INTEGRATED STRATEGY EXAMPLE: YARD WASTE COMPOSTING WITH LANDFILL

To illustrate the application of the data on technologies to the evaluation of options for an integrated MSW management strategy, this section summarizes the energy balance and air and water emissions for:


                             Table 8.4
        TRACE ELEMENTS IN SOILS AND MSW COMPOST
            (Parts per Million)

                                              Proposed U.S.     Proposed European
    Element      In Soil(a)    In Compost(b)    Standards    Community Standards(c)
Cadmium                0.06           3.4 (2.3-7)           18                   1
Chromium             100            223 (159-828)         2000                  30
Copper                20            285 (190-912)         1200                  40
Lead                  10            496 (348-1250)         300                 160
Mercury                0.03           4.0 (0.6-5.9)         15                   0.5
Nickel                40             77 (39-709)           500                  10
Zinc                  50           1008 (596-1370)        2700                 240

(a) Source: Bowen, 1966.
(b) Samples of Fairgrow (from MSW), Appendix G [752].
(c) Source: Hammer, 1992.

Click here for table in WK1 format.


Table 8.5 shows the energy and emissions over a 20-year period from adding curbside collection of yard waste for composting to landfilling alone. The estimates in the table include energy and emissions for normal collection of MSW, the emissions and leachate from the landfill, and the energy recovered from the landfill gas, along with the energy and emissions for collection and transportation of the yard waste and for composting. The results are separated into transportation, processing (composting), and disposal (landfilling the remainder). Table 8.6 presents the same data for the landfill strategy.

Detailed data on yard waste programs are extremely limited. The data used in Table 8.5 were collected by SRI International from community officials of an affluent residential/commercial community in California (City of Palo Alto, 1991). The data should be considered illustrative only; additional examples are needed to draw reliable conclusions.

Although the community has conducted an active program of curbside collection of recyclables for more than 12 years, its yard waste composting program has been operating for only a year. The program operates year round, and because of the mild climate in the area, seasonal variations in quantities collected are not great.

Because of the extensive transportation requirements, the net energy balance for the integrated strategy that includes yard waste composting is a loss. The energy recovered from the uncomposted landfill does not quite offset the fuel use. Air emissions are also higher for the yard waste strategy than they are for landfilling alone.

Energy requirements and air emissions depend on the efficiency of truck use. The factors that influence truck use efficiency include:

The program has high air emissions and large energy requirements per ton of waste because the small quantities of yard waste set out for collection result in inefficient use of trucks. A single stop for MSW at each location produces lower emissions than many separate stops for smaller loads. If trucks are not filled before they return to the landfill, additional inefficiency is incurred. For curbside collection of yard waste, the community uses its largest trucks because they have compacting mechanisms, but they are rarely more than 25% full when they complete their extended routes and return to the landfill. As a result, truck emissions per ton of yard waste collected are up to 30 times the rate for collection for landfilling alone. Clearly, programs that collect larger quantities of yard waste per trip would have dramatically lower emissions per ton.

Details of the calculations used to obtain estimates of emissions and energy consumption are presented in Exhibit II. The computerized version of the data base allows a user to change the collection amounts and the measures of collection efficiency used in this report, and to enter the actual miles traveled.


                                    Table 8.5
                 ENERGY AND EMISSIONS FOR STRATEGY 5:
              YARD WASTE COMPOSTING PLUS MSW TO LANDFILL

                                 Total   Collection   Process  Disposal
Landfill space (assuming a depth
of 50 ft), 10(-5) acres                1.93                                1.93
Solid waste (lb)                       1928                                1928
Energy Required (million Btu)          2.33        2.33       0.003       0.002
Energy Produced (million Btu)          2.12        0.00        0.00        2.12
Net Energy (million Btu)              -0.211      -2.33       -0.003       2.12

Air Emissions
Particulates (lb)                      0.46        0.46
Carbon Monoxide (lb)                  23.24       23.24
Hydrocarbons (lb)                      2.32        2.32
Nitrogen oxides (lb)                   9.30        9.30
Carbon dioxide (lb)                    421                                 421
Water (lb)                             180                                 180
Methane (lb)                          13.82                               13.82
NMOC (lb)                              0.72                                0.72

