Environmental Feasibility of Hydroponic and Aquaponic Systems
Environmental feasibility is also a very important factor to evaluate when considering the commercial implementation of hydroponics and aquaponics. Conventional agriculture poses many environmental concerns with two being excessive land use and water use. According to the United States Department of Agriculture, conventional agriculture is associated with about 80% of the nation’s water use, and this rate can surpass 90% in some western states. The need for more land to expand existing agricultural practice often poses a threat to species whose habitats are subsequently destroyed to make space for farmland. Similarly, the increased use of water for agriculture leads to the pollution of freshwater bodies. According to the Food and Agricultural Association of the United Nations, traditional irrigation techniques and the increased use of pesticides are primarily responsible for the degradation of water quality of freshwater bodies, through pollutant runoff, which has a negative impact on water biodiversity and fisheries. In this article, we will explore the comparisons between traditional agricultural methods and alternative hydroponic and aquaponic systems in terms of water, land, and energy consumption.
In the next 25 years, population growth will cause an increase in water scarcity, with traditional farming practices causing a 40% global water deficit by 2030. When groundwater stores are used up or contaminated, the water once used to irrigate crops will become depleted and global food production will suffer. To support aquaponics systems, the demand for water is less than 100 L/kg of fish harvested, whereas recirculating agriculture systems on other fish farms require an average of 400 L/kg of fish raised. Overall, examining the implications of switching over to aquaponic systems from conventional fish farms indicates promising water conservation. Water conservation is important to preserve biodiversity because without sufficient water, stresses on species lead to global biodiversity loss.
Water shortage has become more prevalent due to conventional agricultural practices, which take up significant water resources. There are other strains on water availability, most notably, global population growth and climate change. Warmer air, a key factor of climate change, tends to hold more moisture and so more water will evaporate from oceans and lakes, leading to a drier environment that can have a negative impact on drinking water supply, which is also used in agriculture. These changes pose an even greater demand for efficient water allocation in the agricultural sector. Based on trends in the rising population, it is predicted that by 2050, agriculture will need to output 60% more food worldwide. Additionally, based on climate change predictions, freshwater availability is likely to decrease and limit agriculture yields by the end of the 21st century since conventional farming practices currently account for 70% of freshwater use worldwide.
Currently, with 95 million land acres protected by the National Wildlife Refuge System, less than 4 percent of the continental United States is dedicated to preserving land and water-based biodiversity. A study from the Center for Sustainability and the Global Environment at the University of Wisconsin-Madison found that croplands in the United States have expanded at a rate of more than one million acres per year. This conversion demonstrates a pattern of encroachment into areas that are significant for wildlife and maintaining biodiversity. Grasslands are the main source of land converted to agriculture in the United States, which is especially detrimental for native pollinators, birds, and plant species. Soil nutrient depletion is another concern in these lands which stems from the intensification of land dedicated to agricultural practices like tilling. In order to mitigate biodiversity loss, we must look towards alternative agricultural methods that require less land for the same crop output.
That being said, with land and water conservation being so crucial to keep up the global food supply, the abundance of renewable energy, such as solar, geothermal, and windpower, should be considered in conjunction with hydroponic systems. Alternative agriculture, although promising, needs more sophistication in terms of energy efficiency. If the government and local grass roots supporters provide subsidies to alleviate some of the initial implementation costs of infrastructure, we will likely see more sustainable and cost-effective systems take hold.
Hydroponics Case Study: Yuma, Arizona
Hydroponic systems have been shown to produce viable crop outputs, as shown by this case study on hydroponically grown lettuce in Yuma, Arizona. This study was done at the School of Sustainable Engineering and the Built Environment at Arizona State University, and it quantified the water and land demands of both hydroponically and conventionally grown lettuce. It was found that per greenhouse unit of 815 m2, hydroponics systems demanded 20 L/kg/yr of water (requiring X L of water per kilogram of lettuce annually), whereas conventional lettuce production demanded approximately 250 L/kg/yr of water per the same land area. This information is shown visually in Figure 3. Based on this comparison, it is clear that hydroponic agriculture is more suited for water scarce areas.
In addition to conserving water resources, hydroponic systems produce higher yields per greenhouse unit than conventional agricultural systems. According to the case study from Yuma, Arizona, per greenhouse unit of 815 m2, hydroponic systems showed yields averaging up to 47.1 kg/m2/yr whereas traditional farming methods were only able to meet an average output of 3.8 kg/m2/yr, as displayed in Figure 4. It has been established that the agricultural sector will need to account for 60% more food output by the mid-twentieth century, which means that farms will either need to expand their lands or find more efficient ways of growing crops. As a prominent consequence of land expansion is the destruction of natural ecosystems, the displacement of native fauna and flora and generally harming biodiversity, hydroponics is an effective mitigation strategy for increasing yields in existing land spaces.
There are notable trends in the amount of farms in the United States and how the acreage of those farms have changed over time. For example, in 1935, the number of farms in the US peaked at 6.8 million with an average of 155 acres per operation (about the size of 117 football fields). In 2017, however, there were only 2.05 million farms in operation, at an average size of 444 acres (about the size of 340 football fields). With 4.75 million less farms in operation today than in the early 20th century, crops have to travel further distances to reach consumers, contributing to greenhouse gas emissions and nutrient depletion.
