Greenpeace would rather have the plutonium "disposed of as nuclear waste" while it is still weapons-grade material, rather than truly converted to nuclear waste and made useless for fisson bombs first.
This is one reason why, despite being an environmentalist, I have little use for today's environmental "movement". The groups who go to great efforts to paint themselves green turn out to be watermelons.
First, while most of us think of toilet output when we think of sewage, the reality of most municipal wastewater is that it has loads of soap in it.
I was talking about sludge, which is quite a bit removed (and concentrated) from the state of raw sewage. As for the soap, if you can separate that and feed it through thermal depolymerization it would be good. Lauryl sulfate (derived from dodecanol) ought to be just the kind of thing that produces good hydrocarbons as output. Ditto stearates.
The beauty of aerobic processes is that most of the water is back in the river in about eight hours. Can the same be done with Anerobic digestion?
I doubt it. Anaerobes seem to require days (high-temperature) or even weeks (low-temperature). The literature I've seen on producing "gobar gas" from manure talks about cycles on the order of 60 days. On the other hand, you are not going to be feeding raw sewage through this process; it's going to take the settled solids and enough water to make a slurry, and that's pretty much it. What's your ratio of solids to total volume?
... did anyone notice that little item on the technology and products part of the web site marked "organic vapor"? What is that? Is it recoverable? Can you burn it for fuel without incurring the wrath of the EPA? Who would want to live anywhere near that kind of thing?
The CARB is already requiring afterburners on bakeries to destroy "organic vapor" produced by yeast, so I suspect that burning the vapor may be a requirement. As for what it is, who knows; do you have any idea what organic byproducts of methanogens have a high enough vapor pressure to come off with the gas? I don't. But if you burn them with the methane (and they don't contain sulfur) you ought to be just fine. The people living nearby would probably like it better than the current vapors.
Believe me, for what we spend on sludge hauling contracts, if there were any better solution, we'd jump at it even if it were more expensive in the short term.
The May 2003 article in Discover which broke the anything-into-oil story to the wider world is here, but it's now subscriber-only. I seem to recall that it quoted conversion products for a mixture of sewage sludge and grease-trap waste, but I can't tell you what they are without the article to cite. Even the Google cache has been purged.
The problems with large scale livestock farming are that you need a pretty good chunk of land to "take the poop" from an operation....
I think that I read somewhere that some hog operations produce the raw sewage of a city of 30,000 people.
They're called CAFOs, Concentrated Animal Feeding Operations. I suspect that these are only economical because they are allowed to dump animal waste with minimal or no treatment; if they had to pay for the remediation required of municipal sewage plants, they would cease to exist and the work would be done in much smaller operations closer to the source of the feed. This would allow the waste to be used as fertilizer on the farms from which the feed came, closing the loop.
Yes, you probably could dispose of the waste using thermal depolymerization. I don't think that this is economical in an era of rising oil and gas prices; being able to cut transportation requirements and recycle gas-derived nitrates (nitrate fertilizers are made from ammonia, which is synthesized from nitrogen and natural-gas-derived hydrogen) is going to have a lower overall energy cost than an inefficient conversion of excrement to fuel, especially if the excrement can be digested for methane with little loss of nitrogen.
Speaking of repeats, do you have any news about how the plant there is working? I heard that it had serious issues with defective welds, but little beyond that.
That would just make too much sense - how dare you!
Engineer-Poet, confounding/. with logic since 2004.
This would also be a great opportunity for large livestock farmers - most of the time they have a surplus of "organic waste matter" and have to scramble to find a place to till it into the ground.
I'm not sure how useful it would be for livestock farmers. In a city, pretty much everything that goes to the sewage plant is quite a distance from where it originated. Unless you can reduce the bulk of the material by a large factor it's uneconomical to ship it very far to close the loop. A feedlot may be in a similar boat, but the livestock farmer who also grows grain and hay has a supply of nutrients (phosphorus, potassium, nitrogen) close to land that needs replacements for the nutrients removed to feed the livestock. Once the major amounts of carbon have been digested for methane, what remains looks like it would be more valuable for fertilizer than as a further feedstock; you certainly don't want to convert nitrate into ammonia (which seems to me what you'd get by putting nitrate into a reducing environment) if you can avoid it.
