Available Funds
What can be done depends on funds, but even reallocating a few percent of world economic output is enough to accomplish much. Annual GDP is $65 trillion (PPP), having for the past several years grown at around 3.6% annually, ~ 40% growth per decade. Even savings in military spending alone, now made unnecessary by one having the power to prevent wars, amount to upwards of $1.1 trillion annually, which is $55+ trillion per 50 years. In far less than the 1000 years, it is not excessively optimistic to anticipate that economic output of the countries currently poor may be made 50+% the per capita income of the U.S. today, increasing world GDP to ~ $210+ trillion annually.
So total world economic output is $3300 trillion to $11000+ trillion per 50-year period.
Electrical Power
Eliminating fossil-fuel usage is a goal, from electricity generation to synthesis of fuel and plastics.
The capital cost of producing nuclear reactors could reasonably be $1000 to $2000 per kilowatt in the near-term, though economy of scale, standardization, and mass-production of thousands of the same unit type would lower costs compared to historical nuclear power plants that have been more individually constructed. So assume no more than $1000 per kilowatt. Then about $1.2 trillion is enough to replace the 1.2 terawatt fossil-fueled component of the world's current 1.85 terawatts of electricity generation.
The world population eventually reaches ~ 9 billion as projected by studies, corresponding to more power demand. If electricity consumption after economic growth reaches the per capita consumption of the U.S. today, the corresponding power demand would be 13 terawatts, more but still workable.
Practically unlimited uranium is available for fuel, affordably extracted from seawater by a method such as the polyethylene fiber technique.
Nuclear-Powered Synthesis of Gasoline, Diesel, and Jet Fuel
To switch away from fossil fuels, not only electricity generation is needed but also replacement fuel for transportation.
While hydrogen fuel is a possibility, a system avoiding having to change so much infrastructure or change vehicles would be to instead synthesize gasoline, diesel fuel, and jet fuel. The Fischer-Tropsch process was used by Germany in WWII to produce synthetic fuel, and it is used by Syntroleum today to produce synthetic diesel fuel and jet fuel from synthesis gas. Syngas is a mixture of carbon monoxide and hydrogen. Although the usual implementation of the FT process is to start with fossil fuels, e.g. natural gas or coal, it is possible to produce the syngas instead starting with carbon dioxide and water, utilizing plenty of energy from nuclear power.
Water can be electrolyzed to produce the hydrogen, and carbon dioxide can be collected from the atmosphere. For this illustration, just calculate energy costs with use of regenerable CO2 sorbents like some proposed as workable for CO2 removal in the air of spacecraft life support systems. For that, regeneration energy demand for thermal decomposition of the carbonates back to the oxides is anticipated as reasonably around 700 to 2000 Btu/lb-CO2. Taking a middle value for this order-of-magnitude illustration, assume 3 MJ of thermal energy needed per kilogram of CO2 removed, which is 11 MJ/kg of carbon.
The first reaction in the Bosch process is CO2 + H2 -> CO + H2O, which occurs rapidly at an appropriate temperature of a few hundred degrees Celsius in the presence of a catalyst. Such can be used to produce the carbon monoxide for the syngas from the collected carbon dioxide. Of course, there are multiple options, some of which may be better than others, and the preceding is just an example. But the net effect is that synthetic gasoline can be produced starting from carbon dioxide collected from the atmosphere and water, using a large amount of nuclear power.
Particularly for the FT process that needs the contents of the reaction chambers heated to a few hundred degrees in the presence of a catalyst, much of the energy needed is merely thermal energy as opposed to it all being electricity. Assume the nuclear reactors produce relatively high-temperature waste heat as tends to be the case with many next-generation designs. And assume 1+ TWt of "waste" thermal power for every 1 TWe of electricity. Each $1 trillion of nuclear power plant capital cost provides 2+ TW of total power. It might be most economical to reduce electrical power requirements for hydrogen production by using reactor heat for the energy to split water in a thermochemical cycle at ~ 800 to 1000 degrees Celsius, eliminating most generator cost. But hydrogen from electrolysis is instead assumed here since it is fully known to be practical if electrical costs are affordable, which is the case.
Gasoline, diesel, and jet fuel all have an energy content around 45 MJ/kg, plus or minus two or three MJ/kg. Aside from inefficiencies, that is the energy required for the overall process, as the fuels are being synthesized indirectly from their combustion products of carbon dioxide and water. Actually, add ~ 9 MJ/kg-of-fuel due to the carbon dioxide collection from the atmosphere, so fuel synthesis requires ~ 54 MJ/kg before inefficiencies. But assume the total may be up to ~ 162 MJ/kg by allowing a factor of 3 for inefficiencies, which would be more than enough.
