There is no such thing as sustainable product, only the by-products of a sustainable system. To be sustainable, first we must establish a closed-loop system and the carrying capacity, then the system must be managed and not over- or under-consumed.

Aquaponics is the embodiment of a sustainable system. At its core it is the creation of a symbiotic relationship between fish and plants. Fish waste in the form of ammonia is turned into nitrite then nitrates by bacteria in the water. When filtered through a plant bed, the plants clean the water for the fish to live in, creating a closed-loop system with two food crops.

A system with a 225-litre volume fish tank will grow approximately ten 15cm plants per week – enough for a decent bunch of basil or salad leaves – on a four-week cycle. To produce decent-sized, edible fish stock (such as 18cm carp) the tank would need to be twice the size of the prototype displayed here. The use of smaller fish is not normal practice in aquaponics, so my research into the ideal stock for a food source system is ongoing. The system needs to be kept in balance, not harvesting too many plants or fish at one time, as this would affect the health of the other produce.

The Free Lunch system proposes a model that makes the most of the vertical space in cities to grow food, as we do not have enough land space to support the people who live in them. By using the usually discarded waste product from the existing aquarium service infastructure to grow food from seed, my prototype system is designed to be developed into a practical and commercially viable system to give office workers a free and sustainable lunch once a month.

www.robmaslin.co.uk
rob@robmaslin.co.uk
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