L. F. Diaz , G. M. Savage and L. L. Eggerth
Most developing countries have various processes aimed at the recovery of materials from the solid waste stream. Studies have shown that, in some cases, local industries have a strong dependency on the availability of secondary materials for re-processing. Some of these materials include: cardboard, various paper products, different types of plastics, and metals.
Unfortunately, the methods used for the recovery of secondary materials are inefficient, disregard the basic principles of occupational health and in some instances cause significant negative environmental problems such as the recovery and reprocessing of automobile batteries at the "home level".
Resource recovery or scavenging as is commonly called, takes place in most urban areas in developing countries. The process is carried out at various stages of the waste management system and in different manners. Some of the most common methods are briefly described in the following sections.
In large urban areas having an active and well-defined commercial area or an area with a large number of apartment buildings occupied by people earning a high income, scavengers typically sort through the waste before the authorized collection vehicle arrives. The most common materials that are recovered include: various types of paper products (cardboard, newspaper, and office papers), some plastics and aluminum containers. In most cases, the scavengers use carts or similar units for the storage and transport of the recovered materials. In areas where there is a relatively high generation of recyclable materials, the scavengers store the materials in specific locations for their eventual collection by commercial trucks. There are isolated cases where scavengers travel from house to house buying secondary materials.
Another method of scavenging takes place during the collection process. In this particular method, the collectors themselves and/or helpers conduct a certain amount of segregation during the loading of the waste into the collection vehicles. The segregation process is facilitated in the situations where open trucks are used which allows for some of the collectors to be stationed inside the vehicle. The recyclable materials are stored either inside the truck or on the sides of the vehicle.
The last and the certainly the most onerous type of scavenging is the one that takes place at the disposal site. Disposal sites, particularly those located in medium and large metropolitan areas attract hundreds and in the megacities thousands of individuals for the recovery of a variety of materials for sale. Some of the scavengers live on or near the disposal site. Living in disposal sites is not only detrimental to the health of the scavengers but, as it has been shown in several instances, it can be dangerous due to slides and fires. The relative closeness of the disposal site to the scavengers' dwellings and other factors make it easy for them to allow the participation of their children and other family members in segregation activities. The scavengers work at the landfills under some of the most precarious conditions and under different climatic situations (from extremely hot to very cold and wet conditions). In some of the very large disposal sites, the scavengers set up their rules and have been known to divide the site into areas where only specific groups are allowed to work.
The authors are well-aware of the fact that scavenging activities play a major role in the survival of many of the people that perform those activities. However, the methods used for the activities reduce the efficiency of the waste management system and most importantly are detrimental to the health of the scavengers.
Scavengers that perform their activities prior to the collection phase, break open bags to have access to their contents or indiscriminately remove other materials from containers and leave them on the street increasing the time required to collect the materials by the formal collection sector. Resource recovery conducted during the collection process reduces the efficiency of the collection system. Scavengers that conduct their work at the disposal sites have a tremendous influence on the speed at which the collection vehicles discharge their contents as well as on the effectiveness and efficiency of the tractors and/or compaction equipment.
Adequate modifications to the existing scavenging systems must be made so that resource recovery is limited to specific locations and those that conduct the process do so under safe and "clean" conditions. Most importantly, children and the elderly must be absolutely prohibited from conducting any kind of scavenging activities.