Difference between revisions of "Edible wall"

Latest revision as of 13:05, 5 January 2016

Introduction

At ESTEE, we (Alexandra Florin and Michka Mélo) work on a project aiming at feeding living green walls from urine to produce food. We will first aim at feeding hydroponics green walls with urine as a nutrients source. We will then identify which edible and/or useful plants are suitable to grow in such an environment.

Our very first step will be to grow nitrifying bacteria (or nitrifyers) to convert urine into nitrate. Such nitrifying bacteria are very important in aquaponics, where we grow fish and plants in the same system, the waste from the fish providing nutrients to plants for their growth. However, fish waste need (at least partly) processing by bacteria to be edible for plants. Such bacteria include nitrifyers, which will transform ammonium from fish waste into nitrate, edible by plants.

Our first “Nitrification in Aquarium” (NA) experiments (NA1, NA2 & NA3) will therefore be adaptations of the first “cycling” step of aquaponics. We will start from an aquarium, an air pump and drippers and some pond water. We will feed the system with urine everyday, as they do with ammonium in this protocol.

From urine to nitrate : how does it work ?

Urea is hydrolysed into ammonium (NH4+) by bacteria containing an enzyme called urease. Ammonium is transformed into nitrite (NO2-) by a first class of nitrifyers, which we will call nitrifyers I. Nitrite is transformed into nitrate (NO3) by a second class of nitrifyers, which we will call nitrifyers II. The transformation of urine into nitrate is called nitrification.

Urea hydrolysis

Urease-containing bacteria are ubiquitous, and urea hydrolysis happens naturally in any traditional toilet system.

When urine is hydrolysed into ammonium, its pH gets quite high (around 8.5). Ammonium is part of an acido-alkaline with ammonia (NH3), which pKa value is 9. Ammonia is a gas. If stored in an open container, ammonia will fly out until pH of hydrolyzed urine reaches 9, causing nitrogen losses and reduced efficiency in converting urine to nitrate. Urine should therefore be stored in a tightly sealed container.

Hydrolysing urine is also a way to sterilize it, as high pH will kill pathogens.

High pH also induces precipitation and slight degradation of minerals.

Nitrifying bacteria

Both nitrifyers I & II are sensitive to nitrite (NO2), which is toxic for them and inhibits the nitrification reaction. We therefore have to feed the nitrifyer culture with small amounts of urine, because a too large amount at once may lead to a high production of nitrite by nitrifyers I, and lead to poisoning of both nitrifyers I & II.

Nitrifyers I have a tendency to make the culture more acidic, and nitrifyers II are inhibited by low pH conditions (below 6). Higher pH conditions (around 8) are therefore more favorable for nitrification [1].

Nitrifyers are sensitive to light [2].

Urea, ammonium & evaporation

Urea is not volatile. Ammonium (in the form of ammonia) is volatile.

Experiments

So far, we performed three experiments, all having a dedicated report page and detailed lab journal page.

Reports for NA1, NA2 and NA3 include introduction, material and methods, main results, discussion and conclusions.

Detailed lab journal for NA1, NA2 and NA3 include day-by-day report of measurements and actions taken.

A summary of the measurements in the form of an Excel sheet can be found here.

Conclusion

NA2 led to a nitrate concentration of 160 mgN/l, which is in the range of the concentration used in hydroponics to feed plants. NA1 and NA3 failed to reach a nitrate concentration above 20 mgN/l.

It is yet unclear why NA2 was a success while NA1 and NA3 failed, further investigation needs to be performed to have a better understanding of the dynamics at stake.

Next steps

To simplify the complexity of the investigation, urea hydrolysis should be performed before feeding urine to our system. Its dynamics should be observed by frequent pH measurement, to observe if it happens within days or within hours.

Ammonium content in urine should be measured before being fed to the bioreactor.

Ammonium/nitrite/nitrate concentrations in the bioreactor should be monitored as frequently as possible after feeding, to have a better understanding of the possible evaporation issue. A second experiment may compare the potential evaporation rate in different aeration rate & bioreactor volume combinations, to test if increased aeration induces increased evaporation.

A protocol should be designed to try to discriminate between failed nitrification, nitrate consumption, or even possibly ammonium consumption by competing bacteria.

