Mark Laurence

Hydroponics - the future of urban food production?

vertical hydroponics by BioTecture

Vertical hydroponic salad wall by BioTecture.

homemade hydroponics

A homemade hydroponics system

hydroponic greenhouse

A homemade hydroponic greenhouse

vertical hydroponics

Vertical Hydroponics in an office environment (image by Kiss + Cathcart Architects). Pick your own lunch!

Hydroponics is “the cultivation of plants in a nutrient solution rather than in the soil”. To many this conjures up the image of something artificial, chemical, hi-tec, un-organic and unhealthy. However, the truth is - or can be - far from this and is suitable - and advantageous - for home made, low tech, organic growing. If you ask why, what's wrong with growing in the soil, my answer is nothing, but not everyone will have access to soil, and there are other advantages also!

The picture at top right shows a vertical vegetable wall developed by my company, BioTecture. Still in prototype form, it could nonetheless easily provide lunchtime salads and other vegetables and fruits to any house or office! Even just used for ornament, vertical walls provide positive effects on health and wellbeing, purifying the air and increasing oxygen. Plants do a lot to counter sick building syndrome.

Let's list some of the advantages of hydroponics:

To counter that, let's list disadvantages:

The lower two pictures show home-made systems, and are included to counter the image of hydroponics being the preserve of the hi-tec science boff type. The principles are very simple to understand and the setup is simple too, the main consideration being the type of system to choose. Whilst there are many variations, there are three main types of systems:

NFT systems were the original hydroponic invention and consist of horizontal tubes or gutters along which a shallow film of water and nutrient runs. Plants are suspended above this and put their roots down into the fluid. The main advantage is that it is very simple, but constant pumping means constant electrical use and greater risk if the pump should fail.

Drip Irrigation/Rockwool systems use a block of inert growing medium (horticultural rockwool, trade name Grodan) as a chemically inert anchorage for the plants. Grodan has excellent water retention properties, so the plants need less volume of water delivered to them to remain moist.

Flood and Drain (Ebb and Flow) systems use an aggregate medium into which the plants root. This is then flooded to a maximum level and the surplus then drains back down to the holding tank, drawing down fresh oxygen to the roots. The cycle is then repeated before the medium dries out.

It is not my purpose here to describe these systems in any more detail, for there is plenty of info about on the web or in books to do that. Rather I would like to introduce the idea of this as a system that can supplement the growing potential of those with small gardens, or in urban situations, balconies or rooftops. It is in urban areas where the coming impact of food security issues will be felt and that is where these systems can empower those who would otherwise have no recourse to growing fresh food.

Whilst this goes a long way towards self-sufficiency, it is not perfect, nor is it a closed-loop system, as external input of nutrient is required. It is theoretically possible to use a mix of greywater and urine, both household wastes, to make a reasonably balanced feed. Great in that we are turning wastes into produce, but there is a small risk of pathogens entering the food chain, so whilst I have heard of it being done, I cannot recommend you try it. Also the nutrient content would vary too much for consistent cropping. I suggest we can do other things with these wastes, such as landscape irrigation/fertigation. Possibly nutrients can be made from comfrey leaves, as this is often used to make an organic liquid feed.

However, hydroponics can be part of a bigger system, which produces more protein and really closes the loops in terms of external inputs. This is a system called Aquaponics, and combines fish production - Aquaculture, with hydroponics, which is the subject of this article.