The systems of collection and disposal are so closely related that they must be considered together. There are two kinds of collection systems, the combined and the separate. The combined system may be further divided.
Many large cities collect garbage, rubbish and ashes separately. Garbage is then incinerated or disposed of by the reduction method. Ashes are used for fill and the rubbish is sorted either at the dumps or in utilization plants and the unsalable material either dumped or incinerated or both.
The separate system is profitable only in the larger cities where reduction plants can be operated at or near a profit, where an incineration plant can be centrally located in order to reduce the cost of haul or the heat can be used to produce power or where the reclaimable rubbish is sufficient to pay for rescuing it.
A system that can be used with nearly all methods of disposal is the separate collection of garbage and the combined collection of rubbish and ashes. This is the most popular system in America, for in many cities garbage is disposed of separately and rubbish is dumped. In many such cases, and especially where the ashes are used for fill, separation is required to allow the disposal of the ashes in places not suitable for mixed material.
In cities which have destructors for the incineration of garbage and rubbish and which use the ashes for fill, the separate collection of ashes and the combined collection of garbage and rubbish is the best system. In some cases a part of the ashes is added to the garbage to aid combustion.
Where the combined collection of garbage, rubbish and ashes is used the city disposes of all these wastes either by dumping or by total incineration.
In a few places furnace ashes are collected separately and rubbish, garbage and stove ashes together. When this system is used the furnace ashes are used for fill and the other wastes are incinerated.
There is considerable difference of opinion as to which plan is desirable, but practically all agree that local conditions should contribute the chief factor in determining which system is the best for a city.
The method of disposal is another factor. Reports agree that if all wastes are collected together as a rule the cost of collection will be less than if each is collected separately.
John H. Gregory, sanitary expert, says that separate collection will be found in many instances to be less convenient at the house and more complicated and more expensive than the combined collection. He asserts that the combined collection will usually prove to be cleaner and to have fewer objectionable features, and with this system it should be easier to secure and to keep a better grade of employees. He points out that the mixing of garbage with rubbish and ashes will prevent in a large measure the blowing about of the latter, will lessen the dust nuisance, and indirectly may lessen the cost of street cleaning. The decomposition of garbage is far less noticeable and from the point of view of preventing a nuisance the receptacles and wagons will not require such frequent cleaning. He says, also, that the fly nuisance is reduced to a minimum and that there is less likelihood of odor should the refuse be stored up for final disposition. As but one type of wagon is required for collection Mr. Gregory believes that the system is probably easier to adopt and easier to enforce, fewer regulations being required.