Fostering Duckweed

Introduction

Baggenstos/Rudolf (Heidy Baggenstos & Andreas Rudolf) are an Art-Collective and have worked with duckweed for several pieces of art.
On this webpage, we publish a summary of all the research underlying the art project and other things we have done, even if they have not directly fed into a piece.
Recognizing the fast growth of a plant in our aquarium triggered our interest. This plant was duckweed. Duckweed is very common and also a native plant in Switzerland. We thus started cultivating duckweed that we had found in ponds close to where we live and wondered what nutrients they might need and how we could provide them. It turned out that it is possible to produce the required nutrients ourselves in a Do It Yourself manner by using our own organic wastes.
Because duckweed is edible we started food experiments and processed the duckweed in a variety of manners.
More and more we got into a closed cycle between the plant and us and established a human-plant ecosystem.

Duckweed in Switzerland is listed on the red list of endangered species. Depending on the type of species, their degree of endangerment is different. In 2017, we started multiplying Lemna gibba, a species that is locally extinct in Switzerland.
What can we do with its taste? Does a species that is almost extinct taste differently from other duckweed species?

The great promises

Duckweed might be the food of the future?
Grown under ideal conditions, duckweed ranges between 25% and 45% protein and doubles its growth every 36 hours. Duckweed produces biomass faster than any other flowering plant. This tiny aquatic plant has tremendous potential for cleaning up pollution, combating global warming and feeding the world. (this is a very optimistic view I have to say)

Bioful: It has potential as an alternative for biofuel production. (Methanol und Ethanol)
Bioremediation: Living Machines for cleaning wastewater.
Biomining: of phosphorus and other minerals/nutrients from wastewater.
Bio-sensors: Duckweeds are used for the detection of heavy metals and organic contaminants.
Animal food: food for fish (tilapia), chickens, pigs and of course ducks! Duckweed integrates very nicely into aquaponics. It can provide all the protein needs for some breeds.
Human food: Depending on strain and growing conditions, duckweeds can have very high protein content of up to 50% of dry mass.
In Space: food production in bioregenerative life support systems in space.
--> source

Features of Duckweed

- Duckweed are the fastest growing higher plants in the world.
--> source: Enzyklopädie Essbare Wildpflanzen 2013 Steffen Guido Fleischhauer / Jürgen Guthmann / Roland Spiegelberger -- and -->here

- Duckweed belong to the smallest flowering plants in the world and spread primarily by vegetative growth. Daughter fronds bud from reproductive pockets on the side of a mature frond. An individual frond may produce as many as 10 generations of progeny over a period of 10 days to several weeks before dying. As the frond ages its fiber and mineral content increases, and it reproduces at a slower rate.

- In fall, they decay and completely disappear from the surface. Beforehand the plant produces small buds, sinking to the bottom and overwintering.
--> source: Swiss Plant Life / Ewald Weber 2009

- Die Wasserlinse existiert unter Wasser und steigt zur explosionsartigen Vermehrung an die Wasseroberfläche auf. Sie stellt damit ein Wesen der mystischen „Anderswelt“ dar, des Reiches der Ahnen und Geister.
- Eine Wasserfläche von 10m2 deckt den Proteinbedarf eines Menschen, selbst wenn der Umweg über Nutzvieh gewählt wird.
- Inhaltsstoffe: Calcium, Carotinoide, Flavonoide, Fette, Magnesium, Oxalate, Phosphor, Proteine mit allen essentiellen Aminosäuren, Schleimstoffe, Spurenelemente, Vitamine und Xanthophyll.
--> source: Wilde Genüsse / Margot Fischer 2014

- Compared with most plants, duckweed fronds have little fiber -- as little as 5 percent in cultured plants -- because they do not need structural tissue to support leaves or stems. As a result virtually all tissue is metabolically active and useful as a feed or food product.
--> source (see: Nutritional value)

- Duckweed protein has higher concentrations of the essential amino acids, lysine and methionine, than most plant proteins and more closely resembles animal protein in that respect. Figure 3 (page 5) compares the lysine and methionine concentrations of proteins from several sources with the FAO standard recommended for human nutrition.
The protein content of duckweed is compared with several animal feed ingredients in Figure 5 (page 7)

- Cultured duckweed also has high concentrations of trace minerals and pigments, particularly beta carotene and xanthophyll, that make duckweed meal an especially valuable supplement for poultry and other animal feeds. The total content of carotenoids in duckweed meal is 10 times higher than that in terrestrial plants;
--> source (see: Nutritional value)

