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PDHengineer.comCourse EN-3021

Solid Waste Management and Waste

Reduction Techniques

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SOLID WASTE MANAGEMENT AND WASTE REDUCTION TECHNIQUES

Why Should Engineers Be Interested?

The management of solid waste is one the United States most protracted policy concerns.

Making room for the 236 million tons of solid waste generated per year is of course a problem.But so are the increasing land use and environmental concerns surrounding the current disposalmethods. Public decision-makers are faced with a wide range of tough choices and uncertainoutcomes. In other words, solid waste is a problem and a problem that should be addressed onmany fronts.

The traditional waste management bureaucracy is dominated by engineers, whether working fora city public works department, a regional special purpose agency, or a private wastemanagement firm. Engineers are also intimately involved in many of the activities that producelarge amounts of waste, such as construction or industrial processes. We as engineers have beensuccessful at designing better and safer disposal methods. But we have been reluctant to effect

strategic planning initiatives that address the whole waste generation and disposal cycle. Sourcereduction, material reuse, recycling, product packaging constraints, or industrial processchangesall are examples of steps that can be taken toward reducing the amount of solid waste.The current production and management mindset, though, is in many ways still focused only onfinding bigger and better methods of solid waste collection and disposal.

This course will outline many of the strategies the engineers can implement to move past thecurrent mentality, to more effectively reduce and manage solid waste. Not all of the techniqueslisted in this course are pure engineering solutions. Many are financial or policy-oriented. Butsince engineers are in the drivers seat in managing solid waste, it is incumbent upon them to beaware of the entire spectrum of possibilities. Indeed, the New Zealand Trust, an organization

dedicated to reducing the amount of solid waste produced in its home country, has explicitlylisted engineers as key participants in the fight to waste less.

This course has many parts. First, since examining the past can often help us plan for the future,the course opens with a brief history of waste management in the US, leading up to currentpractices. It then goes on to describe in simplified terms the technical and operational details ofwaste management today. Finally, it will conclude with a discussion of waste reductiontechniques.

BRIEF HISTORY OF SOLID WASTE MANAGEMENT

Mother Nature as Solid Waste Manager

Humans have been generating solid waste as long as they have been consuming plants and

animals. Ancient human settlements disposed of animal bones, plant residues, and other debrisinto what archaeologists now call middens. Today, these middens are valuable sources ofinformation about ancient cultures.

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The Ohlone Indians of the San Francisco Bay area built huge shell mounds or shell middens ofdiscarded abalone, mussel, and clam shells--staples of the Ohlone diet--along with sediment, ash,and rocks. Over time the mounds grew larger and taller from successive use, accumulatingshells, animal and human remains, ceremonial burial objects, artifacts of everyday use, andarchitectural remains. Over a period of about 3000 years, more than 400 of these mounds were

built around the Bay, and the largest were over 200 feet long and 30 feet high. Archaeologistsnow think that these shell mounds had spiritual as well as practical value.

That is a particularly dramatic example of early solid waste management. Most cultures merelydisposed of solid waste in nearby piles. When humans were sparsely settled and when thecomposition of the solid waste was primarily food waste, management wasnt an issue. Often itwas composted or fed to livestock. If waste was left in place, it would biodegrade. MotherNature was the solid waste manager. This system lasted for thousands of years. However, alongwith the industrialization of the 1700 and 1800s came rising urbanization and risingconsumption, and solid waste gradually became more and more of a problem.

Beginnings of Waste Management

At first, many thought that the accumulation of public refuse was merely a noisome symptom ofliving in a city. Public refuse, which included household wastes, ashes, horse droppings, andlitter, certainly wasnt seen as something that required organized and systematic management. Ifwaste accumulation did become a problem, a privately paid scavenger was employed to cart itaway. It wasnt until the 1880s that the refuse problem began to receive widespread publicnotoriety. At this time, so-called sanitarians began addressing municipal water supply and sewerdisposal issues. These same sanitarians began to turn their attention to solid waste as a newdanger to human health, the third pollution. The public, who already experienced the benefitsof publicly managed water and sewer services, embraced the idea of a publicly managed waste

management effort. Boards of health or health commissions were created and given power overwaste collection and disposal. These boards were usually comprised of elected officials; veryfew boards had medical or technical members.

Early disposal methods were crude. Most cities simply dumped their collected wastes intonearby bodies of water, or, if water wasnt handy, onto vacant lots outside city limits or nearundesirable neighborhoods. In 1880, 40 percent of cities dumped their waste on land or buriedit, 22 percent used it as fertilizer or animal feed, 10 percent dumped it in water, and 1 percentburned it. New York City dumped over one million cartloads of garbage into the ocean in 1886.

As America shifted from a producer to a consumer society from 1880 to 1920, the amount of

waste generated skyrocketed. Part of the problem was the nature of the goods consumed. Massproduction techniques gave rise to new products like gum, razors, and tin cans that had neverbeen made in the home and were cheap enough to be disposable. Second, rising incomes anddeclining prices allowed ever increasing consumption of these items. The result was a 43percent increase in garbage in Pittsburgh between 1903 and 1907. In the same period,Milwaukees increased by 24 percent, Cincinnatis by 31 percent, and Washington, D.C.s by 24percent. In 1905, the average American generated 860 pounds of waste a year.