Then, each 1 TWe of nuclear power plants costing up to $1 trillion with 2 TW total power can synthesize upwards of 389 million metric tons of fuel per year, on the order of 137 billion gallons annually. So 2.8 TWe or $2.8 trillion of nuclear reactors provide power to synthesize 390 billion gallons annually, about as much as the current world annual consumption, the combined total for gasoline, diesel fuel, and jet fuel.
But economic growth and to a lesser degree population growth corresponds to more consumption, so later assume eventually up to 44 TWe or $44 trillion nuclear power plant capital cost for the power to synthesize ~ 5.97 trillion gallons annually. That is the equivalent of current U.S. consumption per person for 9 billion people. Total cost would be more than power plant capital cost alone, but it is still proportionally small compared to the world economic output in that scenario of upwards of $11000+ trillion per 50 years.
There are no net carbon dioxide greenhouse gas emissions from the preceding system. It is as good as hydrogen fuel in that regard. The carbon in the synthesized fuel becomes CO2 released into the atmosphere when burned, but that carbon originally came from CO2 extracted from the atmosphere and will be extracted again, so it is just going in a cycle. This effectively makes all vehicles from cars to aircraft indirectly nuclear-powered with no fossil fuel consumption and no net CO2 emissions.
Like a lot of what is discussed here, the plausibility of the preceding may seem counterintuitive. However, in the real-world, for an interesting project to even get $1 billion or $0.001 trillion is rare and very difficult, yet in this opening post scenario one has "god-like" power to allocate funds, able to use a small but much more significant percentage of the world's $65 trillion and rising annual GDP. A lot can easily be accomplished in this scenario where there isn't the same real-world inertia continuing the status quo.
All figures in this post may be assumed to be only approximations, so I don't have to repeatedly insert qualifying phrases emphasizing imprecision. These are rough, "order-of-magnitude," "back-of-the-envelope" calculations.
Synthesis of Plastics
Yet another oil dependence to eliminate is plastics production. This is actually easier in regard to energy needed than the fuel synthesis. Current world plastics consumption is 150 million tons per year, compared to 1100 million tons of annual vehicle and aircraft fuel consumption, a mass ratio of about 1:7. Also, U.S. per capita plastics consumption versus per capita fuel consumption suggests a plastics to fuel mass ratio of 1:10 for the high economic growth scenario. While the energy requirements per kilogram for plastics synthesis versus fuel synthesis are not exactly the same, they are close, close enough for this approximate discussion.
So 0.4 TWe or $0.4 trillion of nuclear reactors provides enough power to synthesize current world plastics production.
Or 4.4 TWe, $4.4 trillion, suffices to synthesize world plastics production in the growth scenario that may reach 1.7 billion tons consumption annually.
One possibility is a version of the Fischer-Tropsch process that can produce various hydrocarbons from a mixture of hydrogen and carbon monoxide. For example, synthesized ethane can be cracked in steam to produce ethylene, which can be polymerized into polyethylene, the plastic produced in greatest quantity today. Of course, there are multiple options, some better than others, and it is uncertain exactly what would be the ratio of the cost of the synthesized plastic to the cost of plastics from oil today. But the important aspect is that the amount of nuclear power needed to cover world plastics demand without fossil fuel usage can be obtained in this scenario.
Many other compounds can also be synthesized. For example, ethanol can be produced from a hydrogen and carbon dioxide mixture at elevated temperature in the presence of a catalyst; a random example is here.
More on the Nuclear Power Plants
Total nuclear power capacity for the combination of electricity generation, fuel synthesis, and plastics production is 4.4 terawatts (electrical) initially, for current world consumption. Such corresponds to a capital cost for the power plants of $4.4 trillion, which is merely 0.0013 of the $3300 trillion world economic output per 50 years neglecting economic growth.
Of course, actual expense could be far greater than the cost of the nuclear power plants alone, partially due to lesser operating costs but also due to costs for the chemical plants and other new equipment. Existing infrastructure could be utilized whenever possible, as suggested by this system synthesizing hydrocarbon fuels to maximize compatibility with the pre-existing transportation system, not the same difficulty as converting all vehicles to fuel cells.
In the growth scenario with eventually up to U.S. per capita consumption worldwide, the future rich world of 9 billion people needs 61 terawatts (electrical), a power plant cost up to $61 trillion. That is no more than 0.0055 of the $11000+ trillion total economic output per 50 years in that scenario, aside from other non-energy expenses.
Waste heat is not an excessive problem, not even in the economic growth scenario. Assuming 50% efficiency for near-future next generation nuclear power plants, there is 120 terawatts of waste heat, half at the power plants, half where the electricity is used. That is only as much power as 0.07% of the 174,000 terawatts of sunlight intercepting earth in space.
