In Qatar last month, we reported that Norwegian company Yara had teamed with the Qatari government on the Sahara Forest project that will use solar power and sea water to produce food crops such as tomatoes, cucumber, melon, fodder crops, freshwater, clean energy, salt, algae and for biofuel.
Let’s look at this project in more detail.
The metrics? A commercial scale project of 4,000 hectares would supply enough power for the project and export 325GWh a year in addition to 7,500 tonnes of algae oil, and hundreds of thousands of tonnes of food and fodder crops.
Industrial Symbiosis – one system’s wastes are another system’s inputs
Traditionally production systems are set up as a linear process – transferring resources into products, but also ending up with various waste-streams as a consequence. In biological systems this linear process is very rarely encountered.
Organisms that waste resources and energy have very low chances for success. The direction that nature points technology towards is clear — technological systems where the waste product from one technology is used as resource for another. This integrated technological system allows for harvesting beneficial synergies and increased efficiencies of the individual technologies.
The project has seven distinct facilities including concentrated solar power (CSP), saltwater-cooled greenhouses, outside vegetation and evaporative hedges, photovoltaic solar power, salt production, halophytes and algae production.
The project concept and technologies can be implemented in many of the world’s hot deserts including Qatar.
How the symbiosis works
1. Concentrated Solar Power
A simple interface replaces the cooling towers of a typical CSP plant with a saltwater cooling system that utilizes greenhouse roofs to dissipate the waste heat from the CSP process. The heat from the CSP mirrors is used to drive a multistage evaporative desalination system for production of distilled water for the plants in the greenhouse and outside. The waste heat is used to warm the greenhouses in the winter and to regenerate the desiccant used for dehumidifying the air.
2. Saltwater greenhouses
Saltwater-cooled greenhouses provide suitable growing conditions that enable year-round cultivation of high-value vegetable crops in the harsh Qatari desert. The cooling system is an evaporative cooler at one end of the greenhouse. The cool air is supplied under the plants via polythene ducts to ensure that the cool air is distributed evenly along the greenhouse and at low level.
As the air heats up it rises and is expelled via high level openings in the end wall. The middle bay has a twin skin ETFE membrane roof that forms a void over the greenhouse. When the air is passed through the void at night it cools and the moisture in the air condense out to give fresh water that can be used for irrigation of the plants.
By using saltwater to provide evaporative cooling and humidification, the crops’ water requirements are minimized and yields maximized with a minimal carbon footprint.
3. Outside vegetation and evaporative hedges
The water coming from the greenhouse is at a concentration of about 15% salinity. To reduce the water content further, the brine is passed over external vertical evaporators set out in an array to create sheltered and humid environments.
4. Photovoltaic Solar Power
The Pilot Plant is supported by state of the art PV-technology. Dust arresting from the surrounding vegetation and water for cleaning the PV-panels ensure an efficient electricity generation.
5. Salt production
As the water is evaporated from saltwater the salinity increases to the point that the salts precipitate out from the brine. The last stage of this process is taking place in conventional evaporation ponds.
Beyond traditional horticulture and agriculture, halophytes – salt-loving plant species – are cultivated in saltwater. These hardy plants, often already well adapted to desert conditions, are highly promising sources of fodder and bioenergy feedstocks that can thrive in highly saline environments. The Qatar Pilot Facility is implementing and testing a variety of novel cultivation techniques to allow low-cost halophyte cultivation while ensuring no saltwater enters surrounding soil or groundwater aquifers
7. Algae production
A state-of-the-art 50 m3 algae test facility – the only of its kind in Qatar and the larger region – enables commercial-scale research on the cultivation of marine algae species native to the Gulf and Red Sea for use as nutriceuticals, biofuels, and as animal and fish fodder.
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