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Quickly, then, the early disposal methods became inadequate, and public health officialsstruggled with new ways to dispose of the mounting refuse. The 1895 appointment of ColonelGeorge E. Waring, Jr., as street cleaning commissioner of New York City signaled a must-needed shift in solid waste management thinking. Waring was an engineer-cum-sanitarian,already famous at the time for his work with sewers in Memphis. To tackle the daunting solid

waste problem in New York, Waring implemented a multi-faceted approach that targeted wastegeneration and collection as well as disposal. He started a public education campaign toencourage citizens to throw away less, to separate their waste at the curb (into garbage, rubbish,and ashes) to facilitate collection, and not to litter (which was acceptable public behavior at thetime). He professionalized the street cleaning corps. He redesigned the garbage barges so theydumped waste more efficiently and farther from shore. Finally, he built rubbish-sorting andgarbage-reduction plants, where waste would be sorted and salvageable materials, such asrubber, tin, or grease, picked out and resold. The profits from this were used to offset collectioncosts. Warings tenure was short--he left in 1898--but his impact was large. First, he assured thepublic that the municipal government was the best body to handle solid waste. Second, heshowed that technological solutions were very successful. Finally, and perhaps most

importantly, he was key in passing the responsibility for solid waste from public health officialsto engineers, where it has resided ever since. Unfortunately, his other initiatives, such as curbseparation and minimizing waste generation, were not so long-lived.

Emerging Technologies

The engineering community followed Warings lead and approached the waste problempragmatically, with the goal of minimizing cost and maximizing efficiency, particularly withrespect to collection and disposal. The engineers also focused on technological solutions,ignoring issues of waste generation, consumer behavior, or public participation. Two suchtechnologies emerged in the early 1900s as important forms of disposal: incineration and

reduction.

The concept of incineration, or the burning of waste, arrived from Britain in the 1880s. Thefirst incinerator was built in New York City in 1885. By 1908, 180 incinerators had been builtaround the country. Some cities began experimenting with using the incinerators to generateelectricity. New York City built such a plant in 1905. This proved to be too expensive andcouldnt compete with traditionally generated electricity. At first, another fuel, such as naturalgas or coal, was added to the garbage to facilitate combustion. This became too expensive, sothe garbage was burned without the addition of fuel. However, the temperatures achievedwerent very high, which resulted in noxious smoke and incomplete combustion. Incinerationlost favor as quickly as it had gained it, and by 1909, only 70 plants still remained in operation.

Reduction refers to a process of extracting oils from city garbage. It appeared in 1886 inBuffalo, New York, and was intended to give the city saleable byproducts like grease orfertilizer. The idea was greeted with enthusiasm, but due to undesirable side effects, especiallyfoul odors, only twenty-six reduction plants were built by 1913.

Therefore, land disposal, by default, became the primary disposal method. But merely dumpingon vacant land was becoming increasingly objectionable, so engineers began searching for better

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ways of land disposal, and in particular ways to utilize the waste, particularly the inorganicwaste. Using it as fill or reclamation material became popular. Davenport, Iowa used refuse tobuild levees along the Mississippi, for example. The idea was especially popular in the SanFrancisco Bay area. Between 1860 and 1960, the San Francisco Bay decreased in size by 29percent, from 680 square miles to 430 square miles, as communities dumped millions of tons of

garbage and dredging material to generate new land for development.

In 1934, Fresno, California opened the first modern sanitary landfill in the United States. Theconcept of sanitary fill arose in Britain in the 1920s. The method was based on usingengineering techniques to control the putrefaction of organic wastes in an open dump. Layerswere used: 12 inches of garbage were covered by 24 inches of ashes and street sweepings,which was covered by a layer of dirt, and then the cycle repeated. Fresno used the first cut andcover method, in which a huge trench or hole was dug and subsequently filled with thealternating layers of waste and soil. The idea caught on quickly. By 1945, over 100 cities hadadopted the sanitary landfill. It replaced incineration and open dumping as the disposal methodof choice for local communities.

The sanitary landfill was particularly popular among engineers because it solved severalproblems as once. It eliminated the need for curbside waste separation. It had enormouscapacity to meet future increases in waste generation. It was not labor intensive to operate andso was more cost efficient. It was a one-stop solution that was out of sight, out of mind.However, in the 1950s and 1960s sanitary landfills were little more than open dumps withsome dirt and chemicals sprinkled on top. In many ways, they created more problems than theysolved, such as contamination of nearby water sources, methane gas explosions, anduncontrolled fires. In early 1960, the EPA found that 90 percent of landfills could not be calledsanitary because of their effects. At the same time, community opposition to landfills was on therise. In response, in 1965 Congress passed the Solid Waste Disposal Act, which required

environmentally-sound methods of waste disposal. These forces combined to precipitate a newinterest in incineration.