The need for physical support to host nitrifyers should also be investigated and tested.

During experiment & experimental set up design, it should be kept in mind that:

It is wiser to protect the bioreactor from light
Low aeration did not seem to help
Feeding very large quantities of urine to the system did not seem to help
Performing urea hydrolysis before feeding urine to the system will strongly help investigation

Open questions

If you have any elements which would help us solve these open questions, you are most welcome to edit this section. Please add references when possible.

Is nitrifying bacteria growth inhibited by lack of physical support (f.i. clay beads) to host them ?
What are the appropriate pH, light & oxygen conditions for a quick urea hydrolysis by urease-contaning bacteria ?
Which bacteria may compete with nitrifyers for ammonium in the same culture conditions ?

@@ Line 1: / Line 1: @@
-This page is under construction!
+== Introduction ==
-== Contact ==
+At [http://est2e.com/ ESTEE], we ([https://ch.linkedin.com/in/alexandraflorin/fr Alexandra Florin] and [http://fr.linkedin.com/pub/michka-m%C3%A9lo/43/877/169 Michka Mélo]) work on a project aiming at feeding living [https://en.wikipedia.org/wiki/Green_wall green walls] from urine to produce food. We will first aim at feeding hydroponics green walls with urine as a nutrients source. We will then identify which edible and/or useful plants are suitable to grow in such an environment.
-See [[Edible wall#People involved | main actors]]
-== Objectives and context ==
+Our very first step will be to grow [https://en.wikipedia.org/wiki/Nitrifying_bacteria nitrifying bacteria] (or nitrifyers) to convert urine into nitrate. Such nitrifying bacteria are very important in [https://en.wikipedia.org/wiki/Aquaponics aquaponics], where we grow fish and plants in the same system, the waste from the fish providing nutrients to plants for their growth. However, fish waste need (at least partly) processing by bacteria to be edible for plants. Such bacteria include nitrifyers, which will transform ammonium from fish waste into nitrate, edible by plants.
-=== Motivation: upgrading to a multi-functional “living wall” ===
-Our general motivation is to produce food on-site, while valorising excreta (human waste) and combining several advantages. <!-- … why do this? Principles of ecological engineering /circular economy…-->
-In this project, our mission is to upgrade existing “living walls” to combine several functions and characteristics:
-* Grow edible plants (or medicinal, scented… instead of just decorative exotic plants)
-* Fertilise the plants with human source-separated urine only (and avoid using any chemical fertiliser)
-* Purify indoor air, which passes through the soil and root system
-* Use material that is renewable, locally available, … (as much as possible)
-* Have a beautiful planted wall, that increases well-being in offices, inside buildings, or in the city
-Among these functions, we want to focus in priority on valorising human '''urine''' to grow '''edible plants'''. Yerk?! Yes, you read it correctly. And you should get convinced of the many advantages of the reuse of urine for agriculture by reading [[reuse of urine | this]].
-=== System description and constraints ===
+Our first “Nitrification in Aquarium” (NA) experiments ([[Nitrification in Aquarium 1 (Report)|NA1]], [[Nitrification in Aquarium 2 (Report)|NA2]] & [[Nitrification in Aquarium 3 (Report)|NA3]]) will therefore be adaptations of the first “cycling” step of aquaponics. We will start from an aquarium, an air pump and drippers and some pond water. We will feed the system with urine everyday, as they do with ammonium in [http://aquaponie.net/demarrage-cycler-aquaponie/ this protocol].
-<!-- It’s not just pots of plants stacked above each other. It’s not just an outdoor garden fertilised from time to time by urine. It’s not exactly a hydroponic system. All or these are already known. We have a combination of all, tadam…) -->
-''' Soil substitute '''<br />
+== From urine to nitrate : how does it work ? ==
-The vertical “modules” currently consists of panels of a kind of compressed roock wool called [http://www.grodan.fr/ Grodan] (although we might change this in the future if we find another renewable material with the same properties). The plants are planted in holes, and their roots then develop through this 'matrix' and at the back of the panels. Specificity: very little real natural soil, lightweight.<br />
