What waste is produced from slaughterhouses


2. SLAUGHTERHOUSES


2.1. Red meat slaughter process
2.2. Poultry slaughtering process
2.3. Emissions
2.4. Prevention of waste production

2.1. Red meat slaughter process


2.1.1. Description of the slaughter process.
2.1.2. Quantities of by-products

2.1.1. Description of the slaughter process.

Figure 1 presents a flow diagram of a red meat slaughterhouse.

Slaughtering

In slaughterhouses animals are received and kept around in stockyards and pens for 1 day. The animals are watered, but in most cases not fed unless they are kept more than 1 day.

The animals are then driven from the holding pens to the slaughtering area where the following activities take place:

- Stunning;

- Suspension from an overhead rail by the hind legs;

- Sticking and bleeding over a collecting trough. The collected blood may be sewered or processed;

- Hide removal (cattle) or scalding and dehairing (hogs);

In some plants hogs are skinned to eliminate scalding and dehairing. Scalding is a method to loosen hair before removal. For several minutes the hogs are held in a scalding tank at 45°C to 65°C. After scalding, the hogs are mechanically dehaired by abrasion and singed in a gas flame to complete the hair removal process.

- Decapitation;

- Opening of the carcass by cutting;

- Inspection of the carcass;

- Evisceration (removal of intestines and internal organs);

- Splitting and cutting of the carcass; and

- Chilling or freezing.

Meatpacking

Many large scale plants ship whole graded carcasses to retail markets, others perform some on-site processing to produce retail cuts. The processes are the following:

- Cutting and deboning; and

- Meat processing. This includes a variety of operations amongst which grinding, mixing with additives, curing, pickling, smoking, cooking and canning.

Rendering

Rendering is a heating process for meat industry waste products through which fats are separated from water and protein residues for the production of edible lards and dried protein residues. Commonly it includes the production of a range of products of meat meal, meat-cum-bone meal, bone meal and fat from animal tissues. It does not include processes where no fat is recovered.

There are basically two different rendering processes:

- High temperature rendering: through cooking or steam application (5 systems are known: (1) simple cooking; (2) open pan rendering; (3) kettle rendering; (4) wet rendering; and (5) dry rendering.)

- Low temperature rendering (around 80°C). This process requires finely ground material and temperatures slightly above the fat melting point. It results in a better quality lard. The rendering at low temperatures is a highly sophisticated process requiring large throughputs and trained personnel. For many developing countries the system is not suitable. (Kumar, undated).

Handling of viscera, paunch and intestines

Viscera can be recovered as edible products (e.g. heart, liver). They can also be separated for inedible rendering or processing (e.g. lungs).

The paunch contents, ‘paunch manure’ (partially digested feed), is estimated to range from 27 to 40 kg. The paunch can be handled in four ways:

1: Total dumping. All of the paunch contents is flushed away into the sewer.

2: Wet dumping. The paunch contents are washed out and the wet slurry is screened on the presence of gross solids, which are subsequently removed.

3: Dry dumping. The paunch contents are dumped for subsequent rendering or for disposal as solid waste without needless water flushing.

4: Whole paunch handling. The entire paunch may be removed, intact, for rendering or for disposal as solid waste.

Intestines may be rendered directly, or hashed and washed prior to rendering. For the processing of intestines de-sliming prior to thorough washing is necessary.

Categories of slaughter-plants

Plants for red meat slaughtering may be categorized on the basis of the final products. A plant that processes meat into products such as canned, smoked and cured meats is significantly different from a plant with facilities for slaughtering without further processing.

Slaughterhouses and packinghouses (slaughtering and meat processing) may each be divided into two categories on the basis of the quantity of waste produced (EPA 1974).

Slaugtherhouses:

- Simple slaughterhouse:
A plant that slaughters animals and does a very limited amount of by-product processing. Its main products are fresh meat in the form of whole, half or quarter carcasses or in smaller meat cuts.

