Vertical Plant Parfait

Speculative Proposal / Conceptual Design:

Soon after starting this project, we realized the importance of creating a sustainable ecosystem based on symbiotic biological interactions. Without a way of cycling nutrients and resources throughout our system, long-term sustainability is out of the question. To address this problem, we conceptualized and build a symbiotic 3-layer biome. First, we looked for a compliment to the given part of our ecosystem: a leafy, photosynthesizing, houseplant. Because plants consume CO₂ and out release oxygen, fungus acts as a symbiotic partner that takes in oxygen, using it to decompose dead plant matter, and in turn outputs CO₂. Fungi can also be a potential source of protein for humans and facilitate bioremediation to breakdown hydrocarbons (eg: petroleum) in the environment. While this cycle is theoretically sustainable, it’s susceptible to becoming imbalanced because it lacks a way to regulate the proportions of CO₂ and oxygen. At this point, we proposed adding algae to our system. Algae requires heat, light, and CO₂ to grow, and its growth can be encouraged and discouraged by externally controlling access to heat and light. In this way, the algae pool at the bottom of our biome acts as a biological switch that can be encouraged to grow when oxygen levels are too low due to fungal growth, or discouraged from growing when oxygen levels are too high, allowing the fungus time to rebalance the system. Additionally, dead algae can be funneled through our water pump and redistributed as fertilizer for both our plant and fungal layers.

By using the resources we have access to externally on a martian mission, solar radiation and energy drawn from solar panels, our system uses a technology assisted bio-feedback loop that keeps the ecosystem balanced.

Precedents:

We questioned whether our biome would be an entirely closed-loop system or would adapt to the martian characteristics and use its resources at least partially (class constraints revealed these would be natural sunlight and extraction of water). Another idea we have been incorporating into our project is that of diversity, and recreating the natural life-cycle of ecosystems.

We researched things like what plant diversity looked like, what pairs of plants grew well together, life-cycle alignments, and ultimately, searched for symbiotic relationships between plants and other organisms that exist naturally or could develop.

Excited with the idea of adding oyster mushrooms, moss, water bears, or other organisms into our biome, we were particularly interested in lichen, the hybrid of fungi and algae, and the potential exchange of resources the relationship could provide for our houseplant.

Some technologies we were interested in included using Arduino for a pump watering system, raspberry pi infrared camera to analyse plant’s photosynthesis activity, and placement of sensors in order to control the inputs and output of each of our plant layers.

Process:

We were working under the following design decisions: creating layers of diverse life types, encourage the natural process of decomposition, and promoting and controlling optimal growing conditions. Below is our initial idea.

We iterated on heights and spacing of the layers, quantity of each layer in terms of their production and waste, moisture issues, and the overall concept of diversity and co-existence.

And built "paper" mock-ups to test strength and structure for the shelves, attachment methods that would work with the thick glass container, and mesh materials that would give both stability for plants but porosity for air and water exchange.

Prototype:

In our prototype we created our layered ecosystem that would facilitate a symbiotic relationship between all the layers. In order to do this, we needed to create shelving support to hold each layer, moving in the living organism and installing the sensor.

For our individual layers, we made laser cut pieces that were hinged by tape so it could fit through the entrance of our jar. We designed the fungi layer so the holes would allow excess water to pass through more easily and the overall weight of the layer would be reduced. We then mounted window screen material to the front and back of this layer so that any matter from this layer would not be able to permeate into the algae layer below.

For the plant layer, we went with a “hammock” design so that this layer could eventually become an aeroponic system, in which these plants would hang above while the roots could potentially become an embedded part of the fungi layer. As the leaves would die, it would also be able to go into the fungi layer for decomposition. This layer was also laser cut and hinged, with an inner ring connected to an outer ring using elastic. Using elastic helped keep the tension in balance as we moved the layer into the jar. The inner ring also has a mesh pocket sewn onto it, which allows the plant to sit inside it.

The plant layer just required placing the plant into the pocket to complete the layer. For the fungi layer, we had to slice up our mushroom brick so that the substrate could be spread across the layer. As advised by the Internet, we combined the chopped substrate with coffee grounds to give it a some nutrient support.

Our algae layer was moved in last, since we were concerned about having to unfold our scaffolding and having it accidentally be submerged. We ran our pump so that one end was in our bucket of mixed algae and other end was squeezed through the layers so it reached the bottom layer.

In terms of scaffolding, we went through a few iterations. At first we were considering building rods with support (as seen in our paper prototype). Upon seeing the other groups’ laser cut scaffolding structure, we decided that we wanted to make something that would take up less room. As a result, we decided to eliminate any rods and use a metal to glass glue to adhere L brackets onto the sides to hold our shelves. This tactic worked until after we installed the plant layer and noticed the shelves were caving in. In response, we wound laser cutting rings and legs that could be placed to support each layer separately.

As we built each layer, we installed the necessary sensors for each layer. The moisture sensor was placed with the plant layer on top and the temperature sensor was placed on the wall on the fungi layer. The wires are able to extend through the lid opening so that the microcontrollers and power supplies can be on the outside.

Reflection:

In our project we gained a lot of insight about designing symbiotic systems. In creating each layer, we had to think about how we wanted each shelf to support the organism life and interact with the other layers. This lead to specific design choices and also helped us figure out the order in how we installed the organisms in order to prevent the least amount of damage. In creating this system, we also had our general concept figured out, but when we went in to figure out the sensor systems and construction, we still have some things to figure out for future iterations.

We also learned a lot from building within the confinements of our glass container. At first we thought we would be able to use a metal to glass glue to adhere L brackets on the surface where our shelves could sit. Unfortunately our shelves started to collapse after the weight of the organisms had been sitting on top for a while and we had to create a laser cut scaffolding system that could be incorporated into the design. In getting things into the jar, we had to play around with piecing and hinging our pieces so that it could fit into our jar opening and open up. It would be helpful if we work with a differently shaped container in later iterations.

Open Questions and Challenges:

During our critique, one of our visitors (landscape architect) mentioned how these closed loop systems usually require at least three cells. The other visitor also talked about how it was great to have a symbiotic system if all the sections worked together to form an equilibrium. Otherwise, it would be helpful to have control over the different systems in the form of separate containers. Although we think there are a lot of benefits in having these symbiotic systems, it might be good to think about how these sections can be altered/controlled to have optimal growth conditions. In thinking of how the BAA class is working to deploy the system, it would also be useful to think about how we can create a system that could be integrated into the structure of our habitat.