BIOMAN 2011 WORKSHOP MiraCosta College Presenter: Elmar Schmid, Ph.D. “Biofuels Production & Analysis” Session #2 – Algae Cultivation

Microalgae Hold great promise for future biofuels and nutriceuticals production. Microscopically small photosynthesizing life forms. Average cell size around 5-10 μm. Divide very rapidly under suitable growth conditions. Doubling times of algae can be on the order of 8 to 36 hours. Have with 2-4% a much higher photosynthesis efficiency than agricultural plants.

Light Reaction Dark Reaction Algae Photosynthesis Oils Other value products

 Sunlight is emitted radiation or electromagnetic energy.  Electromagnetic energy is transported in rhythmic waves each with characteristic wavelength (λ), frequence (ν) and amplitude (A).  Light travels at a constant speed (c) of 300,000 km/s. The “nature” of light A

 Full range of electromagnetic wavelengths.  Wavelength of visible light reaches from 380nm (or close UV) to 750nm (or near infra-red spectrum).  Green algae only use blue and red part of spectrum. Electromagnetic spectrum

 Fresh water in equilibrium with the atmosphere (0.038 vol% CO 2 ) at 15 o C contains about 14 μM dissolved CO 2.  The K M values for known Rubisco enzymes are in the range between μM.  Photosynthesis rate (and biomass production) increases in response to an increase in CO 2 concentration. From: Light & Photosynthesis in Aquatic Ecosystems: John T.O. Kirk; 2. Ed., Cambridge University Press, 1994; with modifications 184 W/m W/m W/m W/m 2 Dissolved CO 2 in H 2 O at PST Rubisco, CO 2 Concentration & Algae cultivation

 High light intensities reduce the photosynthetic rate and biomass productivity of algae.  Critical value of light intensity is between μE/m 2 /s.  Mechanism is not known, but build up of (UV) light induced oxygen radicals and other chemically reactive intermediates may destroy key components of algae photosystems. Light Intensity ( μE/m 2 /s ) Light compensation point Maximum specific photosynthesis rate Photoinhibition Photooxidation

 Each light wave has a clearly defined amount of energy transported and delivered in small energy parcels, called quanta or photons.  The Planck equation allows calculation of the energy of a photon (or light quant). E = Ћ x ν = Ћ x c/λ Ћ = Planck’s constant = x J s (or x W s 2 ). Light & Energy calculations  The energy delivered by one mol of photons is calculated by multiplying the Planck equation with the Avogadro constant N A (6.023 x ). (2) E mol = N A x һ x c/λ  The unit for equation (2) is called one Einstein or 1 E.  E.g. 1 mol of blue light with a wavelength of 438 nm has an energy of: 2.72 x 10 5 Ws = 272 kWs = 272 kJ

 Solar irradiance is a radiometry term for the power per unit area of electromagnetic radiation at a surface (e.g. algae photobioreactor).  Irradiance due to solar radiation is also called insolation.  Solar irradiance is usually given in Watts per square meter (W/m 2 ) or in micro-Einsteins per square meter per second (μE/m 2 /s).  Values for solar irradiance depends on the latitude and the season and varies between 1,500 μE/m 2 /s (330 W/m 2 ) during winter and 6,000 μE/m 2 /s (1,320 W/m 2 ) during the hot summer months. Solar irradiance & Algae cultivation

Influence of latitude on the annual mean solar irradiance intercepted Graphic©E.Schmid-2010 San Diego MCC PBR (W/m 2 )

Hypertrophic water shed with algal bloom In the 1960s, some lakes in the U.S. and Europe had phosphate levels exceeding 0.6 mg/liter Uncontrolled algae growth in nature

Controlled algae growth in closed photobioreactor Taken from the website of Bioprodukte-Prof. Steinberg GmbH, Germany (

MiraCosta Bubble Column Photobioreactor

Educational bubble column photobioreactor work station Photo©E.Schmid-2010

Important parameter in algae cultivation ParameterUnit Optical density (OD)- Cell countcells/ml Biomass productiong dry/l Biomass productivityg dry/l/d Oil content % (w/w) Oil productivitymg oil/l/d Photosynthesis rateµmol O 2 /mg Chl/h Aeration rateml (ccm) air/min Solar irradianceµE/m 2 /s or W/m 2

Cell counting method Compound microscope Prepare hemocytometer Observe algae at TM 400x Count cells in 4-16 micro-squares Calculate cell density (in cells/ml) Cell density = cell count x DF x 10 4 DF = Dilution factor 0.1 mm 3 (ul)

Mean doubling time “g” Growth constant “k” Mean doubling time “g” = 1/k Cell count at time t 1 : N(t 1 ) Cell count at time t 2 : N(t 2 ) N(t) = N 0 x e k x t N(t) Time tt1t1 t2t2 g = x t / log N(t 2 ) – log N(t 1 ) Microalgae growth curve