INTRODUCTION TO ENVIRONMENTAL SCIENCES
Solid and Hazardous Wastes
I. What Is It and How Much Do We Produce?
A) Solid waste
Solid waste is any unwanted or discarded material that is not a liquid or a gas. Encompasses a very wide range of materials. U.S. produces approximately 11 billion tons per year or 44 tons/person. This represents 33% of the world's total.
98.5% of the U.S. total comes from mining, oil- and gas-drilling, agriculture, and industry. Only 1.5% comes from municipal sources (MSW; garbage from homes and businesses). This still represents 1,500 pounds/person. Only 25% of MSW is recycled or composted. Rest is dumped in landfills or burned.
B) Hazardous waste
Hazardous waste is any solid or liquid that meets any of the following criteria:
1) Contains one or more of 39 toxic, carcinogenic, mutagenic, or teratogenic (birth defects) compounds above established limits. Examples include lead (neurological impacts, birth defects) and dioxins (carcinogenic chlorinated hydrocarbons; affect immune system).
2) Catches fire easily.
3) Is explosive or releases toxic fumes.
4) Is corrosive.
This statutory definition does not include radioactive materials, household wastes, many of which meet one or more of the four criteria, mining wastes, oil- and gas-drilling wastes, liquids containing organic hydrocarbons, kiln dust produced when hazardous wastes are incinerated, and any wastes from small businesses and factories that produce less than 220 pounds per month. Because of these exclusions, only 6% of the 6 billion tons (23 tons/person) of hazardous waste generated each year in the U.S. is regulated by hazardous waste laws.
II. Reducing the Amount of Waste and Pollution We Produce
We can either manage the waste we make more effectively or produce less waste. The former view (high-waste approach) assumes that large amounts of waste are an unavoidable (or even good) consequence of a robust economy. Try to reduce environmental harm by the appropriate management of the waste, if possible.
The latter view (low-waste approach) assumes the waste should not be made in the first place or that those wastes that are unavoidable can be recycled, composted, or reused. One person's waste is another person's resource. Follow a set of priorities for both solid and hazardous waste. Generally, these are, in order, 1) reduce, 2) reuse, 3) recycle and compost (the environmental 3 R's), 4) treat or incinerate, and 5) place in permanent storage. The first three could reduce the amount of waste by 60-80%. Unfortunately, most modern societies reverse these priorities (high-waste approach).
Low-waste approach reduces demand for new non-renewable resources and energy, reduces the pollution caused by using these resources, improves health and safety, reduces pollution control costs and liability, and usually is cheaper in the long run than cleaning up pollution and trying to manage the waste.
Often the payback time for waste reduction initiatives is less than 3 years. The 3M Company reduced its waste by 30%, air pollutants by 70%, and saved over $750 million in waste disposal costs. Waste reduction is good business.
Waste reduction can be realized by decreasing consumption of wasteful materials (precycling), redesign manufacturing processes to use less materials and to produce less waste, use less hazardous cleaning materials in the home, design into products ease of recycling, reuse, and composting, make products last longer (decreases demand), reduce packaging (CDs) and make it environmentally friendly, and institute pay-per-bag (trash taxes) municipal garbage programs.
Reuse of materials is the most efficient way to reduce wastes. Few new resources are required, and energy use and pollution are minimized. This has more benefits than recycling. Examples include refillable drink bottles and cloth food bags. Reuse of soda bottles in the U.S. has declined. Once reused almost 90% of glass soda bottles. Now down to 7%. Some countries in Europe ban non-reusable glass or plastic bottles.
III. The Pros and Cons of Recycling
Can be one of two types. Closed-loop or primary recycling is where the material recycled (post-consumer waste) goes to make the same product (newspaper to newspaper or aluminum cans to aluminum cans). Open-loop or secondary recycling is where the material recycled goes to make something different (old cars recycled into pots and pans). Not as efficient as primary recycling. Usually requires more energy and new resources.
A) Solid waste recycling
Over 25% of MSW now recycled or composted. Slightly over 50% of the population participates in curbside recycling programs. Potentially could raise that to 60-80%. Pay-as-you-throw programs charge for what you throw away, but not for recycling.
Large materials-recovery facilities (MRF) separate mixed urban waste after being shredded into recoverable and recyclable materials (paper, plastic, glass, iron, aluminum, copper) and organics that can be burned to create heat and electricity.
Requires large amounts of trash to make them economically feasible. In a way they promote a high-waste approach. Also produce toxic ash and CO2. May be better to do the materials separation at the source (home or business).
Many recycling systems do not pay for themselves; cheaper to incinerate or landfill the waste. However, usually does not take into account the value of the benefits. The purpose of recycling is not to make a profit; it is to reduce the use of new resources, the production of waste, and to reduce pollution and environmental degradation.
B) Recycling of aluminum, paper, and plastic
About 35% of aluminum is recycled (68% of aluminum cans). Reduces air and water pollution and energy needs by 95+% compared to processing raw aluminum ore.
About 50% of paper is recycled. Has to be reprocessed into new paper with some new pulp added. Requires about 50% less energy, produces 75-90% less air pollution, and about 35% less water pollution than making new paper from trees. However, most recycled paper is from pre-consumer waste (scraps and cuttings). That is, most of the paper the consumer uses is not recycled.
