[Animats]

"but there are substantial areas of future work."

Well, yes.

Most plant mass comes from air and water, not the ground. Carbon, hydrogen, oxygen, and nitrogen all come from the atmosphere. This is why farms don't dig themselves into the ground. If air and water can be made from asteroids, that's most of the raw materials problem by quantity. Hydroponics already works.

Direct synthesis of food from hydrocarbons has never really caught on, although it's been done experimentally and is an area of active research.[1] DARPA has a project.[2] "To address vulnerabilities in food supply chains across a variety of operational and humanitarian scenarios, Cornucopia will demonstrate the capacity to produce all four human dietary macronutrients (protein, carbohydrate, fat, and dietary fiber) in ratios that target Military Dietary Reference Intake (MDRI) daily requirements for complete nutrition. Outputs will be in multiple food formats (e.g., shake, bar, gel, jerky) that meet military nutritional standards and palatability requirements in a system minimizing inputs, handling, and footprint."

[1] https://www.sciencedirect.com/science/article/abs/pii/S09242...

[2] https://www.darpa.mil/program/cornucopia

[adrian_b]

Plants feed on oxidized compounds, i.e. water, carbon dioxide and dinitrogen, plus solar energy. Because carbon dioxide and dinitrogen are very volatile they must be taken from atmosphere.

Reduced organic compounds, like hydrocarbons, are not food for plants, but for fungi or similar organisms, which, like humans, need only dioxygen from the atmosphere.

There already are genetically-modified fungi that can produce the complete proteins required by humans (i.e. whey proteins or egg-white proteins) when fed with cheap carbohydrates and ammonia or a simple amino-acid. There are also fungi that can feed on hydrocarbons.

Creating genetically-modified fungi able to feed on hydrocarbons and produce glucose and proteins for human consumption is not far from the already existing technology. With a serious effort in this direction, this could be solved in a decade or so. The glucose and proteins produced by fungi would be used not only for direct consumption, but also for feeding other microbial cultures that are needed for producing vitamins and essential fatty acids, using the techniques that are already in use today for this purpose.

[thaumasiotes]

Do plants take nitrogen from the atmosphere? There's plenty of it available, but my understanding was that molecular nitrogen likes being molecular nitrogen and is difficult to react into a useful form.

If plants took nitrogen from the atmosphere, there would be no issue of fixing nitrogen in the ground. But instead, that's a huge issue. We also provide nitrogen fertilizer, which is another way of getting it into the ground. Why would we do that?

And similarly, I was pretty sure that most plants got their hydrogen and oxygen from water, which they draw out of the ground with special, purpose-dedicated organs called "roots". Their stylized interaction with the air is carbon dioxide in, molecular oxygen out. That's a source of carbon and maybe a little oxygen. The atmosphere doesn't even contain any significant amount of hydrogen.

[adrian_b]

Plants in the strictest sense, i.e. the terrestrial descendants of green algae, or even in some wider senses, e.g. all green plants or all eukaryotes that have chloroplasts whose origin is in a primary symbiosis or even all eukaryotes with chloroplasts, cannot take nitrogen from the atmosphere by themselves.

Nevertheless, some plants have symbionts that are various kinds of bacteria and which can take nitrogen from the air. The most important of these plants are the legumes, i.e. beans, peas, lentils and all their close relatives.

The ancestor of the chloroplasts, which are the parts of the plant cells that capture the solar energy, were free-living blue-green algae a.k.a. cyanobacteria, which had been able to take nitrogen from the atmosphere for billions of years.

However during the integration of the chloroplasts into the nucleate cells of the plants, when they have lost their ability to live independently, the chloroplasts have been simplified and among the lost features was the ability to take nitrogen from air. Thus the plants do not have this ability and they have remained dependent for nitrogen on bacteria that either live independently or in symbiosis with plants.

Before humans have started to convert nitrogen from the air into ammonia, for fertilizers and other applications, all organic nitrogen came ultimately also from the air, through the blue-green algae or through other kinds of bacteria.

The nitrogen content of natural rocks is negligible. All the rocks with nitrogen, e.g. saltpeter, come from the decomposition of bodies or excretions of living beings.

In all planets that are not cold enough for ammonia to become a liquid or an ice, the nitrogen is almost entirely in the atmosphere.

[thaumasiotes]

> The nitrogen content of natural rocks is negligible. All the rocks with nitrogen, e.g. saltpeter, come from the decomposition of bodies or excretions of living beings.

That's fair, but it seems similar to noting that the oxygen content of natural air is negligible. It's not really relevant to where things get their oxygen/nitrogen.

[AngryData]

The plants certainly don't. However there are certain plants that symbiotically harbor nitrogen fixating bacteria. Most notably legumes and the rhizobia bacteria that live inside root nodules. Common legume plants are alfalfa, peanuts, lentils, chickpeas, and bean species.

[thaumasiotes]

> Because carbon dioxide and dinitrogen are very volatile they must be taken from atmosphere.

I don't follow the logic. These two ideas are definitely compatible - oxygen is very volatile, and it's present in significant quantities in the atmosphere, and therefore can be (and is) taken from the atmosphere.

But they seem to me to be in tension rather than supporting each other. Oxygen is present in the atmosphere, but _because_ it is very volatile, it's constantly reacting with stuff on the ground, which is a process that tends to eliminate it from the atmosphere. What's the reasoning that suggests that the volatility of carbon dioxide means it has to be taken from the atmosphere?

