microalgae oil factories

Second paper published in Marine Drugs (got to love the name!)

The concept about renewable oil production from cultivation of microalgae is more than 50 years old. Algal oil has different qualities and can be used for biofuels, food and feed and as industrial raw material. However, since crude oil is still available and relatively cheap no industrial algae based production is yet in use.

Microalgae are microscopic aquatic plants. They convert sunlight, nutrients (nitrogen and phosphorus) and CO2 to biomass with high oil content. Industrial scale cultivation takes place outdoors and is therefore dependent on sunlight and temperature. At that time (2008), to find an outdoor microalgae facility we had to go abroad and found a collaboration partner in Portugal. They had an aquaculture facility growing algae mainly for feed to fish aquaculture (the climate in the south of Portugal is also very pleasant to work in).

Nann_NR4
Nannochloropsis oculata cells stained with Nile Red seen in an epifluorescence microscope. The yellow color shows the oil droplets inside the cell. Photo: M. Olofsson

Seasonal changes of light and temperature influence biomass production and, as we have shown previously, also the oil content and quality.

One way to boost the oil content in algal cells is to limit the nitrogen supply, but this may decrease the biomass.
So the question was: If we limit the nitrogen supply regularly will there be a net gain in oil production over the year?
In our new study we combined the nitrogen limitation effect with the seasonal effect at two different experiments (spring and autumn). Here we grew a model species, Nannochloropsis oculata (photo 1), at limited nitrogen supply in outdoor flat panel photobioreactors (photo 2) in the south of Portugal.

Our findings: The highest oil production at nitrogen limitation occurred in spring (double compared to control), despite the higher oil content in autumn. This was most likely due to more sunlight available for the algae in spring, resulting in higher biomass production. This in turn produced more oil in total. Other high quality oils (i.e. Omega-3 used for food and feed) can also be produced with both plenty or limited nitrogen supply, while proteins mainly are produced when nitrogen is limited.

To make industrial production of microalgal biomass economically and environmentally sustainable, we propose a 2-steps strategy where algae are grown with plenty of nutrients to reach a high biomass for production of Omega-3, and in the second step nitrogen stress is applied to boost oil production. This means a full commercial utilization of the whole range of products and byproducts (oil, proteins and sugars) with a wide variety of applications. Moreover, we need to use and recycle seawater/wastewater, nutrients, CO2, and to design cultivation systems operating at minimum energy consumption.

P1060233
Flat panel photoreactors in the south of Portugal growing Nannochloropsis aculata at Necton, Portugal. Photo: M. Olofsson

Discussions of this work started 2008, and getting scientists and business managers to plan together was an experience in “priority setting”. The opportunity to work at a “real” algal growing facility was inspiring and a great experience.

Experiments were hectic and exhausting (like always;-)). Centrifuging at full capacity at two different labs until late night, not to mention night sampling. Making tube racks in paper cardboard by the dozen as Falcon tubes for oil extraction were piling up. Or the chloroform fumes knocking you out when opening the oven in the lab. At first we were annoyed that Saturday and Sundays were closed for sampling but it gave us time off to do other things (well needed). Seafood was not bad either! I must give credit to Emmelie for her great work, resilience and patience during the time in Portugal. Sharing a house with a bunch of guys collecting motorbikes and bicycles including all the spare parts you can think of, barbeques and parties every other day and leaving the dishes for days. I will never forget the late night “fish war” as Emmelie noticed a sardine slowly gliding down the wall one morning …
Emmelie was staying for three weeks in a room smelling of petrol, never complained once…
To sum it up: I had a blast!! (Not sure I am speaking for Emmelie though…)

The period for data analyses and writing has been extensively long. Some people say that letting a written material “rest” for some time will in the end improve the quality of the work. Indeed it is true, but there are some limits to this as well!
• Do NOT let it “rest” for more than 3 months in a row!!
• Do NOT allow for more than 3 “resting” periods (6-7 is not to recommend!)!!
• Do NOT perform your work in more than 1 version of the same data analysis software (i.e. not 3 versions of Excel!)!
SAVE your figures and graphs as high quality images DIRECTLY after producing them!

But all of this you already knew of course…

Next paper about the effects of flue gas on algal production coming up…

Martin
/Martin

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