Xref: utzoo talk.politics.misc:8282 sci.misc:1009 Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!husc6!bloom-beacon!athena.mit.edu!jfc From: jfc@athena.mit.edu (John F Carr) Newsgroups: talk.politics.misc,sci.misc Subject: Re: the "greenhouse effect" theory Message-ID: <3851@bloom-beacon.MIT.EDU> Date: 18 Mar 88 00:42:27 GMT References: <22138@bbn.COM> Sender: daemon@bloom-beacon.MIT.EDU Reply-To: jfc@athena.mit.edu (John F Carr) Organization: Massachusetts Institute of Technology Lines: 192 Summary: (long section on energy from garbage) In article <22138@bbn.COM> eli@BBN.COM (Steve Elias) writes: >In article <3772@bloom-beacon.MIT.EDU> I wrote: [ In response to description of the greenhouse effect, which, accelerated by fossil fuel consumption, may raise the level of the oceans enough to flood coastal cities.] SE : nuclear power plants also contribute nontrivial amounts of SE : thermal pollution into the environment, a significant factor SE : in the greenhouse effect, especially if more plants are built. JFC : The quote above reveals a lack of understanding of thermodynamics, > wrong. it reveals that i don't agree with your opinions on > the greenhouse effect theory. > there is no valid model for the greenhouse effect. > either one of our statements are just opinions. if you are aware > of some definitive new research, please do tell. I am not aware of any serious disagreement over the nature of the greenhouse effect, only its magnitude. The Earth must be stable to small additions of heat, since the solar constant isn't really constant. There is a theory (which is somewhat controversial) that Earth+life is self-regulating (i.e., mean temp and atmospheric composition are kept constant). Certainly there must be some reason for the relatively stable climate/atmoshpere. The addition of massive amounts of non- biological CO2 may remove any stability. Remeber that fossil fuel plants produce all the thermal pollution of nuclear PLUS carbon dioxide. [question for any scientists who have studied this: has anyone added biological factors to the computer simulations of the ice ages? Last I read, the variation of the Earth's orbit and some assumptions about the response time of rock gave close results. Maybe feedback through life would improve the fit?] > the issue is only partially a thermodynamic one. planetary and > atmospheric science issues are also key. I called it a thermodynamic issue because the claim was that nuclear plants emit waste heat, and that this heat was important to the greenhouse effect. It can be proved (using thermodynamics) that ALL heat engines produce waste heat, so there is no justification in singling out nuclear power. The magnitude of the total waste heat produced relative to the total heat content of/flow through the atmosphere is much less than the amount of added Carbon Dioxide relative to the total amount (especially while we are cutting down forests). > the "greenhouse effect" is pure theory, whether it is applied to > Venus or Earth. it may be a commonly accepted theory, but it is > far from proven. JFC : Thermal pollution is seperate from the greenhouse effect. > how do you know? seriously! JFC : It is likely JFC : that the Earth is stable to the addition of small amounts of heat. > it is unlikely that your statement can be backed up. > power generation generates far more than a "small" amount > of waste heat, regardless of the resource used for fuel. See above. SE : an important concept: the thermal equilibrium of the planet. SE : nuclear waste heat affects the equilibrium, too. the energy SE : contained in uranium is being released with great speed, on a SE : geologic scale. the same is true for the heat and CO2 from SE : burning fossil fuels. JFC : Nuclear or chemical power plants both produce waste heat. > waste heat is not a global issue unless the energy for it originates > outside the earth/atmosphere system. that's the thermo concept > i'm trying to stress. the greatest thermal danger is from solar > power satellites, or solar farms on earth. Waste heat from any of the heat engines (as opposed to hydroelectric, wind, or possibly trash [see below] power) is effectively from outside, since it would not otherwise have been released into the atmosphere on such a short timescale. JFC : However, chemical plants also produce carbon dioxide which does the real JFC : harm to the heat balance by trapping IR radiation. > neither JFC's nor the hypothesis i am backing is proven. > "my" hypothesis actually belongs to Frank Drake of Cornell U. > his calculations indicate that both solar power satellites, > or a great number conventional power plants, could cause a > thermal runaway or other disaster. I read, long ago, articles on the formation of the solar system (specific