Changing World Tech doesn't have anything on their site for the products available from municipal solid waste, but if a city could use one plant to convert both their MSW and sewage sludge into fuels and stable byproducts they'd eliminate a great many headaches.
When I saw this article I was afraid it was another "microbial fuel cell" thing.
I don't see any reason why dewatered sludge couldn't be fed through an anything-into-oil plant and converted to energy more cleanly than by incineration.
I have been through the CDF at Fermilab. It is an awe-inspiring experience to see a device, bigger than many houses, devoted to investigating the smallest and most fleeting events currently open to human inspection. The huge sliding shield doors which separate the beam line from the zones which are human-safe during operation will give you some idea of how big, and dangerous, small can be.
Most first time home owners buy used, then after they have enough equity, then they are able to consider options.
It's not a huge deal to blow in R-50 insulation in the attic and use soffit, gable, ridge and even powered vents; this is within the capabilities of many do-it-yourselfers. Planting trees is fairly cheap and increases property values. Replacing old, leaky windows with high-performance units is more expensive but also increases the value of the house and comfort levels while cutting energy costs. If you get to the point of re-siding, you can go much further.
In the future, maybe there will be enough energy effecient housing on the market and first time buyers will have the option.
Such measures should be part of all building codes (should have been 20 years ago, IMHO). People buying used housing wouldn't have to put up with as much cheesy, leaky work if we stopped building it that way, and every day we let it continue the problem gets worse.
It was like my car purchases for a long time. They were all under 3K dollars and over 80K miles. Green and effecient were not in the mix. In another 10 years it may be possible to pick up sub 3K dollar hybrids.
All the better reason to get cracking, no? We knew how to build hybrids at least 15 years ago, but it's taken until now to get more than a few models on the market - and most are Japanese. We need to do better.
I can percieve that generally, unless there is a major social move on the viewpoint, it would be just a 'fad' amongst the wealthy / high-society. To make it last beyond that would almost require it to be socially unacceptable on a large scale rather than just 'un-cool', to have a house that is not ecologically friendly. Until the technology comes down in price a little thats unlikely to happen.
Most of the "technology" is just being careful about how energy is used. Here's a for-instance: I've read that the houses in the Solar Challenge competition were run with about 40% of the total energy of the typical house (a house only needs to cut to 70% of typical to qualify as "Energy Star", IIRC). If the ONLY thing you do is adopt high-efficiency envelopes and systems, you are already 3/5 of the way to the goal without installing a single solar device. If you use flat-plate heat collectors for hot water and some space heat, you're even closer before installing any PV cells. The solar-electric systems are one of the last steps, not the first.
One source that I've been unable to locate again actually said that the PV cells use more energy to manufacture than they will produce over their lifetime.
Perhaps because it was true for the earliest cells, but hasn't been for a long time. I've read that current cells have a payback time of 2-4 years depending on type and site, and this figure continues to drop. Some claims are far less.
For the simple answer to cost of instal is check the power requirement for a simple AC unit. Remember they don't like power sags. Now price a solar system big enough to run the AC.
The response you would get from a RE advocate is that your scenario betrays a completely wrong engineering approach, like asking for a skyscraper design using wattle and daub. The first thing you do is minimize your requirements by insulating walls and windows, using infiltration and vapor barriers to keep out humidity, and shading glass to prevent unwanted heat gain. Then you use thermal mass to keep temperature fluctuations down and allow night-time ventilation to keep the building cooler during the day. Only THEN would you use mechanical A/C, and with current systems a least-cost solar chiller would probably not be electric.
Don't expect to run a regular all electric home of just solar.
Part of the problem is the mentality that an all-electric home is "regular", instead of the architectural equivalent of an H2 Hummer.
Expect to use an alternate power source for things like the hot water, heating, cooling and clothes dryer.
Hot water: flat-plate solar collector to supply full heat during summer and pre-heat during the winter.
Heating: insulate and plug air leaks well enough and the heat of the occupants and their activities will do most of the job. You can have a backup heater, like a small propane furnace or wood stove, for the periods when combined cold and dark increase your requirements.
Cooling: see above.