Such is not nearly as much as greenhouse gases influence. Manmade greenhouse gases have an effect equivalent to one or two percent of total sunlight. Geoengineering measures against global warming also counter the effect of the waste heat that is two orders of magnitude less.
Radiation exposure is also limited. Average annual radiation exposure worldwide from nuclear power production is 0.0002 mSv. There is also 0.002 mSv from Chernobyl, although the nuclear power plants would be much safer designs. The important comparison is that annual natural radiation exposure of 2.4 mSv is a number of orders of magnitude greater.
Expanded nuclear power plant generation actually can be a net benefit for health, considering the amount of air pollution and carcinogens previously released by the fossil fuel power plants it replaces. If spending funds to reduce public radiation exposure is a goal, natural radon is the single greatest source of exposure, from which a significant percentage of the population receives even several mSv or more annually, yet few have done a radon test for $15. Nuclear waste storage isn't a problem from a perspective of considering it quantitatively as an industrial hazard, comparing zero deaths per year from nuclear waste storage to many thousands of occupational deaths annually from other causes; optionally it could be sent into space with mass drivers.
There is some interesting discussion of various aspects of nuclear power here. Some studies mentioned there on estimated deaths from fossil fuel power plant air pollution have claims that are questionable from the perspective that extraordinary claims require extraordinary evidence, more evidence. But the author's overall point that nuclear power is better for health is argued well. What nuclear power plants replace is mostly coal, natural gas, and oil; such is illustrated by current U.S. electricity generation being comprised of 49.7% coal and 21.7% other fossil fuels, only 19.3% nuclear, 6.5% hydropower, 1.6% biomass combustion, and 1.3% other renewables.
Nuclear power isn't the only possibility, as other options like utilization of space mirrors and solar power satellites could provide as much power. However, the focus of this whole post is simply to approximately illustrate one solution to each problem, and nuclear power is the most straightforward method for affordably generating tens of terawatts without greenhouse gas emissions or running out of fossil fuels.
Water
What about water? Follow the general trend in this discussion of keeping things simple by just treating all water demand as produced by desalination of seawater with nuclear power. That way there is not any question of water shortage.
Drinking water consumption in itself is relatively small, under 2 gallons per day for 9 billion people corresponding to under 25 billion cubic meters annually. But total water demand is much greater. World water usage is around 5 trillion cubic meters annually, for a combination of industrial, agricultural, and residential use, plus losses.
Particularly with substantial economies of scale, cost would be under $1.70 per 1000 gallons, so producing 5 trillion cubic meters annually by desalination costs under $2.2 trillion annually, under 3.5% of the total world GDP of $65 trillion currently. The preceding cost figure would include whatever power plant energy generation was required.
In the growth scenario where worldwide water consumption per capita may become like that for the U.S. today, water consumption reaches 15 trillion cubic meters annually. A cost up to $6.6 trillion annually is under 3.1% of the corresponding world GDP of $210+ trillion in that scenario.
Both of the preceding cost figures are actually an overestimate with the real situation being still better. Reasons for that include a combination of the following:
1) Much water may be more cheaply obtained from freshwater rather than 100% by desalination.
2) Power costs could be less than that available today, reducing desalination expense. For example, consider if the <= $1000/kW nuclear power plants had capital costs amortized over 50 years at 90+% capacity factor from a long-term perspective (neglecting discount rates), uranium from seawater adding 0.2 cents per kilowatt-hour, plus average operating, maintenance, and additional fuel costs like those of current nuclear power plants. The electricity generation cost then could be under 2.3 cents per kilowatt-hour, perhaps substantially under that after enormous economy of scale, a little like the marginal per-unit cost if 100,000 of a new type of vehicle is manufactured is less than the marginal per-unit cost if only a handful of custom-built ones are produced. With distribution costs and other factors, the electricity price to a residential customer would tend to be multiple times greater, but the cost to a giant industrial user like a desalination plant nearby could be not much more. And actually the desalination plants may make use of thermal power as opposed to just electricity, reducing the cost per unit of energy multiple times further.
3) There are also the beneficial effects of economy of scale on the marginal manufacturing cost of new desalination plants.
4) The agricultural system described subsequently involves vastly less land to irrigate, reducing the agricultural water usage that dominated the earlier figures on total water usage.
Even the preceding level of desalination is sustainable for two reasons: (1) The 1,400,000 trillion cubic meters of seawater on earth are little affected overall by the proportionally miniscule human water usage, and (2) the net salinity of the oceans is unchanged anyway in the big picture, assuming brine is sent back into the ocean, as human water usage on land eventually ends up evaporating and returning to the natural water cycle.
