Everyone talks about how sustainable hydroponics/aquaponics/aeroponics is almost solely based on using less water than conventional agriculture. However, going a little deeper leads to plants growing in massive amounts of plastic, most components which are only designed to last for a single growth cycle to a few years. That is a tremendous amount of plastic waste from something that is billed as 'sustainable'. Sustainable should not generate end-of-lifecycle waste, especially large amounts of end-of-lifecycle waste during the course of a single production cycle.
Well before the current movement to get rid of single use plastics, we were attempting to design a hydroponic system that did not require plastic components. Our primary motivation was cost as spending several hundred dollars to set up a basic system was not in the budget, but longevity was also important. The system should either be self-sustaining or made such that the parts would not need to be replaced on a routine basis. By going beyond currently available plastic systems, entirely new design possibilities become possible.
The first big obstacle was growing media. We had lots of trash, but no rockwool or giant pools of water. We were under water use restrictions due to drought conditions, so getting a few hundred gallons of rain or tap water was not an option for starting our system. Rockwool was not something we could produce on site, and buying peat moss was also too expensive. It also had to be able to cope with both very little water input and collect whatever atmospheric moisture was available.
So we tried using the excess trash as our growing media. After much tinkering, we were able to almost instantly make it into a suitable growing media for plants. Now that we have a great, sustainable media, we need a great, sustainable system to go with it. We are focused on plastic free for two major reasons. The first is that certain components in our media appear to decompose plastic and the second is that we primarily grow outside and most plastics degrade rapidly in direct sunlight. Then there is the added benefit of adding additional beneficial feature by using materials other than plastic (like self-insulating water tanks, a wider range of color options, etc).
We have several promising materials to experiment with building a system from, with the added bonus that not using plastic should also cut our energy needs for pumping water. The system we are designing would be perfect for sustainable urban and peri-urban farming of all types of crops. Food waste could be used to produce more food and livestock feed, while general household waste could be diverted from landfills and used to grow biofuels. Biofuel crops are the perfect fit for questionable waste streams as they do not have to be safe for either human or animal consumption.
The prospect of plastic-free hydroponics replacing landfill disposal of waste is particularly exciting, as one reason this project started was because it seemed incredibly wasteful to throw out anything in the trash. To be able to process most urban waste into a variety of plants for food, fuel and fiber is a big leap forward towards making urban living sustainable. We are excited to be at the beginnings of realizing the full potential of hydroponics as a crop production and waste recycling method.
There are some that suggest that the only route to contain rising atmospheric levels of CO2 is to increase production of biofuels in a manner that sequesters carbon. Plants naturally remove carbon dioxide from the atmosphere through photosynthesis. While we haven't run tests yet, it appears we are sequestering carbon as our growth media gets darker the longer it is used. Using our waste to produce the fuels we need is a simple, elegant solution that can be implemented now and rapidly scaled. Most buildings have roofs, and green roofs are already known to provide many positive benefits, so neither additional farmland nor additional energy inputs would be needed. As a simple solution, it is far less expensive and time consuming than many other ideas that attract funding.
H. Smith, LA Plant Genetics