A Step Farther Out
Page 30
Do it because we can afford it, and it's something we ought to do.
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Since I wrote that, a number of things happened. First, many of my readers did send letters to Congress. Second, President Carter cut the budget for electron-beam inertial confinement fusion research. Third, Congress restored the budget.
At present writing, the chief scientist involved with this research spends as much time in Washington trying to keep his budget as he does in the laboratory trying to make neutrons. He has never met the President, although while he was in Washington Mr. Carter gave an afternoon to Mr. Lovins of "soft energy" fame.
And finally, in Fall 1978, Princeton University announced temperatures of 60 million degrees in their magnetic confinement fusion research facility. This was a real scientific breakthrough; but the news announcement also contained a statement from the Department of Energy: "This achievement does not change the national timetable to fusion energy." Of course it does not: we have no national timetable. The expected date of useful fusion energy in the United States is never.
I don't know why, but the present administration does not seem to want fusion energy.
Can Trash Save Us?
Larry Niven used to live behind a garbage dump. Well, you wouldn't have known it, of course; although his sister used to say he lived in the 'wrong part" of Bellaire, it is not characteristic of that fabled community that you know the municipal sanitary land fill—read garbage dump—is only about half a mile away. On the other hand, the access road to the dump is clearly visible from the San Diego Freeway, and when I drove to Larry's house—which was pretty often back in the days when we were writing THE MOTE IN GOD'S EYE and INFERNO—I couldn't help seeing the endless stream of huge trucks trundling up into the Santa Monica Mountains with their loads of refuse.
Surely, thought I, we ought to be able to do something with that stuff besides bury it in what might otherwise be a very nice wilderness area.
Those who would save the world seem to do so in waves. There are fads in the eco-crusading business, and just now garbage is the big one. I say fad because the 1974 opus AN INDEX OF POSSIBILITIES: ENERGY AND POWER, contains not a single index reference to "trash," "garbage," "waste," or "sewage," and only one tiny reference (under "methane") to use of any of these materials; yet it was supposed to be a compendium of all the ideas on how the energy crisis might be solved. Now, however, you can't pick up a work of that sort without finding article after article on how we could be saved if only we'd use the energy in our sewage and garbage. Unfortunately, none of the articles I've seen give any numbers; they're very similar to the wistful thoughts I had while driving to Larry's house. There's so much waste and trash that surely we can get a lot of energy out of it; can't we?
I don't know. Let's see.
Let's begin by looking at the present energy situation. That turns out not to be easy as you might think; the data aren't collected together into one place, and even when you find the figures they're all mixed up. It takes a lot of patience and determination to come up with a meaningful composite. Energy analysts don't seem ever to have heard of the metric system. Everything is given in terms of British Thermal Units, or tons of coal equivalent (and not everybody has a common figure on how many Btu there are in a ton of coal) or barrels of oil per day (ditto about Btu/bbl.) or kilowatt-hours, or whatever they're enamored of.
I've put together as good a picture as I can, and I've converted everything into ergs (I grew up with the cgs system; if you like the mks system, divide by 107; if you like feet and pounds, get hip). The results are given in figures 35 and 36, which show where the US energy comes from and where it goes.
Now true: the growth projected in Figure 35 makes a number of assumptions which I haven't bothered to list (it assumes a constant real increase in GNP, for example) and the percentages in Figure 36 are going to change if the US population continues stable; but at least we've got something to work with, a way to see just how big a problem we're facing.
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Figure 35
ENERGY IN THE UNITED STATES
Supply and Demand in Ergs (x 1026)
(Calculated from tables in ANNUAL REVIEW OF ENERGY for 1976)
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Now that we know how much power we need, let's find out how much garbage we have to deal with. Actually I shouldn't use the term "garbage" with its strong negative connotation: as the authors of the energy-from-waste section in ANNUAL REVIEW OF ENERGY for 1976 point out, it's precisely that term that makes the most talented administrators avoid the municipal departments of sanitation, and makes waste-collection a job at the very lowest end of the social scale. Instead I suppose I should say "urban mineral resources" or some such. Anyway, we need to know how much of it we have to work with.
The Environmental Protection Agency (EPA), which hasn't heard of the metric system either, guesses that we produce about 3.32 pounds per capita each day (1.51 kg for the more up-to-date among us). Looking at my own household that seems about right. The figure refers to municipal wastes, which is everything thrown away such as trash and garbage, but does not include sewage. Since there are about 250 million of us, we get a rough figure of 415 thousand tons each day, or 15 million tons each year, which probably explains why the cities are running out of sanitary land fill. In metric terms we have 13.7 million tons annually, still a respectable sum. We'll stay with English system for a while because the energy figures I have for what we can get out of municipal waste are, of course, given in Btu/ton. Sigh.