Incinerators had seen a slow but steady growth since their heyday of the early 1900s. In 1969,there were 364 municipal incinerators in operation. However, new environmental legislation andthe new-found interest as a replacement for landfilling sparked radical changes in technology,especially in the idea of waste-to-energy, or the recovery of energy from burning trash. The

idea was not new, of course, but new techniques and economies of scale made the method morecost efficient and more attractive. Large plants, capable of burning up to a thousand tons ofunsorted waste a day, began to appear in the 1970s. Private firms entered the market to buildthese plants. The EPA and many state officials touted incineration as the best method to relieve

landfill capacity.

Incineration never took off. Many local communities saw it as worse than landfills. Smoke andodors, the same factors that doomed incineration 60 years earlier, were the main culprits. Manylocal communities saw it as worse than landfills. In fact, it soon became apparent that the 1965Solid Waste Disposal Act wasnt strong enough. Furthermore, the issue of hazardous wastebegan to receive attention. The result was the 1976 landmark passage of the ResourceConservation and Recovery Act (RCRA). There is probably no other piece of environmental

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legislation as far-reaching, or as troubling to industry, as RCRA. It primarily addresseshazardous waste management, but it does have a significant normal solid waste component thatauthorized money for solid waste research and created an Office of Solid Waste within theEnvironmental Protection Agency. It also established minimum federal technical standards andguidelines for state plans to promote environmentally sound disposal methods, maximize the

reuse of recoverable resources, and foster resource conservation. In general, it adopted aphilosophy of preventing solid waste generation rather than dealing with waste disposal.

RCRA focuses on hazardous waste, where it has been quite successful in curbing wastegeneration. It wasnt as successful in dealing with normal solid waste. In 1990, Congresspassed the Pollution Prevention Act. This Act focused industry, government, and publicattention on reducing the amount of pollution through cost-effective changes in production,operation, and raw materials use.

Waste Management Today

Today, we are left with an uneasy acceptance of the status quo. The two Bsburning andburying, or incineration and landfillingremain the primary disposal methods. Even thoughthe number of landfills in the United States is steadily decreasingfrom 8,000 in 1988 to 1800in 2003, the total capacity is staying relatively constant. New landfills are simply much largerthan in the past. On the other hand, in 1999, there were 102 incinerators, with the capacity toburn up to 96,000 tons of waste per day.

SOLID WASTE MANAGEMENT

At this point, we will move to waste management practices of the present. We will look at thestate of the industry and current waste generation practices. First, we will look at some of the

terms and concepts that will be used later in the course.

Definition of waste

The term solid waste is all-inclusive and encompasses a wide range of different products.Garbage is food wastes: animal, fruit, and vegetable residues. It excludes human waste.

Rubbish or trash is composed of such materials as paper, cardboard, plastics, wood, glass, andcans. Ashes are what remain after the burning of wood, coal, and other materials . Constructionand demolition wastes include such things as concrete, stones, plaster, plumbing parts, and

shingles. Special waste includes street sweepings, roadside litter, dead animals, and abandonedvehicles. Treatment-plant waste includes the sludge and residue from water and wastewater

treatment plants. The term refuse is often used to describe solid waste generated by a householdand so includes garbage and rubbish. The term solid waste has a slightly different definitionunder the Resource Conservation and Recovery Act, the main piece of legislation governingsolid waste. Here, solid waste can be any solid, semi-solid, liquid, or contained gaseousmaterials that have reached the end of their useful life and can be discarded. Solid waste cancome from industrial, commercial, mining, and agricultural operations as well as households.

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Oftentimes, the source of waste is distinguished. Industrial wastes are those that arise fromindustrial processes and usually include ashes, construction waste, and special wastes.Municipal wastes are those that arise from day-to-day life in the city and are the ones we aremost familiar with. They include both household and commercial waste, but also include specialwastes and treatment-plant wastes. Finally, wastes are often divided into hazardous and

nonhazardous wastes. A hazardous waste is one that poses an immediate or long-term threat tohuman, plant, or animal life.

Waste Collection

The mechanism of waste collection is familiar to everyone. Once a week or so, usually early inthe morning, a garbage truck comes to your house to empty your garbage cans. A garbage truckcan carry about five to seven tons of garbage. The trucks have compactors built in, which givesthem greater capacity. Many communities also have curbside separation of recycling, and thesame or a different truck and crew will pick that up.

If the community is small, the garbage truck might go straight to the final disposal location at theend of its route. More usually, the truck will go to a transfer station, where the varioustruckloads of waste are collected and consolidated. Here, the waste is also sorted andcompacted. From the transfer station, the waste goes on to final disposal at either a landfill or anincinerator.

Waste Disposal

As mentioned earlier, the two most common means of solid waste disposal today are sanitarylandfills and incinerators.

Sanitary Landfills

A sanitary landfill is in principle a simple thing. Solid waste is placed into an excavated trench,where a bulldozer spreads and compacts it. At the end of each day, soil is placed over thecompacted waste, in a layer of six to twelve inches deep. This layer is known as the daily cover.The next day, more waste is placed on top of the previous days daily cover, and the processrepeats. This way, the landfill gradually gains height. The final earth layer is called the finalcover, and it is two to five feet thick.

