Reading, PA Reclaims Garbage and Lowers Disposal Costs, April 1946
Officials don't make a "silk purse out of a sow's ear," but they do make soap, glycerin, and fertilizer out of garbage and thereby cut the cost of garbage collection and disposal to $1.30 per ton or 18 cents per capita.
For several years Reading, Pa., has been reducing the cost of its garbage and refuse disposal program by a resourceful reclamation program that processes the garbage, turning it into grease and tankage. This program reduces by approximately 70% the cost of garbage collection. Reading has a population of 110,468 and covers an area of ten square miles.
The department of public safety, which is charged with the responsibility of garbage and refuse collection, divides the city into two parts and makes collections in each three times a week. This puts the collection crews on a six-day-week schedule in order to cover the entire city. The crews work every night except Saturday, starting at 9 p.m. in winter and 10 p.m. in summer. Four crews make the garbage collection; each crew consists of a driver and two helpers. The collections will average 36 tons of garbage per night, although in summer, because of fresh vegetable shells and corn husks, this figure will go to 66 tons per night.
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Underground pits receive the garbage from the collection trucks each day. Pitmen move the refuse to the conveyor shown in the rear of the picture.
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The conveyor brings the garbage to the second floor of the plant and through a chute to the digesters. The digesters hold about 6 ½ tons each of the raw garbage. The Reading plant has twelve. The workman in the picture is sealing one of the digesters. After sealing, the garbage is cooked for three hours in winter and 3 ½ in summer with ninety pounds of live steam.
How the Processing Program Works
To process this garbage, the crews first dump the truck contents into underground pits at the reduction plant. Here a conveyor belt directs the garbage to twelve digesters that cook it for three hours under 90 pounds of live steam. The grease and water are thus separated from the solid portion of the garbage and drawn off into a series of vats where that portion of the grease that can be separated by flotation is drawn off. The residue, a wet powder used as a filler for fertilizer, goes through presses into driers and then through a series of screens to take out rubbish such as rags, paper.
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After being cooked, the garbage drops through the eighteen-foot high digesters into the receiving tanks shown in the lower center of the picture. From these the garbage is carried on an endless apron through pressing rolls that press out the grease and water. There are three machine presses and each tank of garbage takes about one hour to be pressed.
The finished residue needs no further processing to be marketable. The city sells it through a broker under a year-to-year contract. The grease, however, is stored in heated tanks to remove excess moisture and then transferred to storage tanks until there is enough to fill a tank car. It also is sold under a year-to-year contract.
From Garbage to Glycerin
The garbage grease turns into a number of interesting by-products; 95% goes into the manufacture of soap, in the process of which glycerin is produced which the soap companies sell to the government. Part of the grease finds use in the manufacture of stearic acid used in sperm candles. The remainder is refined into a fine lubricating oil with the final end product being made into a heavy roof pitch. Every bit of the grease is then used in some way or another.
Costs covering the operation of the garbage disposal plant have been itemized by the foreman of the plant in a recent report shown in the accompanying table.
A significant point brought out by this tabulation of costs is the low per capita cost of refuse collection and disposal. The $1.30 per ton figure compares favorably with the cost of disposal alone in many cities where the garbage is reduced by incineration, although collection figures are not separated from disposal costs. If they were, the plant would show a comfortable profit.
Analysis of Costs of Garbage Collection and Disposal
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This illustration shows the center series of seven vats into which the grease and water from the machine presses flows. A baffle separates one vat from the next. The grease rises to the top and the baffles hold the grease as it rises to the surface. The men skim the grease back into the troughs bordering the vats. The grease then runs back to the first vat where it is pumped into the storage tanks.
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The grease, after having been held in heated storage tanks for four weeks to remove the moisture, is piped to a waiting grease tank for shipment.
The building which now houses the garbage disposal plant was acquired by-the city of Reading in 1922 when the city took over the collection of garbage and refuse. The building was remodeled and several additions to the plant have been made since that time. The work is under the direction of Charles M. Stoner, Director of the Department of Public Safety.
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The wet solids leave the machine presses and are conveyed ta a drying room. After being dried, the tankage is conveyed onto a screen which removes all rubbish such as rags, paper, tin, cans. The tankage then proceeds by way of an elevator to a second screen of fine mesh. After being screened here, it drops onto a fourth conveyor and returns to the floor. Tankage thus processed is used for a filler in fertilizer.