'Vertical Farm' Produces Zero Waste30 May 2012
US - A new 'vertical-farm' initiative, named The Plant, is under way in Chicago, transforming an old meatpacking plant into a zero-waste farm.
The new concept involves food crops grown on top of buildings in busy city areas. A variety of techniques, including cultivating plants in water and aquaponics, which uses by-products from fish farming to assist hydroponic growth, are used to ensure successful crop growth.
The plant's anaerobic digester uses bacteria to break down organic waste into biogas and material, which can then be used as fertiliser. The plant hopes to create maximum food, with minimum waste.
By 2015, the completely enclosed, odorless anaerobic digester will consume 27 tons of food waste a day, including all of the waste produced in the facility and by neighboring food manufacturers.
The digester will capture all of the methane from that waste, and the methane will be burned in a combined heat and power system to produce 400 kWh of electricity, plus all the process heat needed for an onsite craft beer brewery. Excess heat will be used in an absorption chiller to regulate the building’s temperature.
Recycling will also take place in the aquaponic farm systems. Aquaponics is a closed-loop growing system that creates a symbiotic relationship between tilapia and vegetables.
The tilapia produce ammonia-based waste that is sent through a biofilter where solids settle out and the rest is broken down into nitrates. Those nitrates are then fed to plants growing in hydroponic beds. By absorbing the nitrates, the plants clean the water, which is returned to the fish. The Plant will sell both the fish and the vegetables to local food markets and restaurants, and will do so at a profit.
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