Agriculture
What is the agricultural system assumed? Although the world starts the scenario with regular agriculture, which could be continued, it is interesting to explore here what is possible. Consider what advanced greenhouse agriculture could do if copying some of the techniques affecting crop yield discussed in a NASA study here.
Within the greenhouses, carbon dioxide levels are elevated to 4000 ppm, an order of magnitude above concentrations in the ambient atmosphere, to be more optimal for the plants. There is optimal irrigation and temperature control, plus quarantine countering loss of yield from disease, pests, & insects. Particularly importantly, there are 4 seasons per year instead of typically 1 per year. Growing crops year-round is possible with the temperature control. Combined with increased sunlight up to 24 hours a day and greater sunlight intensity, the study estimated that enormous productivity would be possible, such as 4200 bushels of corn from a single acre in a 4-season year.
Of course, one factor would ordinarily be impractical on earth: the extra sunlight. But even that can be obtained. Area for the plants needed is merely on the order of 44 square meters per person as mentioned here, so enough food can be produced for 9 billion people in an area of 0.4 million square kilometers. Such is small compared to upwards of 48 million square kilometers used for agriculture including pasture today. There was another 5.1 square meters per person estimated for average animal area, but the plant-growing area is what needs the greenhouses.
If a single area, that would be a few hundred kilometers in diameter, though actually it would be a number of areas. A requirement is to illuminate the areas with directed sunlight, increasing light intensity over 0.0008 of earth's surface area.
That can be done with space reflectors in high orbits with large orbit radii so that a mirror would not be eclipsed by earth for more than a small portion of each orbit. For this illustration, just assume 1 micron thick aluminized mylar. Such is thin plastic, a little like weather balloons but thinner as free from nearly all disturbances. Such has been developed for solar sails. Assuming 0.9 microns of mylar and a 0.1 micron aluminum coating, such is 0.0015 kilograms per square meter given its thickness, which is thinner than garbage bags.
Neglecting the slight added mass for a wire frame that could be widely spaced due to no stresses from gravity or wind, 0.6 million metric tons is sufficient for reflectors amounting to around 0.4 million square kilometers total area. Plastic and aluminum have a raw materials cost under several dollars per kilogram, corresponding to under $0.002 trillion. But total cost may be substantially higher, including fabrication expense. However, total reflector expense can still be a small fraction of a trillion dollars, trivial in the context of thousands of trillions of dollars world economic output per 50-years. Components are easily launched into space by the launch system described later.
With the directed sunlight from the mirror, the advanced greenhouses receive intense sunlight almost 24 hours a day. Cooling the greenhouses to compensate for temperature rise from the unnatural local sunlight intensity is possible if necessary. For example, in the case of evaporative cooling with water flow, a cooling effect of X * 100 watts per square meter over the entire 0.4 million square kilometer greenhouse can be obtained with X * 0.49 trillion cubic meters of water per year. Even that would be much less than the trillions of cubic meters of annual desalinated water production described earlier. But the preceding may be an overestimate of requirements, and it may be still less difficult.
The bulk of this does not have to be desalinated irrigation water. Rather, if kept separate, it can be instead mostly seawater. The electricity required for pumping that amount of seawater up to Y * 100 meters ground elevation above sea level with 80+% efficient pumps is nominally just 0.02 * X * Y terawatts. Such corresponds to a nuclear power plant capital cost at $1000/kW of only $0.02 * X * Y trillion. The values of X and Y would be low. Also, the light from the large space mirrors could first be concentrated onto and reflected from smaller space mirrors. The smaller mirrors could have a coating primarily only reflecting the light usable by plants, rather than reflecting all sunlight from far-infrared to UV. That would much reduce the amount of solar radiation unproductively heating the greenhouses, allowing cooling needed to become relatively little, if any.
For a few hundred W/m^2 of light reaching the 0.4 million square kilometer agricultural area, the extra directed light from the space mirrors may affect earth's overall thermal balance by up to hundreds of terawatts, a little like the waste heat from the many nuclear power plants mentioned earlier. However, as before, such is quite limited at a couple orders of magnitude less than the effect of the greenhouse gases of global warming.
What about the materials for constructing the greenhouses? As much as an area of 0.4 million square kilometers seems enormous, it is orders of magnitude less than current agricultural land usage. That helps make covering such an area in lightweight greenhouses possible.
