From: Aquaculture Irrigation Combination

Hydroponically Grown Biomass: The Energy Solution?

The great debate these days has become, how do we break free from fossil fuels and agree on the next great renewable energy resource? Along with all the other benefits enumerated here, IMPS offer truly fecund productivity: optimized to grow woody biomass, aquaculture may be the best answer of all.

Growers of corn ethanol, sugar cane, and switchgrass are loudly stating their cases, but, on a scientific basis, the more logical course lies elsewhere.

First, there are serious improbabilities inherent in using any land crops to supply our energy needs. “There would not be enough farmland to do it—let alone water,” says Clifford Fedler. However, “recycled water aquatic plants could readily do it,” he says, adding that, of course, “any shift to an all-renewable fuel economy would involve a diverse portfolio of resources.”

As it happens, the remarkable vegetation that thrives better than any also delivers, on a per volume basis, the highest energy content: water hyacinth. Once it hits stride in hydroponic aquaculture, the yields are way beyond anything else: per acre, 10–15 times more biomass than the best land-base competitor other than sugar cane (in which the advantage of water hyacinth is still multiple times greater). Comparing it to the much-discussed switchgrass, water hyacinth produces five to 10 times more energy per acre.

Pound-for-pound, water hyacinth also yields twice the fuel caloric value of sugar cane.

And, from a resource efficiency standpoint, all of this bounty comes with a tremendous saving of water—which is fast-becoming equally critical to ramping up renewable energy. Land-based sugar cane, “takes quite a significant quantity of water to produce,” notes Fedler. “That’s water you’re not going to get back to use for other purposes.”

With hydroponic water hyacinth, the water doesn’t get splurged on soil irrigation, and, thus—except for a modest loss through evaporation and at harvest—it is largely conserved through recycling in situ. Although Fedler has not analyzed the water usage differential of competing specific crops, he estimates the advantage of hydroponics over land crops could easily be higher than tenfold. The difference probably becomes even greater when expressed as a proportion against the net energy produced.

Comparatively speaking, expending vast quantities of potable well water to grow cellulosic ethanol—as is now done—“is utterly ridiculous,” he says flatly. However, precisely this is still prominently favored, solely because cane and sorghum starch content easily converts to sugars and, thus, to fuel. Notwithstanding this virtue, hydroponics yield comparatively much higher return on investment. Any other approach is a grave mistake, he cautions.

To process water hyacinth for fuel conversion requires simply drying the plants in the sun a few days, and then cost-effective gasifying. Also, unlike the unsteady output of wind and solar power, biomass of any kind is available always. For that matter, water hyacinth or any biomass plant is actually, he notes, “a good natural solar collector and a storage system.”

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And because plants perform photosynthesis—removing carbon dioxide, which is a greenhouse gas—biomass is carbon-neutral.

What might be the potential impact? Fedler finds that, if all the wastewater from cattle, swine, and poultry lots in the US were somehow recycled to grow biomass, it could supply 80% of our nation’s total electricity.