The name sanitary notwithstanding, landfills can be nasty places. The buried wastedecomposes in an anaerobic environment, so it generates methane gas (so-called landfill gas, or

LFG). Rainwater and water entrained in the waste itself collects and trickles down through thelandfill, picking up chemicals and becoming a toxic product called leachate. Leachate can workits way into surface or underground water sources. Both LFG and leachate must be managed,both during and after landfill operation.

The EPA recognizes four types of landfills: municipal solid waste, bioreactors, constructiondebris, and industrial waste. The names are self-explanatory, with the exception of a bioreactor.A bioreactor is a municipal solid waste landfill that is designed to quickly transform and degrade

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organic waste. The increase in waste degradation and stabilization is accomplished through theaddition of liquid and, in some cases, air to enhance microbial processes. Bioreactors are a new

approach to landfill design and operation that differ from the traditional "dry tomb" municipal

landfill approach.

Incineration

Burning solid waste has been popular in the United States, and it remains a popular in manyothers areas of the world. It has benefits: it reduces solid waste by up to 90 percent by volume75 percent by weight, helps to destroy bacteria and germs, and reduces the amount of waste to belandfilled. After efficient combustion, only residual ash remains for disposal.

Incineration also has its drawbacks. It obviously produces smoke and odor, and the residual ashmust itself be disposed of, usually in a special-purpose landfill called a monofill. The smokeoften contains numerous pollutants, such as cadmium, lead, mercury, dioxin, sulfur dioxide, andhydrogen chloride.

Industry Composition

Today, the solid waste management industry is a mix of public and private sector, of small andlarge firms, of horizontal and vertical integration. In 1999, 27,028 organizations operated in theindustry. Almost 56 percent of these organizations were public sector entities, while 44 percentwere private companies. Of the total, approximately 15,500 (57 percent) provided collection andhauling services only and did not own or operate any solid waste disposal or process facilitiessuch as landfills or incinerators. The remaining 11,500 organizations operated the estimated15,700 solid waste management facilities in the U.S. The private sector owned 53 percent of the

solid waste facilities and the public sector owned 47 percent.

In total, the industry managed approximately 545 million tons of waste. (This number includeswaste that is not classified municipal solid waste by the EPA). Of that total, about 374 milliontons was landfilled; 31 million tons was incinerated; and 140 million tons was recycled. Theprivate sector handled 69 percent all the solid waste recycled, incinerated, or landfilled, while thepublic sector handled 31 percent.

Most private firms are small: a single landfill, or a fleet of garbage trucks. Some are quitelarge. Waste Management, Incorporated, for example, operates 284 active landfills, 16 waste-to-energy plants, 73 landfill gas-to-energy facilities, 160 recycling plants, 293 transfer stations, andover 1,400 collection facilities. Allied Waste Industries, Incorporated, operates in 39 states

through a network of 329 collection companies, 150 transfer stations, 167 active landfills, and 65recycling facilities.

A public sector waste management organization can be a department of the local government.The city of Houston, for example, has a Department of Solid Waste Management. Or it mightbe a special district. The Cuyahoga County, Ohio, Solid Waste District is a dependent district.Palm Beach County, Florida, has a county Solid Waste Authority, which is an independentdistrict.

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It is important to remember that even if a local government does not actually perform wastecollection or disposal, it will often have an agency responsible for managing the private firms.The Solid Waste Agency of Lake County, Illinois, for example, provides technical and businessexpertise to help municipalities manage their solid waste contracts.

Many times, the public and private sector complement each other. In Houston, for instance, thecity Department of Solid Waste owns the landfill and recycling facilities, as well as collects thewaste from about 67 percent of residences and businesses. Private firms collect from theremaining 33 percent. Since this portion tends to be large businesses, private firms collect about65 percent of total waste.

Industry Finance

Many waste reduction techniques are financial or economic in nature. For this reason a briefdiscussion of the solid waste industry financial structure is warranted.

Solid waste agencies generally raise revenue through user fees. These user fees come in varioustypes. The most common type is a monthly or yearly fee charged for waste collection. This feeoften shows up as a separate line item on some other bill like the property tax bill or the waterbill. Typical rates might be $75 a year for a single family residence, $50 a year for apartments.Commercial establishments usually pay based on the size of dumpster they use.

The second user fee is called the tipping fee. This is the fee charged for actually disposing of thewaste at the waste facility. The specific tipping fee structure varies from waste disposal facilityto waste disposal facility, but generally, waste disposal is charged on a per-ton basis. Differenttypes of waste are priced at different amounts. For example, a landfill in North Carolina charges

$29.50 per ton of municipal solid waste, but $59.00 per ton of construction and demolitionwaste. Individuals who visit the landfill are usually charged a flat fee, $20 per visit for example.Since the organization that collects solid waste is not necessarily the organization that operatesthe disposal facility, the tipping fee is a separate fee from the collection fee.

