Duckweed – it's the future.
Common Duckweed – Lemna Minor – could be used to solve several problems on the camp. Under the right conditions, its multiplication rate is phenomenal – doubling its mass every few days. The plant has a high protien content, and can be used to feed fish and chickens. And it can also be used as a feedstock for the production of biogas through anaerobic digestion – with excellent fertiliser as a byproduct.
Have a read of this publication (online ebooklet): DUCKWEED: A tiny aquatic plant with enormous potential for agriculture and environment
Especially in combination with a ‘manure’ filtration system.
Too bad we can’t digest it ourselves…
People in some countrries are reputed to eat duckweed but there is some debate about its safety because of its oxalate levels. But then quite a lot of foods have oxalates in them, and our bodies seem to cope OK – as long as we don’t eat too much 😉
When I can find the time, I want to try out a few alternative ways to grow Lemna Minor – maybe in terraced troughs, and under glass or plastic cloches.
Most years there is a “duckweed problem” on British canals and so growing it in summer, in northern Europe, is not an issue. However, during winter, duckweed sinks to the bottom of the canal – and lies dormant until the following year. If duckweed is to be used as a feedstock for (say) anaerobic digesters – then an easy way needs to be found to keep it growing through the cold seasons.
My name is Donald and I am Dutch.
I think the Universe is trying to tell me something 🙂
Would also be interested in trying an indoor hydro-culture set-up….
to be continued!
Which reminds me: Leaf for Life
and especially (in their library) the “Field Manual for Small Leaf Concentrate Programs”
Most any leaf can be a valueable food source…
Of course the alternative to growing duckweed over winter (or indoors), is to somehow preserve summer-harvested weed for use in the colder seasons.
There are a number of conventional methods used for preserving vegetable matter which could be adapted for use with duckweed. For instance it could be dried and pressed into “duckweed cake”. Alternatively, it could be fermented like grass silage, or maybe even fermented and stored in barrels like sauerkraut.
A useful skill to have anyway for any excess crop!
I’m tracking down some duckweed for my first experiments.
Urban Homestead ‘Food production’ is my primary objective anyway, with upcycled plastics as my main tool(s).
Duckweed is also known in the Netherlands as ‘Waterlinzen’ (water lentil) and even has its own EU-sponsored website http://abc-kroos.nl (dutch only I’m afraid) which also includes a cookbook(!)
Still no luck finding the plant itself though…
The site works (sort of) through Google Translate. 😉
I noticed the other day that there are people on ebay selling small packets of live duckweed – as “culture starters” for tropical fish tanks.
I’ve not found any wild Lemna Minor near where I live (yet). The duckweed floating in the nearby canal is a larger-leafed variety.
2 batches on their way, one from France, one from UK.
Will take great care in studying their way of packaging. If they arrive ‘alive’ and multiply, I should have enough to share (against postage) for anybody interested.
Probably just you @frogfall , but hey, come the zombie apocalypse they will be begging for it!
First Batch of Duckweed arrived yesterday (from France) and seems to be doing just fine. The ‘big leaves’ are not duckweed, but I got them as a bonus (not sure yet what the are yet). I now use them to mark the original batch.
Also started a second batch with just a small amount of Duckweed on tapwater with kelp extract as feed.
Also did a quick tasting, and it tastes just fine.
I think the ‘funny taste’ some people mention is simply dependent on what you feed the plants.
Once I have enough Duckweed, I’ll try pressing and moulding Duckweed cookies et al.
I guess there is always a danger of the water going stagnant – which might affect the taste.
Actually, that could also be a possible source of food poisoning – if the wrong bacteria were to take hold. But as you are used to sprouting seeds, then you are probably already aware of the possible risks. 😉
As in any Hydro culture oxygenate, flow, feed, refresh.
And if it smells fishy, but ain’t a fish (and even then), don’t eat it!
Never hurts to state the obvious, especially on a public forum, so thanks for the addition!
How is the duckweed coming along? Is it surviving OK in a domestic environment? What kind of growth rate (if any) are you getting?
Well, ‘if any’ (growth) is the best result for the first part of the experiment.
Put them in water, add food (kelp), leave them (mostly) alone.
No wonderous growth. Duckweed even started to die off after 20 days.
I am now switching to less passive setups with more active oxygenation of which a spraying/rain setup seems to work best. Kind of makes sense…
They’re slow experiments, in which I’m looking for the minimum requirements for a stable system (including the removal of half the Duckweed every 14 days).
Not sure if it’s going to be interesting as a ‘main’ crop for indoor growing, but I’m sure it can be used as a side-crop in an hydro setup.