- Complex slaughterhouse:

A plant that slaughters and does extensive processing of by-products. Usually at least three of the following operations take place: rendering, paunch and viscera handling, blood processing, and hide and hair processing.

Packinghouses

- Low-processing packinghouse:
A plant that both slaughters and processes fresh meat into cured, smoked, canned and other meat products. Only the meat from animals slaughtered at the plant is processed. Carcasses may also be sold.

- High-processing packinghouse:

A plant that also processes meat purchased from outside. Sometimes, a high-process packinghouse has facilities for tanning operations.

There are also plants that do not slaughter themselves but restrict their activities to the processing of meat (meatpacking). These plants have a waste production comparable to that of a simple slaughterhouse.

2.1.2. Quantities of by-products

The products resulting from slaughtering of cattle are carcasses and by-products. The quantity of animal by-products often exceeds 50% of the LWK. The weight of the carcass, expressed as a LWK-percentage is the so called “dressing percentage” (carcass weight/live weight *100).

Table 1 gives dressing percentages for a few different types of cattle in the U.S.; Table 2 shows dressing percentages for cattle in France. As shown in these tables, a wide variation in dressing percentages exists, mainly related to factors like breed, age and feeding. In many developing countries low dressing percentages (i.e. less then 50%) are common as animals receive less feed and/or feed that is of lower quality than the feed offered in developed countries and because the animals are slaughtered at a higher age than is done in developed countries.

Carcasses still contain quantities of fat and bones (see table 2), most of which will be removed if the carcasses are processed further. This further processing leads to increased amounts of by-products.

U.S. cattle grades

Dressing percentages

Range

Average

Prime

62-67

64

Choice

59-65

62

Good

58-62

60

Standard

55-60

57

Commercial

54-62

57

Utility

49-57

53

Cutter

45-54

49

Canner

40-48

45


Young bulls

Steers

Cull cows

F*

LI*

CH*

CH*

LI*

F*

Carcass (% LWK)

55.6

65.0

61.3

57.0

59.6

50.1

Carcass:

Bone (%):

16.6

13.0

14.3

16.5

16.1

17.8

Musle (%):

68.1

74.7

70.0

65.0

66.1

62.9

Fatty tissue (%):

15.3

12.3

15.7

18.5

17.8

19.3

*: Breeds: F: Dutch/Holstein Friesian LI: Limousin CH: Charolais

Kumar (undated) gives a list of waste products in slaughterhouses in developing countries:

hides, skins, blood, rumen contents, bones, horns, hoofs, urinary bladder, gall bladder, uturus, rectum, udder, foetes, snout, ear, penis, meat trimmings, hide and skin trimmings, condemned meat, condemned carcass, oesophagus, hair and poultry offals (feathers, head).

Only few of these products can be used directly. Figure 2 gives the division of cattle into various product categories. It shows in principle that by-products may be used in full (which would result in low waste production).

Whether complete utilization of all by-products can be realized depends on a number of factors. Ockerman and Hansen (1988) give several conditions that must be met for an effective use of animal by-products:

- there must be a commercial process for converting the animal by-product into a usable commodity.

- there must be an actual or potential market for the commodity that has been produced.

- there must be a large enough volume in one location of economically priced animal by-product material for processing.

- there must be a facility for storage of the perishable product before it is processed and for storage of the manufactured product after the processing.

- there should be a critical mass of highly trained technical operators.

The percentages of by-products in some western countries are presented in Table 3.

Cattle

Pigs

Denmark

England

U.S.