In many ways, the current state of solid waste management and finance is amazingly successful.On average, it only costs a municipality about $70 to $80 to collect and dispose of one ton ofsolid waste. A household may only spend $100 a year on waste collection. Considering thelabor, capital, and transport costs associated with the whole process, these figures are quite lowcompared to other infrastructure services. But since they are so low, there is little incentive tochange behavior.

Waste Generation Patterns Today

In 2003, U.S. residents, businesses, and institutions produced more than 236 million tons of solidwaste, which is approximately 4.6 pounds of waste per person per day or 1680 pound per year.By comparison, European countries such as Germany, Italy, Spain, Switzerland, the Netherlands,and the United Kingdom generate around two to three pounds per person per day.

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When developing waste reduction techniques, it must be noted that the solid waste volumeproduced by a community is composed of a wide variety of different materials. This mix ofwastes is known as its waste stream. Table 1 below shows the waste stream for AlamedaCounty, California, in 2000 (population 1,455,000).

Table 1: Alameda County Waste Stream Composition

Material Groups Tons Disposed % of total

Organics (rubber, wood, textiles, leather) 361,156 23.3

Paper (including magazines and newspapers) 355,288 22.9

Misc. Waste (including computers, construction debris) 252,378 16.3

Food Waste 184,717 11.9

Plastic 164,725 10.6

Yard Waste (lawn clippings, branches, etc) 109,393 7.0

Metals (cans, large kitchen appliances) 95,274 6.1

Glass 29,754 1.9

Total 1,552,683 100.0

Of course, every community will be different. Table 2 below compares Alameda County to thenational average. Also, waste production changes over time as well. Table 3 chronicles thechanges in the national average waste stream over the last four decades. It paints a picture ofchanging consumption habits and also successful recycling programs.

Identifying and classifying the waste stream is the first step in developing any waste reductionstrategies. Numerous methods exist to do this. The California Integrated Waste Management

Board has waste stream calculators on its web site(www.ciwmb.ca.gov/LGCentral/WasteStream). The EPA also has tools on its website(www.epa.gov/osw). Local decision makers must note that both the rate of waste generationand the composition of the waste stream change over time.

Table 2: Waste Stream Comparison in 2000 (% weight)

Material Groups Alameda National

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County Average

Organics (rubber, wood, textiles, leather) 23.3 12.3

Paper (including magazines and newspapers) 22.9 37.5

Misc. Waste (including computers, construction debris) 16.3 3.3

Food Waste 11.9 11.3

Plastic 10.6 10.5Yard Waste (lawn clippings, branches, etc) 7.0 11.8

Metals (cans, large kitchen appliances) 6.1 7.8

Glass 1.9 5.4

Total 100.0 100.0

Table 3: National Average Waste Stream over Time (by % weight)

Material

Groups

1960 1970 1980 1990 2000 2003

Organics 7.5 7.3 9.1 11.6 12.3 13.2

Paper 34.0 36.6 36.4 35.4 37.5 35.2

Misc. Waste 1.6 2.1 3.2 3.0 3.3 3.3

Food Waste 13.8 10.6 8.6 10.1 11.3 11.7

Plastic 0.4 2.4 4.5 8.3 10.5 11.3

Yard Waste 22.7 19.2 18.1 17.1 11.8 12.1

Metals 12.3 11.4 10.2 8.1 7.8 8.0

Glass 7.6 10.5 10.0 6.4 5.4 5.3

Total weight(million)

tons)

88.1 121.1 151.6 205.2 234.0 236.2

WASTE DIVERSION, REDUCTION, AND ELIMINATION

Introduction

As we have seen thus far, the traditional way of dealing with solid waste has been to implementmore efficient collection systems to convey waste to bigger and better disposal facilities. Thistraditional method is based on technology and seeks to minimize cost. As a communityproduces more and more solid waste, the normal response is to build another or a larger landfill.

This approach is fast becoming untenable, for many reasons. Local budgets are becomingincreasingly stretched. Suitable locations for new landfills or incinerators are increasingly hardto find as both urban areas and community opposition grow. Environmental awareness isgrowing too, both in regards to waste disposal and waste generation. Energy and resources arebecoming more expensive. Therefore, engineers and other decision makers need to considerwaste diversion, waste reduction, and waste elimination. In other words, they must move pastthe two Bs and on to the three Rs: reduce, reuse, and recycle.

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The Three Rs

Reduce

Source reduction, often also called waste prevention, (and different from the process of reductiondescribed earlier) refers to any change in the design, manufacture, purchase, or use of materialsor products (including packaging) to reduce their amount or toxicity before they becomemunicipal solid waste. Simply put, source reduction means producing, consuming, and throwingaway less. It can be as complex as redesigning a product to use fewer raw materials inproduction, to have a longer life, or to be used again after its original use is completed. Forexample, the weight of a 2-liter plastic soft drink bottle has dropped from 68 grams to 51 gramssince 1977. That has kept over 250 million pounds of plastic per year out of the waste stream.Reduction can also be as simple as reusing those plastic soft drink bottles after theyre empty.Not only will this keep the bottles out of the waste stream, but it will obviate the need to buy anew plastic bottle. It is important to remember that waste is not just created when consumers

throw things away. Waste is created at every step in the life cycle of a productfrom extractionof raw materials to transportation to processing, manufacture, and use. Source reduction is themost preferable method of waste management since it averts the creation of waste in the firstplace.