Wasserlinsen haben biologische Eigenschaften, die sie für die Reinigung von Gewässern interessant machen und ist darum auch Gegenstand von Forschungsprojekten.
- Ihr Wachstum ist auch unter lichtschwachen bis fast lichtlosen Verhältnissen möglich.
- Sind mixotroph und können einen Teil ihre Energie aus organischen Stoffen gewinnen.
- Stomata sind immer offen -­‐> keine Photorespiration, was eine Energieersparnis für die Pflanze darstellt.
- Unter günstigen Bedingungen sehr schnelles Wachstum (0,7 Tage pro Generation)
- Sind als schwimmende Pflanzen an der Grenzphase zwischen Wasser und Luft nicht auf aerobe Verhältnisse im Wasser angewiesen.
- Werden mit Verschiedenen Schmutz- und Schadstoffen fertig, u.a. auch mit Mikroverunreinigungen
--> source: Andreas Schönborn

- Sie sind in der Lage Schwermetalle aufzunehmen.
- Im Pflanzenbestimmungsbuch von Peter M. Kammer ist erwähnt, dass Lemna Minor L. eine hohe Aufnahme- und Speicherkapazität für Radium, Jod und Brom besitzen.
--> source: Pflanzen einfach bestimmen / Peter M. Kammer 2016

Classification

Duckweed on the RED list

Starting with experimentations

Heidy once get some duckweed in an aquarium store for her fish aquarium. They usually dont sell duckweed, it was for free. Since then, the duckweed overgrows the aquarium constantly. Instead of throwing a quarter of them away once a week, we could make something out of it.

Duckweed Food experiments

We used duckweed in two ways. Once as a source of protein in the cooked dishes and salads.
And once as a flavor and spice for the liqueur and cheese.

Nutrients / Fertilizer and Fermentation

Auswildern (reintroduce into the wild)

From field trial at Stadionbrache we had quite a bit of plants left at the end. We decided to reintroduce them into the wild and brought them to small ponds in our area.
Unfortunately there were no plants left in the following year that survived the winter. It doesn't seem that easy to move duckweed to new places.

Wolffia arrhiza The smallest flowering plant

In 2017 we suddenly recognised some growing Wolffia in one of our containers. We didn't know where they came from, they just growed unintentionally.
We couldn't hibernate them und lost the culture over winter.
In 2018 we startet culturing a new culture of Wolffia arrhiza. We got some sterile plants in flasks from the Landolt Duckweed Collection in Zurich and tried to cultivate them in our conditions.

Lemna trisulca

Lemna trisulca sometimes called star duckweed or ivy-leaved duckweed differs from other duckweed types because it does not float on the water surface like this, but floats in the water below the surface. In addition, their leaves are attached to each other like a chain. As often to read, they occur in quiet, freshwater habitats. We were quite surprised as we found many L. trisulca in Bourges France in a stream that was not even flowing very slowly. They hung in tufts interlocked between other aquatic plants that were rooted on the ground. And that was not an isolated case, most aquatic plants at this spot were surrounded by L. trisulca duckweed.

What we are interested in

- Lemnas sind geniessbar und verfügen über einen eigenen, etwas teichigen Geschmack. Zudem, und dafür werden sie allerseits gepriesen, enthalten sie viele Proteine und alle essentiellen Aminosäuren.
--> Wilde Genüsse / Margot Fischer 2014

- Wasserlinsen gedeihen offensichtlich gut in überdüngten Gewässern und sind sogar auf Klärbecken zu finden.
- Duckweeds grow under a wide variety of conditions, they are generally not found in oligotrophic water (water in which nutrients are in low supply). Exceptions are waters heavily contaminated by waste water.
--> source

Nutrients from urine and organic wastes
- Nutrients for duckweed can come from fertilizer or organic wastes.
--> source (see: Nutrient sources)
- Nutrients for duckweed may be supplied from sources such as cattle dung, pig waste, human urine, biogas plant slurry, leachate from silage or compost or other organic matter in slurry form.
--> source
The same is also mentioned in the article „Duckweed Aquaculture“ Growth conditions: The natural habitat of duckweed is floating freely on the surface of fresh or brackish water sheltered from wind and wave action by surrounding vegetation. The most favorable circumstance is water with decaying organic material to provide duckweed with a steady supply of growth nutrients and trace elements.
--> source (see: Growth conditions)
To cultivate duckweed a farmer needs to organize and maintain conditions that mimic the natural environmental niche of duckweed: a sheltered, pond-like culture plot and a constant supply of water and nutrients from organic or mineral fertilizers. Wastewater effluent rich in organic material is a particularly valuable asset for cultivating duckweed because it provides a steady supply of essential nutrients and water.
--> source (see: Section 1 Biology of duckweed)

