Agricultural-Based Food Production Geoenvironment Stressors - Sustainable Practices in Geoenvironmental Engineering - page 197

0

20

40

60

80

Cu (NA) Zn (NA)

100

Cu (PWA) Zn (PWA)

120

0 20 40 60 80 100 120 140 160

Retention concentration (mg/kg)

FIGURE 6.9
Retention proiles for total Cu and Zn for non-amended (NA) and poultry-waste-amended (PWA). (Data from
Han, F.X. et al., Accumulation, redistribution, transport, and bioavailability of heavy metals in waste-amended
soils. In I.K. Iskandar and M.B. Kirkham, (eds.), Trace Elements in Soil, Bioavailability, Flux and Transfer , Lewis
Publishers, Boca Raton, pp. 145-174, 2001.)

6.5.3 Mitigating Manure Treatment Stressors' Impacts

6.5.3.1 Aerobic Composting

Composting can be used to stabilize manure, particularly storage. This method is pref-
erable over other aerobic treatments that are subject to high operation costs and sludge
production. It is, however, labor intensive and costly due to the requirement for aeration.
The thermophilic conditions of 54°C to 71°C destroy most pathogens. Most of the ammo-
nia is volatilized early in the process. Losses of nitrogen during the composting process,
however, can be as high as 50% (Thomsen, 2000). Mixing with other substrates such as the
bedding is usually required for bulking. Normally, straw or wood shavings are used as
bulking agents with adjustments for nitrogen content to be about 1:20 or 1:40. Compared
with untreated manure, volatilization and leaching of nitrogen, the risk of pathogen spread-
ing and odor release are reduced. Yang et al. (2003) reported that (a) greenhouse gas (GHG)
emissions of compost were 1.9 times less than slurry manure and 1.5 less than stockpiled
manure for dairy manure (Table 6.3), (b) composted liquid pig manure, in comparison
to liquid pig manure was more stabilized in terms of manure carbon, and (c) composted
liquid pig manure produced reduced emissions of carbon dioxide and N 2 O. Vervoort et al.
(1998) determined that composting of poultry litter stabilizes phosphorus and reduced

TABLE 6.3
Comparison of Anaerobic Digestion Residue and Compost for Nitrogen Emissions

Global Warming
(tonnes CO 2 equiv/year)

Acidiication
(tonnes SO 2 equiv/year)

Eutrophication
(tonnes O 2 equiv/year) Treatment for Waste

Anaerobic digestion 654 43 688

Composting by reactor 2618 20 991

Source: Adapted from Dalemo, M. et al., Resources, Conservation and Recycling 24, 363-381, 1998.