Some greenhouses today use as covering 6 mils of an inch thick polyethylene, transparent plastic sheet, treating against UV. The mass of polyethylene needed for that is 1.5 metric tons per hectare (100m x 100m area). Actually, this by itself is neglecting too much of the total mass. There would be a lightweight frame of supporting structure, possibly a multi-layer design to help keep the elevated CO2 inside mostly trapped, and more. For an order-of-magnitude estimate, instead just assume 10 metric tons of greenhouse sheeting and structure per hectare. Then the greenhouses may need around 0.4 billion tons of materials, plus or minus an order of magnitude.
For some general perspective, the 3 to 50 terawatts of nuclear power plants described earlier are synthesizing on the order of 100 billion or 1 trillion total tons of hydrocarbons per half-century, for the initial scenario or the growth scenario respectively. For a small fraction of the power to be utilized to synthesize plastics for the greenhouse construction is possible in this scenario. For additional perspective, for other structural materials, even now world steel production is 1.1 billion tons annually, 60+ billion tons per 50-years even neglecting growth. Growth from 2000-2005 was 6% annually or about a 30% increase in a mere five years.
Of course, total cost for constructing the greenhouses would be more than materials alone. Structures like this can cost up to a few times the cost of their materials. However, if the greenhouses were 0.4 billion tons and cost under $10 per kilogram (> 10x the cost of some materials), estimated cost would be under $4 trillion. That compares to the $3100 to $11000+ trillion world GDP per 50 years.
In this scenario, there is not to be dependence upon limited pre-existing nutrients in greenhouse soil but rather use of artificial fertilizer. If practical, soil-free hydroponics might be used, but, in any case, the plant nutrients come from synthetic fertilizer. Aside from water and carbon dioxide, the greatest nutrient mass needed is nitrogen-containing fertilizer, though there would be lesser amounts of potassium, phosphorous, and other minerals supplied. For the nitrogen fertilizer, the amount needed to be synthesized corresponds to 72 grams of nitrogen content per person per day. If such seems high compared to human intake, it is because total agricultural plant yield is a half-dozen times greater than food eaten by people, especially since there is much more animal feed involved than the mass of meat, eggs, and milk produced as part of the food supply.
Such corresponds to annual production of fertilizer with 0.24 billion metric tons of nitrogen content. The Haber process is used today to produce 0.5 billion tons of nitrogen fertilizer a year, even while consuming only around 1% of the world's current energy usage. So actually less fertilizer is needed in this scenario, due to the greater efficiency of the agricultural system.
Once again compare the 0.4 million square kilometers needed for the preceding system to the 48+ million square kilometers currently used for agriculture including pasture area. And observe literally 99% of current agricultural land usage becomes no longer needed. Such corresponds to the bulk of land currently used by mankind becoming freed to become wildlife refuges and national parks.
A partial counter-effect is some increase in urban land usage. The eventual projected world population of 9 billion corresponds to 9.7 million square kilometers of total land usage for cities. Such assumes a ratio per capita reaching the 1080 square meters per urban resident of the U.S. today. However, that is much less than the 48+ million square kilometers freed from agricultural usage, so the net effect is vastly more space for nature than today.
Biodiversity
While there are millions of total species from bacteria to invertebrates like insects, focus particularly on preserving the biodiversity of the 60,000 vertebrate species, which are mostly fish actually but also include amphibians, reptiles, birds, and 5000 mammal species. Only some are actually endangered, but treat them all as endangered for simplicity in this discussion of some measures to help preserve biodiversity.
The cost of capturing and breeding a suitably large number of individuals of each species would vary. For example, it might be far under $1 million for one particular species of fish, or perhaps vastly greater for some rare and difficult to breed mammal species. Just treat this as $10 million on average per species for breeding eventually at least 1000+ individuals of each species. Also assume $1 million annually per species afterwards. So starting expense is $0.06 trillion, just 0.002% of even the low-end $3300 trillion figure for the world's 50-year cumulative GDP. And the continuing cost is treated as $0.03 trillion per half-century, although eventually even the populations of endangered species could rise enough to become more robust without needing continued human assistance.
Actually, since much more funds would easily be affordable to spend on the project, far greater measures than the preceding alone could be done. For example, the preceding skipped over measures taken to preserve plant species, but much could likewise be done for them. Preservation measures would also include a sampling of invertebrates, fungi, archaeans, and more.
Some of the animals and other lifeforms are eventually sent to space habitats, which helps be extra sure of the survival of each species by having them widely distributed. Even some of the young of the giant Blue Whale can be sent to space with the launch systems described later. Particularly due to unprecedented economies of scale on such a many-billion dollar project, cloning might become relatively affordable, possibly as a supplement to regular breeding when appropriate, or even to be used for cloning some extinct species like the Dodo bird if possible
The preceding biodiversity measures are not a substitute for trying to maintain the whole original ecosystems, particularly since a natural ecosystem involves much more than just a bunch of creatures, being impossible to fully duplicate artificially. But the preceding is a helpful supplement. And, as implied above, a separate measure that causes environmental benefit unprecedented in human history is the new agricultural system that not only stops clearing of wilderness for agriculture but mostly reverses it.
