adapted to HTML from lecture notes of Prof. Stephen A. Nelson Tulane
Up until the last 5 to 10 years or so, the major form of solid waste
disposal in many places was burying in landfills. Today, we can only use
landfills to deposit ash from incineration or debris from construction or
Waste Energy Sites - Incineration sites that use the burning process to
Source Reduction - Reducing the amount of solid waste that is
initially produced. This is the ideal solution, but so far, has been
Reducing Waste Volume
Pigs -- A major source of reducing food wastes until the 1960's.
This practice was stopped because diseases were spread in this manner.
In-sink garbage disposals -- This method doesn't really reduce the
volume of waste; rather, it transfers the waste into the sewer system
(or into the septic tanks).
Composting -- Really a method of recycling, it works very well to
reduce the volume of organic wastes. The waste can the be used in
gardens, fields etc.
Recycling -- Australia recycled much of its garbage until
WWII, when it became unpopular to recycle.
-- Brings up the question: Who should do the sorting, the source or the
Open dumps and sanitary landfills -- Open dumps are often sited in
wetlands, which, along with the fact that they are unlined, make them
very unsafe, in terms of water contamination. Sanitary landfills are
also covered up daily, to reduce vermin and smell.
Incineration-- Beginning to play a much larger part in solid waste
disposal. Incinerated waste has a much smaller volum as ash, which is
a lot easier (and safer) to dispose of.
Ocean dumping This practice is no longer allowed, although at one
time it was fairly popular.
Illegal Dumping-- A prolific disposal method, whether individually
(tossing trash out of a window while driving down the highway) or on a
large scale by industries.
in Waste Disposal
in many developed countries, we produce a ton of garbage per person
per year. This breaks down to a couple of kilograms per
person per day.
Recently, near major cities, the policy of Integrated Waste
Management has become more popular, which involves the following:
Recycle -- First, all of the waste that can be recycled is.
Incinerate -- The remainder of the waste is incinerated, to reduce
its volume (by 90%) and transform it all into ash. Also, the excess
heat generated from the incineration process is used to spin a
turbine, generating electricity.
Landfill -- The ash, along with waste from construction and
demolition practices, is then dumped into a landfill.
Typical Pattern of Trash Disposal
2 - Pilot
Percent of Trash disposed of by
in many places llaw now forbids placing raw garbage into landfills, due to
the dangers of groundwater contamination from landfill leeching.
Sanitary Landfills Site
Should be above the water table, to minimize interaction with
Preferably located in clay or silt.
Do not want to place in a rock quarry, as water can leech through
the cracks inherent in rocks into a water fracture system.
Do no want to locate in sand or gravel pits, as these have high
leeching. Unfortunately, most of Long Island is sand or gravel, and
many lanfills are located in gravel pits, after they were no longer
Do not want to locate in a flood plain. Most garbage tends to be
less dense than water, so if the area of the landfill floods, the
garbage will float to the top and wash away downstream.
Pollution from Sanitary
Volatiles (from Anaerobic processes) include:
Leachates include: Heavy Metals (Pb, Cr, Cd)
Soluble Salts (Chloride, Nitrate, Sulfate)
Modern Landfill with plastic, clay liner and collection pipes to prevent
leachate from entering the groundwater. Vadose Wells are situated in the
unsaturated zone to monitor gas emissions. Things do not
biodegrade in a landfill. Anaerobic processes are the only ones that take
place after the landfill is sealed, and this makes organic decay very
slow, as there is no oxygen or moisture tosupport the decomposition
Reduces the volume of solid waste - only the ash (approximately 90%
reduced in volume) needs landfilling.
Metals may be recovered from the incineration process, and are
usually recycled by the incineration plant.
Converts waste to energy, by using the heat given off by the
incinerating waste to fuel a turbine, which is used to generate
May result in air pollution (although recent regulations severely
restrict the amount of pollution from incineration).
Ash may be a hazardous waste (this is not true in most cases,
although there are exceptions).
Burns at 1800° F.
The following are all methods of initiating source reduction:
Do not purchase as much, or reduce use.
Purchase products with reduced toxics.
Purchase environmentally preferred products.
Purchase products with less packaging.
Purchase concentrated products.
Purchase products in bulk or larger sizes.
Buy multiple use products.
Do not replace for style.
Purchase more durable products.
Maintain properly and repair instead of replace.
Purchase reusable products, and then reuse or donate to charity.
Purchase more efficient products, or use products more efficiently.