Organic Waste

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Organic waste

Organic wastes contain materials which originated from living organisms. There are many types of organic wastes and they can be found in municipal solid waste , industrial solid waste , agricultural waste, and wastewaters. Organic wastes are often disposed of with other wastes in landfills or incinerators, but since they are biodegradable , some organic wastes are suitable for composting and land application.

Organic materials found in municipal solid waste include food, paper, wood, sewage sludge , and yard waste . Because of recent shortages in landfill capacity, the number of municipal composting sites for yard wastes is increasing across the country, as is the number of citizens who compost yard wastes in their backyards. On a more limited basis, some mixed municipal waste composting is also taking place. In these systems, attempts to remove inorganic materials are made prior to composting.

Some of the organic materials in municipal solid waste are separated before disposal for purposes other than composting. For example, paper and cardboard are commonly removed for recycling . Food waste from restaurants and grocery stores is typically disposed of through garbage disposals, therefore, it becomes a component of wastewater and sewage sludge.

A large percentage of sewage sludge is landfilled and incinerated, but it is increasingly being applied to land as a fertilizer . Sewage sludge may be used as an agricultural fertilizer or as an aid in reclaiming land devastated by strip mining , deforestation , and over-application of inorganic fertilizers. It may also be applied to land solely as a means of disposal, without the intention of improving the soil .

The organic fraction of industrial waste covers a wide spectrum including most of the components of municipal organic waste, as well as countless other materials. A few examples of industrial organic wastes are papermill sludge, meat processing waste, brewery wastes, and textile mill fibers. Since a large variety and volume of industrial organic wastes are generated, there is a lot of potential to recycle and compost these materials. Waste managers are continually experimenting with different "recipes" for composting industrial organic wastes into soil conditioners and soil amendments. Some treated industrial wastewaters and sludges contain large amounts of organic materials and they too can be used as soil fertilizers and amendments.

Production of biogas is another use of organic waste. Biogas is used as an alternative energy source in some third world countries. It is produced in digester units by the anaerobic decomposition of organic wastes such as manures and crop residues. Beneficial byproducts of biogas production include sludges that can be used to fertilize and improve soil, and the inactivation of pathogens in the waste. In addition, there is ongoing research on using organic wastes in developing countries: (1) in fish farming; (2) to produce algae for human and animal consumption, fertilizer, and other uses; and (3) to produce aquatic macrophytes for animal feed supplements.

[Teresa C. Donkin ]