Biodiesel algae: research suggests starvation diets damage health

By The University of Sheffield | March 11, 2013

It may be better to tolerate lower oil content in algae grown for biodiesel to boost growth and overall productivity, according to research from the University of Sheffield. The research shows that the commonly accepted method of depriving algae of key nutrients such as nitrogen in order to boost its oil content may be detrimental to overall oil yield in the long term.

“Total oil production depends not just on the oil content of the algal cells but how quickly the cells grow and multiply,” said Stephen Wilkinson of the University of Sheffield’s department of chemical and biological engineering. “We found you get more oil production overall if you give the algae all nutrients they need to grow fast rather than trying to increase the oil in each cell by limiting the availability of nitrogen.”

In a study funded by the Carbon Trust and U.S. consulting engineering firm MWH Global, Wilkinson, along with colleagues from the University of Manchester, examined a species of algae called Dunaliella salina at different cell densities grown at a range of temperatures to determine the rate of growth and lipid production. Some samples were deprived of nitrogen, while others were allowed to grow naturally. During the course of the four-week study, the overall yield from the nitrogen-starved crops was in fact lower than many of the crops that had been allowed to grow naturally.

Another key finding of the study was that productivity could also be increased by increasing cell density. The researchers used centrifugation to create more crowded algal cultures and were surprised to see that this these samples could still grow very well. “Large-scale production of algal biofuels will need big ponds taking up a lot of space,” said Wilkinson, “so anything we can do to squeeze more oil out of a smaller land area is very important.”

The study is published in the Journal of Chemical Technology and Biotechnology.





3 Responses

  1. NAA



    "Changes going on in the algae production industry" Raceway ponds were never meant to be used for industrial algae production. When the Department of Energy initiated the Aquatic Species Program years ago, there was no other choice. Raceway ponds were relatively inexpensive to build, land was plentiful, and raceway ponds could produce enough algae to conduct the research that was needed at that time. Two of the biggest problems that were encountered were contamination and low productivity. Many years later, those problem have still not been resolved, and many raceway pond algae growers, equipment providers and construction companies that built raceway ponds over the years have not only have confirmed these problems but have ended up building and patenting closed-loop algae growing systems. The vast majority have moved away from standard raceway ponds and into commercial PBR's and industrial growing systems that eliminate most of the contamination problems and can generate much larger volumes. The DOE's Aquatic Species Program has completely failed in any commercialization efforts. For years, they focused their research on algae raceway ponds and not on any of the more advanced growing, harvesting and extraction systems. The claim that it was less expensive to build ponds is valid, but, as they say, you get what you pay for, and the researchers were content with the limited quantities they were growing - it boosted their argument that more research was needed. The DoE never considered alternate algae growing systems - its researchers spent time and money investigating alternate energy sources, most of which require feedstock that deplete our food supply. NAA believes that no one at the Aquatic Species Program ever thought of algae as an industry. The National Algae Association is the first non-profit algae production trade association in the US. We have focused on identifying good algae technologies that work and can scale in a commercial environment as well as helping to lower costs of algae production equipment. The costs of materials for commercial closed-loop algae growing systems have come down substantially over the last 5 years. Many new algae companies are moving away from algae raceway ponds and are interested in closed-loop systems. Raceway ponds developed for research will never be used in a commercial environment. NAA has filled a gap that the DoE has not - focusing on lowering the CAPEX and increasing productivity.We have encouraged the creation of new designs through open and honest collaboration.We have been successful in negotiating better pricing of materials. Most importantly, we have been able to test turnkey commercial growing, harvesting and extraction systems at the NAA Test Center. Times are changing.Today, NAA sees a huge change in how algae will be produced going forward. Algae raceway ponds will never be used for industrial algae production. Even though we have had great success testing commercial closed-loop photobioreactors over the last 5 years, we believe the future will bring massive algae growing systems similar to the systems being tested at the Testing Center. Preliminary commercial production testing is very encouraging for addressing growth rates issues, energy inputs and eliminating contamination issues. NAA is very appreciative for all the commercial-scale equipment donations and materials it has received and continues to receive to help make the US a leader in commercial algae production.

  2. Sjjbk



    LiseI can say that here also in Quebec, suprisingly, we don't have very much snow and this moinnrg it was very nice outside. Of course not as warm as in Playa del Carmen but at least, there was no snow storm. Just hope it stays like that for the rest of the winter. I agree with Josee, Ben you are a bundle of knowledge.

  3. Keith E. Coooksey



    A patented process developed by scientists and engineers at Montana State University increases TAG accumualtion by green algae and diatoms 5-10 fold without using N- starvation. Cells are grown to the maximum possible in the medium when sodium bicarbonate is added. As cells are not starved their physiology is not compromized.Howver they don't grow, they just sit there and make TAG! To repond to the NAA response : The Aquatic Species program was very successful as ALL projects being worked upon today have their bases on work supported by DoE. For example, the Nile Red analytical system is used by nearly all labs monitoring TAG accumulation- research or production. The debate on ponds v bioreactors is still not dead as can be seen from the NAA posting. A long term comparison between Solazyme and Sapphire Energy's success (bioreactors v. ponds)will be very informative.


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