How to Dry 100 pounds of Duckweed
Last month, I received a request for a pound of dried duckweed by a biofuel company to be used in ethanol production tests. I figured that as duckweed is 94% water, I’d need close to 100 pounds of wet biomass. I drove up to my favorite pond in Illinois and harvested five 5 gallon bucketfuls. Once home, I unrolled a 30 x 30 ft piece of plastic on the front lawn and started spreading duckweed out.
“You look like you’re drying pot or something,” my teenage son observed as he watched me patiently thin out the clumps in order to insure even drying. I sat back and surveyed the dripping, green mass. Hmmm…. you don’t see a sight like this on someone’s front lawn every day. Good thing we are in the country!
It took nearly a week to dry it all, due to clouds, a couple of rain showers and cool weather. When rains came, I would roll the plastic and duckweed up like a cigar and stowed it under my camper. The half-dried duckweed would start heating up (decomposition) so I only did this twice and then only long enough for the rain to pass by.
After six days, it was dry and brittle. I ended up with a garbage bag full and it weighed seven pounds. I picked out small twigs, tree seeds and leaves out of a pound of it. Then I rubbed handfuls through a colander to insure a uniform consistency. The resulting dried duckweed was dark green and smelled like hay. Very nice. Now to get the results of the ethanol experiment!