Geoengineering
There are a variety of geoengineering measures that may be performed. Different manmade emissions have caused different radiative forcing, some causing heating and some causing cooling, as discussed in the post here, but the overall effect is net warming, with the best estimate for net radiative forcing being around 1.6 W/m^2.
One of multiple geoengineering techniques to counter such is to reduce the amount of sunlight hitting earth. The amount of dimming can be not an excessive problem because the reduction in sunlight needed is limited. For example, reflecting 1.8 percent of sunlight could compensate for a doubling of carbon dioxide in the atmosphere from preindustrial levels. Actually, in this scenario, one is able to perform intervention long before CO2 levels reach 540 ppm, so less than that may be sufficient. Just assume countering 1% to 2% is desired.
Some measures were mentioned in an earlier thread here. For example, using calculations there, plugging in the figure of under 1.8 percent sunlight reflection needed, micron-thick aluminum reflectors in space having a combined mass of 6 million tons could accomplish that. The corresponding "raw materials" aluminum cost is $0.014 trillion, plus $0.02 trillion for electricity powering mass drivers launching the foil to space, at the current price of industrial electricity ($0.06/kilowatt-hour in the U.S., where 1 kilowatt-hour is 1000 watts for 3600 seconds, 3.6 MJ). In this scenario, the mass-produced nuclear power plants cause even cheaper electricity, indirectly even causing cheaper aluminum since its cost depends much on the large amounts of electricity used in production.
Of course, total expense including fabrication would be substantially higher than the preceding alone, but the general situation is apparent: The solar reflectors don't cost much compared to $3100+ trillion world GDP per half-century.
Alternatively, aluminized hydrogen-filled balloons at high altitude in the atmosphere could have a similar effect. Thickness required would be greater than the space mirror but still not more than a few microns, with potentially correspondingly limited expense for the aluminized plastic. However, while the frequency of trash falling back down periodically could be mitigated with larger balloons, the space reflector project helping develop space infrastructure is considered an advantage here.
The earlier post also mentioned the possibility of using large thermonuclear bombs to throw up dust to cause a cooling effect. While such was admittedly suggested in part for fun, it would work for a substantial amount of cooling, considering the observed cooling effect of stratospheric dust and particulates from major historical volcanic eruptions. Assuming well under $0.01 trillion annually seems plausible, and radiation exposure could be limited as implied in the last thread.
Another geoengineering option is more direct deposition of dust into the atmosphere, using the principle of the hydrogen bombs but in a different manner. As implied in an article here, stratospheric aerosol methods are affordable particularly because the residence time of particles of appropriate miniscule size dispersed in the stratosphere is orders of magnitude higher than for particles at much lower altitude.
A 1 percent to 2 percent change in solar flux may be obtained by a reflective aerosol dust loading of 0.02 to 0.04 grams per square meter, with particles of around a quarter-micron diameter in the stratosphere. So 10 million to 20 million tons of dust could suffice. Average dust lifetime is ~ 1.25 years or more, determining the rate of replenishment needed. Although even 16-inch cannons could deliver shells with dust to the necessary altitude, aircraft can disperse dust for less cost. At merely about $1/kg, flight expense might be $0.02 trillion annually.
Yet another dispersion method possibility is coilguns. Assuming at least 40% overall efficiency with the mass drivers, $0.0003 trillion of nuclear power plant capital cost provides 0.3 GW of electricity, enough to fire 20 million tons annually to as high as 20 kilometers altitude. Total expense would be more, but even the particular magnitude of such a proportionally small expense barely matters in this context. A side benefit might be beautiful sunsets.
With sulfates, 0.6 to 1.2 million tons would be enough to reduce solar radiation by the desired 1 percent to 2 percent. The amount of sulfur needed before stratospheric combustion would be as little as 0.2 to 0.4 million tons or less. The aerosol lifetime determining the rate of replenishment might be two years. However, while such requires even less mass than the dust and wouldn't cause much acid rain, it could be much more reactive, so dust might be more environmentally friendly than sulfates.
Iron fertilization of the oceans would tend to have a more limited maximum effect possible than the preceding techniques. It does, though, have advantages of removing some of the carbon dioxide in the atmosphere while increasing the primary production of the oceans. Such might result in more marine life and could be worth trying, as suggested in the other thread.
Given the enormous amounts of nuclear power able to be obtained in this scenario, enormous amounts of other fertilizer could be synthesized, and even forests on land might be fertilized as appropriate to grow and transfer more atmospheric carbon into their biomass.