If it indeed gets approved as fit for human food consumption, I might even be able to get some large scale testing going…
Found this page with some hints and tips for growing duckweed. They are using it to feed fish – not humans – so levels of hygene might be a bit lacking.
– Duckweed prefers slow moving water however, you will notice fastest growth with areas of agitation. Slight agitation, such as where an outlet flows, seems to increase the asexual reproductive process. The duckweed divide quicker.
– Grow in several places. You will find the best micro-climate for production this way. Also, if one spot fails, you have several others producing.
– Do not grow in the same area as you are raising your fish. They’ll eat your crop.
– Surface Area! The more you have the more you will get. Duckweed needs only a few inches of water, but takes as much space to spread as possible.
– Duckweed grows faster in warmer weather. If you want faster yields, make sure your water temperature is over 70°F.
– If your duckweed is turning white, something is wrong. The duckweed is dying.-
Don’t forget nutrients! Duckweed needs more than water and sunlight to grow. We use the tilapia waste water to grow our duckweed, but you can use other nutrients. Compost teas or organic hydroponic nutrients also do well.
– Not all duckweeds are equal. We have experimented with several different species of lemna and have found that lemna minor is our favorite duckweed for production.
– Duckweed has the smallest flower in the world, but we have never seen it. Don’t worry about pollination as means of reproduction. The plant grows and divides asexually, much like a single-celled organism does. Don’t worry about finding tiny bees.
– Duckweed can grow thick! When production is highest, duckweed can grow several inches thick. We have had our pond area full before and it looked like a lawn.
– Don’t forget to add oxygen. If you place duckweed in a pool without aeration the water will eventually go anaerobic. Without oxygen, nothing will grow.
– If you grow in an aquarium you may grow more algae than duckweed. Duckweed naturally limits the growth of algae because duckweed floats and gets the light before the algae. In aquariums this does not happen.
-Slight agitation, such as where an outlet flows.
Confirms the ‘rain’ theory, but also make oxygenation easier
-sure your water temperature is over 70°F.
This one I was indeed wondering about, also could make it possible to use my sprouting water as feed (it heats up, especially when sprouting beans).
-duckweed can grow several inches thick.
Okay, maybe a ‘main’ crop after all. Just surface weed is hardly enough to sprikle a cookie. Several inches? *uck-yeah! (* that’s a D 😉 )
If duckweed is to be used on a large scale, as a biofuel feedstock – then we do need to imagine what that would look like. One problem with current biofuel options is that people expect the crops to be grown “somewhere else” – so to not make any changes to their local scenery. But most of the good land situated “elsewhere” is already being used to grow food – and so biofuel crops simply displace food crops.
For biofuel crops, we need to use “marginal land” – such as hills and mountains. What would that look like? I’m guessing that for growing duckweed, terracing might just work – a bit like the way some rice paddy fields are arranged.
I think it would be a good start to start harvesting it where it grows naturally, instead of trying to eradicate it as a weed.
Or to start using it as a cover on dirty water (like human waste water (which it also filters)).
In my ongoing experiment I found it’s quick to cover any surface area, but does not really grow any thicker from there.
It should form a layer of at least 1 inch to be useful as a crop (one harvest after 10 weeks was not much more than a spoonfull (see picture). In the same time I harvested at least bucket of sprouts from a similar surface area.
Duckweed seems to like heat and ‘rain’ (oxygenating the water by spraying, adding an aquarium pump had little or no effect).
The comming weeks I’m going to be ‘overfeeding’ it, to see if this is a factor. I think it does, as in nature it also seems to like ‘dirty’ water.
And to answer the obvious question: Yes I did eat it (after heating), and yes, it tastes kind of like spinach (after only being fed tapwater and kelp/seaweed-extract).
I can see that any duckweed grown for food is going to need “clean” conditions, but the stuff grown for biofuels should also be good for wastewater remediation.
Many sewage treatment plants are currently building biodigester facilities to generate gas and make electricity. Another stage of water cleanup from duckweed might also help to provide extra feedstock for co-digestion – possibly enhancing the methane yield. The methane yield from pure sewage is not actually that good (although they process such a lot of crap that it is still worthwhile doing). Hence, at some plants they are also taking waste food to add to the digesters.
Unfortunately, some facilities seem to be using non-waste food, such as maize, for co-digestion – just because it is locally cheap.
Interesting paper posted on ResearchGate.
BTW, I thoroughly recommend having an account on ResearchGate. Researchers regularly post copies of their own papers – so people can read them without having to go through university library accounts. That means that private researchers, who don’t have “institutional access”, are not excluded from obtaining the information they need.
In order to grow duckweed, you need a lot of light and nutrients. Its easy to grow if you provide these things. For an edible crop, feed it good nutrients that are safe on food crops. Never feed raw manures or human waste.
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