Denmark

Sweden

U.S.*

U.S.*

Carcass and edible products

62-64

75-80

Carcass, meat and bone

69

56

56

Retail cuts (bone in)

42

Retail cuts (boneless)

41

Organs

4

7

4

2.4

Red offal

6

Bone

8

Edible fats

3-4

10

11

3

16

16

White offal

10

Blood

3-4

3

4

3

4

3

Inedible raw material

8-10

17

6

8

15

Hide and/or hair

7

8

6

1

Hide (cured weight)

6

Waste

20

14

6

12

4

Paunch and manure

8

Shrinkage

2-10

*: different sources

2.2. Poultry slaughtering process


2.2.1. Description
2.2.2. Quantities of by-products

2.2.1. Description

Receiving areas

The inlet to the plant is normally designed in such a way that fluctuations in bird deliveries can be dealt with adequately. This is necessary since the processing capacity has a fixed maximum. At regular intervals birds are unloaded onto the holding areas and attached by their feet to a conveyor belt, transported to the slaughter area.

Slaughtering and packing

The birds are suspended from the conveyor after which the following actions take place:

- Stunning;

- Killing and bleeding by cutting the jugular veins;

- Collection of blood. The conveyor travels through a blood collection tunnel at a preselected travelling speed;

- Scalding. To loosen the feathers, the birds are held in water of temperatures ranging from 50°C to 60°C;

- Defeathering. Feathers are mechanically abraded from the scalded birds, usually by rotating rubber fingers. Removed feathers drop in underlying troughs;

- Washing. The defeathered carcasses receive a spray wash prior to evisceration;

- Opening of the carcass by cutting manually;

- Inspection of the viscera;

- Evisceration, removal of head, feet and viscera;

- Sorting of the viscera to recover heart, liver and gizzard;

- Final washing to remove blood and to loosen tissues;

- Chilling of the carcasses in a waterbath;

- Draining;

- Grading, weighing and packing; and

- Chilling and freezing.

2.2.2. Quantities of by-products

Table 4 gives dressing percentages for poultry in the U.S.

U.S. grades

Dressing percentages

Average

Chicken, broilers

70

Chicken, capon

68

Turkey, broiler

77

Duck, Peking

58

Pheasant

78


The various components of the raw offal can be summarized as follows (El Boushy and van der Poel, 1994):

- total offal (heads, feet, intestine):

15.8%

- blood:

3.5%

- feathers:

6.0%

- moisture:

9.0%

Total:

34.3%.

2.3. Emissions


2.3.1. Solid waste
2.3.2. Wastewater
2.3.3. Air pollution

2.3.1. Solid waste

Table 5 shows the estimated solid waste of slaughterhouses and the meat processing industry in The Netherlands (RIVM, 1994). All the solid waste mentioned in Table 5 has a potential use as fertilizer (manure) or animal feed (fat).

Slaughter process:

manure

5.5 kg/ton carcass weight

fat (pretreatment wastewater)

1.7 kg/ton carcass weight

Meatpacking:

fat (pretreatment wastewater)

2.0 kg/ton product

Intestine handling:

fat (pretreatment wastewater)

2.3 kg/ton product

paunch manure

100 kg/ton product


It would appear that rumen contents and the manure of the stockyards has not been included in the value of manure.

2.3.2. Wastewater


2.3.2.1. Wastewater by red meat slaughtering
2.3.2.2. Wastewater by poultry slaughtering

Kumar (undated) remarks that effluents of slaughterhouses constitute one of the most serious causes of environmental pollution, bad odours and health hazards in almost all of the developing countries.

Table 6 presents some values of the quality of the wastewater in the Netherlands, as recently estimated by the RIVM (1994), while in Table 7 international but older values of wastewater characteristics of the various types of red meat slaughterhouses (see chapter 2.1.1) are presented.