[gus_massa]

Their plan is to use the asteriod material to feed bacterias (it's hidden in the introduction, but explained in the main text). The advantage of using something more complex than air and water is that he bacterias can get energy from it, interad of using light like plants. I guess it's more similar to the method used to cultivate fongus.

---

Anyway, you made me wonder if we can feed plats with sugar instead of light. Can we inject sugar into a potatoe and keep the rest of the potatoe plant happy in a dark place?

Anyway^2, I don't expect plants to be happy with the mix from the asteriods. It's probably some weird combination of small organic molecules. But some bacterias may eat et gladly and produce more usual organic molecules that we can eat.

[hansvm]

Variations of that idea definitely work. Light is optional for plants with adequate nutrient uptake from mediums like agar.

[Simon_ORourke]

> Hydroponics already works.

I read something on wired last year on why urban vertical farming never really took off, and one of the reasons was, if I remember, that these kind of environments increase the likelihood of plant disease and the density makes it difficult to arrest any spread.

So, I'm not too sure that hydroponics at scale is completely solved.

[lupusreal]

The big reason is growing food in wide open fields is almost always more economical. Urban farming is mostly advocated for by people who spend too much time in urban areas and don't have a solid grasp on the scale of the rest of the world.

[Melting_Harps]

> The big reason is growing food in wide open fields is almost always more economical. Urban farming is mostly advocated for by people who spend too much time in urban areas and don't have a solid grasp on the scale of the rest of the world.

While I agree on your conclusion, your reasoning is not entirely correct; urban farming is a byproduct, at east in MI, of a broken food chain wherein people left in the wake of financial disaster (2008) were left to fend for themselves and had to 'return to the land' while still being forced to stay close-by in order to just survive. Detroit was a food desert, the local, state and Federal government did nothing and corporate interests di-vested mainly from any real healthy options or grocery stores, what was left was what plagues the modern American diet (highly processed junk) and when the people of Detroit realized the help was never coming they took it upon themselves to create what has become the largest urban farming operation in the US.

Again, your conclusion may be correct, these people could not leave Detroit mainly for ecnomic reasons and were therefore 'Urbanites,' but rest assure this was not a hobby-farm approach they took, but rather the sullen and resentful resignation that they must feed themselves: what has since occurred has been amazing to watch, many chefs and artists returned back to Detroit and have made it an impact in self-organization and food security circles.

If I had more time I'd also make an argument for why the economies of scale tend to favor open field farming, but isn't that much better due to the vast needs of Govt. subsidies and the ever diminishing returns on investment when it comes to farming, conventional or organic, or in my case when I farmed: biodynamic.

You need only look to US/European farmers following the path of their Indian counterparts in mass suicides due to the unrelenting pressures and high debt loads in order to feed the masses.

Personally speaking, I think a huge missed opportunity was lost when many of the disillusioned in both West/East took to lying flat or quiet quitting etc... what should have been done was incentivize these people with low no interest loans and give them swaths of land to find purpose in regenerative Agriculture in order to remediate the soils and help offset climate control. Instead they just got chopped up in the meat grinder that is the depressing work force where they wallow in depression and suicidal ideation benefiting no one and making society more precarious day by day by making them gravitate towards extremism.

[Iulioh]

It's a price problem, not a technical one

[AngryData]

More directly it is energy/electricity, which is the reason the cost is high.

You need atleast 35 watts per square foot of high quality grow LEDs to grow most crops outside of leafy greens. That is about 1.5 million watts per acre for 12-16 hours per day, which makes it pretty obvious why it isn't economical. And even if we could meet the theoretical efficiency limit of LED lighting technology, it would still take atleast half of that amount of electricity.

[Cthulhu_]

That's the big one. With hydroponics, you need to control every factor, if one grows stuff in nature, you get a lot of it for free.

[RecycledEle]

> It's a price problem, not a technical one.

How do you define "technical problem" if you ignore the cost of the inputs to your system?

[Iulioh]

We can do it but it's an inefficient technology not because we haven't tried but because other methods are too good.

The sun is free, growing lamps aren't.

Hard to beat free energy.

[mandmandam]

Um. Doesn't technological innovation often make things cheaper?

Is this a distinction without a difference, or am I missing something?

[SideburnsOfDoom]

It's a hard ask to make space in high-rises in cities cheaper than farmland.

[mandmandam]

It is, yeah for sure. No argument there.

I do wonder though... How much cheaper is it really? What if the externalized costs were factored in?

Currently all manner of costs are put onto the environment rather than the producer or consumer: Soil erosion, soil degradation, fertilizer and pesticide runoff, biodiversity losses, greenhouse gas emissions, etc... All of which are huge issues, which we can't keep ignoring like we are.

And even after ignoring all that), most of 'the West' still needs to heavily subsidize farmers to make them competitive with imported crops.

[Iulioh]

Uhm.

"cheaper than before" usually yes.

But we are talking about different production methods, maybe hydroponics could never be cheaper than growing stuff in dirt because the production method can be optimized only so much.

An "advanced" (different) production methods is not inherently cheaper than a "traditional" method.

[versteegen]

Hydroponics usually isn't competing on cost, it's competing on other axes, such as having a greater amount of control. Just the same as greenhouses vs growing in the open. Farming is mostly about dealing with or preventing everything that could go wrong.

[evoke4908]

I'm extremely amused (and totally unsurprised) that the military has palatability requirements for soldier chow

[Ekaros]

Well soldiers tend to be armed and trained. Unlike say inmates or school children or hospital patients....