Design for the Environment/Disposal of Non-Recyclables

Non-recyclable waste are solid waste which are not processed nor reclaimed by a city's waste management system. The disposal of these materials are a rising concern in many parts of the developed world where environmental alertness has been a rising trend; This a particularly important issue in the City of Toronto where a long-term waste management solution is not well defined.

For nearly two decades, the Keele Valley Landfill in Maple, Ontario has been the main landfill site for the City of Toronto, after having received more than 26 million tonnes of waste and reaching maximum capacity, it closed in 2002 . Since then, Toronto has been sending its waste across the boarder to Carleton Farms Landfill in Michigan. From January to August 2007, an average of 2070 tonnes of solid waste per day was redirected from Toronto to Michigan . In April 2007, the City of Toronto acquired the Green Lane Landfill Site southwest of London, Ontario in anticipation of the contract expiration with Carleton Farms Landfill .

However, the acquisition of the Green Lane Landfill site has several major environmental, economic and social-political repercussions . In this article, the environmental, economical and societal impacts of Landfilling will be compared to Waste Incineration and Plasma Arc Gasification in hopes of finding a suitable alternative for Toronto's waste disposal of non-recyclable waste.

Carleton Farms Landfill
The Carleton Farms Landfill (Sumpter Energy Associates) in Sumpter, Michigan is currently the reciepient of almost 700000 tonnes of waste per year from the City of Toronto. This facility houses a methane recovery system to recapture and use landfill gases as an energy source; In 1998 when plant operations began, five Caterpillar 3516 engine generator produced 4 megawatts of power, In  1999, two more generators sets were added expanding power generation to 5.6 megawatts. In 2001, a third set of generators were added, boosting power production to 6.4 megawatts - approximately equivalent to the demands of 7000 homes and businesses .

Landfills are not aesthetically pleasing to surrounding communities due to strong odours emissions as well as noise created by the trucks; they also release excessive amounts of Methane, a Greenhouse Gas that is damaging to the environment.

Functional Analysis
The primary function of the landfill, as defined by the Canadian Oxford Dictionary is "the disposal of refuse by burying it under layers of earth.". This implies a permanent solution to the issue of what is to be done with the waste. Toronto views landfills as a solution for permanently handling the City’s current waste production, but it is not sustainable as a long-term solution.

As said before, one benefit of using landfill waste disposal is the ability to produce electricity for sale back onto the public Power grid. The methane gas which escapes from far under the surface of the landfill is collected via an intricate system of closely monitored pipes and sent to one of several engine generator sets run by Sumpter Energy Associates located at the Carleton Farms Landfill site. It was recently published that this generating station is capable of producing 6.4 MW of power, with production expecting to be up to 12 MW in the future.

Economic Input/Output Lifecycle Assessment
The EIOLCA displays a diverse view of the environmental impacts which an alternative may have on a society. In carrying out this analysis, it was necessary to determine all of the economic inputs that are made towards the five lifecycle stages of the landfill.

The most significant of these costs is incurred in transporting the garbage from Toronto to Michigan, and then returning the trucks back to Toronto again to collect the next shipment. Aside from being the largest annual cost associated with landfilling Toronto’s non-recyclables in Michigan, this is also one of the greatest contributors to the environmental unfriendliness of this waste handling alternative. At a cost of ~$3.8 million for the diesel required to make this trip, trucking the trash to Michigan creates 8300 MTCO2E (Metric Tonnes of Carbon Dioxide Equivalent) of greenhouse gases, 1020 kg of releases, and uses 93.1 TJ of energy.

In order to reduce the environmental impact of the waste management system, Toronto must adopt an alternative near or around the Greater Toronto Area to save on fuel consumption. It is for this reason alone that incineration and plasma gasification are very plausible alternatives to landfilling.

Also vital to the successful operation of any modern day landfill is the methane gas collection system. Not only does this entity ensure that the landfill meets local environmental regulations, it is also a means for creating revenue for the private corporations who have a vested interest in the landfill as a money making tool. The total environmental impact of the methane collection system, considering its implementation as well as use, is tallied at 5000 MTCO2E, 14000 kg of releases, and 16000 TJ of energy usage. These results are perhaps skewed due to the EIOLCA model’s inability to handle this economic activity entirely in one sector. As such, this system was grouped into the Water, Sewage, and Other Systems sector, which deals predominantly with water treatment. For the scope of this article, however, the activities in this sector are assumed to be analogous to those related to the operation and maintenance of the methane collection system.

Any “engineered landfill” is one which contains a sophisticated arrangement of materials lining the very bottom of the landfill. The purpose of this is to prevent Leachates from escaping into the Groundwater running beneath the landfill. Given that the State of Michigan has published very little on its regulations and standards, other standards were used to gauge what is generally considered typical - This includes a minimum hydraulic conductivity of 10-8 cm/s. A generally accepted way of achieving this is to use a landfill comprised of clay, a plastic liner, and finally a layer of sand . The plastic in this case is assumed to be 2mm low-density polyethylene. The combined effects of the three layers of the liner are 2600 MTCO2E, 650 kg of releases, and 40 TJ of energy.

