Green wall thoughts

[John CC]

I was just watching one of the green wall videos and I had a couple of thoughts.

1) Pumping air through the pipes and growing medium should not only help in terms of providing atmospheric nitrogen to the plants, and purifying the air, it should also promote aerobic bacterial growth and prevent anaerobic bacterial growth. This should have the following advantages:

a) Aerobic bacteria as I understand it are the microbes which are responsible for taking nutrients that aren't bioavailable and making them bioavailable. So it should actually be helping to make the nutrients in the grow medium more easily consumed by the plants.

Plants thrive in the presence of aerobic bacteria.

b) Anearobic bacteria as I understand it is responsible for causing rotting of roots and bad smells coming from the system. So the air being pumped through the system should prevent or reduce rotting of roots even when they are fully submerged. Look at bubbleponics where roots are fully submerged in water but are constantly being aerated with air stones.

Plants struggle, get diseases, or even die in the presence of too much anaerobic bacteria.

2) One of the issues raised by Tibi was the issue of grow medium falling into the pipes and polluting the water, and the issue of the water quality when it comes out the other end of the pipes.

To clean water in aquaponics systems a combination of a mechanical filter and a biological filter are used. This tends to be a non-biodegradable grow medium covered in aerobic bacteria, such as a perlite or hydroton clay pellets.

If the pipes were filled with perlite it would have the following advantages:

a) any grow medium which falls into the pipes would pretty much stay in place, within a very small distance from where the bottle connects to the pipe, instead of travelling down the pipe if it were empty

b) the perlite would act as a mechanical filter so even if some of the grow medium does travel down the pipes it wouldn't travel far, unlikely to reach the end of the pipes where the water comes back out

c) even the microscopic nutrients which aren't blocked by the mechanical filtration properties of the perlite would be consumed by the biological filtration properties provided by the aerobic bacteria on the surface of the pipes, the same way as happens in aquaponics

d) instead of water sitting in the bottom of the pipes it would constantly be wicked up by the perlite so it's evenly distributed throughout the space of the pipes, helping to prevent rotting caused by plant roots sitting in water

e) the air being pumped through the perlite would be cleaned by the biological filtration properties of the microbes on the surface of the perlite in the pipes increasing the air purification properties beyond just the grow medium in the pots themselves

f) the perlite would act as a wick lifting moisture up to the level of the bottle/pot so potentially no other wick would be required, because the upside-down bottle is just pushed into the perlite causing direct contact between the perlite and the grow medium

The end result is that the water coming out the other end of the pipes could actually be totally clean, free of dirt and nutrients (which cause algae to grow inside the water tub) and therefore can be recycled, and pumped back through the system with less issues.

Essentially it's a way of combining the benefits of aquaponics water filtration with the wick based green wall.

It could also potentially double the amount of surface area for air cleaning microbes to live and therefore greatly increase the effectiveness of the air purification.

The downside is that perlite isn't cheap, and it may need to be replaced occasionally. But if the system is in balance it shouldn't need to be replaced very often so could be worth it in the long run.

Cheers,

John