MONEY FROM RUBBISH

Greymouth Evening Star, 9 March 1939, Page 14

MONEY FROM RUBBISH

EDINBURGH’S LEAD. Typewriters, table-lamps, toy motor cars,' bird cages, alarum clocks, hand grenades, old firearms and am-munition-^—these are just a few of the articles .that are consigned to Edinburgh dustbins, along with ordinary Household refuse such as cinders, tins, rags, bottles, and bones. Other surprising items, recovered from rubbish and wastepaper by the Edinburgh Cleansing Department have included false teeth, fur necklets, banknotes, sheets ■of stamps, wristlet watches, and a jacket, with the sum of 16/1 in one of the pockets, states an article in the “Weekly Scotsman.” For a long time the city’s refuse was either bui'nt or dumped into disused quarries and claypits. A few years ago, however, a comprehensive survey of the situation was made and the Streets and Buildings Committee of the Town Council decided to deal with fhe refuse by mechanical separation in decentralised disposal plants, from which the unsaleable residuals would be transported. The first stage in this scheme was the reconstruction and extension of the works at Powderhall, which were completed in November 1936. The next step was the construction of a modern refuse disposal plant and this was opened in the Spring of this year. Now a third plant is in an advanced stage of erection and this should be completed early in 1939. Apart from stand : by units, or any large increase in the population, these three units, it is stated, should serve the city’s needs for a long time to come. The formidable task of collecting Edinburgh's refuse is tackled between the hours of 7 and 10 a.m. by a fleet of 80 motor and 45 horse-drawn vehicles, Eqch district is visited three times a week, and there are also special collections of trade refuse and wastepaper. The motor vehicles vary in size and design, to suit the different needs of the districts covered. Some of the vehicles are huge, six-wheeled lorries; others take the form of trailers, drawn by easily-manoeuvred tractors. While the ctizeris are dressing, breakfasting, or hurrying to work, these motors, painted a bright green, are buzzing about emptying the household buckets.

The nature of the refuse varies to some extent according to the districts in which it is collected, and gives a clue to the habits and tastes of the inhabitants. For example, in some areas there is a much larger output of empty soup cans and other food tins than in others. It has been suggested that at some future date it might be possible to collect statistics and relate the contents of the dustbins to health and habits in the respective districts.. The refuse disposal plant which was erected at a cost of £50,000, is probably the most up-to-date in the country. It consists of two units, each performing, the same functions. The plant is almost entirely mechanical in ac-

lion, the refuse being handled al one point only. Outwardly, the building resembles a modern factory, with a high chimney at one end and well-kept grounds and approach roads. Incoming vehicles pass on to a weighbridge, where the tonnage of refuse is registered on a large dial and duly recorded. The vehicles then proceed to the unloading house, where the rubbish is tipped into a reinforced concrete receiving hopper of 65 tons capacity. The dust arising from this operation is withdrawn through ducts by a system of fans and passed to a dust-collecting plant, where it is collected in a water trough. At the bottom of the hopper is a conveyor chain which carries the refuse along and upwards to shackers. These permit the smaller elements, such as cinders, dust. etc., to fall through for further separation, while the larger objects are passed on to a rubber belt, conveyer. This is known as the picking table, and it is the only place where the re-fuse is handled. Employees stand on either side, recovering materials of commercial value, such as tins, bones, bottles, rags, etc., which arc deposited in separate receptacles. Perhaps the strangest object that ever passed along the picking table was a tortoise. The little creature was none the worse for its experience, and was given the “freedom” of the grounds.

INGENIOUS INSTRUMENT. Combustible matter is allowed to pass over the end of the picking belt and drop on to an elevator for conveyance to the furnaces. The dust, cinders, and other small objects from the “shakers” fall on to an electromagnetic belt. This is a most ingenious instrument, and allows the dust, cinders, etc., to fall to the rotary screening plant, while any small pieces of ferrous metals, such as nails, bottle caps, and razor blades, adhere to the belt and are carried round and dropped into a bin.

The rotary screens consist of a system of perforated cylinders revolving inside larger cylinders. In the first section, dust is extracted and delivered to a storage hopper. In the second section of the screen, cinders are ejected, but before being conveyed to a hopper, they pass on to a garbage extractor. This is a belt to which garbage clings, and is elevated to the furnaces.

Tlie matter which passes through the screens drops on to an elevator, and is conveyed to the furnaces, along with (lie refuse from the picking belts and the garbage extractor. Trade waste, which is received in a separate unloading house, is conveyed direct to a furnace reserved for this purpose. Fans provide forced draught for the furnaces, thus enabling combustible material to be burned at a high temperature. Before entering the chimney the waste gases from the incinerators pass through an expansion chamber and water trough. where particles of line dust, burnt paper, etc.. ire trapped. The clinker which is withdrawn from the fires is quenched

in enclosed chambers, and later elevated to storage hoppers. The clinker and dust from the respective storage hoppers are used for land reclamation purposes. The recovered cinders have a. ready sale as fuel for slow-combustion boilers. The material recovered at the picking tables is sorted and sold. Tins are pressed into bales in machines which are designed to receive articles as large as a standard dustbin. The size of these machines dispenses with any preliminary crushing of the tins, which are simply shovelled in, to emerge as a homogeous mass, greatly reduced in bulk and convenient to handle. Bottles are steeped in a solution of caustic soda and thoroughly cleaned inside and out by means of a brushing and spraying machine. The machine has a separate hot water supply and is electrically driven. There is a good market for the tins and bottles, and old carpets, pieces of linoleum, articles of aluminium and pewter, and rags and bones all have a commercial value. The financial return from the refuse treated goes a long way towards paying for the maintenance of the plant.