In America practically nothing has been ac complished in the way of utilizing heat from garbage furnaces. Early in 1900 a single gar bage furnace was installed at one of the mu nicipal electric-lighting stations in Chicago, and arrangements were made for a similar installa tion at Grand Rapids, Mich. The combined refuse destructor and electric-lighting plant at Shoreditch, England (a part of the city of Lon don), has attracted much attention. The de structor was opened on June 28, 1897. There are twelve furnaces, or cells, each having a grate area of 25 square feet; six water-tube boilers, with 1300 square feet of heating surface; and a thermal storage tank 8 feet in diameter and 35 feet long, designed to store water heated by the steam at times of small demand for electric lighting. The thermal storage tank does not seem to have been tried at any other garbage furnace. A forced draught, rated at 8000 cubic feet per minute, is ' supplied by three fans, driven by electric motors. The chimney is 150 feet high, with a dust-arrester at its base. Each furnace has a capacity of 8 to 12 tons of refuse in 24 hours, or 96 to 144 tons in all. The aggregate horse-power of the connected boilers is about 1200. During the first two years of its opera tion, the Shoreditch plant consumed about 25,000 short tons of refuse a year. The value of Eng lish refuse for steam-raising purposes appears to run from 5 to 15 per cent. that of coal, assuming a coal that will evaporate 10 pounds of water from and at 212° F. per one pound of coal. This is omitting extremes. Probably 10 per cent. is the maximum safe figure upon which to base esti mates for continuous work, and even that may be too high.
The following particulars relating to some other European refuse destructors have been taken from Goodrich, The Economic Disposal of Town's Refuse (London and New York, 1901). Birmingham has over fifty cells in use, burning about six long tons per cell per day. In 1897 the total amount of refuse burned was 96,309 long tons, out of a total of 200,703 long tons col lected. Leeds also has about fifty cells, with an average capacity of about seven long tons each. Liverpool has some forty-four cells with a capac ity of about seven long tons per cell per day. Manchester, although the first city in the world to put in permanent garbage furnaces (in 1876), still sends some 70,000 long tons of refuse to the dumps each year, but has ordered 18 new cells. At Hunstanton 31/2 long tons of refuse per day is burned, the heat from which furnishes steam sufficient to drive the pumps supplying the town with water. Berlin and Hamburg, Germany, are the chief examples of Continental cities with garbage furnaces. Over twenty furnaces are said to be in use in Berlin, having an estimated capacity of some 1300 long tons a day. Coal is used as a secondary fuel, and it seems that relatively little steam is utilized. Mr. Goodrich appears to have attempted to secure a complete list of all the cities in the world having gar bage furnaces, together with at least a brief de scription of each. His summary, with figures for the United States and Canada, as collected by the Engineering News, is as follows: England, in cluding 18 districts in the metropolitan district of London, 123 cities; Scotland, 6; Ireland, 2; Channel Islands, 1; Continental Europe, 4; South Africa, 2; India, 3; South America, 3; Australia, 4; the East, 3; Canada, 2; United States, 50; total, 203. Outside of Great Brit ain, Canada, and the United States, quite a number of cities may have been overlooked, and possibly 10 to 15 additional cities in the United States should be included. It should be noted, too, that the garbage of 16 of the largest cities of the United States is treated by the reduction process, as stated in more detail below.
American garbage furnaces, as may be seen from what has preceded, have not been so fully developed as English, such superiority as can be claimed for American sanitary engineers in this respect being for the reduction rather than the cremation of refuse. Just how large a part of
the difference between the two countries is due to variations in the character of their respective wastes it is hard to say, since there does not seem to be any thoroughly satisfactory data on this point. In general, it may be noted that some English writers give the average percentage com position of ash-bin refuse as follows: Breeze (or partially burned coal) and cinder, 50; coal and coke, 1; ash, 12; dust and dirt, 20; paper, straw, fibrous material, and vegetable refuse, 13; bones and offal, 0.6; rags, 0.4 ; bottles, tins, metals, crockery, broken glass, 3; total, 100. After the refuse passes an English furnace there remains 20 to 40 per cent. of the original weight in the form of ashes and cinders. It is believed that American garbage, even when mixed with ashes. contains more organic matter than is shown by the figures just given, and that its percentage of moisture is far higher. The latter must be evaporated before the combustible matter can be burned. To add still further to the difficulty of burning American wastes, the ashes, when mixed with the other refuse, appear to contain less com bustible matter than those in England. owing partly to the large quantities of soft coal burned, and that imperfectly, in England. An other drawback to the development of American garbage furnaces is the practice of awarding short-term contracts for disposal, or changing the methods in vogue with each change of city administration. Under all these circumstances it is not strange that American garbage furnaces have not been brought to a higher state of per fection, nor that it is hardly known what they might accomplish in long service under favorable conditions. Some of the most successful fur naces in America follow English practice very closely. Of a list of 50 cities with garbage crematories in the United States, all but 15 had populations of 25,000 or more by the census of 1900. The largest city and most capacious plant in the list is San Francisco, Cal., where a private company owns 32 furnaces, or cells, with a rated daily capacity of GOO tons per day. The company has a franchise under which it has thus far succeeded in compelling the private scavengers who collect garbage, ashes, and other refuse in San Francisco to bring their collections to the furnaces and pay the company 20 cents a load for burning it, the loads not to exceed one cubic yard each. The weight of the refuse is estimated at 800 pounds per cubic yard. On this basis, over 61,000 short tons, or 215 tons a day, were burned in 1899. At both Milwaukee, Wis., and Minneapolis, Minn., large furnaces were under construction early in 1901. A small portion of the garbage of Greater New York is burned in a number of furnaces scattered over outlying districts. The one small furnace in Chicago has already been mentioned. Boston has the distinction of being the only city in the United States with a well-equipped refuse-sorting plant. Light refuse from a part of the city is brought to this station, dumped, shoveled onto an inclined conveyor, from which men and boys sort out various grades of paper, rags, and all other merchantable refuse as the particular kinds pass the person to whom the task of removing it is assigned. The residue is dumped automatically into a furnace and readily burned, producing put in use, including the Warner, Horsfall, and Meldrum. The first American garbage furnace, opened at Des Moines, Iowa, about September, 1887, was designed by Andrew Engle. In De cember of the same year a Rider furnace was fired up at Pittsburg, Pa. At present, the Engle, Dixon, Smith-Siemens, and Thackeray furnaces lead in North America, most of the plants being supplied with either Engle or Dixon apparatus. The Thackeray furnaces at Montreal and San Francisco have inclined drying grates, but larger than those employed in the English furnaces.