Urine as nutrient source
What we want to do is, to produce nutrients from own urine and kitchen waste for duckweed.
First we thought to make a transformation of urine into nitrate, called nitrification. Nitrification is caused by nitrifying bacterias. Urea is hydrolysed into ammonium (NH4+) by bacteria containing an enzyme called urease. Ammonium is transformed by a type of bacteria into Nitrite (NO2-), and in a further step Nitrite is transformed by another class of bacteria into nitrate (NO3).
--> See a project on the webpage of Hackuarium: From urine to nitrate
--> see also: Nitrification
--> See the VUNA project: Nutrient recovery from urine (Eawag - Swiss Federal Institute of Aquatic Science, Bastian Etter)
--> See the publication Nutrient Recovery from Urine and Struvite Production Using Aquatic Plants in Nepal (EAWAG Aquatic research und zhaw life sciences)

But, one of the main nutriens of duckweed is ammonium ion NH4+ (Nitrogen). Besides, human urine contains also phosphorus. It‘s not at all necessary to make nitrate first. You can fertilize the plants with urine directly.
In spring we could meet Bastian Etter (He works on the VUNA project) at EAWAG and we talked about the nutriens in urine. Bastian Etter recommended us to fertilize duckweed with urine directly. Its not necessary to process urine if it doesn‘t contain residuals of drugs. So far as we produce urine by yourself we can ensure that no drugs are contained.
So, we can produce the nutrients by yourself.

Is duckweed a plant-based source of Vitamin B12?

Recently, it was discovered that water lentils contain a natural source of Vitamin B12.
See also this post.
Unlike animals, most, if not all, plants have no B12 requirement for any function, and therefore have no active mechanisms to produce or store B12. It would make duckweed to one of the only vegan, plant-based sources of B12!
Real source foods claims, that one serving of Water Lentil Superfood contains 11% of the daily value and Water Lentil Lean contains 35% of the daily value for B12.
It is appropriate to treat the latest research results with caution. The researchers said that they used a method that does not distinguish between active vitamin B12 and vitamin B12 analogs. More research needs to be conducted and subjected to peer review, before duckweed (or water lentils) can be considered a reliable source of vitamin B12 for humans.

B12 is well known to be synthesized by certain bacteria. A recent study suggests, that bacteria inside the plant (endophytic bacteria) are producing vitamin B12. If so, the plants might have a symbiotic relationship with cobalamin-producing bacteria. (Note: it might be better to use the term "cobalamin" rather than "vitamin B12" because it is not clear if these cobalamins are active vitamin B12 in humans.)
This would be a wonderful discovery.
For the whole B12 topic see also this nice introduction: Vegan Health - Evidence-Based Nutrient Recommendations

Art / Design / Products using Duckweed

- 431art (Haike Rausch and Torsten Grosch)

Market oriented production

A company in Florida grows Lemnoideae plant to produce proteins for several products. It‘s known under the name: LENTEIN TM Plus POWDER



--> On its website, they praise the very good nutrition facts of their duckweed powder.
--> There are also to find datas about comparisons with Soy, Whey, Pea or Chlorella and Spirulina (of course, always in comparison of their powder product)

LENTEIN Plant-Based products are now available (2020)

LemPro Inc. The Company's mission is to develop and produce high quality sustainable nutritional and energy related products, which are "Green" and benefit all aspects of life on earth...
Ceres Biotech Co. Ltd sells common duckweed extract.

Remark to the calcium oxalate of duckweed

Calcium oxalates are often not really mentioned in recipes or texts about duckweed. We think this is because the amount of calcium oxalate in duckweed depends greatly on the calcium content of the water on which they are growing, and how they are prepared for food. But it‘s worth to consider the fact that duckweed belong to the family of the Araceae, and they are toxic.

