Alternative Energy

Published on June 29th, 2010 | by Susan Kraemer

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Economical Energy for a Water Constrained Future

To prepare for our carbon-constrained and water-scarce future, as more and more of the world’s land turns into desert with climate change, researchers at the Masdar Institute in the United Arab Emirates are working on developing a bio-fuel from a crop that can grow on desert soil using salt water.

Inspired by the work of the Seawater Foundation in Eritrea, they are using an interesting new technology called “integrated seawater agriculture” – a kind of a three-stage permaculture cycle – to grow an oil-rich cactus that has never been farmed before, to be used as a biofuel.

Image: Tucson Cactus Society salicornia

Salicornia is one of 10,000 species that can grow in salt water

First they dig a canal from the sea. Initially that salt water is pumped past cages to grow shrimp or fish. Normally farm runoff contains concentrations of shrimp or fish feces that create algae blooms.

But instead of allowing it to flow back to the sea, then they will pump it inland to use as fertilizer to farm Salicornia, which grows naturally (if sparsely) on desert soil with only salt water irrigation.

Finally, the runoff from that saltier irrigation is allowed to flow towards the sea through a mangrove forest, which can grow in extremely salty water. The mangrove forest filters the water back to normal sea water salinity, and absorbs the remainder of the polluted water from the fish farm, and provides leaves to feed the fish. A virtuous circle.

Boeing and the UAW’s Etihad Airways are supporting the project, hoping it will supply jet fuel for use in the carbon-constrained world of the future, and UOP Honeywell is supplying a proprietary biomass conversion technology. Challenges include designing a mechanical harvester that is not damaged by the high salt levels, but the promise is of making a fuel as cheap as petroleum-based fuels.

The cost effectiveness comes from the side income from the fish or shrimp farm, and the free fertilizer and water for the biofuel; while the climate-friendliness comes from using a fertilizer that needs absolutely no fossil-fuels to make or transport, and carbon that gets sequestered in the Mangrove roots. Production would be limited only by how much desert land is available bordered by the ocean.

The Masdar research is looking at how much carbon is sequestered by the Mangroves, to see if it is enough to make Salicornia production carbon-negative, not merely carbon-neutral like most biofuels.

Source: Technology Review





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