-''' Fertigation (= irrigation + fertilisation)''' <br />
+Urea is hydrolysed into ammonium (NH4+) by bacteria containing an enzyme called urease.
-Drip irrigation, with a nutritive solution made of tap water and currently a chemical fertiliser, which we’ll replace by urine. Similarly to a hydroponic system, the solution must contain all nutrients needed by the plants, in a readily available form, and in the appropriate concentration for continuous fertigation (as opposed to punctual fertilisation). <br />
+Ammonium is transformed into nitrite (NO2-) by a first class of nitrifyers, which we will call nitrifyers I.
-This means that the nutrients concentration shouldn’t be too high, because:
+Nitrite is transformed into nitrate (NO3) by a second class of nitrifyers, which we will call nitrifyers II.
-* Too high an ammonium concentration is toxic to plant <ref name=hydroponiefr1 /><ref name=wikinitrateammonium1 />.
+The transformation of urine into nitrate is called nitrification.
-* Excessive fertilisation also causes damages, such as late maturation, sensibility to pests, as well as nitrates accumulating in plants and ultimately reducing blood oxygenation in our organism. <ref name=hydroponiefr2>
-"Les premiers signes d’un surdosage en engrais riche en azote est un feuillage vert foncé….Attention cependant à ne pas confondre les excès d’azote avec les carence en phosphore.
-L’excès d’azote contribue à développer une grosse masse foliaire au dépend du système racinaire. Cette surabondance d’ions azotée concourt au retard de la floraison chez de nombreuse plantes.
+=== Urea hydrolysis ===
-Les solutions nutritives avec excès d’azote entraînent diverses conséquences sur le plan cultural :
+Urease-containing bacteria are ubiquitous, and urea hydrolysis happens naturally in any traditional toilet system.
-– Un excès de végétation peut provoquer un recul de la maturité des plantes,
+When urine is hydrolysed into ammonium, its pH gets quite high (around 8.5). Ammonium is part of an acido-alkaline with ammonia (NH3), which pKa value is 9. Ammonia is a gas. If stored in an open container, ammonia will fly out until pH of hydrolyzed urine reaches 9, causing nitrogen losses and reduced efficiency in converting urine to nitrate. Urine should therefore be stored in a tightly sealed container.
-– Les plantes sont plus sensibles aux attaques des ravageurs et aux maladies fongiques (botrytis, mildiou, oïdium). Cela est le contrecoup de l’excès de végétation : les tissus (tiges, feuilles) sont tendres et constitue une barrière trop fragile pour s’opposer aux pathogènes.
+Hydrolysing urine is also a way to sterilize it, as high pH will kill pathogens.
-– Enfin, une sur-fertilisation en azote, en plus de la détérioration des qualités gustatives, entraîne une teneur excessive en nitrates dans les légumes (essentiellement les légumes feuilles tel la laitue Il n’y a pas de danger pour les légumes-fruit comme les Tomates, Concombres). L’excès de nitrates chez l’homme causent une baisse de l’oxygénation du sang."
+High pH also induces precipitation and slight degradation of minerals.
-http://hydroponie.fr/azote/
+=== Nitrifying bacteria ===
-</ref>.
-<!--ADD SOME  PICTURES -->
+Both nitrifyers I & II are sensitive to nitrite (NO2), which is toxic for them and inhibits the nitrification reaction. We therefore have to feed the nitrifyer culture with small amounts of urine, because a too large amount at once may lead to a high production of nitrite by nitrifyers I, and lead to poisoning of both nitrifyers I & II.
-<br>
-<gallery>
-File:empty-module-Biotecture_08.07.15.jpg
-</gallery>
-'''Plants for vertical indoor garden''' <br />
+Nitrifyers I have a tendency to make the culture more acidic, and nitrifyers II are inhibited by low pH conditions (below 6). Higher pH conditions (around 8) are therefore more favorable for nitrification [http://aquaponie.net/demarrage-cycler-aquaponie].
-Once we figured out the urine fertigation issue, we will identify edible & useful plants adapted to the urine-based nutrients mix. We will also try to design vegetal communities with beneficial symbiotic interactions between plants through [https://en.wikipedia.org/wiki/List_of_companion_plants companion planting]. Companion planting may ease pest control and foster synergetic growth between different species.
