Disposal of waste

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The dominant environmental problem caused by dairy processing is the discharge of large quantities of liquid effluent. Dairy processing produces waste from washing and cleaning steps, and from off-specification product. Examples of sources of waste from milk, cheese and dried powder processing are shown in Fig. 14.5.

The effluent loads from dairy processing depend on the type of product being produced, the scale of the operation and whether a plant uses batch

Milk processing o Overfill o Spillage o Purge of product prior to CIP

o Retained product in poorly drained pipelines o Heat deposited waste o Product defects/returns o Laboratory samples

Cheese processing o Whey o Cheese fines o Separator de-sludges o Cheese brine/salt whey o Waste water from flushing pipelines o Curd losses from curd transfer system

Milk powder o Flushing at start-up and shut down

(concentrates with extremely high biological oxygen demand (BOD)) o Deposit on heating surfaces (protein and CaPO4) o Exhaust loss of fines from driers

Fig. 14.5 Sources of wastage in dairy processing. Source: Hale et al. (2003).

Table 14.10 Summary of American dairy and milk processing plant effluent loadings. Based on DPPEA (1999)

Waste water (ww) from processing

Products--

Range (ww kg/kg milk) Average (ww kg/kg milk)

Milk

0.10

5.40

3.25

Cheese

1.63

5.70

3.14

Ice cream

0.80

5.60

2.80

Condensed milk

1.00

3.30

2.10

Butter

0.80

Powder

1.50

5.90

3.70

Cottage cheese

0.80

12.40

6.00

or continuous processes (see Table 14.10). Small batch processes require more frequent cleaning, with increased losses from product change-over, drainage and cleaning losses. Evaporation processes have the potential to create very high organic loads due to losses during start-up and shut down. Cheese whey, if not used as a by-product, is discharged along with other waste waters and can have a considerable impact on the organic load of the waste from the plant.

Dairy processing effluent generally exhibits the following properties: high organic load due to the presence of milk components; fluctuations in pH due to the presence of caustic and acidic cleaning agents and other chemicals; high levels of nitrogen and phosphorus and fluctuations in temperature (UNEP 2000). Dairy wastes include grease, sugars, nitrogen, phos-

Table 14.11 Composition of various dairy products. Source: Hale et al. (2003)

(g/L)

(g/L)

Lactose (g/L)

Phosphorus (mg/L)

BOD5 (mg/L)

(mg/L)

Whole milk

125

35

36

47

950

114 000

183 000

Skimmed milk

92

0.5

36

47

980

90 000

147 000

Buttermilk

87

5

35

40

900

61 000

134 000

Cream

379

315

28

33

672

400 000

750 000

Condensed milk

260

75

71

98

2050

271 000

378 000

Sweet whey

62

0.5

7.5

47

490

42 000

65 000

Acid whey

56

0.5

7.5

40

160

35 000

60 000

Casein whey

48

0.7

26 400

44 000

permeate

Whey permeate

39

1.5

19 800

33 000

Skimmed milk

957

10

350

519

9950

700 000

950 000

powder

Whey powder

950

12

123

732

6950

600 000

929 000

phorus, acidic and caustic cleaning chemicals; and they have high biological oxygen demand (BOD5) and chemical oxygen demand (COD). The composition of the waste reflects the dairy product being processed and it is possible to identify the source of the waste problem by chemical analysis (see Table 14.11).

Organic loadings in dairy processing effluents vary from 180 to 23 000 mg/L COD. Low values are associated with milk receipt and high values reflect the presence of whey from the production of cheese. Typical levels in the effluent stream from an ice cream and dairy products factory, as reported by Scott and Smith (1997), show loads in excess of 9500 mg/L COD. Milk loss to the effluent can amount to 0.5-2.5% of the incoming milk, but can be as high as 3-4% (UNEP 2000).

