Yeast Cultivation can also Produce Biodiesel from Renewable Waste Resources

The production of biodiesel from algae and microorganisms is a viable alternative to the usual methods of production which include crushed oilseeds and waste vegetable oil (WVO). Most people already know about the use of algae that is currently being developed for a number of different types of biofuels, another possible source of fatty acids for biodiesel that hasn't received much attention can be cultivated using microorganisms or yeast cells. Microorganisms or algae could be the favorable choice in biofuel production due to the theoretical high yield amount of biomass per acre as compared to conventional energy crops which usually include oilseeds such as soybeans. It is estimated that alternative biomass sources such as algae produce 30 times more energy value than these conventional crops. Several yeast cell varieties that have been experimented in with in the past can produce high fatty acids amounts per cell and along with high lipid yeilds. Three types of yeast varieties, those being Cryptococcus Curvatus, Lipomyces Starkeyi & Rhodotorula Glutinis can attain a cell lipid percentage of up to 60 - 70 % [ 1. X. Meng et al 2009 ]. An advantage with the cultivation of yeast cells for biofuels is that they can be grown using dark fermentation. Dark Fermentation is a term that usually applies mostly towards the production of biohydrogen from microrganisms. However, similar fermentation conditions and even carbon feedstocks work for the cultivation of yeasts even though they are not the same choice of microorganisms that usually make hydrogen. However, the same type renewable waste resources used for biohydrogen production can also be applied towards the cultivation of yeast cells towards lipid production. These type of renewable waste sources include wastewater sources, dairy wastes, starch hydrosylates, lignocellulosic wastes and even biodiesel glycerine waste.

Yeast cells also have the advantage of attaining high biomass yields in a short period of time. The growth rate of yeast as well as the actual conversion rate of a carbon source into lipids are very good. For example, with batch style fermentation, yeasts attain cell density yields of around 100 - 150 grams cells per liter, while lipid production rates are around 0.2 - 0.5 grams lipid per liter * hour and a carbon conversion rate of up to 30 % [ 2. P. Measters et al 1996 ]. High lipid yields can be attained by providing an excess amount of carbon feedstock as well as providing a lower nitrogen content in the growth media. In other words having a high carbon to nitrogen (C/N ratio) - (a similar concept in producing a good compost) and other factors such as favorable Temperature, pH and oxygen content provide higher lipid yields [ 3. L. Azocar et al 2010 ]. Companies are already using yeasts to produce biofuels although not towards the manufacture of lipids. One company currently cultivates yeast cells to make isoprenes. Isoprenes represent a large class of natural compounds produced by many organisms, of which plants usually produce a large subset of these compounds called terpenoids. Isoprene, which is a related compound can also be produced by microorganisms. It is used to make materials like rubber. The cost of producing biofuels from microorganisms or algae have some obstacles to overcome, such as processing and refining methods, costs and associated technology improvement needs. Production of biofuels from algae, microorganisms or yeasts may still be a favorable method of choice due to the possible availability of renewable waste resources as carbon sources to produce lipids. The production of biodiesel itself has the potential to manufacture even more biodiesel from the cultivation of yeast cells from the glycerine waste that may accumulate in large quantities as more biodiesel is produced. For example, it is estimated that for every 10 kg of biodiesel produced from certain oilseeds around 1 kg of waste glycerine is made. It is also estimated that even at the current production rate, the pharmaceutical industry only needs 1/3 of the glycerine produced to help manufacture drugs.