-=== Specific objectives ===
+Nitrifyers are sensitive to light [http://aquaponie.net/demarrage-cycler-aquaponie].
-'''Challenge for urine fertigation in a semi-hydroponic system'''
-<!-- ‘ [why we have these questions]
-[Why dilute: odour for indoor, toxicity of ammonium, damage if excess nutrients - ] <br />
-[Why we need to make sure that urine gets nitrified in the panels!] <br />
--->
-We want to :
-* Avoid odours: especially because this version of living walls is designed for inside buildings.
-* Find the ideal urine dilution: to provide the nutrients required by our plants mix, while to avoiding excessive fertilisation and ammonium toxicity. <br />
-* Nitrify urine with the simplest possible system: ideally in the panels.
-In fact, most plants prefer nitrate-nitrogen to ammonia-nitrogen as a nitrogen source, as they are are easily damaged by excessive ammonium nutrition.
+=== Urea, ammonium & evaporation ===
-<ref name="Shinohara2008">
-Shinohara, M., Ohmori, H., & Uehara, Y. (2008). Microbial ecosystem constructed in water for successful organic hydroponics. Nature Precedings.
-</ref>
-<ref name="hydroponiefr1">
-“Cette forme d’azote peut s’avérer toxique selon le type de plante et leur stade de croissance. Ainsi, les jeunes pieds de tomates font une grosse consommation d’ion NH4+.
-L’azote ammoniacale est prélevé en premier par les plantes, avant les ions nitrates.
-Toujours est-il qu’une plante peut se nourrir exclusivement d’ions NO3–, mais que l’apport unique d’ion ammonium NH4+ est toxique pour les végétaux.
-On rencontre cet ions ammonium dans la solution nutritive suite à la dissociation de sels de phosphate d’ammonium (NH4 H2PO4 ) surtout dans le but d’apporter des ions phosphates.
-Cependant, dans la solution nutritive l’ion ammonium fait concurrence au prélèvement d’ions K+, Mg++, Ca++.
-Le professeur Morard recommande que l’ion ammonium NH4+ n’excède pas 10% de l’azote assimilable contenu dans une solution nutritive.”
-http://hydroponie.fr/azote/
+Urea is not volatile.
-</ref>
+Ammonium (in the form of ammonia) is volatile.
-<ref name="wikinitrateammonium1">
-“Au delà d'une certaine dose, l'amonitrate est toxique pour les plantes dites « supérieures » et a été étudiée chez d'autres organismes modèles ou bioindicateurs potentiels (paramécies, mousse, lichens)11 ; cette toxicité se traduit chez la plupart des espèces par une réduction de la croissance, des feuilles plus petites et un retard de développement du système racinaire. A dose plus importante, les symptômes d'une chlorose apparaissent et peuvent conduire à la mort de la plante. [...] La toxicité de l'ion ammonium pour les plantes est encore imparfaitement connue ; elle est généralement attribué à un effet synergique associant :
-	•	une carence nutritive induite par l'excès d'ammonium (qui altère l'absorption des ions métalliques) ;
-	•	une acidification du milieu d'enracinement (qui inhibe la croissance racinaire secondaire) ;
-	•	une perturbation de l'équilibre osmotique de la plante (par modifications du pH intracellulaire) ;
-	•	un désaccouplement du phénomène de photophosphorylation liée au transport d'électrons, suite à l'accumulation d'ions ammonium dans les feuilles ;
-	•	l'altération du métabolisme des phytohormones et de la polyamine.”
-https://fr.wikipedia.org/wiki/Nitrate_d%27ammonium#.C3.89cotoxicit.C3.A9
+== Experiments ==
-</ref>
-This is why most hydroponic solutions contain nitrates, not ammonium <ref name="hydroponiefr1" /><ref name="wikinitrateammonium1" />. However stored urine contains nitrogen in the form of ammonium, which must therefore be converted to nitrate through [https://en.wikipedia.org/wiki/Nitrification nitrification]. This requires the presence of nitrifying bacteria and sufficient oxygenation <ref name="wikinitrification1">"Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea."
+So far, we performed three experiments, all having a dedicated report page and detailed lab journal page.
-https://en.wikipedia.org/wiki/Nitrification</ref>. It is generally the case in soil… <ref name="wikinitrification2"> "In most environments, organisms are present that will complete both steps of the process." https://en.wikipedia.org/wiki/Nitrification</ref> but how about in our living walls, in our soil substitue? Is it a suitable medium to host active nitryfiers?