Pigs

Cattle

BOD

2.4

4.4 kg/ton carcass weight

Nkj

0.6

1.1 kg/ton carcass weight


Slaughterhouses (1)

Slaughterhouse (2)

Simple

complex

Typical Range

Range

Range

BOD

5

1.5 - 14

1.5 - 40

5.5 - 19

COD

10

2 - 40

2.7 - 25

Nkj-N

0.68

0.23 - 1.4

0.2 - 1.4

0.1 - 2.1

SS

5.6

0.6 - 12.9

0.6 - 13

2.8 - 21

P

0.05

0.014 - 0.09

0.014 - 0.086

0.05 - 1.2

Packinghouse (1)

Packinghouses (2)

low-processing

high-processing

Typical Range

Range

Range

BOD

11

5.4 - 18.8

2.3 - 18

6.2 - 31

COD

22

7 - 60

4.1 - 32

11.2 - 56

NKj-N

0.84

0.13 - 2.1

0.04 - 1.3

0.7 - 2.7

SS

9.6

2.8 - 20.5

1.5 - 17

1.7 - 23

P

0.33

0.05 - 1.2

0.05 - 1.2

0.2 - 0.6

Values are estimated from data given by:
(1): Taiganides (1987), probably based on EPA (1974)
(2): EPA (1974)

It has been observed that with a reduction of the water use also the waste load decreases.

Heinen (1994) compared data of water consumption and effluent quality of large scale slaughterhouses in Poland with Dutch data (Table 8).

Consumption in m3/ton “throughput”:

Poland

Netherlands

(4 plants)

(11 plants)

Slaughter

11.6

1.78

Cutting and deboning

3.44

1.41

Processing

7.45

Various

3.77

Effluent:

COD (mg/l)

648

700 (n=3)

COD (kg/ton “throughput”); recalculated

17

2.2


Clearly the Polish industry uses much more water for its processes than the Dutch industry. The difference is enormous, especially as far as slaughtering is concerned (6 times as much). The chemical oxygen demand per m3 of wastewater after pre-treatment is approximately the same as in the Netherlands. The total waste production in slaughterprocess in Poland is much higher (over 7 times) than in the Netherlands.

Comparison of the Polish COD-production figures (Table 8) to the figures of Table 6, shows that the Polish figures are not extreme, while the Dutch figures mentioned in Table 8 are low.

The Polish non-industrial-scale private slaughterhouses have in recent years increased the market share of slaughter from 10% (1988) to 60% in 1993 (Heinen, 1994).According to Heinen, the water use in non-industrial-scale private slaughterhouses in Poland is considerably lower than the water use of industrial-scale plants. This implies that the total waste load per ton LWK in the water will probably be lower than the values given in Table 8.

2.3.2.1. Wastewater by red meat slaughtering

Major contribution to the total waste load.

Production of blood: Of all waste products, the waste in the form of blood has the highest polluting value. Blood itself has a high BOD: 150,000 - 200,000 mg/l, the extreme value being 405,000 mg/l. (Domestic wastewater has a BOD of 300 mg/l). In the killing, bleeding and skinning phases, blood is produced which, when completely sewered, leads to a total waste load of 10 kg BOD per ton of LWK. A waste load of up to 3.0 kg BOD per ton of LWK may occur in wastewater flowing out of the killing-area and the hide-removal-area.

In order to reduce the waste load, attempts should be made to collect and process blood (= drying). Drying of blood can be done by direct heating which produces large quantities of bloodwater (corresponding waste load approximately 1.3 kg BODper ton of LWK) but preferably it is done by indirect (external) heating (corresponding waste load approximately 0.3 kg BOD per ton of LWK).

Paunch: Paunch manure is the second most important source of pollution. It may substantially contribute to the total waste load if not properly handled. Dumping (sewering) of the entire paunch content gives a BOD of 2.5 kg per ton of LWK. There are several ways to handle paunch (see 2.1.1)

Minor contributions to the total waste load.

Stockyards and pens: Waste results from manure and urine, feed, livestock dirt, sanitizers and cleaning agents. The waste will reach the sewer by means of water overflowing from water troughs, by rain and snowwater and pen washdown water. The sewered raw waste, assuming that solid contaminants have been removed, has been estimated at 0.25 kg BOD per ton of LWK.

