Sandia LabNews

Labs-led team tests hydroponic greenhouse method for crops to reduce possibility of future water wars

researcher testing on small trays

It doesn’t take a mathematician –"particularly in water-starved times –"to see the advantage of a method that uses roughly one percent the fresh water formerly needed to grow the same amount of crops: Much more water would be available for human consumption and other beneficial uses than from the small, though real, economies generated by low-flush toilets and low-flow showers.

That’s the magnitude of water savings claimed by Mexican researchers in a specialized hydroponic greenhouse project in arid Chihuahua. These results are now being replicated and tested by a bevy of wireless sensors being installed in a forage-growing greenhouse built barely a stone’s throw from the Mexico border under the supervision of Sandia.

 Sandia work is led by Ron Pate and Phil Pohl (both 6143). Mexican researchers, led by Purdue PhD engineering graduate Hector Gallegos and forage greenhouse system fabricator Francisco Aguirre, as well as other researchers at New Mexico State and the University of Arizona, are also involved in the project.

"The potential savings in water is particularly important in the American Southwest, Mexico, and other water-parched regions like the Middle East and certain lands between India and Pakistan," says Ron, "where the majority of water use is for irrigated agriculture rather than direct human consumption or residential and industrial use." Thus a reduction in agricultural usage greatly increases the amount potentially available for other productive uses.

From 800,000 to 11,000 acre-feet

Preliminary indications are that hydroponic greenhouses in New Mexico, for example, could reduce the current 800,000 acre-feet of water to 11,000 acre-feet to produce an equivalent amount [dry weight] of livestock forage, and do this on less than 1,000 acres instead of 260,000 acres –"the current amount used for New Mexico production of alfalfa. Eighty percent of New Mexico’s water use is agricultural, over half of which goes toward growing forage mostly consisting of alfalfa.

Similar conditions of water use exist in many places in the world.

Conventional farming methods in arid regions lose huge amounts of water through evaporation and over-absorption by soil. Over time, this can also result in soil salination and loss of agricultural productivity. Neither are factors in hydroponic greenhouses, which do not require high-quality arable land to function in the first place.

A cause for war

While agricultural tradition, cultural factors, and economic realities make immediate implementation of hydroponic greenhouse methods for livestock forage doubtful, at least in New Mexico, Sandia is interested because, Ron says, "Discussions at Sandia’s Advanced Concepts Group and elsewhere have targeted disputes over water as possible, if not likely, causes for international conflict or war in the 21st century." Echoes Sandia director Peter Davies (6100), "A large proportion of freshwater usage around the world is agricultural, so the ability to reduce the amount of water needed for it and thus lessen the possibility of conflict is extremely important to the security of the United States and the world."

Says Gerry Yonas (16000), Sandia Principal Scientist and director of the Labs’ Advanced Concept Group (ACG), "Because the ACG looks to future global security issues, we advanced the idea of a bi-national lab between Mexico and the US to deal with border issues that have a potential for conflict. This project is the first fruit of that idea."

Says Jessica Turnley, a Sandia consultant and director of the Sandia-spun-off Bi-National Sustainability Laboratory, "We look forward to using the greenhouse facility to work with Sandia and with scientists and community folk from both sides of the border to develop technologies to help improve the quality of life."

Herds kept alive in drought

Mexican ranchers in times of drought have already used relatively inexpensive hydroponic greenhouses to grow feed to preserve their herds, says Gallegos.

He and his researchers take a keen interest in the US project, taking place just north of the US/Mexico border in Santa Teresa, N.M., a few miles west of El Paso. They come up weekly from Ciudad Chihuahua –"a drive of about 3.5 hours –"to help in design, construction, and implementation of the project.

