Pond Scum as a Renewable Energy Source

Rob Gardner, Assistant Professor

We’ve all felt it and seen it, the slimy green film on the edge of the lake or in the swimming pool that hasn’t been cleaned recently.  Kids like to dip a stick into it, swirl it around, and pull tendrils out of the water while scrunching their noses and saying “yuck”.  It smells, it grows when unwanted, and it can be a pain to clean up; but we overlook a very important property of the “green slime”.  Just like crop plants, it uses sunlight as an energy source and fixes atmospheric carbon dioxide to make more biomass.  However, unlike crop plants, each individual cell is its own “plant” and they are capable of producing a wide variety of chemical compounds.  It all depends on what the environmental conditions are where the algae grows.

Algae growth in a hot spring

Algae growing in a natural hot spring mixing with an alpine stream in Yellowstone National Park. This conditions provides a unique environment for algae to naturally evolve apart from other algae not growing in the stream mixing zone.

Algae are often thought of as little tiny microscopic plants that thrive in sunny wet conditions.  Some sunny wet conditions are sunnier than others, or have a higher temperature, or have other chemical present due to human impacts or natural conditions.  These environmental differences influence where and how the algae grows. So as the algae grows over time, hundreds or thousands of years, they start to adapt their metabolism to better survive in those unique environments.  The ones growing in sunnier conditions figure out how to produce antioxidant pigments to protect themselves from heavy loads of ultraviolet light.  Those growing in lower temperature adapt shorter or less saturated fatty acids so their membranes are more fluid (flexible) in colder conditions.  What we are just now figuring out, is that we can use algae that have these unique capabilities to produce specialty chemicals, biofuels, and feed, so that we don’t have to use fossil fuel resources to produce them.

Here in the Gardner Research Group at West Central Research and Outreach Center and housed at the USDA North Central Soil Conservation Research Laboratory, we isolate and investigate algae that has naturally adapted to produce unique metabolites in an effort to renewably and sustainably offset fossil fuel based production of these chemicals.  One of our primary goals is to enhance biofuel and biodiesel production, using algae as a feedstock, but we also look into high-value specialty chemical production.  We think of algae as a future agricultural crop, a way to produce biodiesel for a farm tractor.  Sometimes crops must be rotated for sustainable production.  As such, the algal crops will need to be rotated, from biodiesel production to a higher-value crop, every so often to offset the costs of biodiesel production.  Therefore, our research group strives to provide timely information and practices for these new progressive crops.