Treatment and disposal of dairy waste is often dependent on the location of the factory. Plants located near urban areas often discharge the effluent into municipal sewage treatment systems after primary treatment to remove fat and solids. For some municipalities, the effluent from local dairy processing plants can represent a significant load on sewage treatment plants. In extreme cases, the organic load of waste milk solids entering a sewage system may well exceed that of the township's domestic waste, overloading the system (UNEP 2000).

In rural areas, dairy processing effluent may be irrigated on to land. If not managed correctly, dissolved salts contained in the effluent can adversely affect soil structure and cause salinity. Contaminants in the effluent can also leach into underlying groundwater and affect its quality. In some locations, effluent may be discharged directly into water bodies via deep-ocean outfalls. Such dumping should meet the London Convention (1972), but dumping is hard to control and the effluent can have a negative impact on water quality due to the high levels of organic matter and resultant depletion of oxygen levels.

346 Handbook of waste management and co-product recovery 14.3.5 Legislation

Environmental legislation has become a strong driver for changing practices in dairy processing to achieve greater eco-efficiency (Honkasalo et al. 2004). New legislation is progressively being developed and implemented as the implications of environmental neglect become apparent and in response to public scrutiny about adverse environmental impacts of the dairy sector. Most countries around the world have introduced policies and regulations to control air and water emissions and waste disposal. Some useful links are given here:

• European Union - Waste Management Policies http://europa.eu.int/scadplus/leg/en/s15002.htm

• United States - Environmental Protection Agency http://www.epa.gov/epahome/rules.html

• Australia - Environmental Protection Agency http://www.environment.gov.au/

• China - Cleaner production in China http://www.chinacp.com/eng/cp_policy.html

• India - National Environment Policy 2004 (draft) http://envfor.nic.in/nep/nep.pdf

The policies cover a range of waste management priorities including: waste avoidance, waste reduction, waste reuse, waste recycling or reclamation, waste treatment and waste disposal. Regulatory standards, which are legally enforceable, provide a strong impetus for the industry to adopt waste avoidance practices to avoid fines and even jail sentences for serious offences.

The main driver for the emerging regulatory trends has been the European Union, in that sustainability serves as a core goal of all public policy (Commission of the European Communities 2001). The policies recognise the multifunctional role of agriculture in addressing non-trade concerns such as the environment and animal welfare (WTO 2000). The EU has also introduced regulations mandating recycling and disposal measures for the food industry that appear to be more stringent than internationally accepted levels. Environmental assessments are increasingly based on life cycle analysis.

In comparison, the United States has not advocated broad environmental goals in the regulation of food and agriculture (Osborne 2004). Individual states have their own laws reflecting varying community concerns; however studies have shown that states with more stringent environmental regulations tend to lose dairy manufacturing to those with less stringent policies (Isik 2004). Increased environmental responsibility is often a response to avoid litigation.

Harmonising regulations internationally would increase environmental performance. It has been shown that introducing waste minimisation practises is both environmentally responsible and results in micro-economic reform; these practices are often highly profitable to firms, with short payback periods (Nguyen & Durham 2004). Multinational companies such as Nestlé advocate the harmonisation of environmental laws, regulations and standards in order to eliminate existing and future trade barriers (Nestlé 1999). Environmental policies, at the international level, are guided by the international environmental standard ISO 14001 and by the United Nations Environment Programme (UNEP) sponsored by OECD.

The international standard ISO 14001 was developed along the same lines as ISO 9000 but is concerned with environmental management systems (EMS). The aim is for companies to achieve sound environmental performance by addressing their attention to the potential environmental impact of their activities, products or services. The general purpose of this standard is to provide assistance to organisations implementing or improving an EMS. An EMS will provide order and consistency so that an organisation can address environmental concerns through the allocation of resources, assignment of responsibilities and ongoing evaluation of practices, procedures and processes.

The UNEP addresses the need for cleaner world production through the publishing of guides and information. UNEP has defined cleaner production as the continuous use of industrial processes and products: to increase efficiency; to prevent the pollution of air; water and land; to reduce waste at source; and to minimise risk to the human population (UNEP 2000).

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