Slaughtering: During the slaughtering the following wastes are produced (Edible offals are excluded because these are considered as meat (by-products)):

- Blood and tissue produced during hide removal fall on the floor. External contamination of the hide with dirt and manure is a secondary source of pollutants. The waste load is also increased as a result of cleaning-up operations in this area.

- Wastewater is produced from intentional overflow from scalding tanks that contain blood, dirt, manure and hair (0.15 kg BOD per ton of LWK). The fluming of the mechanically removed hair also results in wastewater containing residual hair, blood and dirt after recovery of the bulk of the hair (0.4 kg BOD per ton of LWK). Recovered hog hair may be be dumped as solid waste, washed and baled for marketing (0.7 kg BOD per ton of LWK) or it may be hydrolysed by pressure cooking (1 kg BOD per of LWK).

- Slime and casings from intestines. De-sliming and casing washing add 0.6 kg BOD per ton of LWK to the raw waste load;

- Inedible offals that are produced are hair, recovered from fluming water, heads and carcass trimmings, lungs and paunch. They also contribute to the amount of wastewater.

Meatpacking: Cutting and deboning operations produce trimmings, blood, bones and bone dust. The total of raw waste loads for meat processing plants (including cutting and deboning) has been estimated at 5.7 - 6.7 kg BOD per ton of product. Meatprocessing operations produce a raw waste load from:

- Blood, tissues and fat that reach the sewer during cleaning activities;

- The curing of solutions containing sugar and salt. Pickling can cause a high chloride waste, only 25% of the curing brine remains in the product.

- Baking, smoking etc. and energy use (contributing to air pollution).

Edible Rendering: Both wet-rendering and continuous rendering at low temperatures produce polluted tank water containing residues of fat and protein (2 kg BOD per ton of LWK).

Table 9 summarizes the potential wastewater emissions of red meat slaughterhouses (no water prevention).

kg BOD/ton LWK

Remarks

1 stockyards and pens

0.25

solid contaminants are removed

2 blood

10

all blood sewered

3 cleanup hide removal

3

depends on cleanup practices

4 scalding, dehairing

0.15

overflow scalding tank

0.4

flume water

0.7

washing of recovered hair

5 paunch

2.5

in case of total dumping sewer

1.5 - 2

in case of wet dumping

0.2

in case of dry dumping

0.6 - 1.0

in case of whole paunch handling

6 intestine handling

0.6

7 rendering

2

8 general cleanup

3*

depends strongly on cleanup practices

Potential emission:

24.9 - 25.8

9 meat packing

6

kg BOD/ton product!!

*: authors’ estimate (not mentioned by Barnes).

2.3.2.2. Wastewater by poultry slaughtering

Table 10 shows characteristic values of waste flows of a poultry slaughterhouse.

Major contribution to the total waste load

Evisceration: For medium-to-high capacity poultry plants, it has been estimated that offal flume-water from continuous flowaway fluming contributes a raw waste load of approximately one-third of the total plant load (presented in Table 10). Values of 1.7 - 13.2 kg BOD per ton of LWK with a common average of 3.4 kg BOD have been reported (Barnes et al., 1984).

Production of blood: Because of the high BOD of blood, the same observation with respect to the contribution of blood to the total waste load applies to poultry plants. Chicken blood contributes 4.5 kg BOD per ton of LWK if completely sewered.

Minor contributions to the total waste load

Receiving areas: Waste load values of the receiving area vary widely since they are derived from the quantity of dirt, manure and feather deposits which vary with the length of holding time.

 

(1)

(2)

Poultry slaughterhouses

Poultry slaughterhouses

Chicken

Turkey

Range

Typical

Range

Range

BOD

3.3 - 25

1 - 9

5 - 30

6.8

COD

5.9 - 45

1.8 - 16

1 - 30

15

NKj-N

0.15 - 12.2

0.4 - 1.9

SS

0.1 - 22

0.6 - 10.9

3 - 25

3.5

P

0.054 - 2.5

0.034 - 0.2

Values are estimated from data given by:
(1): EPA (1974)
(2): Taiganides (1987)

Slaughtering and packing:

Waste water:

- Scalding tanks containing settleable residues and feathers. Approximately 8 litres of wastewater per bird are produced as a result of overflow (0.6 - 3.1 kg BOD per ton of LWK).

