Beyond production systems

Previous section Livestock and greenhouse gases

Processing of livestock products

Environmental challenges

Global market integration and commercialization greatly increases the volume of animal waste. Waste products from subsistence consumption are spread so thinly through the environment that the absorptive capacity of the natural resources is hardly reached. However, with increasing income, an increasing proportion of animals and animal products go through market and processing channels before consumption. So an increased level of processing comes on top of an increased demand, causing even greater levels of waste production. Milk is processed in relatively small quantities, because of its highly perishable nature and its relative high share of consumption for subsistence.

Slaughterhouses and meat processing plants, dairies and tanneries all have polluting potential. This pollution is usually confined to limited geographic areas not directly attributable to any specific production systems. The most important environmental impact of animal product processing results from the discharge of waste-water. Discharge of waste-water into surface waters leads to a reduction of dissolved oxygen, which reduces or destroys aquatic life, while nitrogen and phosphates may cause eutrophication and result in oxygen depletion. Furthermore, effluents from tanneries may contain toxic compounds, such as chromium (Verheijen, et al., 1996). There is a negative impact of waste discharge on biodiversity. In addition, there are a number of serious human health hazards involved.

The environmental challenge is thus threefold:

State and driving forces

Table 5.8 Potential waste water emissions of a red meat slaughterhouse.
Source kg BOD
per ton LW
Stockyard and pens 0.25 solid contaminants are removed
Blood 10 sewer disposal of blood
Cleanup hide removal 3
Scalding, dehairing 0.7 washing of removed hair
Paunch 2.5 sewer disposal
Intestine handling 0.6
Rendering 2
General cleanup 3
Meat packing 6
Total polluting potential 26.05
Source: Verheijen et al., 1996.

Growing population pressure and urbanization, rising incomes and changing consumer habits are the main underlying causes for increasing environmental degradation resulting from processing activities. In the developed countries, processing plants have been pushed away from the large cities and enforcement of regulations on effluent discharge have greatly reduced the environmental problems. In developing countries, insufficient infrastructure and weak institutions prevent this. On the other hand, there are fewer by-products because a higher proportion of the animal is usually consumed.

Slaughterhouses. Concentration of waste production in one given area is the main problem, rather than waste production as such. Small-scale home processing usually does not lead to excessive waste loads, if units are geographically distributed. In large-scale production, considerably more effort is needed to keep waste production at an acceptable level, to use by-products efficiently and to treat waste.

In most developed countries, the slaughter activity is centralized. Consumers prefer lean meat and only a few selected offals such as brain, kidney, sweetbread, and tongue are eaten. For this reason, the carcass is often deboned at the slaughterhouse and cooled before being sent to retail outlets. As a result of this, large quantities of by-products such as bones, lungs, spleen, and other organs are left behind at the slaughterhouse, as inedible offal. Generally, the clean fatty material is processed separately into edible fat. Other parts may be used to produce composite bone-cum-protein meal or individual products like bonemeal, meatmeal and bloodmeal. Modern abattoirs are well equipped with facilities such as running water, steam, power, refrigeration, transport, etc. by which to process and put to further use all edible and non-edible by-products (e.g. for human consumption, pet food, feed industry or fertilizer).

In developing countries a large variety of slaughter sites and levels of technology exist. Slaughter sites can vary from simple slaughter slabs to modern slaughterhouses. Large-scale industrial processing units import complete sets of technologies from developed countries, although often without the respective rendering or waste treatment facilities. Slaughterhouses, especially those around urban centres, often discharge blood and untreated wastewater, and destruction of sick animals is inadequate (Kaasschieter, 1991). Fresh blood coagulates in drains, where it becomes putrefied, causing bad odours as well as sanitary and environmental problems. Edible and inedible by-products are frequently wasted during the process due to insufficient skills and discipline in slaughtering, poor equipment, low incentives for recouping by-products, and lack of regulations and their enforcement. Most slaughterhouses in the developing world are public enterprises, lacking the funds to maintain quality operations. Slaughter fees need to be kept low to prevent illegal slaughter, and these meagre revenues are often used for other purposes than the operation and maintenance of the abattoir.

