What about the fact that our agriculture system is (mostly) open loop? Every time you harvest food and consume it, where do the waste products end up? I think we need to also work on closing this loop.
Not the OP, but essentially you take vegetables out of a field. You eat the vegetables. You poop. Your poop ends up in a sewage treatment plant. Nothing ends up back in the field. Instead we add fertilisers that we have mined out of the earth for the macro nutrients.
It's not just sewage either. Every time you till the earth, you expose it to the air. This oxidises the minerals and often makes them unavailable for the plants. Because the fertiliser we add is very water soluble it drains through the water table and ends up in the rivers and eventually washes out to sea (or just clogs the rivers with algae).
Tilling and pesticides also kill the organisms that are responsible for moving nutrients around under the earth. Additionally, we tend to plant mono-culture crops with short root structures. This stops a variety of plants from breaking down nutrients in the soil and moving them to the top layer of humus. So either we till deeper (exacerbating the problem) or we essentially lock all of the nutrients below the level that the plants can access.
In the end, you basically are slowly extracting all of the bioavailable nutrients out of the soil, and depositing them in the sewage treatment fields. At the same time you are oxidising what's left and washing everything else out to the sea. Any fertility that remains is below the access of the plant roots (and probably not in a form that can be utilised right away).
"Closing the loop" means looking at the places where we are losing fertility and making sure that it is looping back. So, if you take nutrients out in the form of food, we return it in the form of sewage. You avoid tilling and you plant a variety of crop varieties that circulate the nutrients in the soil layer. You avoid adding highly water soluble salts that simply leach out of the soil and into the water table.
It sounds simple-ish, but it's actually quite a bit challenge. We don't really do a lot of research in this area (as far as I can tell). Most agricultural research is geared toward increasing yields and reducing costs as opposed to sustainability.
It is not just a bit of a challenge, it is a huge challenge that requires so many things to change in the infrastructure. There are many who have researched this problem and have published their results. But it requires some expense which many of the farmers cannot afford and certainly the corporations that control the various associated industries don't want to put funds into as it would drastically reduce their control and profits.
Minerals are leeched from the field into the plant/animal matter, which you then eat, which you then poop, which then enters a waste treatment plant, which then enters a tributary which then enters the ocean. There is no way for these minerals to make their way back to the field in question, so you have a 'one way' (aka 'open loop') process. If you want a truly sustainable method, you need to 'close the loop' and find someway to get the important minerals and other elements back to the fields so that plants can continue to grow there. Or figure out how to make plants not need the specific minerals.
That is actually not true, sewage can be treated and processed into 'biosolids'. I remember seeing a documentary about this, where they produced fertilizer from sewage in nyc
I have heard of a seaweed farming company on here recently. The idea is you can harvest seaweed that absorbs nutrients from the sea, and use that for fertilizer. This is an ancient idea, but hopefully it could become common again.
