59

LENS

FARM

URBAN

expanded clay, which acts as a synthetic

soils for the plants to root into. The tank

below is the fish tank, so it’s about 60 L.

We have a pump that pumps water up

from the bottom tank to the top tank.

There’s an overflow level set and a

standpipe, and once the water reaches

the right level it just returns back to the

fish tanks. That continues for 15 minutes,

so it floods the top tank for 15 minutes to

provide the nutrients to the plants and

there’s a timer on the pump, so that cuts

out and it drains back down,

so it’s without water for 45

minutes. That’s how the roots

get their oxygen.

It’s a very basic question,

but what sort of tools would

you need to make one from

scratch? You’ve been to

Screwfix, bought the Ikea bins;

what else would you need?

PM You need a drill and a couple of drill

bits, pipe cutters, and that’s it. It’s about as

accessible as you can get.

And the expanded clay, where do you get

that from?

PM You an get that from all good

hydroponic supply stores. It’s about £15

for a bag of that. We’re just developing

another version that doesn’t use the

expanded clay; one of the problems with

this is that it’s heavy and it’s expensive to

ship. It’s really dusty and it’s a nightmare

to wash it clean, so we’re doing a floating

raft system which uses insulation board,

and that sits on top and the plants just

float on the raft.

The Produce Pods you’ve got here are

all growing lettuce and herbs and soft

things; is there potential for something

more solid like potatoes?

PM Starchy food, yes. Theoretically

there’s no reason why you can’t. Instead

of using expanded clay, you would use a

softer medium like coconut husk, so the

vegetables can root into that. In Japan

they’ve done a lot with aeroponics, where

they mist water up on to the root tubers,

so you see the potatoes just growing in

fresh air, having the nutrients misted on

to them.

The reason we concentrate on leafy

greens and on herbs is that they’re

perishable, and that’s where you get the

highest rates of waste. We import most of

our herbs and leafy greens from southern

Spain and Italy, and about 60% doesn’t

actually make it to us because it doesn’t

transport well, so it makes more sense

to be growing those perishable items in

cities so you can maintain the freshness,

the nutrient density. There’s a lot less

waste. Whereas a potato, for example, it

makes sense to grow it in a field outside

a city, because they store and transport

really well.

So I guess the aim is not to replace

standard agriculture but to

complement it?

PM The aim is to take the pressure off.

People often say to us “aquaponics,

hydroponics, what about the soil?” Jens

and I first met through permaculture, a

real deep appreciation for the soil and

the whole process. So we just think

this is part of the solution that can

take the pressure off, to allow for more

sustainable organic farming practices.

The technologies in aquaponics and

hydroponics will continue to evolve, so

that we’ll be growing other foods besides

leafy greens.

JT There’s an absolute time bomb waiting

to go off with soil nutrients and that’s

why we need these alternative ways of

growing stuff to supplement this while

we fix the problems that we’ve got with

the current system. The current farming

system is completely extractive. In some

farms the soil is just there to provide

somewhere to grow the food, it’s just a

matrix for the plant roots, so it’s basically

dead in a lot of places. There are areas

in the USA where they grow potatoes

and it’s completely dead, there’s just

sand. So you have to bring everything

in, bring all your fertiliser

in. And then, because all the

fertiliser washes away in the

rain anyway, you constantly

have to have those inputs.

Everything’s running off, and

that’s what ’s causing ocean

dead zones and rivers are

dying because of all the run-

off from agriculture. It’s been

known about for decades,

but it’s only now getting to

a point where it’s really becoming a

serious problem.

You mention the USA; how far down

the road are we in England to that in

terms of agricultural dead zones? You

go down to Cambridge, to what used to

be the Fens, and the soil looks like peat,

it’s completely black. That doesn’t look

like it’s in any danger of running out

of nutrients any time soon. Should we

be as worried as Americans about our

food production?

JENS Probably, but it depends on the area.

Each place is different, and just by looking

at the soil you can’t really tell anything:

different soils have different structures.

The important thing is what is it like to

grow on that soil, what are the inputs

that you need? I think we all need to be

worried, because it’s a worldwide problem.

The food web is so fundamentally

interconnected, there’s so much coming

from different areas. The year before last,

for example, you couldn’t buy any salad

for a while because they had floods in

Spain, so all the salad harvest failed. That

was it for us: no salad!

”

The reason we concentrate

on leafy greens and on herbs

is that they’re perishable,

and that’s where you get the

highest rates of waste

”