Incidentally, the ANNUAL REVIEW article also gives an estimate of 250 million tons municipal waste daily, of which 175 million is domestic; and that simply can't be right. It may include sewage, which we'll deal with separately; but it's still far too large.
All right: we have this incredible pile of waste, now what can we do with it? Well, if it were dry we could burn it, with due regard to cleaning up the stack gasses to avoid pollution; and in fact that's what's done with a lot of it (and sometimes without worrying about the pollution aspects, either). Few places make any effort to capture the energy from that burning waste. The stuff is merely incinerated to reduce the volume. Surely there is a significant amount of energy released, though, and if we can tap it, will we be independent of Arab sheiks and Liberian tankers?
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Figure 36
ENERGY IN THE UNITED STATES
WHAT DO WE USE IT FOR?
(Calculated from tables in ANNUAL REVIEW OF ENERGY for 1976)
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The standard figure for the energy content of municipal waste is about 10 million Btu per ton, but there's a joker, that's per ton of dry weight. Unfortunately, a lot of municipal waste is anything but dry, and it takes a good bit of energy to get the water out of it before it will bum at all. Still, let's assume we've dried it, somehow, and it's all ours.
We cannot yet burn it in steam boilers. The stuff consists of all kinds of things: discarded metal beds; tin cans; old Six Million Dollar Man toys; food scraps; dead animals; discarded vacuum cleaners; coffee grounds; and you name it. It must be pulverized and sorted, and that takes energy. It also takes either a very high or a very low technology: that is, one way to sort it is by human labor, but we'd probably have to increase the size of the army before we could put the unemployed to work doing that; thus we have to build highly sophisticated equipment, with magnets, grates, air-stream sorters, and the like, and those cost money, and municipalities raise money primarily through property taxes, and home-owners are ready to revolt already; but let's assume all those problems solved, and we've done the sorting. How much energy can we get from our rubbish?
Comes now the math: tons times energy/tons times a mess of constants I won't bother to give. The results are interesting: 1.6 x 1025 ergs, or 4.4 x 1011 kilowatt-hours. In other words, if we captured all the energy from our rubbish we could produce about 2% of the energy we used in 1974. Significant, yes. Important, perhaps. But it won't save us from Arab oil and s
inking tankers.
Alas, things are worse than that. No industrial process is 100% efficient, and electrical generation is no exception. With present technology the best we've been able to do at burning rubbish is 27% efficiency, which means that if all our municipal waste were burned in the best boilers we know how to build, we'd get 1.2 x 1011 kW-hrs, or, coincidentally, some 2% of the electricity generated in 1974—and we have not counted in costs, the energy needed to process and dry, or indeed much of anything.
We could go another way. If we can persuade industries to build alongside the rubbish-disposal system, or take the rubbish to their plants, so that we can use the steam directly without turning it into electricity, we get 66% of the energy value, and that's a respectable 7% of all the process steam used in 1974; well worth trying for, if it doesn't cost too much.
So. What are the costs of all this? The ANNUAL REVIEW gives some figures, which I have recalculated to give Figure 37. (I recalculated because theirs were based on plants processing 275 tons unsorted refuse per day, an awkward figure at best.) They still don't mean very much; is this a low or a high cost? Well, one figure readily available is the capital cost per installed kilowatt of electrical power. That ranges from around $500 for a coal-fired plant to over $1000 for some kinds of nuclear.
Assuming 27% efficiency for a refuse-burning electrical plant, we find the capital cost per kW is $1103: 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. I suspect that my figures for nuclear power costs are a bit low; they're based on research done a couple of years ago, and the court and environmental impact statement costs of nuclear power are now about as high as the costs of the hardware; but even so, the refuse-plant generator is expensive.
Or is it? After all, the cities have to get rid of the refuse somehow. If we subtract off the costs of sanitary land-fill, and a number of the 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. The Department of Water and Power would scream bloody blue blazes if told they had to spend that kind of money; while many of DWP's senior administrators, people you can't do without, would go job-hunting if told their lordly department was to be combined with Sanitation. Moreover, the City Council would impeach anyone suggesting the kind of capital fundraising (and consequent increase in property taxes) a large-scale electricity-from-rubbish project would require.
Still, if we were starting over, if we could look at cities as total systems, rather than as a series of independent departments; it would make a great deal of sense to get rid of our refuse and extract the energy out of it at the same time. We could not run the city on its own garbage, nor is garbage a particularly efficient way to get electricity; but since you have to get rid of the stuff anyway, you might as well take out what you can, and the total system costs probably justify the initial capital expense.
Whether in this age, given what we've already spent, it makes much sense is not so obvious: you have to look at each city independently. I suspect that LA could sell the land set aside for sanitary land-fill (another department heard from: although Recreation and Parks knows it can't keep that land forever, right now they're not turning loose) for enough to build some good-sized plants; but I haven't done the numbers. In places where land values are not so high as here, it's more dubious.