Clothes dryer: Use a clothesline, it's free. Failing that, use a tumble dryer fired by natural gas or propane; this will require less than half the fuel needed to feed an electric dryer.
Things like the dishwasher, electric dryer, AC, electric heat, and un-effecient refrigeration (fridge and freezer) would have to be replaced.
A high effeciency fridge is a serious chunk of change. I've looked into them.
If you're dependent upon electric resistance heat, the rest of your list appears to pale by comparison. This still does not keep you from insulating your attic, putting awnings over your windows, planting deciduous trees to shade your walls in the summer, and watching your tradeoff between the remaining lifespan on your fridge/freezer and a new model.
It used to be that people living off-grid who wanted refrigeration either used a propane-fired absorption unit or a Sunfrost. This has changed, with some major brand offerings being nearly as good as a Sunfrost and a lot cheaper. The best fridges at the appliance store can be run on solar electricity cheaper than the cost of running mains power a half-mile.
A centrifugal switch does actually sound like a better way of doing it.....
That's why so many single-phase capacitor-start motors use them (you are parading your ignorance around).
If you are going to pay for inverters anyway, it may well be cheaper to use a 3-phase induction motor with variable-frequency drive; you lose some efficiency in the slip but the armature is much cheaper than permanent magnets. Such motors have essentially replaced DC servomotors.
You would need about 15 m^3 of storage to absorb a 6" (~15 cm) rainfall over 100 m^2 of roof. That is a LOT of volume to work into anything, unless you have a patio to use as the top of a storage tank.
For the masses, 15 cubic meters is 15,000 liters or just shy of 4,000 gallons.
Thin-film solid-oxide fuel cells. Ballistic-electron photovoltaic converters. The former is a big refinement of the best that had come before, and the latter is brand new AFAIK (not that I'm a guru on the subject but I follow the field a lot more closely than the vast majority of/.'ers).
You can assume that something old is new and special, or that something new is old hat. Both are mistakes, with consequences.
Algae is pretty impressive, but doesn't hold a candle even to present-day solar panels (and the energy from solar cells does not require conversion in a heat engine to make it useful). The advantages of algae are that they reproduce themselves and oil is more easily stored. Looks like the combination could be a winner.
Here's what I was replying to, in case you missed it:
Exactly the reason you'd not see a planet made of the stuff. Your cross-sections are just too high; meaning your chances of a neutron escaping one atom and hitting another that much more likely. Once you get past a certain mass, you've created a bomb.
Regardless of bombardment, iron does not emit neutrons with enough additional energy to cause a chain reaction (which you admitted when pressed), so your statement in the great-grandparent is simply not relevant to the discussion. Compression can increase the density of any material (not just plutonium), and a 3x compression of a very large iron core would be sufficient to create a planet twice the diameter of Earth but 56 times its mass and thus 14 G surface gravity, QED.
(not that pure natural uranium can support a chain reaction either, you have too much fast-neutron-eating U-238 and no moderator.)
With high-yield rapeseed, 3% of the arable area of the US would be needed to cover its need of oil for transportation.
Consumption of diesel fuel in the USA in 2002 was 2.455 million barrels/day, or 39.4 billion gallons per year. At the high yield figure of 145 gallons per acre and 100% conversion to biodiesel, that would require the production of 271 million acres, or 425 thousand square miles.
Total area of the USA is 3,618,784 square miles, so you're talking 12% of the total land area (including Alaska) and a much higher fraction of the arable land.
Note that if you want to replace the gasoline as well, you have to multiply that figure by about 4.5. This is clearly not possible.
If you are arguing that the power requirements of vehicles powered by electrolytic hydrogen are minimal, you are very much mistaken. The transmission grid has plenty of unused capacity during off-peak hours to move the required wattage, but the energy to fill that capacity has to come from somewhere. We're running our nuke plants flat-out most of the time, hydropower is limited, wind is a paltry few GW, natural gas supplies are tight; this means burning more coal in those few plants which aren't base-loaded and also runnng flat-out.
If I recall correctly, the efficiency of the electrolysis/fuel cell cycle is about 50%. Some types of batteries do much better, at 80% or so. You're going to need a lot more power to run cars on electrolytic hydrogen than on batteries, and the difference between the two is something like 30% of current consumption - far from trivial.
