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The Nitty-gritty on Duckweed

February 28, 2016

Yes, yes, I know… Over the past three years, my blog about duckweed has drifted to everything from duckweed to decks to wood-fired ovens to skinny-dipping in hot tubs. As there are now nearly 200 posts, it is getting hard for folks to find duckweed info they need. .Am going to fix that here shortly with a new page on the site. Just give me a couple weeks..

I am  traveling abroad quite a bit these days, currently starting duckweed pilot projects  in four new countries. . I’d always dreamed of doing this sort of thing and what do you know- wishes do come true.

Playing catch up with you all on the nitty-gritty of duckweed production and applications:

  1. Duckweed has value as an animal feed for just about any animal you can think of.  Peacocks like it. So do rabbits. Haven’t tried it on monkeys yet though.
  2. If you come to me with a bioenergy project with duckweed, I will run, screaming in the other direction. Only exception is waste water to duckweed and then it had better be in country where energy prices are through the roof. Do I sound a bit frustrated here?
  3. Expect to be disappointed if you try to use off-the-shelf fertilizer on duckweed. It will not work unless you tweak the heck out of it.. Start with mimicking duckweed’s former natural habitat- water, mud, a dilute waste nutrient contribution (a bit of manure, etc…) a bit of shade,  wind protection, etc…Which leads me to #4
  4. Consider that you are culturing an eco-system, not a mono crop. It’ll make your life easier.Even duckweed needs beneficial relationships with bacteria, etc…
  5. Duckweed’s primary limiting factor is nitrogen. Shoot for 20ppm ammonium if you have a tester. Build up duckweed’s tolerances and if all other nutrients are there and your pH is around 7 or lower,  you can ramp up to 60ppm. ammonia/ammonium. Just watch out though. You’ll have more duckweed than you know what to do with. What can get you there? Manure from cows, hogs, goats, or sheep will do it but don’t overdo it. Biomethane effluent works well but with ALL forms of fertilizer- test the heck out of it first in graduated amounts and see what works best.

 

3 Comments leave one →
  1. WILLIAM FLACK permalink
    May 21, 2016 2:09 am

    REALLY HAVE ENJOYED FINDING AND READING YOUR POSTS THIS PAST YEAR! I AM EXPAT IN THAILAND WITH POND I WISH TO USE FOR GROWING LEMNA MINOR.
    DO YOU KNOW A LEMNA SOURCE IN THAILAND WE CAN ACCESS FOR STARTING OUR POND? YOUR COMMITMENT AND ENERGY ARE SINCERELY APPRECIATED!.THANK YOU!

    Like

  2. Ell permalink
    April 10, 2016 5:53 pm

    You keep mentioning how fast duckweed grows. Do you have a measured growth rate (at a certain temperature, pH, etc.)?

    Like

    • April 11, 2016 10:28 am

      Hi Ell, 85 degree air temps over a period of time will get you water temps that are close to optimal. pH of 6.5-7.0 is ideal. Nutrient loads are another story, based on your local and water types. A good rule of thumb is to monitor a wild pond of duckweed in your area and mimic good growth patterns with similar water quality and nutrient loads. Depending on your climate, duckweed can produce upwards of 40 plus dry tons of biomass per year. Low end would be 5-10 tons on a seasonal basis, IE Minnesota or Michigan.

      Like

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