Portable Greenhouse

Grow-bed and mature micro-greens (housing not pictured)

Design Goals

The idea for the Portable Garden, my final project in “Food and Emerging Technology”, came about from reflecting on the “virtual cost” of long supply chains in our food system, as well as the human cost of distancing producers from the driving forces of agricultural markets. Another issue I’d hoped to address was the disruption of biodiversity resulting from homogeneous industrial production at the regional scale. Since the goal here was to grow as small as possible, micro-greens, which may be sewn in tight proximity and harvested in under two weeks, were the natural choice of produce.

Originally intended to be a self-contained “grow case” equipped with high-power LEDs, timed light cycles and a solar power supply, my focus gradually shifted to hyper-affordability and sustainable sourcing. While there was no consideration of green/microclimate structural design, this is a huge point of interest for further generations of portable greenhouses.

Multiple-Orientation Feature

A swivel mechanism, when combined with planters weighted a cement mixture, allowed for multiple configurations of the housing to provide darkness during germination, light exposure during the sprouting phase, and an upright hand-carrying mode. This feature obviated the use of LEDs or electronics in favor of a simple mechanical solution.

The Build

The build process was relatively simple but required substantial hardware resources. The complete list of resources included:

  • 1X Wine Crate (any wooden box will work)
  • 3X 1L plastic bottles
    • 2X for grow-beds, 1X for compacting concrete while curing
  • Concrete Mixture (needs improvement — see Improvements)
    • 1 Part Cement
    • 6 Parts agricultural vermiculite
  • Hardware
    • 1X Reciprocating Saw
    • 1X Tape Measure
    • 1X Level
    • 1X Shop File
    • 1X Power Drill
    • 1X 1″ boring bit

Experimental Procedure

Once two grow-beds had been cut and cured, it was time to get planting! However, there remained a couple a big questions to be answered. First, given the wide variety of micro-greens that are routinely grown, what would be the best species to plant? Having started the project in October, the choice was narrowed-down to late-season produce.

Furthermore, it was unclear whether coconut fiber* or vermiculite, a more conventional starter, would be a more suitable growth medium. Therefore, the following experiment was derived:

Experimental Results:

Varietal/SubstrateCoconut HuskVermiculite
LettuceXO
SpinachXX

Two grow-beds of distinct growth medium (coconut husk and vermiculite) were partitioned in half and covered with two different seed varieties (lettuce and spinach) in identical proportions. Then, both grow-beds were simultaneously exposed to identical phases of germination, water, and day-night cycles until which point that the harvest could be confidently assessed.

As conveyed by the results-table above, the combination of Lettuce and Vermiculite was the only sample that achieved a standard of successful growth. Further harvests repeatedly showed great results using this combination, as shown in the photos below.

The Final Product

Basking in the sunlight in full photosynthesis.
Longer germination made these delicious sprouts “long-legged” for easier clipping.

Improvements

Double-sided Housing

Further generations of the design should implement a second housing encasement inwardly joined by a hinge, which may provide insulation from exposure during transport while doubling the growth capacity.

Concrete Mixture

Since the concrete mixture (1P Cement : 6P Vermiculite) was prone to crumbling, an intermediary mixer such as sand shall be introduced in place of some of the Vermiculite in future builds.

Sources

*Coconunt Husk, or “coir”, is the medium recommended by Larry @ City Hydro

Thanks to Professor Stephanie Bardin and the Fall, ’17 class of “Food and Emerging Technology” at the New School for your feedback and guidance!

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