-For this reason, we first want to test the 'nitrification in Grodan' (our soil substitute), and then proceed to test 'nitrification in modules' (fully assembled living wall modules). <br />
-<!-- Should we could explain more? Or in the respective sections? E.g. *  Importance of aeration = of how panels are covered -->
+Reports for [[Nitrification in Aquarium 1 (Report)|NA1]], [[Nitrification in Aquarium 2 (Report)|NA2]] and [[Nitrification in Aquarium 3 (Report)|NA3]] include introduction, material and methods, main results, discussion and conclusions.
-'''Questions for experiments''' <br />
+Detailed lab journal for [[Nitrification in Aquarium 1 (Lab Journal)|NA1]], [[Nitrification in Aquarium 2 (Lab Journal)|NA2]] and [[Nitrification in Aquarium 3 (Lab Journal)|NA3]] include day-by-day report of measurements and actions taken.
-# '''Nitrification in modules''' - Does nitrification of urine take place in our soil substitutes? Is it quick enough? How it it influenced by the following factors?
-## Inoculation (none / with nitrifying solution)
-## Dilution factor (between 1:10-1:50)
-## aeration properties of the panels (free surface / covered with a plastic sheet / active aeration)?
-## Different soils, i.e. different source of microorganisms (none? / special for germination, sterilised / garden compost / field, without chemicals? / inocculated with an nitrifying culture)
-# What is the ideal '''dilution rate'''?
-## Limit to prevent odours
-## Appropriate dilution to reach at least the same performance as the chemical solution (or compare between dilutions) – in these modules
-# How do '''different edible plants''' grow under these conditions? Which are the most adapted?
-## First selection: common herbs that grow well
-## More interesting other plants: 2nd run, or first just in pots vertically – pre-test the dilutions
-:::: Could we start this last point in parallel during the nitrification experiments, or if it takes very long to build the structure, or in collaboration with Vertikal Farms ? (TBD)
-=== People involved ===
+A summary of the measurements in the form of an Excel sheet can be found here.
-'''Main actors''': [[User:Alecoloop|Alexandra]] & [[User:Michka|Michka]] (easy to find on [[Slack]] or by [mailto:michka.melo@est2e.com e-mail])
+== Conclusion ==
-'''Participants''' (have helped us so far):
+[[Nitrification in Aquarium 2 (Report)|NA2]] led to a nitrate concentration of 160 mgN/l, which is in the range of the concentration used in hydroponics to feed plants. [[Nitrification in Aquarium 1 (Report)|NA1]] and [[Nitrification in Aquarium 3 (Report)|NA3]] failed to reach a nitrate concentration above 20 mgN/l.
-* at Hackuarium:    Of course [[User:Shalf|Yann H.]] & [[User:hekkcess|Yann P.]] and also Clément Drévo., Miram Ryf …
-* colleagues at ESTEE:   Saida N., Théodore B., Tomas R.
-'''External partners''': We cooperate with the enterprises [http://www.biotecture.uk.com Biotecture] and [http://www.livinggreencity.com Living Green City UK]. They produce and install living walls inside and outside buildings. Biotecture have provided us with the core of the modules and share some know-how. The team at Living Green City UK, in London, currently focus on air filtration function. We are in contact with them especially to ensure the integration of the different functions.
+It is yet unclear why [[Nitrification in Aquarium 2 (Report)|NA2]] was a success while [[Nitrification in Aquarium 1 (Report)|NA1]] and [[Nitrification in Aquarium 3 (Report)|NA3]] failed, further investigation needs to be performed to have a better understanding of the dynamics at stake.
-Friends and '''related projects''':
+== Next steps ==
-Vertical / urban farming, aquapony, and such species: Vertikal farms, Exodes Urbains, others met
-'''Communication''':
+To simplify the complexity of the investigation, urea hydrolysis should be performed before feeding urine to our system. Its dynamics should be observed by frequent pH measurement, to observe if it happens within days or within hours.
-[[Slack]] channel: [https://hackuarium.slack.com/archives/wg-edible-wall #wg-edible-wall]
-== Activities ==
+Ammonium content in urine should be measured before being fed to the bioreactor.
-=== Overview of project parts ===