Reuse

Reuse is closely tied to source reduction. Reusing products decreases both the amount of post-consumer solid waste, but also reduces the amount of waste created in the production of thoseproducts. Simple ways to reuse include using cloth napkins, using refillable pens orrechargeable batteries, and turning empty jars into leftover food containers. It also includes

donating or selling old or unwanted clothing and other items. Reuse is considered better thanrecycling. Resource recovery, a term closely related to reuse, refers to the extraction of usefulraw materials, such as glass or metal, or energy from solid waste.

Recycle

Recycling is the best-known technique for reducing the amount of solid waste generated.

Recycling means reusing materials and objects in their original or changed forms rather thandiscarding them as wastes. Recycling turns materials that would become waste into materialsthat can be reprocessed for re-use.

Recycling is one of the best environmental success stories of the last decade. Recycling,including composting, diverted 64 million tons of material away from landfills and incineratorsin 1999. In general, the US recycles about 28 percent of its waste. Some typical recycledmaterials include car batteries, recycled at a rate of 97 percent, paper and paperboard at 42percent, and yard trimmings at 45 percent.

Targeting Waste Generation

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What follows now is a long list of possible waste reduction and waste elimination techniques,specific methods of implementing the Three Rs. As stated earlier, not all of these strategies arepurely engineering but can be broken into three categories: technological, financial, andpolicy. They are in no particular order and of course are not appropriate in all situations. Whenthinking of solid waste reduction, it is important to remember that waste is generated at every

step in the process that brings a product to market, from resource extraction to manufacture topackaging to consumption. The techniques listed here are not revolutionary. Colonel Waringused many of them over 100 years ago in New York City. But they do require changes inthinking and changes in behavior.

Technological Tools

Waste-to-Energy

One form of resource recovery can be found in the waste-to-energy (WTE) plant. A WTE plant

burns waste as a way to produce electricity, allowing the energy in solid waste to be recovered

as electrical energy. One pound of waste can keep a 60-watt light bulb burning for 5 hours, or alow energy bulb for as long as 24 hours. The WTE plant is characterized by highly controlledcombustion supported by extensive air pollution control and ash management systems. In atypical process, the waste is first sorted to remove any large noncombustible material. Fromthere, it enters the combustion area, where it is burned at a temperature of about 1800

oF. The hot

gases from this combustion are used to generate steam, which in turn is used to generateelectricity. The gases then go through a scrubbing process, which cools them, neutralizes anyacids, and removes particles.

There are currently 89 waste-to-energy plants operating in 27 states, handling about 95,000 tonsof solid waste a day (the waste produced by 41 million people). These waste-to-energy plants

generate about 2,500 megawatts of electricity to meet the power needs of nearly 2 millionhomes.

Gasification and pyrolysis are two emerging technologies for turning waste into energy fromwaste streams of a uniform or homogenous nature. In gasification, a thermo-chemical processheats biomass in an oxygen deficient atmosphere to produce a low-energy gas containinghydrogen, carbon monoxide and methane. The gas can then be used as a fuel in a turbine orcombustion engine to generate electricity. Pyrolysis is similar, but the biomass is heated in thecomplete absence of oxygen. Gas, olefin liquid, and char are produced in various quantities. Thegas and oil can be processed, stored and transported, if necessary, and combusted in an engine,gas turbine, or boiler. Char can be recovered from the residue and used as a fuel, or the residue

passed to a gasifier and the char gasifed.

Landfill gas to electricity

Another form of resource recovery is to take the methane gas generated by landfills (landfill gas,or LFG) and use it to generate electricity. Most commonly, this is done at the landfill itself.The electricity is generated in the same way as at any coal- or natural gas-fired electrical power

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plant. An LFG-to-electricity system has three basic components: the gas collection system,which gathers the gas being produced by the landfill; the gas processing and conversion system,which cleans the gas and converts it into electricity; and the equipment which connects to theelectrical grid.

A LFG-to-electricity system at the Central Landfill in Johnston, Rhode Island, which receivesabout 90 percent of the states solid waste, supplies as much as 12.3 megawatts of electricalpower, enough capacity to serve roughly 17,000 households. The landfill then sells thiselectricity to a local subsidiary of New England Power.

Landfill reuse

While not strictly a waste management tool, its worthwhile to take into account that the landfillwill one day be full and, with proper precautions, available for other uses. That day may notcome for 20 to 30 years, but these are the time horizons often contemplated in city plans. Theurban fringe may have extended that far by then. It is not uncommon to turn waterfront waste

dumps into marinas or parks.

