AlteredEgo comments on Solarpunk is plants on buildings

[–] AlteredEgo@lemmy.ml -2 points 4 months ago (11 children)

A skyscraper with solar panels covering its southern face can produce a lot of vegetables. Sure, maybe carb-heavy vegetables still need to be done outdoors, but a balanced diet requires more than carbs.

You need the chemical energy to survive and that requires a lot of light to convert. That is the "critical path". Forget about vegetables, they are not important to solving the food problem.

You're so arrogant but fail to understand the basic engineering and math problems. This is a waste of time.

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[–] wonderingwanderer@sopuli.xyz 2 points 4 months ago (10 children)

You act so smug, but you don't seem to realize that warehouse farming is already a thing. This isn't some personal utopian fantasy theory of mine, it's a thing that already exists and can be implemented at a larger scale to solve problems ranging from food deserts, malnutrition, transportation costs, winter spoilage, pests, water consumption, run-off, and habitat destruction due to the agricultural demands of feeding several billion people.

There are specific wavelengths of light that plants use to do photosynthesis. Those wavelengths can be isolated, and there are special LEDs designed specifically for this purpose. They're quite efficient. Or you can use fluorescent lights, albeit they're less efficient than LEDs. You don't need the full spectrum and intensity of direct sunlight, and in fact that can be harmful in hot/dry climates or during droughts, especially as global warming accelerates. Warehouse agriculture has much higher yields than outdoor farming because you can control the climate perfectly while keeping out pests and diseases.

As for fertilizers and compost, they can be used in warehouse agriculture with more efficiency and with less environmental impact than in conventional farm fields. So your chemical energy point is moot.

You talk to me of the engineering and math problems, but clearly you're the one who fails to understand them.

Don't you know how much environmental destruction is currently due to clearing more space for agriculture? And you think that won't get worse as the world population nearly doubles in size, unless we start doing multi-story warehouse farming to feed major population centers?

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[–] AlteredEgo@lemmy.ml 1 point 4 months ago* (last edited 4 months ago) (9 children)

you don’t seem to realize that warehouse farming is already a thing.

No, you're just wrong. It is a thing for profitable vegetables or leafy greens or strawberries, but not for producing calories. It will not feed 15 billion people.

With something like 3 kWh of solar irradiance per day per m² you get a pretty abysmal <5% efficiency for producing food calories compared to the 20% efficiency of solar panels. So you quintuple the amount of land you need with solar panels, maybe a little less with higher efficiency indoors. Less with kite power. Again less with fusion power. It's still alot of embedded energy.

I made this table to see how many square meters actually feeds a person, very rough numbers but all I've found. It's less than 250m² in moderate climates to produce 2.2 kcal food. If we stop eating meat and "luxury foods" from around the world we drastically reduce energy costs and reduce land use so we can rewild like 90% of the current arable land.

Conclusion: There is no shortage of land to feed 15 billion people.

And why grow your vegetables and fruits and strawberries far off, or in a bunker, when you can build a million local greenhouses in your community that could additionally serve as food gardens or parks in colder weather?


	Kcal / acre / year	Kcal / m² / day	kWh / m² / day	Efficiency from 3kWh sunlight	Land m² / person	Protein %
Potato	15,000,000	10.0	0.0116	0.39%	219	9.50%
Potato Ireland 2017 FAO	14,163,653	9.5	0.0110	0.37%	232	9.50%
Potato USA 2019 FAO	15,858,541	10.6	0.0123	0.41%	207	9.50%
Potato Oregon 2019 USDA	20,940,336	14.0	0.0162	0.54%	157	9.50%
Potato Simplify Gardening	18,036,045	12.1	0.0140	0.47%	182	9.50%
Sweet potato 3x hypothetical	93,000,000	62.2	0.0721	2.40%	35	7.00%
Rice	11,000,000	7.4	0.0085	0.28%	299	8.10%
Rice USA 2018 FAO	14,655,018	9.8	0.0114	0.38%	224	8.10%
Soybeans	6,271,628	4.2	0.0049	0.16%	525	36.40%
Chickpeas	6,013,636	4.0	0.0047	0.16%	547	20.50%
Chickpeas China FAO	8,329,810	5.6	0.0065	0.22%	395	20.50%
Chickpeas Israel 2017 FAO	9,494,407	6.3	0.0074	0.25%	347	20.50%
Chickpeas Turkey	1,440,259	1.0	0.0011	0.04%	2284	20.50%
Pinto Beans						23.70%
Corn	15,000,000	10.0	0.0116	0.39%	219	10.40%
Corn Jordan 2018 FAO	58,323,364	39.0	0.0452	1.51%	56	10.40%
Corn USA 2018 FAO	18,413,214	12.3	0.0143	0.48%	179	10.40%
Wheat	4,000,000	2.7	0.0031	0.10%	822	14.50%
Wheat Ireland 2017	15,670,035	10.5	0.0122	0.41%	210	14.50%
Oats 175 bu/acre	1,125,399	0.8	0.0009	0.03%	2923	17.00%
Chlorella	86,045,604	57.5	0.0667	2.22%	38	58.40%
Solein solarfoods.fi	193,371,336	129.3	0.1500	5.00%	17	65.00%
Microalgae 5% hypothetical	193,371,336	129.3	0.1500	5.00%	17	57.47%