issue: outside of what bounds would the Earth form like Venus [runaway greenhouse effect] or Mars [the opposite, never enough air to heat the surface]). The conclusion from this and other sources I have seen is that beyond some limit of temperature and CO2 concentration, the greenhouse effect grows very large. My impression is that in extreme quantities either CO2 or heat can cause the effect, but that it is much harder to do with heat alone. Think of CO2 as a catalyst, very small quantities of which can produce great effects. (Thermal energy is spent heating up the earth, which would then cool on a timescale of days if it were removed. CO2 produces a permanent increase in temperature, and remains afterward [until production is slowed enough for biology to take over]). SE : when natural gas burns, the products are CO2 and water. SE : natural gas can be produced by fermenting garbage -- reversing SE : the CO2 production process... >>This is an ideal case, assuming perfect combustion (another article mentioned >>nitrous oxides; there may also be CO) and an effective large scale conversion >>of garbage. I think I've seen figures showing that garbage can not produce >>more than a very small fraction of our energy needs; I'll check these. And I have... My source is an essay titled "Can Trash Save Us" by Jerry Pournelle, from a book called "A Step Farther Out" (a collection of essays on the future of humanity and some of the technical problems and promises). It was written in 1977; relevant changes between then and now are: increase in oil prices (since we import almost the same fraction of oil now as then, this shouldn't be too important to the general conclusion) and increase in energy consumption relative to trash production (I assume this on the grounds that trash is proportional to population, but energy use grows faster.). In answer to the question: how much energy can trash give us "...1.6x10^25 ergs [per year], or 4.4x10^11 kW-hours. In other words, if we captured ALL the energy from our rubbish we could produce about 2% of the energy [which JP uses to mean all forms, not just electricity, since oil imports go to others forms also] we used in 1974. Significant, yes. Important, yes. But it won't save us from Arab oil and sinking tankers." He goes on to say, assuming an efficiency of 27%, trash could produce 2% of the electricity generated, not counting processing, drying, and plant construction (or any of the costs). About costs: [quotes _Annual Review of Energy_ for figures] "[cost] ranges from around $500 pe kW for a coal-fired plant to over $1000 for some kinds of nuclear. Assuming 27% efficiency...capital cost per kW is $1100, much higher than other kinds of plant costs, which explains why electrical utilities aren't terribly interested. For $1100 a kW they can buy a nuclear BREEDER plant, whose operating costs will be lower than the value of the fuel produced." [He notes that nuclear costs are going up, and I note that the gov't doesn't like breeder plants because they produce Pu, which can make bombs.] "...If we subtract off the costs of sanitary landfill, and a number of other expenses of disposing of that growing mound of trash that gives mayors nightmares, our electrical plants begin to make sense after all: but only if we look at cities as a total system, and city budgets aren't prepared that way. Believe me, I know: I've been Executive Assistant to the Mayor of Los Angeles." [goes on to say that is not possible to raise taxes enough to build such plants, nor to persuade relevant agency to be joined with the lowly sanitation department.] Next part asks "can sewage save us?" [I paraphrase to save space] 1 ton sewage produces 225 m^3 methane = $80.00 [in 1977]. With plant costs (and interest on same) it costs $5.50 a ton to turn sewage into methane including profits from sale. [Interest is higher now, but so is fuel cost.] When Southern Calif. Edison tried to do research to make conversion more efficient, the government stopped them. The theoretical maximum, counting animal waste, is the same as for trash: 2% (which is 10% of natural gas use [reference year also 1974, we use more energy now]). You also get fertilizer out of this process. Conclusions: The total from waste is then 4-5% of energy use, assuming perfect efficiency. It helps, but isn't the answer. His recommendations: research into more efficient crops (which could then be turned into fuel without starving that part of the world which we feed), ocean thermal energy, and fusion; and tax breaks for insulation/solar homes [which I think we now have] and companies which want to do research into conservation and/or improved energy production. John Carr "No one wants to make a terrible choice jfc@Athena.MIT.EDU On the price of being free"