Also of interest is the toll that the liner takes in decreasing the rating of this waste disposal method. A much better and more environmentally friendly alternative would be to use recycled automobile tires as a primary component of the leachate collection system. Tests have demonstrated that high quality (HQ) shredded tires have average Hydraulic Conductivities spanning a range from 0.67 to 13.4 cm/s. Given that the standard for Toronto’s Keele Valley Landfill was maintained at a strict minimum of 10-8 cm/s, recycled tires are not a be-all and end-all solution, however would provide great relief to the amount of clay that is currently required to line a site. At a GWP MTCO2E of 2280, this is the third highest contributor to the landfilling process as a whole, and therefore it would be highly advantageous to be able to reduce this impact to the environment. Upon consideration of these, the most predominant contributors to a landfill’s pollution, it becomes much clearer why alternatives must be investigated. A landfill not only is a place of concentrated gas releases, but also triggers economic activity in many other highly polluting sectors. An ideal solution is perhaps one which utilizes the garbage more effectively, and more appropriately handles it before being left for its final resting place.

Streamlined Lifecycle Assessment
The Streamlined Lifecycle Analysis offers an alternative method of comparing alternatives based on a relative ranking of various factors throughout the product’s life. In comparing SLCA rankings of Carleton Farms Landfill to incineration and plasma gasification, landfill ranks the lowest. This owes in large part to the high energy usage required in the primary stage. This stage includes shipping the garbage to Michigan, as well as operation of the methane gas collection system and daily garbage collection and on-site compacting.

Also contributing heavily to the low score are the solid and liquid residues associated with the primary and secondary process operations. These results parallel those demonstrated in the EIOLCA, which shows consistency as well as reaffirms the accuracy of the results demonstrated here.

Unlike the end of life stage of an incineration plant or a gasification plant, the end of life of a landfill does not equate to the cessation of different releases. Many solid, liquid, and gaseous residues continue to be emitted. For this reason the total End of Life stage of the landfill score a three.

To further increase this rating, it would be most beneficial to reduce the energy inputs required to perform the primary process operations. Mainly the garbage transport from Toronto to Michigan.

Societal Analysis
A landfill’s impact on society is apparent immediately upon entering into its vicinity. As Michigan residents have complained, the smell of Toronto trash fills the air as soon as the trucks start to come in for the day. This dilemma is inherent in operating a landfill, and little may be done to contain the problem. Although the methane collection system is a step in the right direction and trucks are sealed to contain odorants, the trash is still crossing the border, and continues to have noticeable impacts on residents of Michigan and southern Ontario Another issue of the particular system utilized by Toronto is that the waste matter must be transported such a long distance before arrival at its final destination. This has Michigan officials exasperated because of the added traffic creating congestion and adding extra pollutants to their air.

Landfills also affect the property values of nearby homes and businesses. A recent study on the issue in Toronto indicates that “larger landfills have greater adverse impacts on property values than smaller landfills, implying consumers perceive ... differences in external costs.” This may also be a function of the amount of waste that the fill handles, with a larger one being perceived as a more pronounced nuisance. Also important to note is that the larger a landfill, the longer it is likely to be open for, and this will also hinder the ability of the society to develop in that area.

In general, landfills have a significant impact on society, although once closed, these impacts become hardly noticeable and therefore make it a humble contender as a method for dealing with the disposal of non-recyclable materials.

Cost Analysis
For the purposes of this section, all costs are calculated on an annual basis. Therefore, one-time costs are divided by the thirty year expected useful life of the landfill. As an example, we shall consider the end of life costs of the landfill. These are one time costs, and their total is $10,500,000. This number was divided by the thirty years, and then the time value of money was accounted for, thus determining the equivalent payment in 2008 dollars required annually while accounting for the rate of inflation.

The costs of a landfill derives from much more than the immediate monetary considerations; much of the costs incurred by a landfill comes in its later stages of life. The Mackinac Centre for Public Policy suggests that companies invest between $750,000 and $1 million per acre to meet state and federally imposed regulations

The equivalent annual cost for operation of a landfill is approximately $9 million. Once again this cost is highlighted by the estimated $2 million required for operation and maintenance of the methane collection system. Other operational costs are, for the most part, limited to diesel fuel consumption and electricity consumption. Given that this landfill is so large, the costs associated with it are quite significant. However, when amortized over several years they become much more manageable figures.