Calcium oxalate is not a nutrient (nor a beneficial source of calcium), and it can be toxic in large doses.  Duckweeds can contain up to 2 — 4 percent oxalic acid equivalents by weight.  However, oxalate also is found in a great many leafy and very nutritious vegetables, including spinach, swiss chard and others. Elevated calcium in the water favors formation of calcium oxalate crystals. Their content can be lowered by growth on low-calcium medium.
Dry heat has been used to break down calcium oxalate in other foods. Cooking — boiling or roasting — would also kill any bacteria et cetera on or in the duckweed. Some suggest, to boil the duckweed, change water and then blend it.
--> Eat The Weeds and other things, too

Die Giftigkeit vieler Aronstabgewächse ist vom Verhältnis der in der Pflanze vorkommenden gelösten Oxalate zu den als Raphiden verfestigten abhängig.
Oxalsäure an sich ist in heissem Wasser einigermassen gut löslich. Das heisst, dass wir einen Bestandteil der giftigen Stoffe durch Kochen stark verdünnen können. Ausserdem besteht die Gefahr der Raphiden darin, dass sie oft in Zellen vorliegen, die unter Druck stehen. Ausgelöst können diese Zellen die Nadeln wie kleine Pfeile in die Schleimhaut von Rachen und Magen stossen. Durch den Kochvorgang wird dieser Überdruck aufgelöst, so dass nach längerem Erhitzen keine Vergiftungserscheinungen mehr zu erwarten sind. In grösseren Mengen sollten Wasserlinsen nur prozessiert zu sich genommen werden. Am besten zu Brei kochen.
Calcium oxalate crystals (raphides) like double-pointed needles.
—> Pflanzliche Notnahrung : Survivalwissen für Extremsituationen Johannes Vogel 2014

Oxalsäure ist die einfachste Dicarbonsäure und recht gut in Wasser löslich. Oxalsäure ist in höherer Konzentration giftig. Die wasserlöslichen Natrium-, Kalium-, und Ammoniumsalze wirken ätzend auf die Schleimhäute des Magen-Darm-Traktes, wodurch sie eine starke Reizwirkung ausüben. Oxalsäure kommt in vielen essbaren Wildpflanzen vor. Man findet die Verbindung in höheren Konzentrationen auch in vielen gängigen Nahrungsmitteln wie Mangold, Spinat und Roten Rüben. Geringe Konzentrationen sind in vielen Lebensmitteln wie Tomaten, Tee (insbesondere schwarzer Tee und Pfefferminztee), Kakao und sogar in Schokolade zu finden.
--> Enzyklopädie Essbare Wildpflanzen 2013 Steffen Guido Fleischhauer / Jürgen Guthmann / Roland Spiegelberger

Landolt Duckweed Collection

The Landolt Duckweed Collection contains samples of every known species of duckweed in the world.
The purpose oft the collection is to preserve these species in order to provide living samples available for research and also to provide a forum for the exchange of information.
The duckweed collection is located at Spiegelgasse 12 in Zurich.
www.duckweed.ch

Recipes

- Wasserlinsenelixier nach Hildegard von Bingen -- and -->here
- Wasserlinsenpüree
- Wolffia Aziza im Quark
- Wolffia Used For Nutritious Gourmet Dishes

Im Buch Köstliches von Sumpf- und Wasserpflanzen von Dr. Markus Strauss, 2013 sind einige Rezepte zu finden:

- Klare Gemüsebrühe mit Wasserlinsen
- Indisches Linsengericht mit dreierlei Linsen
- Würzige Linsensauce zu Nudeln


- Sommerliche Gazpacho aus Roter Bete und Wasserlinsen

Ein Rezept-Tipp von S.66: Wasserlinsen sind auch in roher Form lecker. Man kann sie wie Sprossen verwenden: Als Beimischung in Salaten, Dips, und Brotaufstrichen. Auch zum Garnieren von belegten Broten, Salaten und Gemüsegerichten sehen sie apart und aussergewöhnlich aus.
Webseite von Dr. Markus Strauss

Wasserlinsen-Paratha
Zu finden in: Wilde Genüsse - Das Kochbuch Margot Fischer 2014

Cookbook Waterlinzen, heerlijk en gezond from Aquatische Biomassa Concepten – Kroos

Further Links

There is a vast amount of scientific research and available information on the Internet about duckweed.
Here a selection of useful links:

- Duckweed Aquaculture - A NEW AQUATIC FARMING SYSTEM FOR DEVELOPING COUNTRIES
- DUCKWEED: A tiny aquatic plant with enormous potential for agriculture and environment
- Synthetic Media for Growing Duckweeds
- The Charms of Duckweed
- Lemnaceae species:
- A More detailed list of the Lemnaceae species:
- Eat the weeds / Foraging with Green Deane, A useful article about duckweed
- Open Source Ecology
- LemnaPedia
- LemnaTec Literature
- ILA - International Lemna Association
- RDSC - Rutgers Duckweed Stock Cooperative State University of New Jersey. (A duckweed collection available for researchers)

Sponsors and Supporter