Hydroponics and other alternative agriculture systems can achieve localized food production in both rural and urban areas. To examine cities in particular, localized food production has a host of benefits, from less required transportation, greater nutrient richness, efficient land allocation from vertical farming techniques (which are especially viable in urban spaces), and reduced food waste. According to research from the Natural Resources Defense Council, of all food grown in the United States, up to 40 percent goes to waste between harvest and consumption. Localized food production has the potential to limit waste because produce can be purchased by the community sooner after harvest. Hydroponically grown lettuce is often sold with the roots still intact, which also increases lifespan and thus decreases waste. Finally, if a multitude of hydroponic farms were distributed throughout the United States, the food distribution would become localized and farm workers could better identify the demand for certain crops by the people in their specific area. With this understanding, farmers will be able to only grow what they need, and there will be less food waste.
Hydroponic systems have a host of benefits when compared with conventional farming, but one cannot argue that these systems are perfect alternatives. There is a lot of progress to be made in one area in particular, which is energy consumption. As shown in Figure 6, in the Arizona case study, researchers found that hydroponically grown lettuce has energy demands of 90,000 ± 11,000 kJ/kg/yr, whereas conventional farming called for just 1100 ± 75 kJ/kg/yr. This illustrates how energy availability is a huge factor bearing on the sustainability of alternative agriculture systems. That being said, with land and water conservation being so crucial to keep up the global food supply, the abundance of renewable energy, such as solar, geothermal, and wind power) should be considered in conjunction with hydroponic systems. Hydroponics is a promising technology that needs more sophistication in terms of energy efficiency. If the government and local grass root supporters provide subsidies to alleviate some of the initial implementation costs of hydroponics infrastructure, we will likely see more sustainable and cost-effective systems take hold.
A way to mitigate the large energy expenditure of alternative agriculture systems would be to implement rooftop hydroponic farms with retractable roof systems in urban areas with less space. Thus, instead of relying entirely on LED lights to grow the produce, sunlight could be used as supplementation. This is one potential way to reduce the energy input of hydroponic systems, and with the proper research and investments, more technological innovations can be explored to increase the viability of alternative agriculture. Thus, although the high energy demand of hydroponics is a downside, it can be overcome through innovations in renewable energy alternatives and improved efficiency. For more information about improving the energy efficiency of hydroponics systems, reference the article from Alternative Agriculture.
Aquaponics Case Study: Hawaii vs. Maryland
Aquaponics also produces a considerable output of produce in addition to its benefits in resource management. Dr. David Love from Johns Hopkins University and Dr. Kanae Tokunaga from the University of Tokyo conducted a case study of five commercial aquaponic farms in Hawaii and in one teaching facility in Maryland to address two main questions:
- What does the use of resources such as water, energy, feed, and labour look like?
- What are the economic outputs of these small scale farms?
Overall, the study found that the Maryland system used 36m3/yr while the Hawaii system only used 5.1 m3/yr. This data can be found in Figure 8 on the right. The researchers accounted for this difference as the Hawaii system made use of natural rainwater while the Maryland system used exclusively pipe-line drinking water. They do note that the use of 100% rainwater systems are very rare in the United States and that the actual makeup of water resources would approximately consist of one-third of operations using exclusively municipal water, one-fifth using exclusively groundwater or well water, and one-third combining reliable sources like municipal water with rainwater and surface water while the rest utilize 100% rain-fed systems. If instead commercial aquaponics farms could aim to use as much rainwater as they could, then it would be much easier to make up for the water loss. The structure of the system will help address the issue of runoff of pollutants, the biggest issue with conventional agriculture, while using less water than conventional methods as well.
One of the advantages of implementing aquaponics systems that the study suggests is implementing these commercial systems in lands lacking fertile soil, which is vital for the growth of many commercial crops. Since aquaponics doesn’t rely on soil, but rather water and fish, these systems can be implemented even where there is no soil. This means that there will not be as much of a need to expand farming lands into natural habitats when crops that can be grown through aquaponics are grown that way.
Environmental Impact: Conclusion
In summary, it has been proven that hydroponic and aquaponic systems have numerous benefits in promoting sustainable agriculture. The main two benefits discussed here were water and land conservation, which specific case studies referenced from Arizona, Maryland, and Hawaii. The main drawback of alternative agriculture systems that remains pervasive today is the significant energy demand for controlled-environment farming. We have explored some renewable energy alternatives here, and a more in depth discussion on energy can be found in the Prototype – MIT Exhibit article within the Alternative Agriculture drop down menu. There is a dire need for innovations in the agriculture industry that support a sustainable future. The Terrascope Class of 2024 believes that hydroponic and aquaponic systems are the best implementations to achieve this goal. For more information about the economic feasibility and costs of implementing hydroponics and aquaponics systems, reference the article from the Alternative Agriculture drop down titled Economic Feasibility.