The goal is not to create an ice age, and not all geoengineering measures need to be done at once. The preferred geoengineering method here is space reflectors, not really needing the alternatives, though ocean fertilization might be a supplement. While an option, use of particulates would be more complicated. Adjustable almost like dialing a thermostat, space reflectors are quite useful.
Any of the above geoengineering measures could be ramped up gradually, first starting at a tiny fraction of the final goal, monitoring all effects, then increasing to full-scale deployment over a period of time.
Scrubbing Air and CO2 Sequestration
Though more expensive than the preceding geoengineering methods, the ideal could be to remove carbon dioxide from the atmosphere to make up for past emissions, such as dropping levels from 380 ppm now back down to pre-industrial levels of 270 ppm. Part of that might be done by ocean fertilization and other measures involving biological sequestration. But, to avoid questions of scaling issues, just calculate here for doing so abiotically.
As discussed earlier, scrubbing carbon dioxide from the atmosphere is estimated to require 3 MJ per kilogram of CO2 collected. Let's assume that the total power needed after inefficiencies is not more than double that. Since $1 trillion of the nuclear power plants delivers 1 terawatt of electricity plus 1+ terawatts of relatively high-temperature "waste heat" thermal power, such corresponds to the power to remove 10.5 billion tons of CO2 from the atmosphere per year. That is 530 billion tons in 50 years.
Total extra carbon dioxide in the atmosphere beyond pre-industrial levels amounts to 880 billion tons. So $1.7 trillion suffices for the capital cost of building enough nuclear power plants to power restoring the atmosphere to pre-industrial levels of CO2, at a rate corresponding to completion in 50 years.
Of course, there are additional costs. Something must be done with the huge quantities of carbon dioxide being collected each year. The preceding just obtains concentrated carbon dioxide, with the carbon still in its oxidized form that resulted from its past combustion during fossil fuel burning long ago. Some of the collected carbon dioxide can then be used in plastics synthesis, for the elevated CO2 concentrations within the advanced greenhouse agriculture structures, and for other purposes. The bulk of excess CO2 might be sequestered. For example, underground reservoirs could store more than 3 trillion tons of CO2 or rather store all of the 900 gigatons actually removed.
Alternatively, though requiring more energy, the excess collected carbon dioxide could be instead converted back to solid carbon plus oxygen by the Bosch process, which is CO2 + 2H2 -> 2H2O + C. That requires nominally an additional 13 MJ per kilogram of carbon dioxide broken down, due to the energy needed for the hydrogen consumed in the process. Allowing a factor of 2 for inefficiency in electrolysis, there is 26 MJ of electricity consumption per kilogram of carbon dioxide. Doing so with the desired 18 billion tons of CO2 each year for 50 years requires 14.5 terawatts of nuclear power plants.
Of course, total expense would be higher than the nuclear power plant capital cost alone, but this shows the overall picture. As usual, the $14.5 trillion power plant capital cost may be affordable, considering the $3100 to $11000+ trillion world economic output over a half-century.
The excess solid carbon or graphite is basically the equivalent of coal. It may be buried underground, running the process of fossil fuel burning in reverse, or better uses may be found for it. Whether through carbon dioxide collection followed by sub-surface sequestration of the CO2 or by subsequently breaking down the CO2 instead, either way carbon dioxide levels in the atmosphere are dropped.
Not all of these measures are strictly required, nor does the relatively large expense relative to gain of some measures compared to alternative allocation of funds necessarily actually maximize human welfare. But the preceding works for an illustration.
Expansion Into Space
The ultimate future of mankind lies in space, and, in this scenario, one can make it happen relatively fast.
First, referencing some past posts is helpful:
Introduction to launch costs: here
What happened historically, why there are no cities in space so far: here
The earlier posts covered topics like how current launch costs are thousands of times energy expense, but they can be reduced.
With mass drivers, an astronomical amount of equipment can be put into space. In this scenario, 0.1% of the $3100 trillion to $11000+ world GDP per 50 years corresponds to 3.1 to 11 terawatts of nuclear power plants.
But actually 3.1 terawatts would be orders of magnitude more than needed, as that would be enough to power sending 54 billion tons to space, with mass drivers having around the efficiency of this using around 90 MJ of electricity per kilogram launched.
Even sending a million tons of equipment to space is more than enough for further space expansion to switch to using extraterrestrial resources almost 100%. That much equipment could be launched in 5 years of operation by a mass driver running on a 600 megawatt nuclear power plant.* In the units usually used in this post, that is a 0.0006 TW nuclear power plant, with a capital cost of only $0.0006 trillion at $1000/kW. Of course, total expense for the whole project would be much higher, but expansion into space could be started for well under a trillion dollars.
