Black Or Yellow, There’s Gold In That Thar Wastewater

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The Intertubes have been humming with the news that a modern-day gold rush could be about to descend upon your friendly neighborhood wastewater treatment plant, but we’re thinking it’s not necessarily going to be all about those little yellow nuggets. A research team at Rice University has just come out with a new study showing that oil-rich algae can thrive on municipal wastewater, which means that biodiesel or “black gold” could also be in the works.

Keystone, schmeystone!

algae biofuel wastewater

Tapping Wastewater For Energy

We fangirl over wastewater treatment plants because you could recover renewable biogas from wastewater as well as renewable hydrogen. As massive pieces of infrastructure, they also make good sites for harvesting hydrokinetic energy, solar energy, and wind energy.

This is the first wind we’ve gotten about algae biofuel potential, though.

Ironically enough, the new Rice algae biofuel study took place deep in the heart of oil country, at a municipal wastewater treatment plant in a suburb of Houston, Texas.

As you can see from the photo above, the team set up a dozen 600-gallon tanks at the site and pumped them full of wastewater that had already undergone part of the treatment process, to remove suspended solids.

They used three different kinds of algae including blue-green algae or cyanobacteria, which as the name suggests is actually a form of bacteria, not a plant.

The results were pretty promising. You can get all the details from the journal Algae under the header “Low algal diversity systems are a promising method for biodiesel production in wastewater fed open reactors.”

For those of you on the go, the bottom line is that in the best conditions (using a single strain of algae rather than mixing the three), more than 80% of lipids were converted to FAME, which is short for fatty acid methyl ester, which is fancyspeak for biodiesel.

To ice the cake, FAME is more closely related to fossil diesel than other biofuels made from land plants.

Algae Biofuel To The Rescue!

Municipal wastewater treatment plants are gigantic, energy-sucking pieces of public infrastructure, and given the global strain on water resources, there will need to be more and better treatment plants.

That all adds up to more energy and more expense, but piggybacking a treatment plant with algae biofuel — or for that matter, any of the above-mentioned renewable energy sources — could help offset some of those costs.

In that regard, the team also found that in addition to churning out FAME, the algae provided an energy-efficient form of wastewater treatment, removing 91% of nitrate-N and 53% of phosphorus.

Whither Algae Biofuel?

We took note when the US Navy started checking out algae biofuel a few years back, but we have to admit we haven’t been paying too much attention lately. According to the Rice team, apparently the algae oil industry’s interest has shifted to cosmetics, nutraceuticals, and other higher-value products.

However, in a report last September our friends over at the National Renewable Energy Laboratory made a case that the economics of algae biofuel are pretty solid (if you follow that link, see page 73 for the summary).

Our sister site specializing in alternative fuels,, also recently noted that while the corn ethanol craze has run its course, algae and other non-food sources still have market potential.

The Rice team also gets props for pointing out that growing algae on municipal wastewater could help to wean algae growers off their dependence on chemical fertilizers.

We’ll second that, with the added note that by growing their algae on wastewater, algae growers can cut down on their use of not-wastewater.

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Photo Credit (photo cropped): E. Siemann/Rice University.

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Tina Casey

Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

Tina Casey has 3141 posts and counting. See all posts by Tina Casey

5 thoughts on “Black Or Yellow, There’s Gold In That Thar Wastewater

  • So you pull out the suspended solids and run them through digestor to get methane and a cleaner solid.
    Then use the liquid (full of nitrogen) to feed the algae to make biodiesel.
    The first step is already in action in many places.
    This second step gets more benefit.
    Maybe one day waste water treatment will be a profit center.

  • This technology will probably become operational about the same time as most vehicles shift to all electric systems with newer long distance battery packs. Those biosolids are better utilized as a soil amendment and fertilizer. The algae could follow the same path if the diesel vehicles have become obsolete

    • Aviation will probably continue to use liquid hydrocarbons long after other uses have died.

  • Yes, we know that waste water contains nutrients but what is it doing to solve all the other issues with algae growth. This is a non-story.

Comments are closed.