PS: Solein claims 5% by splitting water into hydrogen using solar power and then using hydrogen to feed single celled organisms. If we ever find a way to split water into hydrogen directly using fusion we'd be set. But until then it's not more efficient than other food algae (also about 5% efficient, which is already great for mostly protein).

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[–] wonderingwanderer@sopuli.xyz 1 point 4 months ago (8 children)

If you think leafy greens are only good for making a profit, then you're the one who's wrong. Nutrition is about more than just calories. Someone who doesn't get enough calories gets malnourished, someone who doesn't get enough nutrients gets malnutrition. It's two different things. Vegetables are necessary and you can't just write them off, much as you seem to want to.

Also, a vertical warehouse operation has multiple stories and can have panels mounted all up the southern face. You don't need to have an entirely horizontal solar farm, so no it doesn't quintuple the land you need.

And yes, eliminating meat from the common diet can help to rewild arable land, but that's a completely separate conversation and not an argument against warehouse agriculture.

Saying there's no shortage of land to feed 15 billion people is irresponsible though, because without any major changes to the way things are done, feeding 15 billion people would absolutely result in more habitat destruction.

And why grow your vegetables and fruits and strawberries far off, or in a bunker, when you can build a million local greenhouses in your community that could additionally serve as food gardens or parks in colder weather?

You don't seem to understand the issue at all. Building a million "local" greenhouses takes up space. Each greenhouse has a footprint. The millionth one over won't be very "local."

The point of warehouse farming (rather, one of the points), is that it can be done in urban centers where there's no space for greenhouses. It's literally a solution for food deserts and transport costs associated with the majority of food being produced in rural areas. Warehouse agriculture brings food production closer to population centers. I've already pointed that out multiple times and you just seem to ignore it.

If we ever find a way to split water into hydrogen directly using fusion we'd be set.

That's not what fusion is at all. I've already corrected you on this, which you also ignored.

Nuclear fusion is when you take two atoms and fuse them into a different kind of atom. The simplest form is making one helium atom from two hydrogen isotopes.

It has nothing to do with "splitting water into hydrogen." We can already do that. It's called electrolysis. Plants need more than just hydrogen though, so I'm not sure what your point is there.

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[–] AlteredEgo@lemmy.ml 1 point 4 months ago (7 children)

That’s not what fusion is at all.

You didn't correct me, you misunderstood me. Keep up lol. See https://en.wikipedia.org/wiki/Radiolysis#Hydrogen_production

Solein (single celled microorganism) can use hydrogen and oxygen as fuel to produce carbo hydrates and protein. Needs co2 and some minerals too of course. If you could genetically engineer it to taste good and look less like puke, it would be perfect.

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[–] wonderingwanderer@sopuli.xyz 1 point 4 months ago* (6 children)

Okay, good luck with that. You go feed your people hydroslop and I'll build warehouse farms and we'll see whose people have better nutrition.

Also, the radiolysis page says nothing about fusion. The nuclear waste it talks about repurposing is from fission reactors. Keep up.

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[–] AlteredEgo@lemmy.ml 1 point 4 months ago (5 children)

More radiation, more hydrogen splitting. Anyway it was just an idea which you took to imply I don't even understand what fusion is.

