Page 387 - Materials Chemistry, Second Edition

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358 Waste Management Practices: Municipal, Hazardous, and Industrial
A.10.1.2.2 Forecasting Landfill Emissions
To predict emissions of landfill gases, you have to select the model parameters, identify the length
of operation of the landfill, enter the MSW in place or the acceptance rates of MSW, and generate
a report.
Length of Operation: Specifying the length of operation of the landfill can be more complicated
when forecasting emissions. If precise years of operation (e.g., 1960, 1990, and 2005) are known,
they can be entered for the time variables (e.g.,Year Opened, the Current Year, and the Closure Year)
and the model functions normally. However, when precise dates are not known, the length of oper-
ation of the landfill can be specified with generic year numbers, such as 0001 (Year Opened), 0015
(Current Year), and 0016 (Closure Year).
Landfill Capacity: The model algorithms require that a design capacity be entered prior to enter-
ing yearly MSW data, i.e., even for a landfill not yet in operation, the total landfill capacity must be
specified before any other information about the MSW in the landfill can be entered. The MSW
estimator may be used to determine the landfill capacity from estimated landfill dimensions.
Landfill Waste: For each year of operation, the amount of landfill MSW must be entered as
either a MSW in place or an acceptance rate. For years in which no such data are available, esti-
mates must be provided. The Autocalc function can assist the user in entering estimates for years in
between those in which MSW acceptance rate or the amount of MSW in place is known.

A.10.1.2.3 Emissions Forecasting Example
In the current situation, only partial MSW data are available for a number of years in the life of the
landfill. You need to estimate emissions for a landfill which has a capacity of 6,800,000 Mg and
opened in 1957. The current year is 2003, and in 2002 the landfill was at half capacity (i.e.,
3,400,000 Mg). You have MSW data for each year between 1965 and the current year, but no data
before 1965. Your data show that, from 1965 to 2002, a constant rate of 80,000 Mg/year of MSW
was accepted by the landfill. You need to estimate emissions for the life of the landfill to determine
applicability with MSWLF regulations. This landfill has no co-disposal and is scheduled to close in
the year 2015.
To begin, enter the Year Opened (1957) in the box on the command bar. Then enter the Current
Year (2003) in the adjacent box, and input the landfill capacity specified (6,800,000 Mg) in the
Landfill Capacity box. Applicability to landfill regulations needs to be investigated; therefore, the
CAA default parameters should be used. Under the Defaults menu, select the CAA item. Under the
Parameters menu, indicate, with a check mark, that No Co-disposal is selected.
To input the Acceptance Rate data from 1965 to 2002, the Autocalc function from the Edit menu
can be used. Move the cursor to the acceptance rate cell for the year 1965. Input 80,000 Mg/year in
the Acceptance Rate box on the command bar. Move the cursor to the cell for the acceptance rate
in 2002. Enter 80,000 Mg/year in this cell as well. Then highlight all the cells between and includ-
ing 1965 and 2002. The Autocalc function will input the value 80,000 Mg/year into the Acceptance
Rate column for each year between 1965 and 2002.
Examine the MSW in Place value for 1995. How much waste has accumulated in the landfill to
this point?
As of 2002, however, we know that the landfill was at half capacity. Therefore, the waste
entered between 1957 and 1964 must total 3,400,000 – [value for 2002] ___________ Mg. We
will assume that the MSW accepted was evenly distributed between 1957 through 1964.
Enter the remaining data necessary to run this scenario with the Autocalc function. Begin by
entering the waste accumulated between 1957 and 1964 (i.e., the difference calculated above, in
Mg) in the MSW in Place cell for the year 1965 (the year in which any waste accepted in 1964
would appear as accumulated waste in the landfill). The waste acceptance rate for 1964 will now
appear to be this missing value. These data will be adjusted with the next step.