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| Abstract
In most developing countries today, the recovery of materials for recycling relies on the activities of human scavengers. This paper discusses the role of scavengers in the recovery of organic wastes that are then used in integrated biosystems. It analyzes several integrated biosystems in the past and present, as well as opportunities for the incorporation of scavengers into them. This paper argues that integrated biosystems in which scavengers take part can be traced back several centuries, and that a great potential exists in developing countries for the development of integrated biosystems in both urban and rural areas. Introduction The informal recovery of materials from waste is a common survival strategy for the poor. In fact, the World Bank estimates that up to 2% of the population in developing countries survives by scavenging. These individuals recover various types of materials for reuse or recycling, including organic wastes. Two types of scavenging activities could be distinguished: recovery of materials for self-consumption and for sale. Each individual scavenger can engage in either or both types of activities. Among the materials that scavengers salvage for self-consumption are: food to eat, discarded clothes, furniture, appliances, and any other item they can use to satisfy their needs. The items recovered for sale, on the other hand, are determined by demand for particular materials. Scavenging activities, thus, are determined at a large extent by economic factors and not environmental considerations. These activities do provide environmental benefits to society but they are only positive externalities generated by scavenging. The rest of the paper examines some integrated biosystems that include the recovery of organic wastes carried out by scavengers. Integrated Biosystems in the Past The recovery of materials from waste by scavengers has been carried out for thousands of years. Obviously, the items recovered and the circumstances in which scavenging takes place have changed dramatically over time. When humans lived a nomadic existence waste disposal was not a major concern, since wastes were usually dumped around people’s foraging areas. The wastes generated by hunter and gatherer groups was mostly organic in nature, such as bones, feathers, shells, the inedible portion of fruits and vegetables, as well as ash from fires, old stone and pottery items. With the advent of agriculture and permanent settlements in the Neolithic, the wastes generated had to be disposed of. In time, it became apparent that some wastes could be reused or recycled. Archaeological evidence suggests that metal scrap and metallic objects no longer useful may have been melted and recycled as early as 3,000 B.C., the beginning of metallurgy. With regard to organic wastes, it became clear that food leftovers could be used to feed domesticated animals and that excrement -both from humans and from animals- could be used as fertilizer and for other purposes. By the year 5,000 B.C. human groups living around the Mediterranean had domesticated animals -pigs, goats, sheep and dogs- that were fed with food wastes. In time, it was realized that the waste products of one activity could be used as inputs for another, and that interlinkages could be established to form what we now call integrated biosystems. Many cultures became aware of the opportunities to use organic wastes productively as a resource that could be utilized in agriculture and petty commodity production. In Classical Greece, for instance, around 500 B.C. scavengers in Athens -one of the largest cities on the Mediterranean at the time- recovered organic wastes from households and form sewers to be used as fertilizer in nearby agricultural fields. At the time scavengers in Athens performed most of the collection of mixed wastes generated in the city. Scavengers sorted materials while conducting their collection activities. Athens created the first municipal dump known in the western world, and the city council enacted an ordinance requiring scavengers to dispose of the wastes they collected at least one mile from the city walls. Farmers could also obtain organic wastes at the dump to use them as feed for their animals and as fertilizer. Athens also enacted the first known edict against throwing refuse into the streets. In ancient Rome, scavengers also collected solid wastes and excrement on the streets. They sold the excrement to farmers to be utilized as fertilizer. Other organic wastes were fed to domesticated animals. Scavengers then known as "manure merchant" collected excrement from the trenches that served as sewers and sold it to farmers. An important part of the wastes generated in the city was flushed out through sewers -particularly through the "Cloaca Maxima", Rome’s main sewer, installed around 500 B.C.- and then into the sea. The Tiber River had to be dredged and cleaned periodically, which produced materials that were also applied as fertilizer in the fields. The Romans discovered that urine, too, could be utilized productively. Urine was collected in clay pots at homes, public baths, and at fullers’ establishments, where people could urinate in them. Urine collecting was reportedly such a good business, that Emperor Vespasian (A.D. 69-79) imposed a "urine tax" on the collectors activities. Two remarkable examples of integrated biosystems in antiquity refer to East Asia and Mexico. For centuries, Chinese farmers have collected human excrement or "night soil" from roadside public latrines and used as fertilizer in their fields. The demand for excrement was so strong that farmers also purchased excrement collected by scavengers in urban areas. Night soil was so valued by Chinese farmers that they referred to the containers used to store it as "honey pots." The World Bank estimates that one-third of China’s fertilizer requirements have been satisfied by night soil, maintaining soil fertility for centuries. In pre-Columbian Mexico, Aztec scavengers collected human excrement
from the public latrines that existed at the time. The excrement was utilized
as fertilizer and in the tanning of hides. The excrement was so valued
by farmers that it was bought and sold at the Tlatelolco market, the city’s
largest. Each household in the Aztec capital of Tenochtitlan had containers
to store urine, which was used as mordant in the dyeing of fabrics. Food
leftovers were fed to fatten the edible dog. The Aztecs had backyard gardens
and agricultural fields floating on the lakes that surrounded their capital.
Sometimes these fields were anchored to the bottom of the lake by planting
trees so that the roots take hold and the fields do not move around. These
floating fields had a high productivity, since they did not lack
water or fertilizer, and various species of plants were grown there (no
monocultures).
Another common practice at the end of the nineteenth century was the "reduction" of wastes. In this process, dead animals and organic wastes were cooked in vats to produce grease -used in the manufacture of perfume, lubricants, glycerin, candles and soap- and a residual used as fertilizer. Scavenging and Integrated Systems Today
In several Philippine localities, scavengers collect ashes that result
form spontaneous combustion that occurs often at the open dumps that receive
the bulk of wastes generated. The ashes are then sold to farmers to be
used as fertilizer. Scavengers also collect fish bones and other discarded
fish parts to be sold to 'patis' (fish sauce) makers.
Other variations of the system just describes are possible. In Mexico, experiments are under way to feed earthworms with biosolids from sewage sludge. The earthworms are then fed to chickens, and the chicken droppings can be used either to feed fish or to form a full circle by feeding earthworms. The biosolids can be composted, and the compost can be used as food for fish, and so on. Several scavenger groups in Colombia and the Philippines conduct vermicomposting operations to reduce the volume of organic wastes that need final disposal, as well as to use the droppings as fertilizer, and the worms can be used as feed to chickens or to obtain enzymes to be used in the biochemical industry.
Conclusions Several past and contemporary examples have been described that involve
the recovery of organic materials from the waste stream by scavengers for
use in integrated biosystems. Even though the term 'integrated biosystems'
is of relatively recent use, the existence of these systems can be traced
back several centuries. Individuals and societies in antiquity realized
- probably in a gradual process that organic wastes from one activity could
be actually a resource and that waste materials could be utilized as an
input for other productive activities, such as farming, leather tanning,
making of saltpeter, potash, dyeing of textiles, cleaning of clothes, and
other activities.
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