The Regrow Project is a student research project funded by the University of Texas at Austin Green Fee Grant. In this experiment, we are regrowing food from scrap hydroponically while measuring the crop yield, water and energy consumption.
It is known that some common foods will regrow into new plants from their food scrap. These foods, specifically lettuce and other leafy greens, broccoli, cauliflower, onions, potatoes and other root vegetables, can theoretically regrow into new plants assuming there is enough meristematic tissue remaining on the food scrap. In early trials of the experiment, we had the most success sprouting new roots in water. With this, we decided to perform the experiment in a raft hydroponic system.
As of Fall 2017, we are currently in the process of conducting the first trial of this experiment. Below is our system design and results so far.
Trial 1 Photos
The design of our hydroponic system featured two grow tubs (one for regrown food scrap and the other for control plants grown from seed), that drained into a filter bucket (to capture large sediment, specifically coconut coir grow media), and then finally to drain into a water reservoir. From the reservoir water was pumped back into the grow tubs to re-circulate the water. Standing pipes were placed in the grow tubs so water level could fluctuate between 25 to 30 gallons, mimicking a “flood and drain system” (known to produce optimum plant growth as it exposes roots to more oxygen without drying them out).
Results So Far
For our first trial with the regrown lettuce, we saw five out of eight lettuce stumps regrow into new plants. We ran this trial for 28 days and observed a yield of 5 plants until the last 2 days where we saw a yield of three plants. We are still in the process of growing our control lettuce plants from seed.
Due to unexpected disruptions in the experiment, we can’t make a clear comparison on water and power consumption from the regrow plants to the control plants. However, we anticipate our next trial will have significantly more control and we will be able to compare “lettuce to lettuce” yield, water and energy consumption.
Trial 1 Data
Click on Image to Enlarge.
Experiment Challenges and Lessons Learned So Far
Our greatest challenge so far has been fighting leaks at the junctions between the grow tubs and pvc pipe. Despite the use of bulk-head fittings and rubberized paint at points of contact, leaks continue to occur. We believe this is due to the plastic of the tubs being too thin. These Sterilite tubs (made of plastic #5, Polypropylene) are designed to be storage bins and not to hold water. For the next trial of our experiment we plan to rebuild the recirculating raft system with containers designed to hold large amounts of liquid.
The great city of Austin, Texas is famous for having very unpredictable weather. Despite planting our lettuce in October, we experienced spikes in temperature up to 90 degrees Fahrenheit for several weeks during the trial. Lettuce and other winter crops thrive in temperature ranges of 50 – 60 degrees Fahrenheit. When temperatures exceed this range, lettuce and other winter crops will produce inedible flowers instead of lettuce heads. With this, we did see significant growth in several of our lettuce plants, however this growth went towards producing lettuce flowers instead of a lettuce head. For the next trial of our experiment we will be moving to a temperature controlled greenhouse.
Towards the end of our first trial, we saw algae begin to appear in the tubs with the plants. Algae is a photosynthetic organism that grows in water when exposed to light. Algae can be harmful to plants and aquatic life in that it competes with other organisms for oxygen and nutrients in the water. Before the algae appeared in our grow tubs, five of the eight plants were regrowing. However, with the algae appearing we noticed our yield reduced from five to three plants. We do not claim this correlation is causation for our loss in yield. There are many other factors that could have contributed to this. However, for our future trials we will work to reduce the amount of water exposed to sunlight to hopefully prevent algae growth.
After conducting a second, and possibly third trial of regrowing lettuce hydroponically, we plan to also grow broccoli, and onion plants. We anticipate running this experiment for several years and reporting updated results as they come. After the completion of this experiment we hope to have enough reliable data to assess whether or not these common foods could be realistically regrown at scale and if the water and energy savings would be such to make this a sustainable process.