Sean Edward Paquette SHWPCE Exam April 7, 2014 Problem 1

Sean Edward Paquette SHWPCE Exam April 7, 2014

Problem 1

A new housing development will accommodate 10,000 people in a suburban location somewhere in the North East region of the USA. A component of the development plan concerns the proper management of the solid waste produced. For planning purposes, assume a “typical” waste stream composition (e.g. Table 2-3; Fig. 4-2, text). A new landfill with a life of 30 years will be built for the disposal of refuse. The developers are also considering the possibility of building a waste to energy plant.

Estimate the total amount and composition of the refuse generated by the inhabitants of the new development each year.

I estimated the total amount and composition of the refuse generated by the inhabitants of the new development using two different methods. The first method (Red) I used the actual 2008 US population and ratio the new housing development of 10,000 people for an estimated 8,187 tons (18,338,026 lbs.) of refuse and a composition illustrated in the below table. The second method (Blue) I assumed an average 4lbs. of waste per person per day and used the given composition percentage below to calculate the new composition. Method #2 (Blue) estimated a total of 6,524 tons (14,614,600 lbs.).

Therefore, to conclude with a more accurate estimate I averaged the two methods together, the result is identified in the right column, highlighted in yellow.

RPI Spring Semester 2014 Sean Edward Paquette


Problem 2


If waste diversion is zero and no waste to energy plant is built (i.e. all waste originally generated goes to the landfill), how many trucks are needed to collect the trash in no more than an eight-hour shift?

The total number of trucks needed to collect all the trash for 10,000 citizens in no more than an eighthour shift is 13, this assumes one day of trash for 10,000 citizens. There are two factors to examine for this problem, the first is transportation time and the second is truck capacity. For, this problem I have calculated each truck can hold a maximum of 10,000 lbs. although I am only filling each truck to

3,521lbs. This is only because the volume of customers needed to be served in a given day. Each truck can only service 780 customers. A potential area of economic savings for the city would be to research replacing the 20 yd³ trucks with smaller more fuel efficient vehicles. If time was not a factor, you could fill the trucks full and only need 5 trucks.



Problem 3


For zero waste diversion and no waste to energy plant: a.

Estimate the size and shape of the landfill required

The landfill is a ramp method/layout. This landfill is a square landfill with the following dimensions: 60ft deep; 472ft wide; 472ft long with a total capacity of 494,289.38 yd³ and an expected lifetime of 30 years services a community of 10,000 people. The landfill design also has a compaction density of 1,200 lbs/ft³ and a soil covering of 20% yearly refuse.



Problem 3

A new housing development will accommodate 10,000 people in a suburban location somewhere in the North East region of the USA. A component of the development plan concerns the proper management of the solid waste produced. For planning purposes, assume a “typical” waste stream composition (e.g. Table 2-3; Fig. 4-2, text). A new landfill with a life of 30 years will be built for the disposal of refuse. The developers are also considering the possibility of building a waste to energy plant. b.

Estimate then the amount of leachate produced and the pipe spacing in the leachate collection system

The estimated leachate produced is 7,146.68 gallons/day or 27,053.12 liters per day. The estimated distance between pipes in 0.74m



Problem 3

A new housing development will accommodate 10,000 people in a suburban location somewhere in the North East region of the USA. A component of the development plan concerns the proper management of the solid waste produced. For planning purposes, assume a “typical” waste stream composition (e.g. Table 2-3; Fig. 4-2, text). A new landfill with a life of 30 years will be built for the disposal of refuse. The developers are also considering the possibility of building a waste to energy plant. c.

Estimate the amount the landfill gas generated as a function of time and the total pressure drop required to keep the gas flowing out of the landfill when using a 6in. diameter PVC pipes.

The estimated amount of gas generated after 30 years is 1,240,251 m 3 . See problem 3d under total

amount of gas produced after 30 years. The flow rate of gas generated as a function of time is 62.71 ft/sec with the assumptions stated below. The pressure drop is 0.029 feet, based on the identified assumptions below.



Problem 3

A new housing development will accommodate 10,000 people in a suburban location somewhere in the North East region of the USA. A component of the development plan concerns the proper management of the solid waste produced. For planning purposes, assume a “typical” waste stream composition (e.g. Table 2-3; Fig. 4-2, text). A new landfill with a life of 30 years will be built for the disposal of refuse. The developers are also considering the possibility of building a waste to energy plant. d.

Estimate the maximum amount of energy that can be produced by burning the methane in the landfill the gas with 40% efficiency. The typical energy consumption rate per capita in the US is 350 GJ/yr.; What fraction of the energy needs of the community can be provided by the combustion of the landfill gas.

The maximum amount of energy that can be produced in the landfill totaling 30 years is 12.18 GJ.

The fraction of the energy needs of the community that can be provided by combustion of the landfill gas over a time frame of 30 years is 0.12%.





Problem 4

Assume instead that the community decides to impose mandatory waste segregation at the household level in order to achieve 100% diversion of ferrous and non-ferrous metals, glass, paper products and plastics but no waste to energy plant is built. a.

If the trash is collected weekly by two separate collection trucks (one for the diverted stream and another one for the rest of the refuse), how many trucks are needed to collect the trash in no more than an eight-hour shift?