- Chilling. Chiller overflow is high to prevent bacterial contamination (0.4-2.5 kg BOD per ton of LWK);

- The final wash water contains blood and tissue (0.7 kg BOD per ton of LWK);

- Whole bird washing after defeathering (0.06 kg BOD per ton of LWK)

- Defeathering; The underlying troughs are flumed to collect the feathers.

- General plant clean-up; up to 50% of the BOD can come from cleaning operations.

Solid waste:

- Feathers recovered from the flume water of the collecting troughs;
- Head, feet and viscera.

2.3.3. Air pollution

Slaughtering is an activity that requires great amounts of hot water and steam for sterilisation and cleaning purposes. In the process of generating the energy for heating, gasses are emitted (CO2, CO, NOx and SO2).

Emissions of CFC’s and NH3 into the air are the result of evaporation of chilling liquids and of the stripping of chilling and freezing-machines, when out of use.

The smoking of meat products and the singing of hogs in a gas flame to complete the hair removal lead to the production of mainly CO2, CO and NOx and obnoxious smells.

The overall energy used in Dutch slaughterhouses and the meat processing industry is estimated at 137 kWh/ton of carcass and about 28.7 m3 gas/ton of carcass (RIVM, 1994). The degree of air pollution caused by the generation of energy depends on the type of process for which the energy is needed. The processes of “dehairing”, “water heating” or “production of electricity” each lead to different levels of emission.

Based on estimates of the RIVM (1994), emissions of CO2, CO and NOx resulting from the burning of gas for heating and steam production are for the dutch situation as indicated in table Table 11.

Process:

Air emission:

Heating by burning gas:

CO:

0.02 kg/ton carcass weight

CO2:

28 kg/ton carcass weight

NOx:

0.01 kg/ton carcass weight

Dehairing pigs: (using gas)

CO:

0.06 kg/ton carcass weight

CO2:

6.5 kg/ton carcass weight

NOx:

0.015 kg/ton carcass weight


Table 12 shows the energy use of Polish large scale slaughterhouses and comparable figures for the dutch situation. According to Heinen (1994) Polish meat plants are highly inefficient in their energy-consumption.

The energy-use in non-industrial scale private slaughterhouses in Poland seems to be considerably lower than that of industrial scale plants, probably because of a lower level of process-automation. The amount of energy needed for non-industrial cutting and deboning is considerably lower than that required in large scale plants, but the energy needed for non-industrial processing is more than twice as high, probably a matter of economies of scale (Heinen, 1994).

Gas (m3)

Steam (GJ)

Electricity (kWh)

Polish

Dutch

Polish

Dutch

Polish

Dutch

Slaugther (per ton carcass)

1.52

10.02

4.83

227

50

Cut and debone (per ton carcass)

2.28

1.10

55.6

12

Processing (per ton product)

15.0

4.61

187

200

Rendering (per ton input)

21.1

3.7

338

117

Other (per ton overall)

2.1

1.57

39

11

2.4. Prevention of waste production

Practices as discussed in this section are generally called ‘housekeeping practices’. The quality of overall cleaning-up practices determines to a large extent the total waste load produced. It has been established that the waste load decreases with a decrease of the water being used(see e.g. the comparision in Table 8).

With reference to the process outline in figure 1, the following actions may contribute to waste(water) reduction. BOD data are from several slaughterhouses and from literature reported by Barnes et. al (1984). BOD values are values of the untreated final wastewater.

Red meat:

- As much blood as possible should be collected and processed. Indirect heating can reduce the amount of wastewater (and thus the waste load), compared with direct heating from 1.3 to 0.3 kg BOD per ton of LWK.