Dioxin/furan {10(-6)lb}
SO(2) {10(-3)lb}
HCI {10(-3)lb}

Antimony {10(-6)lb}
Arsenic {10(-6)lb}
Cadmium {10(-6)lb}
Chromium {10(-6)lb}
Lead {10(-6)lb}
Mercury {10(-6)lb}
Nickel {10(-6)lb})
Zinc {10(-6)lb}
Total heavy Metals {10(-6)lb}           NA                                  NA

Effluent
Leachate (gal)                        77.12                               77.12
Leachate (lb)                          643                                  43
Chloride (lb)                          1.09                                1.09
Sodium (lb)                            0.7                                 0.7
Potassium (lb)                         0.58                                0.58
COD (lb)                               0.15                                0.15

Arsenic {10(-3)lb}                    82.90                               82.90
Cadmium {10(-3)lb}2.89                 2.89                                2.89
Chromium {10(-3)lb}                    157                                 157
Copper {10(-3)lb}                     41.50                               41.50
Nickel {10(-3)lb}                      104                                 104
Lead {10(-3)lb}                       46.30                               46.30
Mercury {10(-3)lb}                     5.78                                5.78
Zinc {10(-3)lb}                         NA                                  NA
Total Heavy Metals {10(-3)lb}          440                                 440
AOX (lb)                               1.04                                1.04

(a) Yard waste composting.

(b) This is total dioxin/furan as specified by EPA in CFR, 1991a.




Click here for table in WK1 format.



                                    Table 8.6
ENERGY AND EMISSIONS FOR STRATEGY 1: LANDFILL WITH GAS RECOVERY

                                 Total  Collection   Process  Disposal
Landfill space (assuming a depth
of 50 ft), 10(-5) acres                2.00                                2.00
Solid waste (lb)                       2000                                2000
Energy Required (million Btu)         0.081       0.079                   0.002
Energy Produced (million Btu)          2.20        0.00                    2.20
Net Energy (million Btu)               2.12       -0.079                   2.20

Air Emissions
Particulates (lb)                      0.02        0.02
Carbon Monoxide (lb)                   0.79        0.79
Hydrocarbons (lb)                      0.08        0.08
Nitrogen oxides (lb)                   0.32        0.32                     NA
Carbon dioxide (lb)                    225                                 225
Carbon dioxide—combustion (lb)         212                                 212
Water (lb)                             188                                 188
Methane (lb)                          14.34                               14.34
NMOC (lb)                              0.75                                0.75

Dioxin/furan {10(-6)lb}
SO(2) {10(-3)lb}
HCI {10(-3)lb}

Antimony {10(-6)lb}
Arsenic {10(-6)lb}
Cadmium {10(-6)lb}
Chromium {10(-6)lb}
Lead {10(-6)lb}
Mercury {10(-6)lb}
Nickel {10(-6)lb})
Zinc {10(-6)lb}
Total heavy Metals {10(-6)lb}           NA                                  NA

Effluent
Leachate (gal)                          80                                  80
Leachate (lb)                          667                                 667
Chloride (lb)                          1.13                                1.13
Sodium (lb)                            0.73                                0.73
Potassium (lb)                         0.60                                0.60
COD (lb)                               0.16                                0.16

Arsenic {10(-3)lb}                      86                                  86
Cadmium {10(-3)lb}                      3                                   3
Chromium {10(-3)lb}                    163                                 163
Copper {10(-3)lb}                       43                                  43
Nickel {10(-3)lb}                      108                                 108
Lead {10(-3)lb}                         48                                  48
Mercury {10(-3)lb}                      6                                   6
Zinc {10(-3)lb}                         NA                                  NA
Total Heavy Metals {10(-3)lb}          457                                 457
AOX (lb)                               1.08                                1.08

(a) This is total dioxin/furan as specified by EPA in CFR, 1991a.

Click here for table in WK1 format.


Important Integrated Strategies Described in the Data Base

-OR-

Table of Contents