Waste Incineration
Waste incineration is the removal of waste via combustion using high temperature furnaces. Modern waste incinerator utilizes Cogeneration as well as Waste to Energy (WtE) technologies where electricity is produced from the incineration process. In our discussion, a WtE incineration will be assumed for the City of Toronto.

To begin the incineration process, the waste is brought into the facility via trucks to the tipping floor where large and recyclable objects are removed by the workers . Waste that is now suitable for incineration is then loaded into a two-stage incinerator where it is combusted. Gases released from the primary combustion process are transferred to a second stage chamber where they are further refined to produce large amounts of heat. This heat is captured using a recovery boiler that produces steam which in turn drives a turbine to produce electricity . During combustion of the waste, ash is produced and is collected from the incinerator and transferred to a landfill .

The use of waste incineration is discouraged by environmentalists due to high CO2, Dioxin and Furan emissions. Steam vapour from plant smokestacks is also an aesthetics concern to some.

Functional Analysis
Incineration waste disposal is not only the simple task of burning garbage, major considerations must be made when choosing the type of incineration facility to be built since valuable energy can be harvested through the waste combustion process. In this article, an Energy from Waste (EFW) or Waste to Energy (WtE) facility will be assumed for the City of Toronto.

In the WtE waste incineration process, garbage which had been screened for any large objects are combusted at high temperatures; Any ash solids remaining from combustion are then collected for landfilling while fuel gases from incinerating waste are further combusted to heat boilers. The steam produced from the boilers are then used to drive turbines to produce electricity which can be used internally at the facility or sold back to energy providers.

Modern incineration facilities are outfitted with emission filtering systems and cleaners to reduce the pollutants that are released into the air. These systems greatly reduce the NOx, SO2, particulates, etc, released into the environment. Unlike the landfilling of untreated waste, incineration greatly reduces the volume of the waste produced, resulting in a more efficient use of landfills (only the incineration ash is landfilled).

Cost Analysis
Based on estimates from 2006, the City of Toronto had produced about 1 million tonnes of waste where 70% of that value were non-recyclables. As the City has proposed to diverge 60% - 70% of the total waste produced to be recycled, the cost analysis was performed assuming 400,000 tonnes of waste was to be incinerated in the future.

Estimation of plant/facility costs were based on the proposal of an incineration facility in the Durham/York Region. The estimated total construction cost to erect a plant capable of processing 400,000 tonnes of waste per year was $250 million. The operation cost of a waste incineration plant is high compared to a landfill, working out to be approximately $76 per tonne of waste. This gap can be reduced by accounting for the elimination of the transport fees to the Michigan landfill from Toronto.

A major cost benefit of waste incineration is the resale of power generated by the facility, WtE incineration plants generate approximately $12 million of power per year.

Societal Analysis
The societal impacts of a waste incinerator are profound. Waste incinerators smokestacks are not very visually appealing to the neighbours of such a facility, and their downwind odour emissions are not very pleasing. As such, incineration plants will have to be built outside of the City of Toronto. But as the city continues to expand, location finding becomes more and more difficult, it is not easy to find a convenient site for such a plant that is also isolated from any large communities nearby since the public tends speaks out against the use of waste incinerators.

Streamlined Lifecycle Assessment
Even though the streamline life cycle assessment (SLCA) does not look into the alternative of incineration in depth, it does provide a quick way for the ranking of different waste disposal alternatives. On the SLCA, Incineration scored lower than Plasma-Gasification and higher than landfilling.

The SLCA also provides a way to identify an alternative's shortcomings and benefits in each life stage. For the incinerator, high gaseous emissions and high energy use resulted in an general overall low score for the incineration alternative. This is because high temperatures must be maintained to allow for complete combustion of the waste to occur, and this requires a lot of energy. Also, the combustion of garbage emits large amounts of pollutants, thus a low score for the gaseous resided is rewarded.

Economic Input/Output Lifecycle Assessment
The waste management sector is a major user of energy from many different sources. This value is comparable to the low score awarded in the SLCA. Also the amount of carbon dioxide (CO2) and other Greenhouse Gases released by the waste management sector is very high. The most important figure found by completing this assessment was the Global Warming Potential (GWP). The waste management sector contributed to more than 93% of the total GWP, where it releases 4,390,000 metric tonnes of CO2 equivalent.

The values found in the EIO-LCA corresponded with similar low scores in the SLCA. This help to reinforce the understanding of the incineration process and how it contributes positively and/or negatively to our environment. But because there is no way to compile a fully comprehensive EIO-LCA it is hard to decide definitively whether incineration is the best alternative to land filling.

Plasma Arc Gasification
Similar to WtE incineration, Plasma Arc Gasification takes advantage of the abundance of potential energy in garbage; Plasma Gasification is an incineration process with an excellent energy recovery ability, it makes use of high electrical energy and high temperatures to break down waste into organic gases and inorganic solids . If accurately managed, processing waste at plasm temperatures can very well be a greener solution to traditional incineration and landfills. Although still in its early development stage , Plasma incineration has already shown to have many advantages over traditional forms of waste removal.