However, contrary to popular belief, wastes in landfills dont biodegrade or decompose quickly.Available oxygen is quickly used up beneath the soil covers, and so the decomposition processbecomes anaerobic and proceeds slowly. Although it isn't known long how this process lasts,some experts estimate that it will take between 300 and 1,000 years for a landfill to stabilize,or for the wastes to be completely decomposed. Even after a landfill is closed, all theenvironmental control measures, such as landfill gas collection and leachate monitoring, mustcontinue. Very few modern landfills have reached the stage where they no longer need long-term care and management. The idea of a park or even a housing development on top of an oldlandfill may sound distasteful, but with the right measures just described, it is a valid option for

landfill reuse.

Financial Tools

Increase Tipping Fees

Applying full social cost accounting techniques to solid waste collection may lead to highertipping fees. Increasing tipping fees to levels that incorporate the full cost of externalities, bothpositive and negative, into solid waste calculations, internalizes all costs. This in turn could alterwaste generator and consumer behavior to decrease waste generation. The EPA has begun toembrace the concept of full cost accounting as a powerful waste management technique [32].

Variable User Fees (Pay as You Throw)

Pay as You Throw (PAYT) is the term used to describe the application of variable user fees tosolid waste. As described earlier, in most communities, households or businesses pay a flatmonthly or yearly fee for solid waste collection, despite the amount of waste generated.Obviously, there is no incentive, then, to minimize waste generation. Under a PAYT program,however, a household is given an incentive to reduce waste generation. Typically, a household

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is given a choice of various sizes of garbage can. The bigger the can, the higher the monthly feeassociated with waste collection. (In urban areas, a garbage can might be substituted with aspecial garbage bag; waste collectors will only collect waste in the proper bag, and the bagpricing scheme will be the same). This provides a price incentive to reduce solid wastegeneration. A recycling program goes hand-in-hand with a PAYT program to provide an outlet

for the diverted wastes. (There is always the concern, though, that this could lead to increasedillegal dumping of solid waste. An enforcement effort probably should accompany theseprograms).

Advance Disposal Fee

This is essentially a fee designed to cover the externalities associated with disposal of theproduct. A modest fee is added up-front to the cost of electronic andother big-ticket items suchas computers, printers,appliances and vehicles, which is redeemed at the end of their lives tohelp cover recovery, dismantling, or recycling.

Deposit/Refund Systems

Some experts have advocated robust deposit/refund systems, also known as bottle bills. Underthese familiar schemes, a deposit is paid when the product is purchased but returned to the buyerwhen the product is recycled. This system is not new for such things as soda bottles, but there isno reason why the idea cant be applied to many other products. It also creates meaningfulincome and employment opportunities.

Policy Tools

Landfill Bans

By progressively banning from landfills toxic materials and materials for which markets exist orcould realistically exist in the future, waste generators are forced either to enter those markets orreduce their production of those types of waste material.

Extended Producer Responsibility

Borrowing a page from the Resource and Recovery Act, a more radical approach is to imposecradle-to-grave material management responsibility on municipal solid waste generators, as isalready done for hazardous waste. Since waste generators would have legal or financialresponsibility for waste, they will likely produce less of it.

Thrift Stores

Thrift stores are remarkably efficient venues for recycling and reusing post-consumer goods.Goodwill stores, for instance, re-sell almost 99 percent of what they receive in donations. Andthey arent marginal operators, either; Goodwill and Salvation Army stores, to use two commonexamples, generate over $14 billion a year in their combined revenues. Unfortunately but notsurprisingly, thrift stores often fall victim to zoning regulations. In many cases, local citizens see

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thrift stores as magnets for undesirable people and so agitate against them in the form of enactingzoning changes. In other cases, thrift stores, which operate on paper-thin budgets, cannot meetstandards for building appearance or similar requirements and are forced to close their doors. Inshort, then, policymakers could actually make a significant step toward solid waste solutions byconsidering thrift stores in their proper context and working to enable them.

Product Content Standards

Designers can specify recycled-content or low-waste products in design, construction, andprocurement contracts. The building industry is one of the largest sources of solid waste, and soif recycled-content material and material-efficient procedures are designed into buildings orspecified in contracts, significant waste reduction can result. Engineers can also specify qualitystandards on things like compost or mulch, to guarantee a certain, reliable level of quality. Thisin turn will encourage greater use in agriculture, where current uncertainty in compost and mulchquality is an obstacle. Finally, engineers and local officials can prohibit certain products. Boththe cities of Los Angeles and Berkeley, California, for instance, have old-growth-wood-free

purchasing ordinances in place. Oakland, California, passed a measure to change the local taxtreatment of raw materials for goods manufactured in the city. This particular measure had aneconomic development purpose, but theres no reason a similar measure couldnt be passed toinfluence product content.