"The difference [between our projects and this one] is the sensors Sandia is installing to check things there," Gallegos said in a telephone interview from Chihuahua. "Normally we only use a humidity sensor to know when to run our irrigation." The Sandia-placed sensors and computer simulations will tell him how to grow crops still more efficiently, he says. "We need to review the amount of water used in the greenhouse; the only way to do this is to determine accurately the amount needed at every step." Also, he says, the Mexican tests used only readily available wheat and corn; the Sandia tests include triticale, sorghum, barley, and oats.

"We want to be aware of microclimate variances," says Ron. "We want to know how feed grows from changes in temperature and location and time of watering. That will help us modify the design and operation of the greenhouses."

The way it works

The dense array of sensors in the 8m x 18m (26 ft by 59 ft) greenhouse will monitor light, temperature, relative humidity, and air pressure. The data, collected every few minutes, will be sent by phone line to a remote computer for analysis. "We expect that the [greenhouse] system will not be as slow-moving or spatially homogeneous as one might think in terms of environmental change," Ron says. "Every time the water system pops on, the local temperature around the plants drops relatively quickly." Water sprays from quarter-inch nozzles for 20 seconds into plants growing in a series of plastic trays stacked on metal racks, whenever a humidity sensor or a back-up timer trips a control circuit. To lessen labor and also protect against mold, the researchers are exploring the development and use of trays that themselves would be edible by livestock, thus making washing and sanitizing trays unnecessary.  Such tray material could also add nutrition content to the overall forage product, making it a more balanced ration for the livestock.  Consumption of water, seed, and labor are also being monitored.

The nutritional quality of the hydroponically grown plants will be determined by Clint Loest, a professor of animal nutrition at New Mexico State University, whose lab will compare results of feed testing with the animals’ actual requirements.

"This is definitely unique in the animal forage area," he said. "If we can get the animals to perform just as well on greenhouse forage, that would be an incredible advance. It would be such a breakthrough that we might even give up a little performance if it’s going to save so much water."

The hydroponic greenhouse, also known as "protected agriculture" or "controlled environment agriculture," also controls and modifies light reaching the plants. Experiments will reduce light intensity and restrict certain frequencies, using a variety of shading mechanisms to avoid overheating and improve plant growth. 

The "speaking plant" approach

Says Gene Giacomelli, director of the highly regarded Controlled Environment Agricultural Program in the Agricultural and Biosystems Engineering Department, University of Arizona, "Sandia has advanced technologies that can be added to lower the cost of traditional environmental sensing." In addition to the wireless technologies currently being installed, Giacomelli mentioned a possible "speaking plant approach," where very small, lightweight, inexpensive sensors are put directly on each plant to monitor the plant’s water status, temperature, and growth rate. "We envision these [futuristic] sensors linked together [via wireless communications], possibly on every plant, so the plant tells the control system directly what it needs, instead of merely monitoring air around the plant. The plant may have other needs these [more distant sensors] don’t tell us. This will be the highest tech going."

He complimented Sandia researchers for seeking out expertise to complement traditional Sandia strengths. "They recognized that when you apply technology to a biological system, you can’t just plunk it in there without having biological expertise to apply the high tech in a practical way."

The solar way

Experiments are also being planned to use the blocked light to create another asset: solar-generated electrical power. (Greenhouse pumps, timers, and sensors are already powered by freestanding solar modules that change light into electricity, which is then stored in batteries for nighttime use and during cloudy weather conditions.)

 "Greenhouses could be a solar source," says Sandia researcher Vipin Gupta (6233), "because sunlight has to be filtered in arid areas to prevent crop damage because it is too intense. The challenge is to create reliable, effective materials to use that part of the spectrum the plant is not interested in using to produce power that can be put on a grid as well as operate the greenhouse." Vipin is currently based at the University of Texas at El Paso’s Materials Research Technology Institute and serves as a local focal point for the project. Sandia technologist Ed Baynes (4148) is based in Las Cruces and provides technical support for the greenhouse. Nina Berry and Jesse Davis (both 8961), with two summer student interns, are helping implement the wireless networked sensor array and cell phone data link, expected to be installed in mid-September.