The answer to the energy crisis may be for every family to own a cow. Or a horse, or best of all, a few hogs. If you think that's a lot horse manure, you're right.
As every eccentric who ever ran a car on chicken droppings knows, manure can be fermented to produce methane, a truly natural gas that is the same stuff that arrives in private homes via pipeline. Only lately, however, has the study of the fragrant original become serious at the government level.
There is more manure lying around than most people think - 237 million metric tons (a metric ton is equivalent to 2,200 punds) per year, according to the report of a conference on bioconversion held last year in Washington. If only the cattle contribution - 195 million metric tons - could be processed. It would produce 4 trillion cubic feet of methane, or 18 per cent of our curent gas use, the report said.
However, it is difficult to persuade cows to deposit their daily 38 pounds of product in one suitable collection place. "You can't put a bag under every cow's tail, and even if you did, who would change the bags" said Roscoe Ward, program manager for this sort of study in the Department of Energy's biomass fuels branch.
The input and output figures have been closely studied, of course. One cow-day's worth of dung can be dried and fermented to yield methane equal in burning power to 0.4 gallons of gasoline of gasoline. There seems to be correlation between manure potency and odor. Horse manure, smellier than that of cows, stronger: a horse day's 66 pounds will yield the same amount of methane as one cow-day's worth.
Pig dung, which is so frangrant that West German law requires it to be held for three months before it can be spread on farmland, is the most powerful of all: it takes only 15 pounds to produced by 66 pounds of horse manure.
The greater the stink, the higher the octane," summarized English inventor Harold Bate as he demondtrated his hog manure-mobile in 1973.
The DOE biomas fuels branch spent $1.9 million last year building and operating experimental manure-fuel stations in Nebraska. Colorado and the state of Washington. Another project, the biggest yet, is going up at a Florida feelot to process 25 tons of manure a day (over-dried).
These projects are tiny compared to those in mainland China and India, where small farms and villages have been using manure-fired mathane generators for the last 20 years. An Indian village of 500 persons, 250 cattle and 100 houses can produce enough energy from the dung to poer 10 pumps, one lighbulb and cookstove per home and five small cottage industries with power and fertilizer left over. As many as 25,000 are in operation, according to C.R. Prasad in a 1974 Economic and Political Weekly article.
In China, a $20 methane generator and one pigean supply the cooking and lighting needs of one family, and 410,000 are in operation there. There are some problems: the machines require daily maintance, there is some danger of exposion if the methane is not drawn off properly, and they are pretty much restricted to warm areas since the fermentation process all but stops when temperatures drop below 50 degrees Fahrenheit.
Once again the problem is in the collection of the product. "Manure is exereted from animals at nearly the optimum temperatures for methane frementation . . .(but) unfortunately the risk of an explosion prevents the location of a . . . digester (to produce the methane) within or under the confines of a lovestock building," wrote D.D. Senulte and others at the ernational Solar Energy Society meeting in Winnipeg, Canada , last year.
That means it must be reheated to ferment properly, not to mention stirred and watched so that the vat doestn't blow up. The real problem, however, according to DOE's Wade, is that manure is a prettysmall resource in the United States.
"We're using as a stepping stone to other waste - crop residues, forestry leaving, seawood . . . We could grow 4 billion to 3 billion tons a year of trees, sugarcane, whatever on marginal land not used for agricultural production, and make methane out of that," he said.
Rotting vegetation in swamps produces metnane all by itself, swamp gas that sometimes ognities to form what are frequently mistaken for unidentified flying objects. Urban waste decaying in landtills does it too. Startled homeowners on old landtill peoperties have seen their houses begin to smoke and their houses catch fire.
The Maryland Environment Service state agency has tested the Texas landfill in Baltimore Country, which is no longer used, and found that experimental wells produce a gas that is 50 per cent methane. More probes are set at that landfill and at others in Montgomery and Howard Counties, "just to see whether or not we can tap it, said agency administrator Michael T. Long.
Human waste in the form of barge is being processed at another Maryland Environment Service facility near Annapolis to produce $340 pounds of "Refuse-Derived Fuel", a burnable product, for every ton of raw trash. The same thing is being done by a different process at the D.C. Incinerator Number Five on Bening Road, and many other places nationwide, but most projects are still in the experimental stages.
Only three projects have DOE funding to try to get methane from human sewage, since it arrives at the treatment plant, with so much lime and water that extraction costs nearly as much energy as is produced. One of the three projects utilizes cows.
The Anflow project at Oak Ridge, lll, national laboratories, uses fluid from cow stomachs to start the fermentation precess. In one elegant step, the methane, fertilizer and water that can pass Environmental Protection Agency standards for riverers.
It works fine on 5,000 gallons a day, but Charlotts Rines, DOE's Urban Waste Programs manager, doubts it would work on the scale of Washington's Blue Plains sewage flow, 120 million gallons a day.
"Where would you get enough cow stomachs" she said.