Plastics now make up 20% by volume of MSW. Take hundreds of years to biodegrade, if ever. Only about 5% of plastics are recycled. Problem is there are so many different types of plastics. Need to be separated which is very labor intensive. Also, it still is cheaper to make new plastic from oil than to recycle old plastic. Probably better to reuse plastics for the same purpose.
C) Composting: A form of recycling
Fungi and bacteria decompose biodegradable organic material (paper, food wastes, leaves, wood; about 35% of MSW) into a humus-like material. Can be used as a fertilizer or as topsoil. Can be done indoors and outdoors by individual homeowners and at community facilities. Objectionable odors must be controlled and must insure that toxic materials are existing landfills (already stinks!) or are in remote areas.
IV. Ways Of Getting Rid Of or Storing Waste
Some waste that can't be recycled or reused is inevitable. What can we do with it? Four major choices: detoxification, burning, burying, and exporting.
A) Waste detoxification
Turn hazardous waste into non-toxic material. Can be done through chemical treatment, incineration, encapsulation, and bioremediation.
Bioremediation uses bacteria and fungi to render the material harmless, either by consumption or conversion. This process mimics natural decomposition. May be able to genetically engineer a specific organism for a specific waste. Applied to many different kinds of waste and also water pollution. May also be much cheaper than other forms of hazardous waste disposal. At present works best on organics.
B) Burning waste
About 15% of MSW and 7% of hazardous waste is burned in incinerators. Mostly done at high-volume mass-burn incinerators, which burn unsorted, mixed waste. Even the most efficient and well run emit toxic air pollution (lead, mercury, dioxins) and produce toxic ash. They also are very expensive to run and operate. Japan burns 75% of its MSW in thousands of incinerators, although there are health concerns.
C) Burying waste
1) Municipal Solid Wastes
In the U.S., 60% of MSW buried in sanitary landfills designed for the long-term holding of garbage. Modern ones are sited on geologically stable ground, lined with clay and plastic and topped with clay and soil. Perforated pipes underneath the landfill collect any leachate (garbage juice), which is then treated like raw sewage before being released into local waters. Monitoring wells are used to check for leakage and spread of leachate into the surrounding groundwater.
If properly constructed, sanitary landfills reduce water and air pollution (no burning or leakage), reduces odors, keeps pest to a minimum, handle huge volumes of waste, can be used for recreational purposes after being closed and covered, and provide a viable source of methane for producing electricity and heat. Few ever work as advertised!
Most leak, emit odors, and often material doesn't degrade even after decades. Older landfills often are nothing more than abandoned, soil-covered toxic pits that pollute the surrounding air, ground, and water. They account for about 20% of all Superfund sites. Even modern landfills eventually leak. May be able to "clean" landfills by constant washing with water and the collection of the resulting leachate.
2) Hazardous wastes
Hazardous waste requires special handling. Liquids often injected into deep wells below the groundwater. Hope is that the dry porous rock will store liquids indefinitely and isolate it from groundwater and the surface. Has become the method of choice for hazardous liquids. There are concerns about long-term monitoring.
Surface impoundments are supposed to be sealed on the bottom with a plastic liner to prevent leaks. Solids settle to the bottom and volatile compounds evaporate. However, 90% of these either leak or do not have proper liners.
About 5% of U.S. hazardous waste is concentrated and stored in drums that are stored in special landfills.
Problem with many of these techniques is that when problems arise, the operators declare bankruptcy and federal or state governments are then responsible for operations and clean up. One suggestion is to store wastes in specially designed containment buildings. These would be constructed at the local level, reducing the long distance transport of the waste and the possibility of accidents.
D) Exporting waste
Some U.S. cities with no place to put their waste are exporting it to other countries, particularly developing ones. These countries have either no or much less stringent disposal regulations. Often done under the guise of recycling. A 1994 agreement banned much of this waste exporting, although the U.S. failed to support the ban. 97 nations now ban the importation of hazardous waste.
V. U.S. Hazardous Waste Regulations
A) Resource and Conservation Recovery Act (RCRA)
Passed in 1976 and amended in 1984. Requires EPA to identify hazardous wastes and to set standards for their management. Also provides guidelines and financial assistance to states to implement waste management programs.
Requires permits for all companies handling more than 220 pounds/month of waste. Requires "cradle-to-grave" monitoring. Suffers from lack of personnel to oversee the 750,000 waste producers and 15,000 haulers and disposers. Violators often not prosecuted or punished in any meaningful way.
B) Superfund Act
Passed in 1980 and amended in 1986 and 1990. Formal name is the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Established a fund to identify and clean up abandoned hazardous waste sites. 86% of the funding provided by taxes on hazardous waste producers.
Based on the principle of the polluter pays. Works if culprit(s) can be identified, forced to pay, and has the funds to do so. Otherwise, money from the Superfund is used. Generally results in years of lawsuits and legal proceedings before anything is done.
Presently, over 1000 sites still on the National Priority list. Almost all have had an emergency clean up. List may expand to nearly 10,000 with total costs exceeding $1 trillion. Military, DOE, and Department of Interior sites add even more to the list.
There is no simple, easy, inexpensive solution to the storage or destruction of toxic waste. Best not to make the stuff to begin with.