Zero Impact Farming is a concept we developed to describe farming with minimal use of resources, and minimal impact on the environment. This encompasses water and electricity use, soil degradation, pollution and other environmental diseconomies, land efficiency, labor efficiency, and inputs consumed or destroyed in the production process. We strive to make our footprint as small as possible!
Kunia Country Farms LLC, the Farm, operates a deep water culture aquaponic system to grow mainly leafy greens. Currently, we grow Manoa lettuce, red and green oakleaf varieties, and baby lettuces and microgreens.
Our 18 grow beds are covered by styrofoam floats as you can see in the adjacent photo. Thus, the system has very little evaporation. We have four uncovered fish tanks, 12 feet in diameter each, and one covered sump tank. The ratio of uncovered water in our system is about 3%.
In the past year and a half, under commercial growing volume, we have added minimal water. We have actually lost water to overflows during sustained rainfall. One inch of rain adds 7,500 gallons to our system.
Land Use Efficiency
Aquaponic farming is one of the most efficient farming technologies currently in use. The one acre farm can produce between 3,300 and 5,000 heads of lettuce each week depending on the growing season. Heads are grown on 4 foot by 4 foot styrofoam rafts, 36 heads to a raft for the Manoa variety. There is very little "tending" required during the growout period, so we can build the troughs very close together and pack the rafts tightly as well. Each trough holds about 1,725 heads of Manoa lettuce, so 18 troughs hold a little over 31,000 heads.
Rafts are lifted to a shaded harvesting area, and immediately cooled in an adjacent walk-in reefer. Harvesting in a separate shaded area means the growing field can be loaded to optimum density. Rafts can be removed for harvest from the downstream end of each trough.
Hawaii has the highest average electricity rates in the US. Our rates range from 33 cents per KWH on Oahu, up to 44 cents per KWH on the island of Lanai. Generally, Hawaii is more than double the national average, with New York having the second highest average of 18.6 cents per KWH. It is imperative for us to conscientiously use electricity.
The Farm runs a minimum of equipment: one variable speed water pump, two blowers for aeration, and the walk-in reefer. We will soon add a second variable speed pump, so the two pumps can each run more efficiently at half power. Blowers are a 24/7 necessity for the health of the fish and produce, but the reefer is run only for harvest and produce pickup twice a week. Pictured at left is the reefer just prior to shutdown.