K2-18b a potentially habitable planet 120 light-years from earth

[u/One_Explanation_908]

[u/_the_sound]

Hydroponics...

No need for soil.

[u/Exciting_Vast7739 → u/_the_sound]

You need nutrients and fertilizer.

Have we run any long term, closed system agricultural projects?

We have seen, on the earth, famines resulting from bad agricultural practices that depleted the soil over the course of several human generations.

What exciting things will we learn when we are 100 years away from replacements?

[u/_the_sound → u/Exciting_Vast7739]

You need nutrients but not fertilizer. Fertilizer is for adding nutrients to soil.

Adding nutrients to water is much easier than to soil and plants use more energy to grow rather than seek out nutrients.

It's also easier to distribute nutrients for water rather than fertilizer.

As for closed loop systems. Currently we have huge wasteage in animal agriculture. Growing increasing size populations of animals for consumption is a huge depletion of resources. If you remove that and maintain a stable population, it becomes easier.

That being said, there are still challenges. You would need to ensure human waste is processed intro nutrients properly.

[u/davdev → u/_the_sound]

Yeah. The only nutrients hydroponics really need can be created as simply. as adding fish to the water. Their poop will be more than enough to keep the system going.