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Drying Duckweed Efficiently

January 31, 2014

Today I posed this question to our ILA Round Table members during our biweekly meeting, “Since drying duckweed is what I consider the greatest hurdle to overcome in developing a duckweed industry, what are our options at this stage?”

Their answers included…

1. Align with a company with excess/waste heat

2. Solar drying

3. Geothermal- either low grade or high and heat pump

4. Hydrothermal     ”                       “

5. Partial drying to save on energy costs

6.Use other drier sources of mixtures as in animal feed components to moderate moisture content

7. Start a secondary facility that you can do cogen with your own waste heat

8. Hybrids of any and all of the above.

9. Use wet duckweed instead of dry and skip the entire issue. :)

Thanks Rolf, Louis, Mark, Ron, Loren, Susan, and Hamdi for your contributions on this subject.

5 Comments leave one →
  1. Sue permalink
    June 25, 2014 1:41 pm

    Solar tumble dryer? Or would that require too much energy/expense.

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  2. April 24, 2014 8:27 pm

    I came across your blog when searching for low tech small scale sustainability. Growing duckweed or harvesting it is decidedly easy but what about storage options for temperate climates when duckweed isn’t available. Other than indoor hydroponics which isn’t realistic for most people once freezing temperatures arrive the duckweed harvest is finished. Other than drying are there any reasonable storage options on a small scale. I contemplated using a weighted press or hydraulic press to form duckweed into a mold which would also press out much of the moisture and facilitate drying. These “molded bricks” of duckweed could then be placed on a rack for further drying which would also facilitate handling. I haven’t tried this but the concept is interesting. I don’t know if the duckweed would remain compressed of if there needs to be some type of matrix to hold it together. I could envision a small scale homesteader using a hydraulic woodsplitter or similar device to press duckweed into a mold for future storage. I look forward to your response. I also blog so I enjoyed reading your posts. Keep up the good work.

    coldturkeyleftovers.wordpress.com

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    • April 27, 2014 10:16 pm

      John, great post! Storage options for duckweed-pelletizing duckweed that has been dried down to 15% moisture, silage made up of duckweed, molasses, etc…, frozen duckweed for aquarium fish and turtles, and loose duckweed hay.
      Duckweed has a slightly waxy coating on its fronds which make it harder to dry than, let’s say, lettuce with the same water content.. Keeping a thin layer of duckweed while drying is important. Molded bricks would mean that there is less surface area to let water evaporate.
      Your website is fascinating. Glad to meet another Mother Earther!
      Tamra

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  3. February 17, 2014 3:05 pm

    Wayne,
    Am going to experiment with a similar system next month. I am first trying to use wet or near-wet duckweed in as many applications as I can before I resort to drying the meal. (fresh feed, fermentation, etc…) The warm air is the tough part as concentrated solar is the cheapest, but also the most limited for large quantities.I like your analogy of worm harvest. It’s all about using gravity and least cost energy inputs. :)

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  4. Wayne Martin permalink
    February 8, 2014 2:32 pm

    To harvest worms they use a screen tube that rotates on the access as the dirt (with worms) is slowly fed into the tube. The tube is at a slight slant so the worms eventually work their way to one end. The dirt ends up falling through the holes in the tube.
    What if you used a tube similar to that to dump the duck weed into. You would of course have to reduce the holes in the tube screening to keep the duck weed from falling out. As it tumbled in the tube it would be aerated. Warm air could be blown through the tube to help remove the moisture content.

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