by Melissa Pernell
Space farming research can help us improve controlled environment agriculture (CEA) systems so we can grow our food in a more resource conservative manner.
Controlled Environment Agriculture: Indoor growing environments that rely on pumps to circulate fertilizer in a water solution (i.e. hydroponics) and use energy efficient technology such as LEDs to provide photosynthetically-active light for plants. Sensors are used to monitor environmental conditions like temperature and humidity.
The International Space Station’s model of food production has a lot in common with how we ought to design our food distribution systems here on Earth. Interestingly, support for centralized food production in cities in gaining a lot of traction through the local foods movement. That is because people understand that growing food close to consumers uses less fossil fuels than growing food in the countryside and then shipping it into the city.
However, recent studies show that this is not entirely true: It is still more energetically expensive to grow food locally with CEA in city centers, but not by much. If current trends in renewable energy continue, it will soon cost less energy to grow food indoors using artificial lighting and high tech environmental controls than to ship food from traditional agricultural areas. Because of NASA’s research on light emitting diode (LED) technology, we now have energy efficient grow lighting available for agricultural use. The development of LED lights was motivated for space exploration, but the improvement and application of this technology has made CEA economically possible.
Before LEDs, indoor growing systems required obscene amounts of energy with grow lights like metal halide and high pressure sodium, meaning that only growing cash crops like marijuana could be economically feasible in these systems. With improvements in LEDs, we are just now starting to hit the economic/technological threshold where we are beginning to see the proliferation of CEA operations within cities. These systems are being built in populated areas close to consumers, conserving the fossil fuels currently used to ship produce across the country. With inevitable improvements in solar grid technology, these city-based CEA systems will soon use far less fossil fuel energy than shipping produce in from rural areas.
Even with the current energy costs of CEA, these systems are still more ecologically sustainable than soil based agriculture. Soil erosion is an unfortunate consequence of our current intensive agricultural paradigm and this is especially true for the annual crops that require soil disturbance for planting and harvesting. In contrast, CEA systems are predominantly hydroponic, which means that the soil that would have been used to grow that annual crop can now instead be devoted to perennial trees and shrubs which are able to capture carbon and rebuild farmland soils.
Annual vs. Perennial Crops: Annual crops must be planted from seed and harvested every year. An example of this type of crop is a carrot. In contrast, perennial crops are planted once and continue to produce for years afterwards. Berries and fruit trees are typically selected for perennial landscapes.
Some farmlands can even be left fallow to return to the complex forest ecosystems that can fix far more carbon and house a wider diversity of wildlife than is tolerated in farmland ecosystems. This is an important concept to consider when we think about habitat destruction and carbon release that occurs as a result of traditional soil based farming practices. CEA makes possible a paradigm shift that will solve several environmental issues all in one shot.
However, the source of nutrients for hydroponic CEA systems is seldom discussed. The nitrogen used in hydroponics relies on the Haber-Bosch Process, an energetically expensive method for fixing atmospheric nitrogen into a form that is usable by plants. Furthermore, the remaining mineral nutrients used in hydroponics are obtained from mining which causes habitat destruction and toxic run-off. Not only that, but the supply of these minerals is limited. For example, it is estimated that there are about 40 years left of mineable phosphorus stores available. After that, the only source left will be the phosphorus derived from animal waste.
There is a very necessary impetus to understand how to recycle plant nutrients from waste in a safe and sustainable manner, rather than depleting our natural resources by continuing to extract new resources. Fortunately, much of the research on nutrient cycling is funded by studies aimed at understanding these processes for application in space colonization. The holy grail of this research is the development of a resilient and truly closed loop ecosystem. Transforming waste into food in a closed system is the alchemy we need to master in order to make it over the first hurdle of self sufficient Martian colonization.
Closed Loop Ecosystem: An ecologically stable system consisting of the appropriate composite of microorganisms and higher organisms capable of nutrient cycling. A truly closed loop ecosystem does not require any input of nutrients from outside the system and no losses of nutrients occur or “fall out” of the cycle. A stable closed loop ecosystem is able to resist fluctuations in the populations of any particular species, thus preventing extinctions of species vital to the delivery of nutrients to other members of the system.
By creating CEA systems that function independently from nature, like we aim to do during space colonization, we are removing the pressure that we have imposed on Earth’s ecosystems when we converted so much forest and prairie into farmland. When annual crops are grown indoors, close to consumers, the farmland that was once used in a soil depleting way can be dedicated to growing perennial trees and shrubs that contribute to soil building, water table stabilization and carbon sequestration.