- Paunch can be handled in different ways (Barnes et al, 1984):

1. dumping in full into the sewer, which leads to a waste load of 2.5 kg BOD per ton of LWK

2. wet dumping (washing out and screening the wet slurry on gross solids); estimated waste load of 1.5 - 2 kg BOD per ton of LWK

3. dry dumping (dumping for subsequent rendering or disposal as solid waste without needless water flushing): estimated waste load of 0.2 kg BOD per ton of LWK;

4. whole paunch handling (removal of the entire paunch, intact, for rendering or disposal as solid waste):

a: after washing, an estimated waste load is produced of 0.6 kg BOD per ton of LWK (paunches are marketable as pet food);

b: washing and bleaching lead to an estimated waste load of 1 kg BOD per ton of LWK (paunches are marketable as tripe).

- Dry animal pen clean-up reduces the amount of wastewater. If the pens are covered, no rain or snowwater can enter, which reduces the amount of of wastewater

- Hog hair, recovered from the dehairing process, can be disposed as solid waste, washed and baled for direct marketing, or hydrolysed by pressure cooking for marketing as a feed supplement.

- Heads and lungs should be rendered;

- Intestines may be rendered directly, hashed and washed prior to rendering, or processed for further use (in the case of hog intestines). Large hog intestines may be used as sausage casings or as surgical sutures.

- Tankwater (from the rendering process) can be evaporated. This will reduce the waste load from 2 to 0.5 - 1 kg BOD per ton of LWK. Evaporation on the other hand consumes energy which will lead to CO2 production.

Poultry:

- Flow-away systems have resulted in quick and efficient processing in modern plants. However, the costs of flowaway systems and of wastewater treatment may be such that the development and use of automated dry viscera handling methods are encouraged.

- Stunning before killing reduces the overall loss of blood. Without prior stunning, blood will be splashed over a wide area and may also contaminate feathers.

- Dry cleaning before washing the receiving area;

- Use of chiller overflow water as make up water in scalding tanks;

- Recovered feathers may be disposed of as solid waste or pressure cooked to hydrolyse the otherwise low nutritional value protein, keratin.

- Use of screened water from defeathering operations in feather flumes;

- Head, feet and remaining inedible viscera may be collected for disposal or inedible rendering.

- Re-use of final evisceration wash waters in other subprocesses and use of special nozzles that minimize water use;

- Potential re-use of screened chiller water overflown elsewhere in the plant.

RIVM (1994) reported also some possibilities for waste prevention: Table 13.

Process

Waste-prevention

Slaughterprocess:

Air:

- mainly energy saving

Water:

- dry animal pen clean-up
- dry transport (poultry-slaughterhouse)
- less loss of blood
- more dry cleaning
- fast separation of meat and water
- improve defatting-process waste water

Solid Waste:

- increases when waste water prevention increases (manure, fat).

Meatpacking:

Air:

- mainly energy saving

Water:

- separate meat and water as much as possible
- more dry cleaning
- improve defatting-process waste water
- application of steam-tunnels or high pressure-systems for cooking meat

Solid Waste:

- increases when waste water prevention increases (fat).

Intestine handling:

Air:

- energy-saving

Water:

- application of dry rendering
- keep paunch manure separated as much as possible

Solid Waste:

- increases when waste water prevention increases (manure, fat).

Utility-processes*:

Air:

- improve efficiency chilling-machines and chilling practices (keep doors close, repair leakages)

Water:

- use as less (warm) water as possible during cleaning-up

*: e.g. waste water purification, chilling, cleaning-up

One of the conclusions of an investigation of waste prevention in ten slaughterhouses in the Netherlands is that in modern western slaughterhouses good results can be achieved by using simple means (Provinces Gelderland and Overijssel, 1994). Possible reason for this is that environmental aspects have received little attention compared to the attention for the efficiency of the slaughter process.