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Once the farm's in operation for a while, I'd assume they could compost a lot of the waste material picked up during harvesting. I'm not sure about tomatoes; ar

Once the farm's in operation for a while, I'd assume they could compost a lot of the waste material picked up during harvesting. I'm not sure about tomatoes; are the plants destroyed during harvest and grown from seed each season? Some crops are certainly handled that way.

maxerickson 10y ago
The plants will survive for more than 1 season but as practical matter they would be culled at the end of their productive period. The stems and such are mostly water and a little bit of carbon, I guess other sources of nitrogen would have an excellent ROI (a modest amount of fertilizer vs high capital and labor costs).
jessriedel 10y ago
I don't think hydroponics is a completely closed cycle, so there still has to be a source of nitrogen/ammonia https://en.wikipedia.org/wiki/Nitrogen_fixation https://en.wikipedia.org/wiki/Nitrogen_fixation which is ultimately very energy intensive https://en.wikipedia.org/wiki/Haber_process https://en.wikipedia.org/wiki/Haber_process
- pm90 10y ago
  That was an enlightening read! I had no idea that humanity was so dependent on one process for so much of its essential existence! If you think about the context in which we are operating though (desert with a lot of sunlight) it might be possible to colocate a solar powered reactor producing all the ammonia required for the hydroponic farms in the desert. This is just handwaving though: it seems like apart from electricity, the next biggest input is natural gas. While this may not be a problem in, say, Saudi Arabia, probably would be in Namibia.
  - maxerickson 10y ago
    With cheap enough power you can just tear the nitrogen out of the air. https://en.wikipedia.org/wiki/Birkeland%E2%80%93Eyde_process https://en.wikipedia.org/wiki/Birkeland%E2%80%93Eyde_process
- SEJeff 10y ago
  Hmmm I wonder if there would be a way to also grow green beans / soy beans, which always deposit nitrogen as a byproduct of their own growth. I have a mini urban farm in my teensy Chicago back yard and Rotate beans, cucumbers, and tomatoes to ensure the soil contains the right nutrients.
  - lostlogin 10y ago
    Have a look at this link, which I think I found on HN sometime ago. Hydroponics and fish working together in Detroit. www.modeldmedia.com/features/indoorurbanagriculture052014.aspx
feralmoan 10y ago
or add an aquaponic cycle to solve the nitrate side of the equation (and yield fresh fish, to boot)
- lostlogin 10y ago
  I added this link earlier which is following this idea, its a great story www.modeldmedia.com/features/indoorurbanagriculture052014.aspx
  - deleted 10y ago
    [deleted]
  - feralmoan 10y ago
    I love Detroit :D (btw Tilapia are illegal in Australia, they're extremely invasive, but there must be a local anlog)
bjelkeman-again 10y ago
In general the plant is discarded once a year. The growers normally get seedlings from a specialist that grows from seed. The tomato plan contain mild toxic content, and is quite smelly so not even goats seem happy to eat it. Not sure what they actually do with composted tomato plants. https://en.m.wikipedia.org/wiki/List_of_poisonous_plants https://en.m.wikipedia.org/wiki/List_of_poisonous_plants
- ChoHag 10y ago
  Leave it long enough to grow it into more tomatoes.
  - lostlogin 10y ago
    Tomatoes are ridiculously easy to grow from seed. If you let any tomatoes fall to the ground you are guaranteed to spend every year forever after dealing with hundreds of tomato plants.
    - ChoHag 10y ago
      Until you've got enough leaves and other detritus, there won't be any ground.

maxerickson 10y ago

The plants will survive for more than 1 season but as practical matter they would be culled at the end of their productive period. The stems and such are mostly water and a little bit of carbon, I guess other sources of nitrogen would have an excellent ROI (a modest amount of fertilizer vs high capital and labor costs).

jessriedel 10y ago

I don't think hydroponics is a completely closed cycle, so there still has to be a source of nitrogen/ammonia https://en.wikipedia.org/wiki/Nitrogen_fixation https://en.wikipedia.org/wiki/Nitrogen_fixation which is ultimately very energy intensive https://en.wikipedia.org/wiki/Haber_process https://en.wikipedia.org/wiki/Haber_process

pm90 10y ago
That was an enlightening read! I had no idea that humanity was so dependent on one process for so much of its essential existence! If you think about the context in which we are operating though (desert with a lot of sunlight) it might be possible to colocate a solar powered reactor producing all the ammonia required for the hydroponic farms in the desert. This is just handwaving though: it seems like apart from electricity, the next biggest input is natural gas. While this may not be a problem in, say, Saudi Arabia, probably would be in Namibia.
- maxerickson 10y ago
  With cheap enough power you can just tear the nitrogen out of the air. https://en.wikipedia.org/wiki/Birkeland%E2%80%93Eyde_process https://en.wikipedia.org/wiki/Birkeland%E2%80%93Eyde_process
SEJeff 10y ago
Hmmm I wonder if there would be a way to also grow green beans / soy beans, which always deposit nitrogen as a byproduct of their own growth. I have a mini urban farm in my teensy Chicago back yard and Rotate beans, cucumbers, and tomatoes to ensure the soil contains the right nutrients.
- lostlogin 10y ago
  Have a look at this link, which I think I found on HN sometime ago. Hydroponics and fish working together in Detroit. www.modeldmedia.com/features/indoorurbanagriculture052014.aspx

feralmoan 10y ago

or add an aquaponic cycle to solve the nitrate side of the equation (and yield fresh fish, to boot)

lostlogin 10y ago
I added this link earlier which is following this idea, its a great story www.modeldmedia.com/features/indoorurbanagriculture052014.aspx
- deleted 10y ago
  [deleted]
- feralmoan 10y ago
  I love Detroit :D (btw Tilapia are illegal in Australia, they're extremely invasive, but there must be a local anlog)

bjelkeman-again 10y ago

In general the plant is discarded once a year. The growers normally get seedlings from a specialist that grows from seed. The tomato plan contain mild toxic content, and is quite smelly so not even goats seem happy to eat it. Not sure what they actually do with composted tomato plants. https://en.m.wikipedia.org/wiki/List_of_poisonous_plants https://en.m.wikipedia.org/wiki/List_of_poisonous_plants

ChoHag 10y ago
Leave it long enough to grow it into more tomatoes.
- lostlogin 10y ago
  Tomatoes are ridiculously easy to grow from seed. If you let any tomatoes fall to the ground you are guaranteed to spend every year forever after dealing with hundreds of tomato plants.
  - ChoHag 10y ago
    Until you've got enough leaves and other detritus, there won't be any ground.