REFERENCES

1. "Biodiesel Production from Oleaginous Microorganisms", Renewable Energy vol 34 pg 1-5 [2009] by Xin Meng, J. Yang, Xin Xu, L. Zhang, Q. Nic, M. Xien

2. "High Density Cultivation of the Lipid Accumulating Yeast Cryptococcus Curvatus using Glycerol as a Carbon Source", Applied Microbiology & Biotechnology vol 45 pgs 575-579 [1996] by PAEP Measters, GNM Huijbents

2. "Biotechnological Processes for Biodiesel Production Using Alternative Oils", Applied Microbiology & Biotechnology vol 88 No 3 pg 621-626 by L. Azocar, G. Ciudad, HJ Heipieper, R. Navia

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KEYWORDS: Cryptococcus Curvatus, Lipomyces Starkeyi, Dark Fermentation, Renewable Waste Resources, Biodiesel Glycerine, Isoprenes, High Production Biomass, Yeast based Biodiesel, High Lipid Percentage per cell, Rhodotorula Glutinis, Starch & Whey Hydrosylates

Photos taken from the Web Album of Picasa

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Collection & Processing Businesses for Animal Fats, Cooking Oil and Trapped Grease are good for the Biodiesel Industry

The use of animal fats should be competitive with plant sources of oils used to produce biodiesel. Animal fats such as lard and tallow are cheaper per pound than crushed oil from plant sources such as soybeans, cottonseed, canola and others [ 1. Ash 2010 USDA ]. Companies that are involved with both the collection and processing of used oils, greases and fats should become an industry in demand in the future. In my home state, Arizona, there are already several waste grease based biodiesel manufacturing companies that also offer collection services. This is the case for Grecycle (Tucson, AZ) and also AZ Biodiesel (Phoenix, AZ). Used Animal Fat collection is already becoming a large industry that is available for biodiesel production. The use of animal fats in biodiesel production has risen and should continue to increase in the near future. Currently, at least 10 percent of our biodiesel supply consists of animal fats, whereas in Canada it is nearly 90 percent. It is estimated that nearly 5.5 billion liters (>1 billion gallons) of biodiesel could be produced from used animal fats in the US [ 2. Goodfellow - SANIMAX ]. In fact, this may be a modest figure because poultry fat should account for a larger portion of used animal fats in the future. The figure above demonstrates that 80 percent of used fats and oils are mostly from greases or animal tallow (beef) versus lard or poultry fat [ 3. Goodfellow - SANIMAX ]. Poultry consumption has increased by three times the amount since the 1960's, whereas pork and beef consumption have been fairly steady in the several past decades. This has already brought great opportunities to larger companies involved with the poultry industry such as Tyson Foods.

It is estimated that Tyson Foods alone produces more than 2.3 billion pounds of chicken fat each year which is estimated to make at least 300 million gallons of biodiesel. A variety of companies are becoming diversified in the types of greases, fats and oils they collect and also are getting involved in the pre-processing (or direct processing) of these renewable resources. Companies such as Sanimax are involved with the collection of animal byproducts from meat rendering plants (ie beef) as well as spent cooking oil or trapped grease. The collection of trapped grease that may come from various sources is another needed service for the emerging biodiesel industry. Otherwise, trapped grease might otherwise be placed in landfills since it cannot be simply dumped into sewage systems. These collection companies also get involved with the pre-processing of waste fat, grease and oil sources by converting them into yellow grease, tallow or other processed animal fats. The collection and pre-processing of fats, grease or oil is a good business since the production of biodiesel from raw fats or used oil may also contain high amounts of what are called Free Fatty Acids (FFA). The higher amounts of Free Fatty Acids in animal fats or greases is what also sets them apart from plant based oils used in biodiesel production. If the FFA content is greater than 1 percent of the total mass of the used grease or fat, a minimum of one extra processing step is needed in order to convert it into usable biodiesel. In the future, animal fat collection / processing companies may also become involved with used animal wastewater. It has been known that used animal wastewater from meat rendering or dairy milk production can be converted into other usable chemicals through the use of fermenters.

REFERENCES

1. "Oil Crops Outlook 2010", USDA Economic Research Service Publication [2010], Ash M., Wittenberger K.,

2. "Biofuel Production from Animal Fats : A North American Perspective", Sanimax Energy (2008 or later), Goodfellow Jeremy

3. Same as Reference 2

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