But the overall point is that you don't need anything like this. If you stop producing meat and resource or energy inefficient foods like almonds we have more than enough land to feed even 20 billion people. There is no need to invent superfood or vertical farming. It's not the critical path. Much more important is saving heating and cooling in buildings and reducing the amount of transport and infrastructure spread we need.

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[–] wonderingwanderer@sopuli.xyz 1 point 4 months ago (4 children)

Except fusion waste isn't radioactive, it's just helium. The fuel is literally already hydrogen, so I don't know why you would even want to fuse hydrogen into helium just to try to split a water molecule. You literally do electrolysis to split the water to get the hydrogen to use in a fusion reactor to make helium and release a ton of energy. There's no radioactive material involved.

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[–] AlteredEgo@lemmy.ml 1 point 4 months ago (3 children)

This is just speculation, more like a "if someone figures it out". We don't have working fusion yet anyway. Fusion does produce radiation, which can be used to split additional water. Or maybe this might be impossible with a fusion reactor setup. Normally the radiation is used to heat water and convert it into steam to drive a turbine. But specifically to grow food, hydrogen production could be more efficient. Say in a space colony too far away from the sun.

Otherwise, light and photosynthesis will basically always be the most efficient to grow calories for sustenance.

BTW there is also the concept of aneutronic fusion to directly generate electricity without steam turbines.

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[–] wonderingwanderer@sopuli.xyz 1 point 4 months ago (2 children)

There's no "figuring it out." Fusion waste isn't radioactive. You can't do radiolysis with it.

There's a difference between radiation and radioactivity. Heat and light are radiation. Radiolysis requires radioactivity.

It's not "more efficient" to take hydrogen, apply fusion to turn it into helium and generate power, and then use that power to "split" water molecules.

You already have the hydrogen from doing the electrolysis. The closest thing you could do is capture the power generated by the fusion and convert it into electricity, and then use that electricity to do more electrolysis. I'd have to look at the specific numbers to calculate loss, because fusion is weird and generates enormous amounts of energy, but it also isn't captured with 100% efficiency. And besides, it takes power to run the fusion reactors, which is currently the main hurdle in the way of running it at scale.

If you're in a space colony though, water is too precious to be splitting into hydrogen and helium. You would probably just get your hydrogen directly from a gas giant instead.

Otherwise, light and photosynthesis will basically always be the most efficient to grow calories for sustenance.

So we've come full circle, and you've admitted that nuclear fusion cannot generate calories. Great.

You also continue to ignore macro- and micro- nutrients. Dietary requirements are more than just "calories."

Lastly, aside from aneutronic fusion being hardly more experimental than it is theoretical, that's a complete red herring and has nothing to do with what we're talking about.

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[–] AlteredEgo@lemmy.ml 1 point 4 months ago (1 child)

So we’ve come full circle, and you’ve admitted that nuclear fusion cannot generate calories. Great.

Sure it can't, because it doesn't exist. I said that outside some fantastical sci-fi technology like fusion directly producing hydrogen, sunlight will always be more efficient to produce calories. And you only need a radiation source for radiolysis, radioactive waste is only one source of it.

Every single method we have to produce chemical energy is less efficient than sunlight and plants.

Because solar panels, LEDs, hydrolysis, all have low efficiency. You loose massive amounts of energy and therefor space when your goal is to produce calories.

And sure we need vegetables and for that vertical farming is fine, great even, except for calories. But if we wanted to solve climate change, the infrastructure like solar panels and pumps contain a lot of embedded energy that you could save. It's only profitable under capitalism and land hoarding and in a society where we consume way too much meat.

One economic collapse or global conflict and all our complex supply chains go away. So if we're dependent on tractors and heavy machinery and fossil fuel and fertilizers, or on or robots and electronics or LEDs or solar panels just to produce food - the vast majority of people remain slaves to industry for their very basic needs.

The real solarpunk for me is potato farming. Or some sci-fi genetic engineering to produce shrubs that produce all sorts of food without needing tilling or fertilizer.

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[–] wonderingwanderer@sopuli.xyz 1 point 4 months ago

So much of what you're saying is actually an argument in favor of warehouse farming and you don't even realize it, that it's obvious you've never read the requisite literature, and I'm done trying to explain this to you.

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