Recently, an uprising occurred in the organic movement to revoke USDA organic certification for hydroponically grown produce. There are many reasons for the uprising, chief among them the fact that it is technically illegal according to the USDA National Organic Program standards to label hydroponic fruits and vegetables as organic (see sidebar).  The debate also raises an interesting question about the effects of this technologically-advanced produce growing method on climate change. Are there benefits of large-scale hydroponic farming in an age of climate change?

Cameron Holley, professor at University of New South Wales in Australia, believes large-scale hydroponic farming may be beneficial for the climate. “The controlled environment of hydroponic farming can facilitate better management of pests and nutrition, which in turn reduces potential externalities like nutrient or pesticide pollution,” he said. “This can help to reduce potential threats to ecosystems, whose resilience is already facing significant risks of disturbance due to climate change.” An environmental lawyer and empirical researcher focusing on natural resource management, Holley also noted that hydroponic farming has potential advantages for water management, making it more suited to coping with water stresses and scarcity caused by climate change.

UC Davis Professor Heiner Lieth focuses on crop ecology of greenhouse and nursery crops, greenhouse environment control automation, modeling of ornamental crops, and automated irrigation and specializes in hydroponic agriculture. He said one reason hydroponic plant production uses water more efficiently than other farming systems is that the water and nutrients are recycled.  “Hydroponics is about water management with systems that are designed to capture irrigation run-off. The leachate is then processed through filtration, clean-up, and blended with new water, and additional fertilizer injection, to be used again. This repeats as often as feasible. That means until things build up in the water which the plant does not take out (sodium, boron, etc.). At some point, after several (hopefully many) uses of the water, it then is discarded,” he said. “If you compare this approach to greenhouse production with a non-hydroponic approach,  you find that hydroponics is much more efficient in terms of total water and fertilizer use.”

Yet there is a higher energy investment in hydroponic agricultural production than in field production. Electricity is needed to move and aerate the water and to light the greenhouses at night. Because hydroponic growing tends to be an intensive and fast process compared to field production systems, greenhouses require heating in winter, often by using fossil fuels.  Hydroponic systems can also benefit economically by injecting additional CO2 into the plants so that they can grow faster. “So it is a complicated calculation to identify whether, as a system, one is more or less efficient than another in terms purely of CO2 balance,” said Lieth, adding, “I am not aware that [hydroponics] would affect the climate at all!”

If, as Professor Lieth suggested, hydroponic production has little to no effect on the climate, the question that remains is: is an agricultural system that has NO effect on climate change acceptable? In an era where every action counts– and the potential exists to mitigate climate change by using regenerative production systems that create a negative carbon effect– is it enough to stand by and effectively do nothing?

Hydroponics uses soilless culture with designed substrates, mixes and sometimes a completely liquid culture with no solids in the root zone. Thus, Hydroponic production systems offer no opportunity to sequester soil carbon, as does traditional “dirt farming.”

“Carbon sequestration can play a big role in making a cropping system carbon neutral or (better) negative,” said Phil Robertson, Distinguished Professor of Ecosystem Science at Michigan State University. Other management factors that would affect the carbon neutrality of a hydroponic system include:

1) energy used for lighting or irrigation,

2) energy used for any other management inputs, and

3) nitrous oxide and methane emissions.

“To [determine whether hydroponic production is climate-smart] requires a full life cycle analysis of different hydroponics configurations,” said Robertson. There may be researchers working on that, but this reporter couldn’t find any. In contrast, abundant research conducted throughout the world and reported in earlier issues of this column proves that to survive we must do more than stop emissions, and that produce growers have a lot of power to make a difference.

“We must remove and bury a very significant amount of carbon. Photosynthesis, exudates, stabilization through fungal digestion and finally sequestration in long-term deposits is the only feasible way to do that,” said Jack Kittredge, Soil Carbon Program Coordinator for NOFA/Mass. “Yes, most of the carbon put into the soil is labile and will not last. But the amount is so vast (15% of all atmospheric carbon moves into plants through photosynthesis each year) the small percent which is stabilized and sequestered can become very significant very quickly.”

Celebrated author-farmer Eliot Coleman said continuing research into the soil micro-biome is opening whole new vistas for a truly “biological” agriculture. “The organic farming philosophy can transform our human relationship with the planet. However, that’s only if we protect the meaning of the word organic, so there is no confusion with a non-sustainable, hermetically sealed, input-driven, technology-dependent system.”