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.
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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:
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.
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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 dioxideÑcombustion (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.
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Important Integrated Strategies Described in the Data Base
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