Energy, water and nutrient impacts of California-grown vegetables compared to controlled environmental agriculture systems in Atlanta, GA
Steven W. Van Ginkel, Thomas Igou, Yongsheng Chen*School of Civil and Environmental Engineering, Georgia Institute of Technology, 200 Bobby Dodd Way, Atlanta, GA 30332, United States.
Citation
Van Ginkel, S.W., T. Igou, and Y. Chen. 2017. Energy, water and nutrient impacts of California-grown vegetables compared to controlled environmental agriculture systems in Atlanta, GA. Resources, Conservation and Recycling 122:319-325. Https://doi.org/10.1016/j.resconrec.2017.03.003 (Links to an external site.)
Background
This paper compares the efficiency of California Based traditional vegetable agriculture to hydroponics and aquaponics systems. Efficiency is defined by water usage, energy and nutrient input as it relates to crop yield. California is the leader in fruit and vegetable agriculture; therefore the rest of the United States is reliant on their system. However, California is also susceptible to severe drought, which can lead to reduce yields. Additionally, California has very large watershed, which can cause runoff of fertilizers in ponds, lakes and other bodies of water. Therefore to mitigate the environmental footprint of agriculture production, the author’s suggests that future generations focus on urban agriculture. Aquaponics is a system that allows the production of vegetables and fish, while reducing the input of fertilizers, and using waste byproducts as the source of nutrients. The authors show that this system reduces the nutrient input, water usage and is more productive that traditional based vegetable production. Therefore the purpose of this paper is to compare and contrast the productivity of each system.
Experimental Design
California vegetable data was derived from www.casestudies.ucdavis.edu. Data was taken for several crops including tomato, spinach, strawberries, peppers, and broccoli. The data displays yield, nutrient input, energy input for each crop. The data was normalized by dividing each component by yield per acre. For hydroponics, there was one grower who grew lettuce and leafy greens in shipping containers. The data was normalized for energy (lighting and cooling) and water usages over a year divided by yield per container. For aquaponics, there were three growers, one from Hawaii and two from University of Virgin Islands and Atlanta, GA. All growers used deep-water culture and grew leafy greens. The data was normalized for energy and water utilized over a year divided by the yearly productivity. Data from all three systems was then compared using statistical analysis.
Results
Areal Productivity
When comparing hydroponics and aquaponics there was no significant difference in the areal productivity. However, there was a significant difference between the ponic-systems and the California-based system. Ponic-systems were found to be 10 to 29 times more productive than the California-based system. In addition, areal productivity in hydroponics could be substantially improved increasing vertical production in closed environments.
Energy Usage
Hydroponics uses 30 times more energy (lighting, cooling) than the California-based system. There was no significant difference in energy usage between aquaponics and California-based system. However there were differences in energy usage between aquaponic growers, therefore it is would be wise to compare each aquaponic grower to the California-based system in the future.
Water Usage
California-system uses 66 and 8 times more water than hydroponics and aquaponics. There were differences in water usage between hydroponics and aquaponics, however the authors suggests that results maybe skewed due to the lack of data points.
Conclusion
Based on the authors study, it seems that ponic-systems are overall more efficient than California-based system. They believe that these systems should be integrated into urban cities. By integrating such systems, cities become less reliant on vegetable and fruit production from California. At the same time it reduces the negative environmental footprint. Nevertheless, the biggest challenge will be to address the socio-economic challenges in integrating the system into urban environments.
1. What are some challenges in integrating ponic-systems into urban cities?
A few challenges that come to mind have to do with infrastructure and city laws or ordinances. In terms of infrastructure – ponic systems require water. Clean water. It isn’t a consideration that we have to think about much in the Midwest but there are plenty of places where water is scare. It has to first be used for the people living in the cities and what is left can go to agriculture. Is that enough to support huge indoor vertical farming operations? Even for small operations, many cities have tons of red tape around putting up high-tunnels and greenhouses. The monetary and time cost of complying with policy and zoning requirements can be a huge barrier to starting up an operation in a city. Also, the cost for getting some square footage in a city will continue to increase as more and more people move into cities, the cost/revenue of ponics systems may not hold up for many who attempt it.
Indoor farming actually can recover water from the air by condensation naturally occurring at the A/C unit. This aspect attracts venture companies who want to do more food production in arid or semi-arid areas. Other challenges you mentioned are true.
If you were a traditional based grower, what kind of information would you want to have to consider shifting your vegetable production to ponic-systems?
To successfully manage multiple biological systems (fish, bacteria and plants) a grower would need specific knowledge of each species in the ponic system as well as how those species interact. Comprehensive environmental monitoring and gradual adjustments to the environment are likely necessary to maximize productivity in the system. More research is needed to recommend specific protocols, this also depends on the scale of the operation.
If I were a traditional based grower, I would need to know the cost of shifting my operation from traditional production to a ponic-system. I would need to know the cost of a greenhouse/warehouse, the cost of new equipment, etc. Additionally, I would need to ensure that there is a market for my ponic-grown product. Finally, I would need to evaluate the potential of selling my equipment that was used for traditional growing or if any of this equipment could be used for my new ponic operation.
There are lots of options, but a few things I would want to know are the current profit-margins to expect from ponic systems at different scales, price differences of vegetables produced in ponic systems vs. field, expected locations for growth in ponic agriculture, state of current/future competition, facilities and production start-up/maintenance costs, distribution differences compared to field vegetables, and consumer demand for unique selling points of ponic vegetables (e.g. organic, quality traits).
Seems like integrating two and potentially three biological systems into one hydroponic or aquaponic system is more challenging than it looks like especially in aquaponics. Environment and organism such pathogens not only affect one system it affects both. I wonder if a niche market can pay enough to maintain such a system commercially viable. More research is needed to provide a friendly manual to producers on how to manage the temperature in winter, disease, nutrition and deficiencies, biological cycles, and potential revenue.