Highlighted in purple is the total yearly refuse diverted and highlighted in yellow is the remaining refuse.

The total number of trucks needed to collect the diverted stream refuse for 10,000 citizens in an 8-hr period is 13 trucks. Furthermore, the total number of trucks needed to collect the remaining refuse for

10,000 citizens in an 8-hr period is 7 trucks. Therefore, the total number of trucks to pick up a total refuse collection for 10,000 citizens is 6 trucks. Again, the limiting factor is the 8-hr time frame, this makes it very hard to fill an entire 20 yd³ truck with the recycle crew requiring 2 minutes per stop and only servicing 4 customers.



Problem 4

Assume instead that the community decides to impose mandatory waste segregation at the household level in order to achieve 100% diversion of ferrous and non-ferrous metals, glass, paper products and plastics but no waste to energy plant is built. b.

Estimate the economic value of the diverted waste:

The economic value of diverted waste is the profit generated when the waste is recycled rather disposed in landfill and incinerators. When waste is improperly disposed and not recycled, the embodied energy and natural resources are lost. Therefore, when recycled, material is saved, disposal costs are reduced, energy is generated and new recycle based jobs are created. The market value is calculated by multiplying the commodity prices by the quantity of recycled material. The diverted refuse in problem 4 is paper, glass, ferrous metals, other non-ferrous metals and plastics. The economic value of the diverted waste is $1,054,920.00 per year assuming a total of diverted waste of 9,045,496 lbs. Assumptions on price per pound are listed below.



Problem 4

Assume instead that the community decides to impose mandatory waste segregation at the household level in order to achieve 100% diversion of ferrous and non-ferrous metals, glass, paper products and plastics but no waste to energy plant is built. c.

What would be the increase in the life of the landfill as a result of the diversion?

The increase in the life of the landfill as a result of diversion is 36.5 years.



Problem 4

Assume instead that the community decides to impose mandatory waste segregation at the household level in order to achieve 100% diversion of ferrous and non-ferrous metals, glass, paper products and plastics but no waste to energy plant is built. d.

Estimate the maximum amount of energy produced by burning the methane in the landfill the gas with 40% efficiency. What fraction of the energy needs of the community can be provided by combustion of the landfill gas?

Refuse decomposes in the landfill, creating methane gas which rises to the top of the landfill and is collected in pipe. The methane is then burned to generate electricity. The maximum amount of energy that can be produced in the landfill totaling 30 years is 5.5 GJ. The fraction of the energy needs of the community that can be provided by combustion of the landfill gas over a time frame of 30 years is

0.05%.





Problem 5

Finally assume that besides the mandatory waste segregation porgam a waste to energy plant is built and that the recovered paper products and plastics in the diverted streams are combines with the rest of refuse to produce shredded RDF. a.

Estimate the economic value of the diverted waste without the paper and plastic

The economic valie of the diverted waste without the paper and plastic is $273,002.10.



Problem 5

Finally assume that besides the mandatory waste segregation porgam a waste to energy plant is built and that the recovered paper products and plastics in the diverted streams are combines with the rest of refuse to produce shredded RDF. b.

Assume the particle size distributions of the raw feed and the shredded product are as in

Figure 5-25 in your text and use the Bond work index method to estiamte the yearly shredding energy requirements to produce the desired RDF



Problem 5

Finally assume that besides the mandatory waste segregation porgam a waste to energy plant is built and that the recovered paper products and plastics in the diverted streams are combines with the rest of refuse to produce shredded RDF. c.

Estimate the amount of air required for combustion of the RDF (with 100% excess) and the amount of energy produced. What fraction of the energy needs of the community can be provided by combustion of the RDF with 40% effieiceny



Problem 5

Finally assume that besides the mandatory waste segregation porgam a waste to energy plant is built and that the recovered paper products and plastics in the diverted streams are combines with the rest of refuse to produce shredded RDF. d.

What would be the increase in the life of the landfill as a result of diversion and waste to energy conversion? Assume that the ash goes to the landfill

The life of the landfill increases only by 4.05 years from the original 30 year expected life.



Problem 6

Which of the three alternatives would you recommend and why?

Based on the three options proposed in this exam, (Option 1) the zero diversion and no waste to energy plant, (Option 2) a mandatory waste segregation at the household level in order to achieve 100% diversion of ferrous and non-ferrous metals, glass, paper products and plastic but on waste to energy plant is built and finally (Option 3) a mandatory waste segregation program a waste to energy plant is built and that the recovered paper products and plastics in the diverted streams are combined with the rest to produce RDF, I would select Option 2. I selected (Option 2) a mandatory waste segregation at the household level in order to achieve 100% diversion of ferrous and non-ferrous metals, glass, paper products and plastic but on waste to energy plant is built because you increase your landfill life by 36 years and an economic value addition to the city’s budget of about $1 million dollars per year due to the household level segregation program. This additional money can go to public improvements or private incentive program for recycling and reusing refuse. Option 3 was a consideration about the yearly economic value wasn’t as large and it was cost addition money to build and maintain a waste to energy plant. With Option 2 the city can set a goal and allocate money to funding a future waste to energy plant.


Sean Edward Paquette SHWPCE Exam April 7, 2014 Problem 1

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