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III. Factors Affecting Phosphorus Composition in Organic Wastes

III. Factors Affecting Phosphorus Composition in Organic Wastes

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Table IV

Farm Gate Phosphorus Balances for Selected European Pig and Dairy Farmsa (in kg P haÀ1)

Pig



Dairy



Denmarkc



Spaind



Francee



Swedenf



Belgiumg



Denmarkh



Spaini



0

0

0

5859

561

0



21

0

0

182

9

1

0

213



9

0

94

0

0.4

0

0

103



4

0

49

0

5

0

0

58



13

0

10

31

5

1

0

60



5

0

43

0

0

0

7

55



22

0

0

11

0

1

0

34



6

13

0

7

0.2

0

0

27



1

0

17

0

0

0

0

18



141

12

46

0

199

14

93



40

0

49

0

89

14

86



0

0

17

0

17

41

29



12

2

23

0.2

37

23

61



0

23

10

0

33

22

60



0

18

5

0

23

11

68



0

7

7

0

14

13

52



0

1

9

0

10

8

55



Input

Mineral fertilizer

Manure

Fodder

Concentrates

Animal products

Atmospheric deposition

Net stock exchangel

Total input



6420



1

0

95

0

0

0

À27

69



Output

Organic fertilizers

Arable products

Animals and animal products

Other

Total output

Surplus

Utilization (%)



2945

0

2355

64

5364

1056

84



0

16

30

0

46

23

67



Francej



Swedenk



G. S. TOOR ET AL.



Belgiumb



a



Adapted from De Clerq et al. (2001).

Farm with no agricultural land and 2000 fattening pigs, with 2.5 cycles per year.

c

Means of 13 farms with total area of 79 ha (7 ha of grassland, 1 ha of fodder, 57 ha of cereals, 9 ha of oilseed rape and field pea, 4 ha of fallow). Eight of

the pig farms produced piglets at an average of 22 piglets per sow per year and housed an average of 387 sows. The remaining five farms housed 216 sows

with a mean annual production of 3988 pigs.

d

Farm with 14 ha of rainfed barley and 1018 pigs in a 5 month cycle.

e

Farm with 27 ha of wheat, 22 ha of maize, and 220 sows. Farm sold 3920 fattening pigs in 1999. Farm exports 1250 m3 of slurry per year to neighboring

farms due to animal waste management constraints.

f

Farm with 73 ha of arable cropland and 2300 fattening pigs per year.

g

Farm with 33 ha of grassland, no arable crops, and 39 dairy cows.

h

Means of 26 farms with total area of 85 ha (27 ha of grassland, 26 ha of fodder, 23 ha of cereals, 7 ha of beet, 2 ha of fallow) and 128 dairy cows.

i

Farm with 10 ha of grassland/fodder maize/potato rotation and 23 dairy cows.

j

Farm with total area of 58 ha (27 ha of grassland, 13 ha of wheat and maize, 15 ha of forage maize, 2 ha of set aside) and 42 dairy cows.

k

Farm with 48 ha of arable cropland, 42 dairy cows, 15 heifers, and 40–60 beef cattle.

l

Mainly due to changes in stocks of fodder and slurry between two consecutive years.

b



CHARACTERIZATION OF P IN ORGANIC WASTES

11



G. S. TOOR ET AL.



12



Table V

Phytic Acid (Inositol Hexaphosphate) Content in Some FeedstuVsa



FeedstuV

Grain sorghuma

Barleya

Soybean meala

Normal cornb

Low phytic acid cornb

a

b



Total P (%)



Phytic acid (%)



Phytic acid

as % of total P



0.31

0.38

0.61

0.27

0.27



0.21

0.25

0.37

0.19

0.10



68

66

61

70

37



Adapted from Lott et al. (2000).

Adapted from Raboy et al. (2000) Raboy and Gerbasi (1996).



Addition of mineral P (calcium phosphates) is necessary in the diets of

nonruminants (poultry, swine) because these animals lack the inherent phytase enzyme in the digestive tract (Bedford, 2000) and cannot digest phytic

acid present in the diets. The majority of organic P (61–70%) in feed grains,

such as maize, sorghum, and soybean meal, which are commonly fed to

poultry and swine consist of phytic acid (Table V) (Lott, 1984; Nelson et al.,

1968). Phytic acid may bind with diVerent minerals, such as Ca, Fe, Zn

(Sandberg et al., 1993), and proteins (Thompson, 1993), in the animal

digestive tract due to presence of strong negative charges on its surface

(Dao, 2003). This may result in reduced uptake of these minerals thereby

causing nutrient deficiency problems such as anemia and osteoporosis

(Oatway et al., 2001). The development of corn cultivars with lower concentrations of phytic acid should help to increase utilization of feed P by

animals and may provide another alternative to reduce P excretion in

manures. For example, Raboy et al. (1984, 2000) and Raboy and Gerbasi

(1996) have developed low phytic acid corn that has similar total P levels to

nonmutant hybrids but lower levels of phytic acid (37% of total P) and

higher levels of inorganic P (63% of total P) (Table V).

Klopfenstein et al. (2002) suggested that using the latest advances in diet

management, such as adding phytase, feeding closer to animal requirement,

using higher bioavailability feed ingredients, adding vitamin D3 metabolites,

and choosing low phytic acid ingredients could result in a 40% reduction in

total P in poultry waste. Studies by Angel et al. (2005), Applegate et al.