-Details on these activities will be found in the following sections (title level 2 or links to separate pages).
-* Urine Fertigation
-** Urine collection and storage – install DIY waterless urinal
-** Nitrification in aquarium – design and grow a community of nitrifying bacteria (NA)
-** Wall structure and irrigation system – design & build
-** Test the nitrification in Grodan (soil substrate) (NG)
-*** experiment NG1 - Grodan samples, initial inoculation, several urine dilutions tested
-*** experiment NM2 - with inoculation through different soils
-** Dilution test: planted experiment 1
-** Dilution test: planted experiment 2
-* Vegetal Community
-** Nursery: design, build and plant
-** Selection guide for different conditions  (such as indoor/outdoor, light, space, etc.)
-*** Select and gather plants for the first experiments
-*** Matrix for indoor walls
-* Integration of air filtration
-** This will come later. Idea taken into account in the part “nitrification in  modules”
-=== Experimental plan ===
+Ammonium/nitrite/nitrate concentrations in the bioreactor should be monitored as frequently as possible after feeding, to have a better understanding of the possible evaporation issue. A second experiment may compare the potential evaporation rate in different aeration rate & bioreactor volume combinations, to test if increased aeration induces increased evaporation.
-This [[Media:Experiment_Plan_11.08.2015_-_attach_to_wiki.pdf‎ | document]]
-shows an overview of the experiments planned, to which questions they should answer, and their sequence depending on the results of the first ones.
-[[File:Experiment_Plan_11.08.2015_-_attach_to_wiki.pdf‎ | document]]
-==== News: ====
+A protocol should be designed to try to discriminate between failed nitrification, nitrate consumption, or even possibly ammonium consumption by competing bacteria.
-::<li> 13.07.2015 We've received the empty modules!
-::<li> 22.07.2015 [http://wiki.hackuarium.ch/index.php?title=Openhackuarium_vol._55_-_22.07.15 openHackuarium vol.55] small presentation of project plans
-::<li> 23.07.2015 First results: our nitrifying culture is active!
-== Urine collection & storage ==
+The need for physical support to host nitrifyers should also be investigated and tested.
-See the page [[DIY waterless urinals]] (This may serve also to other projects!)
-== Nitrifiying culture (NA) ==
-We'll create a page with more details when we see the first results!
+During experiment & experimental set up design, it should be kept in mind that:
-<!-- Internal: see exp p. – nitrifying culture – internal doc – V1.docx -->
+* It is wiser to protect the bioreactor from light
-==== Quick reminder of objective ====
+* Low aeration did not seem to help
-Grow a culture of nitrifying bacteria adapted to diluted urine.
+* Feeding very large quantities of urine to the system did not seem to help
-It can then serve in 1° for us to:
+* Performing urea hydrolysis before feeding urine to the system will strongly help investigation
-* Inocculate our modules with the suitable microorganisms, if needed
-But also to:
-* Start an aquaponic system (with fish etc)
-* Stabilise diluted urine, with the effect of removing pathogens and smell => home fertiliser that's better than simple urine
-=== Inspiration / background ===
-We got inspiration from this
+== Open questions ==
-* [http://aquaponie.net/demarrage-cycler-aquaponie protocol to start an aquaponic system]  (in french)
-They want to keep the ammonium conc very low, good for fish. Target 2-4 ppm, increased by 0.5ppm daily. But in our case, we want a culture adapted to much higher concentrations; at least those used for fertigation. Try to go faster?
-... more to come
+If you have any elements which would help us solve these open questions, you are most welcome to edit this section. Please add references when possible.
+* Is nitrifying bacteria growth inhibited by lack of physical support (f.i. clay beads) to host them ?
+* What are the appropriate pH, light & oxygen conditions for a quick urea hydrolysis by urease-contaning bacteria ?
-== Wall structure and irrigation system ==
+* Which bacteria may compete with nitrifyers for ammonium in the same culture conditions ?
-== Test the nitrification in modules – experiment ==
-== Dilution test: planted experiment ==
-== References ==
-<references/>
-[[Category:Work In Progress]]
-[[Category:Projects]]