processing wastes generate two types of fermentable feedstocks which are solid based types such as pulps, but just as importantly they generate processing effluent or wastewater. Wastewater from food processing has a good amount of carbon based chemicals such as the case with dairy wastewater. It is generated from the processing and cleaning of dairy facilities and contains waste products such as milk, lactose, fat and proteins. Dairy wastewater, like other sources are also an environmental concern and are often treated in areas such as lagoons or ponds. An excess of suspended solids can create pollution problems in fresh water bodies where chemical conditions are changed such as Biological Oxygen Demand (BOD). Companies often specialize in treatment equipment or technologies to process wastewater effluent before it reaches fresh water bodies. Adding a process such as biohydrogen production may also be another method for wastewater treatment from industry. Organic based wastewater can be generated from processing plants such as palm oil, apple, sugar and tofu. Cellulosic waste from crop residues such as sweet sorghum and corn stover is another likely candidate for hydrogen dark fermentation but could also be used to make further biofuels such as continued ethanol production. It may also be possible to reuse wood based product waste for hydrogen fermentation. Studies have been done using bioreactor sytems with a variety of the above waste feedstock sources to determine which types produce a higher volume of hydrogen production [ 3. Gao et al ]. Of most sources it was found that cheese whey waste and swine manure produced a larger amount of hydrogen per bioreactor system. It was also determined that cattle based manure produced more hydrogen than dairy manure. In summary, biohydrogen can be made from a large array of renewable waste resources. However, many of these waste resources are already implemented to make compost, animal feed, further biofuels, bioenergy and further chemicals from fermentation. For example, sugar beet waste can be used to make pharmaceutical products, livestock feed or ethanol production. Sugarbeet wastewater also already has uses such as irrigation. In other industries such as dairy, there are multiple sources of fermentation renewables in the form of manure, wastewater and whey. Wastewater effluent from industries that contain organics are a logical area for biohydrogen since they serve the dual purpose of remediation and energy production. Overall economics, practical implementation and policy decisions may determine the production of biohydrogen from renewable waste resources.
REFERENCES
1. "Potential Use of Thermophilic Dark Fermentation Effluents in Photofermentative Hydrogen Production by Rhodobacter Capsulatus", Journal of Cleaner Production Vol 18 No 1 pgs S23-S28 [2010] by E. Ozgur, N. Afsar, T. Vrije, M. Yucal, P. Clausen, I. Eroglu
2. "Biohydrogen Production from Biomass and Industrial Wastes by Dark Fermentation", International Journal of Hydrogen Vol 34 pg 3277-3287 [2009] by M. Chong, V. Sabaratnam, Y. Shirai, M.A. Hassan
3. "Hydrogen Production from Agricultural Waste by Dark Fermentation", International Journal of Hydrogen Energy Vol 35 Issue 19 SI pgs 10660-10673 [2010] by X. Gao, E. Trably, E. Latrille, H. Carrere. J.P. Streyer
Photos taken from Picasa Web Album and NASA photo archive
KEYWORDS: Hydrogen Generation from Renewable Wastes, Crop Residues, Cellulosic and Lignocellulosic Wastes, Dairy and Cattle Manure, Dark Fermentation, Biohydrogen Production, Food Processing Waste, Dairy Wastewater, Biodiesel Waste Glycerine, Cheese Whey, Carbohydrate Based Food Processing Wastes, Sugar Beets, Potato Processing Waste, Sweet Sorghum, Tofu, Fruit & Citrus Wastes
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