Let's leave rubbish for a bit and get down in the sewers. If garbage can't provide more than a fraction of our energy needs, can sewage save us?
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Figure 37
THE COSTS OF GETTING POWER FROM WASTE
All figures in constant 1978 dollars per ton (2000 lbs) of unsorted refuse per day. Source: ANNUAL REVIEW OF ENERGY, Vol 1, 1976; Annual Reviews, Inc., Palo Alto, California.
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To begin with, sewage is valuable. That should be obvious: it is only the very wealthy western nation that can afford to throw away such a valuable resource. Indeed, we spend a lot of money and energy merely to throw it away, after which we burn a lot of valuable coal and oil to generate electricity in order to fix nitrogen to make fertilizer-fertilizer that's not as good as the high-nitrogen sewage we pollute rivers with.
Secondly, there's a long technological history of using sewage as a fuel source: begin with the Indian peasant, who uses buffalo chips to cook his food, and proceed to modern methane generators.
Finally, even if we don't use sewage as fertilizer—and thus by-pass the long series of inefficiencies involved in the generation and transmission of power, fixation of nitrogen, etc., culminating in commercial fertilizer—the stuff has a high energy content.
In other words, using sewage as an energy source has a lot going for it. There are several ways to go.
First, as agricultural nutrient, allowing the crop to be the actual energy-storage system. This is widely done in the Orient, with detrimental side effects: the honey-bucket is a pretty certain means of spreading epidemics. Surely we can do better than that.
Second, as methane source: shovel sewage into a tank, let ferment in the absence of air, and out comes methane. Methane is also known as natural gas, and is rather valuable; indeed, natural gas is the most critically short item in our energy budget. A pound of dry sewage solid will produce about 3 to 5 cubic feet of methane, which sells at $3.53 per 100 cubic meters. Now my source book, with a straight face, gives both those figures in the same paragraph. I'll translate: a ton of sewage produces some 225 cubic meters of methane, and the gas is worth about $80.00. The methane production pretty well sterilizes the residual, which can then be used as high-nitrogen fertilizer. (But we will have to use some of the methane as fuel for drying it before we can sell it.)
Finally, we can produce the methane and then burn the residual. It has been calculated that doing that will let us build a system that operates at zero profit provided that we charge about $5.50 a ton dump fee: that is, those who wish to dispose of sewage must pay us.
Why is this? We're getting valuable fuel out of the system; surely we need not charge a dump fee? Ah, but the plant itself costs a lot of money, and that money isn't free. If the plant already existed, it would make a profit; but the "profit" is lower than current interest rates, and thus the dump fee. Another of the little points usually forgotten by those who are faddishly out to save the world.
On the other hand, technology improves, and one commercial utility, Southern California Edison, was at one time trying to find ways to use sewage as fuel: they contracted to take the entire sewage output of one of the smaller southern Calif. cities free and get rid of it by burning it in their boilers. They didn't quite know how to make that work, but they were doing the research, when along came the Public Utilities Commission to tell them to stop. It seems that wasn't a justifiable use of the rate-payers' money. Utilities shouldn't engage in fuel research, they should generate power. Thus we were all protected by our government, and now a government agency will have to do the necessary research if sewage is to be burned at a profit.
Still, just how much energy could we get from this source? Well, each of us produces about .25 pounds (yeah, I know, but all the other numbers I could find were in the English system and I give up) of dry solid each day. That's 11 million tons a year; if it all went into methane generation systems we'd get 90 billion cubic feet of methane annually, and at 994.7 Btu per cubic foot that's 9.6 x 1023 ergs or 0.19% (2 tenths of a percent) of the 1974 energy budget. Sigh. It's unlikely to save us, isn't it? However, don't despair. We can also add the animal wastes, which amount to some 25 million tons a year, and get up to 2000 billion cubic feet of methane, 2.1 x 1025 ergs, or 2.6% of all energy used in 1974. Better than that, it's just about 10% of the energy we obtain
ed from natural gas in 1974—i.e., we could cut natural gas consumption by 10% a year. It's not the Earth, but it's something.
Of course it's also expensive, and technologically some time away. What I've given are some maximum theoretical figures, not what we could do tomorrow morning if we set our minds to it.
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Let's see: 2% from human and animal sewage; another 2% from municipal refuse; add in another percentage point just in case: and we've come up with a grand total of 5% of the 1974 energy budget, provided that we can use ALL of the energy from our sewage and garbage and other trash. Since we cannot possibly capture 100% of that energy, I leave it to you to guess at the actual efficiencies; and I think you now see why engineers, as opposed to faddists, don't think we can run the United States on its own garbage heaps.