What the Science Actually Says About Water Usage in Modern Farming

If you've spent any time researching sustainable farming methods, you've probably heard the claim: "Aquaponics uses less water than hydroponics." It's repeated across blogs, social media, and even some industry publications. But is it actually true?

As operators of a modern vertical hydroponic farm, we decided to dig into the peer-reviewed research. What we found challenges the conventional narrative and reveals that the real story is far more nuanced than most people realize.

Where the "Aquaponics Uses Less Water" Claim Comes From

The claim that aquaponics is more water-efficient than hydroponics typically originates from studies comparing aquaponics to drain-to-waste hydroponic systems not modern recirculating systems like NFT (Nutrient Film Technique) or aeroponics.

Drain-to-waste systems, as the name implies, deliver nutrient solution to plants and then discard the runoff. While these systems still exist (particularly in some large-scale commercial greenhouse operations growing tomatoes, peppers, and cucumbers) they represent an older approach to hydroponic farming.

Modern indoor vertical farms, including ours, use closed-loop recirculating systems where water is captured, filtered, and reused continuously. The only water lost is through plant transpiration (which is biologically unavoidable) and occasional nutrient solution changes when chemistry drifts too far from optimal levels.

What Peer-Reviewed Research Actually Shows

The Purdue University Study (Chen et al., 2020)

One of the most rigorous comparisons comes from researchers at Purdue University, who conducted the first study to evaluate hydroponics and aquaponics using identical system infrastructure. This is critical; most previous comparisons were flawed because they compared systems with different designs, scales, and operating conditions.

The Purdue study found that aquaponics produced 45% lower environmental impact than hydroponics when factoring in fossil fuel use, global warming potential, water acidification, and eutrophication. However the difference was largely driven by the energy source, not water efficiency.

Indiana (where the study was conducted) gets nearly 60% of its electricity from coal. When the researchers modeled using wind energy instead, the two systems became essentially equal in environmental impact. The study explicitly noted that "by using wind energy, farmers can reduce their environmental footprint enough to make these two systems essentially equal."

The Arizona State Comparison Study

A study published in the International Journal of Environmental Research and Public Health compared hydroponic and conventional lettuce production in Arizona. The results were striking:

•      Hydroponic water demand: 20 ± 3.8 liters per kilogram per year

•      Conventional field farming water demand: 250 ± 25 liters per kilogram per year

That's a 92% reduction in water usage for hydroponics compared to traditional agriculture performance that matches or exceeds aquaponics claims. We go into more depth on water usage inside of hydroponic farms in a past article if you would like to learn more.

University of Bologna Aeroponics Research

Research from the University of Bologna's experimental vertical farm found that high-pressure aeroponic systems increased water use efficiency by 114% compared to ebb-and-flow hydroponic systems. When researchers added dehumidifier water recovery to the system, water use efficiency improved by an additional 206%.

These numbers demonstrate that system design and management practices matter far more than whether fish are present in the water.

The Hidden Water Costs of Aquaponics

Aquaponics advocates often overlook several factors that affect true water efficiency:

Fish Tank Volume Requirements

Aquaponic systems require substantial water volume just to house the fish. Industry guidelines suggest 8-10 gallons of water per pound of mature fish. For a 200-tower system, this translates to 4,000-5,000 gallons of water that must be maintained—water that a hydroponic system simply doesn't need.

Fish Tank Surface Evaporation

Open fish tanks experience evaporation from the water surface a loss that doesn't occur in enclosed NFT channels or aeroponic chambers. While this can be mitigated with tank covers, it represents an additional engineering challenge and potential water loss.

Water Embedded in Fish Biomass

When fish are harvested, the water contained in their bodies leaves the system permanently. While this is also true for plant biomass in hydroponics, the fish component adds an additional water export pathway that pure hydroponic systems avoid.

The Real Numbers: Water Usage Across Systems

Based on the published research, here's how different growing methods compare for lettuce production:

•      Traditional field agriculture: 30-50 liters per kilogram (some estimates as high as 250 L/kg)

•      Drain-to-waste hydroponics: 5-8 liters per kilogram

•      Recirculating hydroponics (NFT/DWC): 1-3 liters per kilogram

•      Aeroponics: 1.6 liters per kilogram (with optimized systems even lower)

•      Aquaponics: 3 liters per kilogram (per 2024 commercial greenhouse study)

The data shows that well-managed recirculating hydroponic and aeroponic systems can match or exceed aquaponics water efficiency without the complexity of managing fish health, water chemistry for two different species, and the additional infrastructure requirements.

Why the Comparison Matters

We're not here to disparage aquaponics. It's a fascinating and valuable approach to food production that offers genuine benefits, including:

•      Dual protein and vegetable production from a single system

•      Elimination of synthetic fertilizers (fish waste provides nutrients)

•      Educational value and engagement with natural biological cycles

•      Near-zero discharge of nutrients into the environment

However, the claim that aquaponics is inherently more water-efficient than hydroponics is misleading when applied to modern recirculating systems. The comparison only holds when aquaponics is measured against outdated drain-to-waste hydroponic methods.

The Bottom Line

Both well-designed aquaponic and hydroponic systems can achieve remarkable water efficiency using 90-95% less water than traditional field agriculture. The key factors that determine water efficiency aren't whether fish are present, but rather:

1.    Closed-loop design: Recirculating systems dramatically outperform drain-to-waste

2.    Environmental control: Managing temperature and humidity reduces transpiration losses

3.    System maintenance: Preventing leaks and optimizing irrigation schedules

4.    Water recovery: Capturing condensation from HVAC systems for reuse

At our farm, we've chosen NFT hydroponics because it gives us the water efficiency we need, the crop consistency our customers expect, and the operational simplicity that allows us to focus on growing the freshest, most nutritious greens possible.

The next time someone tells you aquaponics uses less water than hydroponics, you can ask them: "Compared to what?" The answer matters.

References

Chen, P., Zhu, G., Kim, H.J., Brown, P.B., & Huang, J.Y. (2020). Comparative life cycle assessment of aquaponics and hydroponics in the Midwestern United States. Journal of Cleaner Production, 275, 122888.

Barbosa, G.L., et al. (2015). Comparison of land, water, and energy requirements of lettuce grown using hydroponic vs. conventional agricultural methods. International Journal of Environmental Research and Public Health, 12(6), 6879-6891.

Carotti, L., et al. (2023). Improving water use efficiency in vertical farming: Effects of growing systems, far-red radiation and planting density on lettuce cultivation. Agricultural Water Management, 285, 108365.

University of Wisconsin. Comparing the Sustainability of Aquaponics and Hydroponics Food Production Systems. Dairy Nutrient Knowledge Base.

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