The main benefits of Plasma Arc Gasification is its ability to convert all of its gaseous by-products into electricity and its solid by-products into construction materials, creating a nearly zero-emission conversion process. However, as we will see later, Plasma Gasification is not a flawless solution.

Technical Analysis
The largest benefit of using Plasma Gas Gasification is the reduction of environmental impacts. By separating waste matter into individual ions at very high temperatures, there is minimal formation of solid residues - about 60 times less than a conventional incinerator. In addition, instead of creating ash as a solid by-product, there is the formation of valuable metals and Slag; Furthermore, plasma incineration produces a beneficial gas product known as Syngas which can be refined into a fuel to produce energy.

On average, a Plasma Incinerator plant can burn 75,000 tonnes of municipal waste per year, generating a total of 7.9 MW of power (3.6 MW to the grid).

Economic Input/Output Lifecycle Assessment
The air polluting outputs from a Plasma Gasification Plant are relatively low because the gasification process does not involve combustion, thus the process does not generate as much pollution as a regular incineration plant. However, according to the EIOLCA, the “Waste management and remediation services” sector contributes to much of the Methane releases from the plant - accounting for about 33100 metric tons a year of CH4. However, syngas is created from synthesizing CH4 and H2O, according to this equation:


 * CH4 + H2O → CO + 3 H2

Negating the effects of much of the methane release.

A Plasma Arc Gasification plant that processes 75000 tonnes of waste releases 35800 kg (35.8 tonnes) of toxic waste a year - less than 0.001% of the total waste processed.

Streamlined Lifecycle Assessment
The chief benefit of Plasma Gasification is its ability to provide self-sustaining power while supplying power to the grid, as such, the energy sector of the SLCA for Plasma Gasification process receives a perfect score. Another perfect score was given to the liquid residue section, due to the extreme heat of the process, there is no possibility of liquid formation. Also, most of the solid and gas residue generated by a plasma incinerator are beneficial.

The plant maintenance process is very energy consuming due to the strict operating standards for a Plasma Gasification plant, a careful filtering process is required to purify the solid and gaseous byproducts in order to minimize the toxic release into the environment. Thus, the energy use sector for the maintenance life stage has a relatively low score, but due to this careful filtering process, an insignificant amount of gases and solids are released into the environment, granting a perfect score for the gas and solid residue sectors.

Cost Analysis
Recent studies claimed that:

Compared to a landfill which charges only around $35 per tonne of waste, it would cost about $172, per tonne, to dispose garbage at a plasma incineration plant.

Plasma Gasification is not a cheap alternative to traditional landfilling or incineration. The maintenance costs of a plant that incinerate 75000 tonnes of waste is almost $150 per tonne, such a plant will also require an additional $115 dollars for the collection and transportation of the waste, plus roughly $25 per tonne for miscellaneous and overhead costs. This would results in an average of $290 per tonne of Municipal Solid Waste equivalent to $21.75 million per year of operational costs.

For the City of Toronto, a Plasma Arc Gasification plant will cost $1.452 billion (at 5% interest, compounded yearly, over 40 years) to build, operate and decommission at the end of 40 years. The accumulated revenues from to electricity and slag sales will recover $176.6 million. Thus to break even, the plant must charge an extra $355 per tonne of waste. Such expenses make it almost impossible for a city to implement Plasma Arc Gasification as a waste disposing alternative. This is the greatest disadvantage of a Plasma Incineration energy plant. However, with further upscaling of this technology and the rising electricity prices; Plasma technology may become affordable and feasible.

Societal Analysis
A Plasma Gasification plant has the lowest environmental impact out of all three alternatives. Site location for the plant is also quite easy due to the small size of these plants. This alternative has the same societal impact on neighbouring communities as traditional incinerators.

Recommendations
Incineration and Plasma Gasification are just two of the many countless alternative solutions to landfills. When designing for the environment, the most important factor is the impact that a design has on the environment; it was determined from above that plasma gasification had the most potential because it can efficiently remove waste and generate energy at the same time, however, it was also determined that plasma gasification is also the most expensive option, rendering it ineffective by current standards.

Comparing between landfills and incinerators, it can be seen that landfills have less environmental impacts throughout its implementation and operation stage, however, its impact on the environment continues long after its end of life - Whereas an incinerator’s effects on the environment halts almost immediately after its end of life.

The City of Toronto should continue to use the Carleton Farms Landfill until the end of the contract, while using the time between then and now to research on a more efficient Plasma Gasification process, since in order for Plasma Gasification to be adopted, more research on Gasification technology must be done. The city should avoid building an incinerator since it does not make sense to build an incinerator now; just to render it obsolete once a plasma gasification plant comes about.