Addressing widespread obscurantism. Algal ponds qualify as a crop.  As such, the key metric is their biomass yield, in grams of Dry Weight biomass produced per input mole of photosynthetically active photons or g_DW/E.  Yet, over seven decades of research has focused on strain selection and optimization to achieve high growth rate under excess light in the laboratory setting. As a result, pond annual yields remain poor. My 2011 publications do address this misconception (in a more subtle way) but did not get any traction.

As if botanists were selecting corn strains based on fast growth from seedling to 5-in, then transferred that corn strain in the field and got surprised that the yield was unpredictable. As we know when we shop for an automobile, speed and efficiency are distinct parameters, and yet that fact has escaped most researchers in the algae field.

Algal biomass potential. Photosynthetic algae have the potential to achieve very high biomass productivity, on the order of 65 g_DW/m²/day (yearly average) or 96 tons/acre/year (16-fold higher than corn), assuming a solar irradiance of 5.3 kWh/ m²/day, a 70% efficiency, and unialgal non-filamentous species. These values correspond to a biomass yield of 1.7 g_DW/E, with a theoretical maximum of 2.49 g_DW/E. Current yields are on the order of 5-18 g_DW/m²/day.

Why is my approach so different? My mindset is deeply rooted in my (bio)Chemical Engineering training, which afforded the versatility to gather elements in distinct fields. But the key was that my roommate in Manchester in 2008 was Beena Nandha, a PhD student in Botany at the time. Beena helped me understand that algae are also plants, and plants are most efficient when they are… dark-adapted! If a sound effect could punctuate this statement, it would be “tan tan taaaan”!

Algal cultures triality. Building upon the wave-particle duality of photons, algae behavior can be fully understood (and optimized) if three fundamental distinct properties are taken together. Algae are: 1) a population, whose density affords self shading according to Beer’s law (or close enough).  2) individual photosynthetic cells, which perform best under low photon flux per cell. 3) fluid particles that follow the laws of fluid dynamics.

Resulting strategy and implication. Since photons are particles eaten by algae like fish eat pellets, sufficient photon dilution across the population can be achieved at high density (see articles below) provided the appropriate flow pattern. Imagine a very dense crowd of actors running around on the stage taking turn in the spotlight to share “time under the spotlight” equally, since the actors in the front shade the actors in the back.

Under such regime, algal growth is linear. Namely, P = Φ^DW · I₀, which states that the biomass production is proportional to the amount of fully absorbed incident light.  In this case, simple nutrient mass balances apply.

Algae-yield

Tutorials coming soon. After a painful year optimizing trace metal formulation, I am now able to routinely achieve linear growth (up to 3 g/L so far) under low light to determine the yield Φ^DW in g_DW/E. Painful because I operated blindly unable to quantify metal uptake, and painful because I had to get prosthetics in both thumbs. Both issues are now resolved, and I will welcome you soon in “the basement” to go over the techniques and data analysis.

Publications.

Holland AD, Dragavon JM and DC Sigee. Methods for Estimating Intrinsic Autotrophic Biomass Yield and Productivity in Algae: Emphasis on Experimental Methods for Strain Selection. Biotechnology Journal. 2011 6:572-583. https://doi.org/10.1002/biot.201000260

Holland AD and D Wheeler. Methods for Estimating Intrinsic Autotrophic Biomass Yield and Productivity in Algae: Modeling Spectrum and Mixing-Rate Dependence. Biotechnology Journal. 2011 6:584-599. https://doi.org/10.1002/biot.201000261

Holland AD., Dragavon JM. (2014) Algal Reactor Design Based on Comprehensive Modeling of Light and Mixing. In: Bajpai R., Prokop A., Zappi M. (eds) Algal Biorefineries. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-7494-0_2 Please note my mistake page 31: it should be “0.102 mol C/mol photons”.