4 ms·

Fertilizers can be more than urea, like ammonium nitrate. Urea is also used, although many times it is treated for controlled release. Apart from that, some mat

by chicob 4y ago

Fertilizers can be more than urea, like ammonium nitrate. Urea is also used, although many times it is treated for controlled release. Apart from that, some math is in order. Let's say I need 200 kg/ha of a 12-6-6 NPK fertilizer for post-sowing 10 ha of some crop, like corn. (This is a little short of 180 lb/ac for a total of ~25 acres. I'm in Europe, and I don't know what would be a typical value for the US). This fertilizer has 12% w/w of total nitrogen, so for the total area my needs are 240 kg of nitrogen (~530 lb). An adult will produce an average of 1,4 L (0.37 gal) of urine daily, with a nitrogen content of 8,83 g/L, so this means a total of 12,36 g/day, or 4,5 kg/year (~10 lb/year).[1] So I'll need the urine that 53 people pee for a whole year for this single crop. A six tower pivot has something around 4 or 5 times that area. And this area can be used twice a year for different crops. The average US farm has 445 ac.[2] [1] https://en.wikipedia.org/wiki/Urine#Characteristics https://en.wikipedia.org/wiki/Urine#Characteristics [2] https://www.statista.com/statistics/196106/average-size-of-farms-in-the-us-since-2000/ https://www.statista.com/statistics/196106/average-size-of-f...

noodlesUK 4y ago
I’m curious though, how many people would that 10ha of corn feed? My understanding is that it would be a lot of corn…
- chicob 4y ago
  The average yield for corn in the US for 2021 was 176.5 bu/ac. This is around 11,9 ton/ha. For 10 ha, a total of 119 ton.[1][2] How many people this would feed is hard to tell, because it depends on the kind of corn. Some corn is meant for human consumption, some other for livestock feed (which in turn is meant for human consumption. But as a rough estimate one can add these two to find an order of magnitude. In 2008, the USDA broke down the usage for maize, with 133,4 Mton (5250 Mbs) for livestock and 8,3 Mton (327 Mbs) for human consumption. That year, the US population was around 303.5 million people, so that gives an average of 467 kg (1030 lb) a person each year.[3][4] So those 10 ha would produce enough corn for 240 people for a whole year.[5] [1] Assuming around 15% moisture content. [2] https://www.dtnpf.com/agriculture/web/ag/crops/article/2021/08/13/us-average-corn-yield-176-5-bpa-51-5 https://www.dtnpf.com/agriculture/web/ag/crops/article/2021/... [3] https://en.wikipedia.org/wiki/Maize#Human_food https://en.wikipedia.org/wiki/Maize#Human_food [4] https://www.populationpyramid.net/united-states-of-america/2008/ https://www.populationpyramid.net/united-states-of-america/2... [5] I ended up doing the calculation in imperial units, to minimize rounding errors.
  - chicob 4y ago
    This comment might come a little bit too late, but I wouldn't want to give the impression that these numbers suggest using urine as fertilizer is self-sustainable. It is not self-sustainable, and it might not be sustainable in the long term. For many reasons: - First of all, urea as a fertilizer is not completely effective, because some of it will be drained. Urea can be treated for slow release, but this requires processing. And even in this case, some of it will just be degraded by bacteria (some bacteria will turn it into compounds that plants can use, but generally urea content will fall with time). - I used total nitrogen from urea, but in reality a part of that nitrogen does not come as urea. - I also used average yields, which depend on the usage of more powerful fertilizers. Fertilizing with urea alone will lead to smaller yields. Let's say that average yield woud drop to 50% and that I would need not 53 bu 80 people's yearly urine. That would mean I would only provide enough corn for 120 people each year, for a input of 80, which gives a ratio of 3:2. Seems good enough. Unfortunately this is not the case. Human urea is the result of human diet and metabolism, which gets nitrogen from many different protein sources. Self-sustainability means that those 120 people would have to eat only corn and meat from corn-fed livestock, or trade this for other protein sources (which would only externalize this unsustainability: some other people's diet would have to change). Even if it were possible to keep up with the same urea output without severe weight loss, this would not be enough: - First of all, plants use nutrients to grow many inedible parts, and that is an important drain of nitrogen. This also means all plants, not just the ones we eat. - Livestock would still need food sources other than corn. The above assumptions assume well-fed cattle. Finally, as someone already noted in another comment, human urine contains a significant amount of salt, and without its removal this could lead to excess salinization that would render the soil infertile in the long term. And the higher concentrations of urea needed could also worsen the already present problem of eutrophication. But using urine might still be a great help with local, temporary unavailability of better fertilizers.
Gordonjcp 4y ago
> Fertilizers can be more than urea, like ammonium nitrate ... which you have to keep locked up, because terrorists. Usually they're smart enough to avoid hanging around in rusty white Ford Transits with Irish plates, but you'd probably not be too surprised to see the numbers on that.
- chicob 4y ago
  All fertilizers and pest control products are locked up. And each year I have to give the government proof of fertilizer usage, with up to date inventories, invoices and fertilization tables for all crops that used solid fertilizers. I also have to sign terms of responsibility provided by the suppliers. I had some stuff stolen in the past, but never fertilizer.