On the other hand, with the current market penetration of electric vehicles you could do things either way and it would be cheap, especially if you used off-peak electricity exclusively. It's when you begin converting substantial parts of the vehicle fleet that the impact would be felt; you'd have to make big investments in the generating part of the infrastructure, mostly to replace low duty-cycle peaking generators burning expensive fuel with high duty-cycle or base-load plants burning cheap fuel.
The vehicular power requirements of the United States average close to 200 GW. Then you have losses in transmission, conversion and storage. Total US electric generation capacity in 2002 was about 900 GW.
No it couldn't. Curve of binding energy peaks at element 26 (Fe); osmium is up at atomic number 76. Osmium is always going to be too rare to make whole planets, as you noted.
... you can't compress uranium much more than it already is.
Au contraire, compression is one of the ways that very sub-critical masses of fissionables are turned into bombs (neutron reflectors are another). Peak densities are several times the STP solid density. Perhaps you never wondered why implosion designs are used for nuclear weapons; that's one reason.
So let's see, we need to pack 56 earth masses into 8 earth volumes. Going from rock to nickel-iron gets you a factor of 2.4 or so, which yields 19.2 masses; if the heat of formation helped to boil off the materials of lower density it wouldn't surprise me. Could compression push the density up by another factor of 3? If conventional explosives can do it in a small package, it seems likely. Are there any high-pressure physicists who can offer a pointer to research here?
The average density of Earth is about 5.5 g/cc, while the surface rocks average 3.5 g/cc. There are two reasons for this:
The Earth's core is made largely of iron, which is much denser than rock.
The core matter is compressed by the pressure of the overlying material.
If you took Earth and doubled its size with no other changes, you'd have a surface gravity of about 2 G. If you tripled the diameter of the core at the expense of the mantle (more metals in the star, more metals in the planet), you'd increase the density of the mantle zone from ~4 g/cc to 8-10 g/cc; this would give you 6-9 G at the surface. Factor in some additional compression due to the overlying mass, and I could see 14 G surface gravity.
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This is one reason why, despite being an environmentalist, I have little use for today's environmental "movement". The groups who go to great efforts to paint themselves green turn out to be watermelons.
The Pu in question has already been converted to plutonium oxide; there is nothing to burn, and it is extremely stable.
Yes, you probably could dispose of the waste using thermal depolymerization. I don't think that this is economical in an era of rising oil and gas prices; being able to cut transportation requirements and recycle gas-derived nitrates (nitrate fertilizers are made from ammonia, which is synthesized from nitrogen and natural-gas-derived hydrogen) is going to have a lower overall energy cost than an inefficient conversion of excrement to fuel, especially if the excrement can be digested for methane with little loss of nitrogen.
Speaking of repeats, do you have any news about how the plant there is working? I heard that it had serious issues with defective welds, but little beyond that.
Changing World Tech doesn't have anything on their site for the products available from municipal solid waste, but if a city could use one plant to convert both their MSW and sewage sludge into fuels and stable byproducts they'd eliminate a great many headaches.
I don't see any reason why dewatered sludge couldn't be fed through an anything-into-oil plant and converted to energy more cleanly than by incineration.
I have been through the CDF at Fermilab. It is an awe-inspiring experience to see a device, bigger than many houses, devoted to investigating the smallest and most fleeting events currently open to human inspection. The huge sliding shield doors which separate the beam line from the zones which are human-safe during operation will give you some idea of how big, and dangerous, small can be.
Heating: insulate and plug air leaks well enough and the heat of the occupants and their activities will do most of the job. You can have a backup heater, like a small propane furnace or wood stove, for the periods when combined cold and dark increase your requirements.
Cooling: see above.
Clothes dryer: Use a clothesline, it's free. Failing that, use a tumble dryer fired by natural gas or propane; this will require less than half the fuel needed to feed an electric dryer. If you're dependent upon electric resistance heat, the rest of your list appears to pale by comparison. This still does not keep you from insulating your attic, putting awnings over your windows, planting deciduous trees to shade your walls in the summer, and watching your tradeoff between the remaining lifespan on your fridge/freezer and a new model.
