Cost-Benefit Analysis of Using a Recirculating Fertigation System as an Alternative to Conventional Drain-to-Waste for Container Food Crop Production.

Conventional drain-to-waste hydroponic practices pose a number of cost-related and environmental issues. In this case “Conventional drain-to-waste” hydroponics is defined as the practice of watering plants with irrigation to a point in which fertigated water escapes the growing medium and begins running off.  This fertigated drainage, or the irrigation water mixed with fertilizer, is discarded entirely as waste, whereas in a “recirculating fertigation system”, the drainage is collected, recycled, and pumped back into the irrigation system to continue feeding the plants.

Negative impacts of conventional drain-to-waste systems include high costs associated with single pass nutrients[1], high water consumption[2], and the exposure of fertigated drainage into the surrounding environment. A recirculating fertigation system may be capable of addressing these particular inefficiencies.  However, the installation of a recirculating system comes with higher upfront costs, ongoing operational costs, and other inherent risks associated with a more complex hydroponic system.  Perhaps these potential costs and risks are why a nationwide survey of greenhouse and nursery crop growers in the United States showed that only 12% of the polled growers were interested in implementing water conservation measures[3], despite increasing nationwide water shortages and restrictions.  

With seemingly no relatable cost-benefit analysis available to prove whether or not a return on investment (ROI) is possible on a small scale, there is little incentive for small farmers to make this leap.  Thus, the objective of this study is to determine whether a recirculating fertigation system is a cost effective, suitable and sustainable alternative to conventional drain-to-waste practices.  

This project seeks to analyze whether a recirculating fertigation system can provide a cost effective, suitable and sustainable alternative to conventional drain-to-waste practices for small scale farms in the Northeast United States.  The primary objectives, therefore, are:

1. Firstly, what are the true costs (material, labor, operations) associated with retrofitting one greenhouse from its current drain-to-waste setup, into a recirculating fertigation system? What nutrient-related cost savings, if any, can be achieved with the recirculating system throughout the course of one grow cycle?  How do these savings compare to the conventional drain-to-waste approach? Finally, over what period, if any, can a Return on Investment (ROI) be expected with the recirculating fertigation approach?
2. Secondly, what is the suitability of running a recirculating fertigation system in the Northeast?  In particular, is it possible to maintain comparable water quality, plant health, and crop yield levels when employing the recirculating system?  What unforeseen challenges will arise as a result of this system?
3. Thirdly, is the recirculating fertigation system any more sustainable than the conventional drain-to-waste system?  When studying the metrics of nutrient consumption, water consumption, and fertigated wastewater runoff, how does the recirculating system compare to the conventional drain-to-waste methodology?