by chicob 4y ago

noodlesUK 4y ago

I’m curious though, how many people would that 10ha of corn feed? My understanding is that it would be a lot of corn…

chicob 4y ago
The average yield for corn in the US for 2021 was 176.5 bu/ac. This is around 11,9 ton/ha. For 10 ha, a total of 119 ton.[1][2] How many people this would feed is hard to tell, because it depends on the kind of corn. Some corn is meant for human consumption, some other for livestock feed (which in turn is meant for human consumption. But as a rough estimate one can add these two to find an order of magnitude. In 2008, the USDA broke down the usage for maize, with 133,4 Mton (5250 Mbs) for livestock and 8,3 Mton (327 Mbs) for human consumption. That year, the US population was around 303.5 million people, so that gives an average of 467 kg (1030 lb) a person each year.[3][4] So those 10 ha would produce enough corn for 240 people for a whole year.[5] [1] Assuming around 15% moisture content. [2] https://www.dtnpf.com/agriculture/web/ag/crops/article/2021/08/13/us-average-corn-yield-176-5-bpa-51-5 https://www.dtnpf.com/agriculture/web/ag/crops/article/2021/... [3] https://en.wikipedia.org/wiki/Maize#Human_food https://en.wikipedia.org/wiki/Maize#Human_food [4] https://www.populationpyramid.net/united-states-of-america/2008/ https://www.populationpyramid.net/united-states-of-america/2... [5] I ended up doing the calculation in imperial units, to minimize rounding errors.
- chicob 4y ago
  This comment might come a little bit too late, but I wouldn't want to give the impression that these numbers suggest using urine as fertilizer is self-sustainable. It is not self-sustainable, and it might not be sustainable in the long term. For many reasons: - First of all, urea as a fertilizer is not completely effective, because some of it will be drained. Urea can be treated for slow release, but this requires processing. And even in this case, some of it will just be degraded by bacteria (some bacteria will turn it into compounds that plants can use, but generally urea content will fall with time). - I used total nitrogen from urea, but in reality a part of that nitrogen does not come as urea. - I also used average yields, which depend on the usage of more powerful fertilizers. Fertilizing with urea alone will lead to smaller yields. Let's say that average yield woud drop to 50% and that I would need not 53 bu 80 people's yearly urine. That would mean I would only provide enough corn for 120 people each year, for a input of 80, which gives a ratio of 3:2. Seems good enough. Unfortunately this is not the case. Human urea is the result of human diet and metabolism, which gets nitrogen from many different protein sources. Self-sustainability means that those 120 people would have to eat only corn and meat from corn-fed livestock, or trade this for other protein sources (which would only externalize this unsustainability: some other people's diet would have to change). Even if it were possible to keep up with the same urea output without severe weight loss, this would not be enough: - First of all, plants use nutrients to grow many inedible parts, and that is an important drain of nitrogen. This also means all plants, not just the ones we eat. - Livestock would still need food sources other than corn. The above assumptions assume well-fed cattle. Finally, as someone already noted in another comment, human urine contains a significant amount of salt, and without its removal this could lead to excess salinization that would render the soil infertile in the long term. And the higher concentrations of urea needed could also worsen the already present problem of eutrophication. But using urine might still be a great help with local, temporary unavailability of better fertilizers.

Gordonjcp 4y ago

> Fertilizers can be more than urea, like ammonium nitrate ... which you have to keep locked up, because terrorists. Usually they're smart enough to avoid hanging around in rusty white Ford Transits with Irish plates, but you'd probably not be too surprised to see the numbers on that.

chicob 4y ago
All fertilizers and pest control products are locked up. And each year I have to give the government proof of fertilizer usage, with up to date inventories, invoices and fertilization tables for all crops that used solid fertilizers. I also have to sign terms of responsibility provided by the suppliers. I had some stuff stolen in the past, but never fertilizer.