* Let's illustrate how this figure works: Since 600 MW is 600 MJ/sec, the result is 600 MJ/sec * 3600 sec/hr * 24 hr/dy * 365 dy/yr * 5 yr = 94,600,000,000 MJ or ~ 90,000 TJ.
Since actually not just a fraction of a trillion dollars but rather even up to literally thousands of trillions of dollars could be spent on space over the first century alone if such is made one of the main priorities, what could be accomplished would be particularly astronomical.
Rockets with designs a little like the Sea Dragon could be used for transport of people, who would need far lower tolerable acceleration than the cargo mass driver. However, in this case, with plenty of funding available, mass drivers could be built long enough to launch people into low earth orbit with only very little use of a rocket thruster at the end. At some number of millions of dollars per kilometer of length, such would cost billions of dollars, but anything not many trillions is relatively minor in this context.
Other Measures
There is vastly more beneficial to do in this scenario with "god-like" power than the selected technological and environment-related measures mentioned here alone. For example, as implied here, some measures based on quantitative decision-making could save lives in developed countries for as little as under $100,000 per life saved on average, or sometimes statistically as little as hundreds of dollars per life saved in some third-world countries. A huge number of lives could be saved for a given allocation of funds.
Literally millions of lives can be saved per year. For example, there are around 2 million deaths from malaria in the world annually, yet such is quite preventable as illustrated by the U.S. and some other countries having practically eliminated it; for example, the U.S. dropped from 15000 cases in 1947 to 2000 cases in 1950, then eradication was announced in 1951. And a program for major malaria control in the most afflicted continent (Africa) has been estimated as costing $3 billion annually, $0.003 trillion a year. When even 0.1% of the current world economic output of $65 trillion annually amounts to trillions of dollars per half-century, a lot could be done for proportionally little cost, like causing a significant portion of the total 57 million people dying each year to live longer.
But covering everything possible in this scenario for health, education, infrastructure, and more would take too long and get off-topic.
Additional Technological Options and the Long-Term
What is discussed in this post are merely sample technological options, among multiple possibilities. For example, the majority of the nuclear power generation ends up fulfilling roles that might alternatively be fulfilled mostly with concentrated thermal power alone. Hydrogen might be produced thermochemically from water rather than needing electrolysis, and most of the other chemical processes involve heating reactants to high temperature in the presence of a catalyst.
With 1 micron thick aluminized mylar, space reflectors massing around 11,000 metric or 150,000 metric tons could redirect 9 terawatts or 120 terawatts of sunlight respectively. And if total cost is X per kilogram, the cost of such is only around $0.000011 * X trillion or $0.00015 * X trillion respectively. Short of an astronomical value of X, costs are relatively limited. As good as the economics are for the mass-produced nuclear power plants, the preceding might cost even fewer trillions of dollars and be an alternative to most power generation.
Concentrated onto a relatively tiny region, corresponding to the top of reaction chambers for thermochemical decomposition of water and more, such concentrated sunlight could locally maintain temperatures at the appropriate number of hundreds of degrees Celsius.
As another example, vehicles running directly on electricity might optionally replace those running on synthesized gasoline. Vehicles running on rails would be more suited to automation. Propelling a vehicle along a track where it physically can't get off course doesn't require nearly as sophisticated AI as driving a vehicle on a road. Such could lead to fast, cheap, automated package delivery as well as passenger transport.
And much is possible in less than a thousand years, including life extension, telepresence technology, artificial intelligence, self-replicating factories, interstellar colonization, and more. But the focus here has been more conservative to illustrate what could be accomplished with application of technologies not needing major research before implementation, such as the existing technology of nuclear power plants.
Comments
Timeframes haven't been illustrated in detail, but an initial priority to accomplish quickly would be to get the first 2.8 terawatts of nuclear power plants online to provide power for synthesis of current gasoline, diesel, and jet fuel consumption instead of producing it from oil. That involves 2.8 trillion dollars for capital costs of the power plants, plus more for other expenses. Such would act as a countermeasure to peak oil effects. The nuclear-powered process using atmospheric CO2 is environmentally better and more sustainable than having synthetic fuels from coal.
If the world's current economic growth rate is not damaged, total world economic output in the subsequent 50 years could be much more than $3100 trillion. The power plant expense could pay for itself many times over. And more funds means more can be accomplished for almost any goal.
Of course, this scenario with one having "god-like" power is totally different from the real-world, so the preceding doesn't have much to do with what actually happens. Still, it was an interesting exercise.
Global Warming: You're God
Moderator: Edi