It used to be that people living off-grid who wanted refrigeration either used a propane-fired absorption unit or a Sunfrost. This has changed, with some major brand offerings being nearly as good as a Sunfrost and a lot cheaper. The best fridges at the appliance store can be run on solar electricity cheaper than the cost of running mains power a half-mile.
If you are going to pay for inverters anyway, it may well be cheaper to use a 3-phase induction motor with variable-frequency drive; you lose some efficiency in the slip but the armature is much cheaper than permanent magnets. Such motors have essentially replaced DC servomotors.
For the masses, 15 cubic meters is 15,000 liters or just shy of 4,000 gallons.
You can assume that something old is new and special, or that something new is old hat. Both are mistakes, with consequences.
The only newsy thing about this is the interest from makers of space probes; the thermoacoustic engine has been around for a while (combine with a thermoacoustic chiller and you've got a gas-liquefaction system with no moving parts; here's another one from 1999) and the page from LANL on thermoacoustic systems is almost two years old already. These guys were plugging their sound-to-electricity converter some time ago.
High-yield rapeseed, 145 gallons/acre/year (1.52 KWH/m^2/year)
Algae-derived oil, 50000 gallons/hectare/year (212 KWH/m^2/yr)
Silicon PV cells at 15%, receiving 700 W/m^2 average, 6 hrs/day: 230 KWH/m^2/yr
Future PV cells at 50%: 766 KWH/m^2/yr
Algae is pretty impressive, but doesn't hold a candle even to present-day solar panels (and the energy from solar cells does not require conversion in a heat engine to make it useful). The advantages of algae are that they reproduce themselves and oil is more easily stored. Looks like the combination could be a winner.
(not that pure natural uranium can support a chain reaction either, you have too much fast-neutron-eating U-238 and no moderator.)
Total area of the USA is 3,618,784 square miles, so you're talking 12% of the total land area (including Alaska) and a much higher fraction of the arable land.
Note that if you want to replace the gasoline as well, you have to multiply that figure by about 4.5. This is clearly not possible.
If I recall correctly, the efficiency of the electrolysis/fuel cell cycle is about 50%. Some types of batteries do much better, at 80% or so. You're going to need a lot more power to run cars on electrolytic hydrogen than on batteries, and the difference between the two is something like 30% of current consumption - far from trivial.
On the other hand, with the current market penetration of electric vehicles you could do things either way and it would be cheap, especially if you used off-peak electricity exclusively. It's when you begin converting substantial parts of the vehicle fleet that the impact would be felt; you'd have to make big investments in the generating part of the infrastructure, mostly to replace low duty-cycle peaking generators burning expensive fuel with high duty-cycle or base-load plants burning cheap fuel.
The vehicular power requirements of the United States average close to 200 GW. Then you have losses in transmission, conversion and storage. Total US electric generation capacity in 2002 was about 900 GW.
Iron isn't fissionable. Neither is nickel. Try again.
So let's see, we need to pack 56 earth masses into 8 earth volumes. Going from rock to nickel-iron gets you a factor of 2.4 or so, which yields 19.2 masses; if the heat of formation helped to boil off the materials of lower density it wouldn't surprise me. Could compression push the density up by another factor of 3? If conventional explosives can do it in a small package, it seems likely. Are there any high-pressure physicists who can offer a pointer to research here?
- The star's temperature yields its luminosity, and indirectly its mass.
- The Doppler shift and period of the wobble yields the planet's mass as a fraction of the star.
- The amount of light blocked by the planet yields its area, and thus its size.
- From size, you can calculate volume. Density = mass/volume.
If the star is close enough and the planet heavy enough you can cross-check the wobble using astrometry.- The Earth's core is made largely of iron, which is much denser than rock.
- The core matter is compressed by the pressure of the overlying material.
If you took Earth and doubled its size with no other changes, you'd have a surface gravity of about 2 G. If you tripled the diameter of the core at the expense of the mantle (more metals in the star, more metals in the planet), you'd increase the density of the mantle zone from ~4 g/cc to 8-10 g/cc; this would give you 6-9 G at the surface. Factor in some additional compression due to the overlying mass, and I could see 14 G surface gravity.Still doesn't hold a candle to Mesklin.