(2003), Maguire et al. (2004), and Toor et al. (2005c) have confirmed these

observations that feeding P to requirement, including high available P corn

(or low phytic acid corn) in diets, and supplementing diets with phytase can

reduce total P excretion in poultry litters and swine manures by 40%.

Similarly, P excretion in finished pigs manure can be reduced by 30–40%

with dietary P management (Baxter et al., 2003; Pierce et al., 1997). Overall, these studies have concluded that the reduction of P overfeeding and



CHARACTERIZATION OF P IN ORGANIC WASTES



13



supplementation of phytase is a sound management practice that should be

recommended to reduce total P excretion in the manures.



2.



Dairy Diets



Excess P is often added to dairy diets due to the common supposition that

P helps to maintain a better reproduction rate. This belief is largely based on

a study conducted by Hignett and Hignett (1951) in the United Kingdom,

where diets contained 0.10–0.25% P prior to P supplementation, however, most present day dairy diets contain greater than 0.30% P without

P supplementation and sometimes as high as 0.40 to 0.45% P. The National

Research Council’s current recommendation (National Research Council,

2001) as well as a number of other studies (Dou et al., 2002, 2003; Karn,

2001; Valk et al., 2000; Wu et al., 2001) propose that the P content in diets

can be safely reduced to between 0.32 and 0.38%. These studies have shown

that reduction of P in dairy diets will lead to reductions in P in manures. Dou

et al. (2002) analyzed fecal samples and reported that increasing dietary

P levels led to a higher concentration of total P in feces. Toor et al. (2005d)

sampled 40 dairy farms in Mid‐Atlantic United States and calculated that

there will be about 40% more P to manage each year on dairy farms using

high‐P diets (mean of 21 farms: 5.1 g total dietary P kgÀ1) than on farms

feeding low‐P diets (mean of 19 dairy farms: 3.6 g total dietary P kgÀ1).

In summary, the modification of dairy and poultry diets by reducing

P concentration in diets and adding phytase and using low phytic acid

foodstuffs in poultry and swine diets can result in manures with approximately 40% less total P. Therefore, with the advent of the new century, we

have new feeding management strategies for dairy, poultry, and swine that

may result in manures with diVerent chemical composition.



B. ORGANIC WASTES HANDLING EFFECTS

Prior to land application or other oV‐farm usage of organic wastes, they

must be removed from animal houses and municipal treatment plants and

transported to a storage facility or directly spread on land. Major waste

handling and treatment factors that influence the amount and forms of P in

manures are: type and amount of bedding material (e.g., straw, saw dust, wood

shavings, paper and sand, nonlegume hay, alfalfa), addition of feed additives (e.

g., phytase enzyme in poultry and swine diets) and manure amendments (e.g.,

aluminum sulfate in poultry litter), manure accumulation time, amount of

water used to flush the house (e.g., in dairy parlors, typically 145–300 liter

water is used per cow per day), and storage time prior to land application.



14



G. S. TOOR ET AL.



The following sections describe the major treatment and storage practices

used today.

1.



Treatments



Organic waste treatments consist of physical and chemical to biological

processes, which are often needed to reduce the volumes of waste, destroy

pathogens, control odors, and improve palatability. These treatments

can also modify the physical, chemical, and biological characteristics of

wastes, resulting in heterogeneity in P speciation from one production site

to another. The following section summarizes the common treatments.

a. Physical Treatment Physical treatment of wastes involves solid–liquid separation by sedimentation or screening and is mostly used for dairy

and swine manures and biosolids. The separated solids can then be composted, reused as bedding, or feed, or pelletilized, or directly applied to soil

as an amendment. The liquids can be used to flush the animal house to

remove manure before using to supply plant nutrients. The major advantage

of this process is lower transport costs due to reduction in waste volume,

which can be of significant concern in large animal production facilities.

Other alternative methods of manure use, primarily for poultry litter and

biosolids, include drying, incineration, and pyrolysis. A detailed discussion

of physical treatment processes for wastes has been provided by Moore

(1993) and Day and Funk (1998).

b. Chemical Treatment Organic wastes can be treated with chemicals

to precipitate particulates and colloidal matter, to control pH and odor, and

to enhance biological treatment. The most commonly used coagulants in

wastewater are aluminum sulfate, ferric sulfate or chloride, and lime. Some

polyelectrolytes and polymers have also been used in biosolids and manures

(Dao and Daniel, 2002; Dao et al., 2001). In poultry houses, sodium bisulfite

is used for NH3 control, litter acidification, and for pathogen reduction

(Salmonella and Campylobacter) (Moore et al., 1996; Yang et al., 1998).

Another common chemical additive used today in poultry houses is aluminum sulfate (alum), which reduces soluble inorganic P concentrations and

NH3 emissions (Moore et al., 2000; Sims and Luka‐McCaVerty, 2002).

Usage of alum and aluminum chloride to reduce soluble inorganic P in

swine manure has also been documented (Smith et al., 2001).

c. Biological Treatment Biological treatment can significantly reduce

the solids content of waste by the action of biological organisms in the

presence (aerobic) or absence (anaerobic) of oxygen, thus changing the

physical and chemical properties of the waste. Wastes are composed of



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