Green Building

Government can incorporate green building standards in local ordinances or in construction

contracts. Green building is defined as design and construction practices that significantlyreduce or eliminate the negative impact of buildings on the environment and occupants.. Theprinciples of green building cover many topics, stretching from indoor air quality to water

supply. However, most importantly for purposes of this paper, they also address the generationof construction and demolition waste. Currently, 136 million tons of waste are generated eachyear in the construction and demolition of buildings. This represents a substantial fraction oftotal national solid waste production, and clearly any steps to reduce this waste will havesignificant impact. Numerous cities already have some sort of green building policy, includingSan Jose, California, and Portland, Oregon. The city of Pleasanton, California, recently adopteda green building ordinance for commercial buildings. Such a green building ordinance can becontroversial, however. The Pleasanton Chamber of Commerce opposed the ordinance becauseit felt that commercial buildings would become more expensive to build and that Pleasantonwould thereby lose a competitive edge.

Mandatory Corporate Environmental Reporting

Ensure that all businesses produce waste plans and report on their progress towards targets. TheCity of Berkeley, California, recently considered a measure to prohibit the sale of non-fair tradecoffee; it is not inconceivable that similar measures could be passed that require local businessesto disclose their solid waste information.

Resource Recovery

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Many commentators such as the Sierra Club and others feel that current disposal methods arewasteful because they destroy products and raw materials that could be recovered and reused.For this reason, they support the emerging trend of resource recovery parks. According to theCalifornia Integrated Waste Management Board, a resource recovery park is the collocation of

reuse, recycling, compost processing, manufacturing, and retail businesses in a central facility.The public can bring all their wastes and recoverable materials to this facility at one time.Resource recovery parks also sell or give away reused and recycled-content products.

Resource recovery parks can be quite successful. One such park, located in San Leandro,California, recovered a significant amount of materials as seen here in Table 4.

Table 4. Recovered Materials, 1999

Material Tons

Wood/green waste 119,505

Curbside recyclables 84,532

Dirt 15,881Concrete 7,275

Paper 3,706

Appliances 1,998

Scrap metal 1,690

Tires 1,554

Total 236,141

The results in Table 4 are even more impressive when one considers that San Leandro is inAlameda County. If we compare the numbers in Table 4 with those in Table 1 above, we seethat resource recovery parks are serious business: the park diverted 15 percent of the Countyswaste. However, resource recovery parks often need help from local government, in the form ofamenable zoning, promotion, and financial assistance.

Other Strategies

The New Zealand Trust is an organization dedicated to making New Zealand produce no netwaste by 2020 (the Zero Waste campaign). They have developed several other waste reductionstrategies. These strategies are not necessarily within the responsibility or authority of

engineers, but they are noteworthy nonetheless.

Deconstruction Standards

Create guidelines and standards for deconstruction ofbuildings to ensure maximum capture ofreusablematerials.

Low Interest Loan Fund

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Establish a low interest loan fund for businesses developingsystems and new uses for recoveredmaterials.

Resource Recovery Infrastructure

Ensure that every wasting opportunity at home, in thestreet or in the factory is matched by, orreplaced with aresource recovery opportunity. Make resource recoveryvisible, accessible, andmore convenient than otherwaste disposal options.

Stockpile Resources

Ensure that every landfill or transfer station has sufficient storage space available to stockpileresources until buyers are found. In some cases mono filling would be appropriate.

Separate at Source

Establish mandatory wet/dry separation at source.

Extended Operator Liability

Operators are responsible for long term environmental effects of waste disposal facilities(landfills, incinerators etc).

Grant Programs

Provide funding for start-up projects and community education initiatives that promote low-

waste measures but that have difficulty finding funding.

Community Education Programs

Develop community education campaigns that helpeveryone to participate in waste reduction.

School Education Programs

Develop resources for schools to teach waste minimization.

Training and Research

Support the establishment of a waste reduction sector, to design and test new technologies andresearch new materials andprocesses.

Measurement and Monitoring

Implement formal measuring and monitoring systems to enable measurement andmanagementof progress towards waste reduction targets.

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Community Ownership of the Waste Stream

Give private and non-profit enterprises in the recyclingand resource recovery industry access tothe wastedresource stream.

Facility Standards/Permits

Create standards for resource recovery and recycling facilities that would be part ofspecifications for contractsand would also give the public confidence to use thesefacilities.

Materials Exchanges

Create a network of materials exchanges to enable industry to feed off each others waste

products.

Recycling Targets for Businesses

Challenge business to excel in recycling throughmandatory recycling targets.

Grants/Tax Incentives

Provide support for industry to use recycled materials in new and existing products throughresearch and development grants and tax incentives.

Branding Systems for Low Waste Businesses

Develop criteria for low waste businesses that, if meeting the set criteria, would be able todisplay arecognized brand. This brand could be similar to the well-known recycling symbol.

Packaging Levy

Establish a minimum packaging levy on all nonbiodegradable and non-reusable packaging.

CONCLUSION

Solid waste is still our third pollution. Managing it and especially reducing and minimizing its

generation should be a goal of everyone. Engineers in particular have a role in wasteminimization because of both their involvement in producing waste and their leadershippositions in waste management and disposal. Tackling the solid waste problem is a multi-faceted task, and this course was intended to provide engineers with an understanding of thesolid waste situation in the US today and a glimpse into the numerous and diverse wasteminimization and reduction strategies they can implement.

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