In processing technologies, there are important economies of scale in waste treatment and by-product utilization. Large-scale industrial processing usually facilitates a high utilization of by-products such as blood or bones and good waste management. Enforcement of regulations is easier than with small-scale processing.

Slaughtering requires large amounts of hot water and steam for sterilization and cleaning. Therefore, the main polluting component is waste water. In waste water, there is a huge concentration of agricultural compounds, including fat, oil, protein and carbohydrates , which are biodegradable compounds, but require a high BOD to bio-degrade. In addition waste water usually contains insoluble organic and inorganic particles which are called suspended solids. Slaughterhouses typically produce solid wastes of 100 kg paunch manure per ton of product and 6 kg of fat (RIVM, 1994). The main polluting agent in wastewater is blood which has a high BOD (150,000 to 200,000 mg/l). Table 5.8 gives an overview of the potential waste water emissions of a typical red meat slaughterhouse, where environmental concerns are not built in. Poultry slaughterhouse have much lower potential BODs, usually not exceeding 10 kg BOD per ton of liveweight.

Tanneries. Globally, 78 percent of the total processed hides are cattle and buffalo, 15 percent sheep and 7 percent goat skin (FAO, 1995). The tanning process can be divided between beamhouse operations, tanning and finishing. Hides are usually tanned twice. For the first step, mineral or vegetable tanning is practised. Mineral tanning is the most popular method for large-scale tanning today. For the second step, retanning, a combination of agents is used, mostly vegetable compounds. In traditional vegetable tanning, barks and nuts are used throughout the entire tanning process instead of chromium. Verheijen et al. (1996) estimate that worldwide 60 percent tanning is based on chromium, while 40 percent is vegetable tanning (including aniline). In the United States, a little over 20,000 hides are tanned per day; 4,700 (23.5 percent) with vegetable tannins and 15,300 (76.5 percent) with chromium (Hemingway and Karchey, 1989). Although vegetable tannins are bio-degradable, they still constitute a considerable burden on the environment.

In most developing countries tannery effluent is disposed of by sewer, discharging to inland surface waters and/or irrigating land. High concentrations of salt and hydrogen sulphide present in tannery waste water affect water quality and can cause bad taste and odour. The suspended matter, such as lime, hair, fleshings, etc. make the surface water turbid and settle to the bottom, thereby affecting fisheries. Chromium tannin is toxic to fish and other aquatic life. When mineral tannery waste water is applied on the land, the soil productivity is adversely affected and some of the land may become completely infertile. Due to infiltration, groundwaters are also adversely affected. Discharge of untreated tannery effluent to a sewer causes deposition of calcium carbonate and choking of the sewer.

Dairies. Worldwide, cattle contribute 87 percent of total milk production, whereas buffalo, sheep and goats contribute 9, 2 and 2 percent, respectively. In the developed countries, the bulk of milk is factory-processed. In the developing countries, home or village processing or consumption of processed is much more common. In Africa, it is estimated that 80 to 90 percent is home processed or consumed raw whereas for Latin America, this share averages about 50 percent (FAO, 1990). Coagulated milk and cheese curd are solid wastes of minor importance.

The level of processing milk varies greatly. It ranges from simple pasteurization to sophisticated cheese products. Waste water production is the major environmental concern, mainly resulting from cleaning operations. In addition, fossil fuel is consumed and CO2 emitted during pasteurization and sterilization of fresh milk and during the production of milk powder or condensed milk. CFC and NH3 emissions from chilling machines are of some importance.

General. All processing results in the production of waste water, mostly in large quantities, and its discharge is the biggest environmental problem. Waste water is polluted with biodegradable organic compounds, suspended solids, nutrients and toxic compounds (particularly chromium and tannins from tanneries). This results, directly or indirectly, via a reduction of dissolved oxygen, into a deterioration or destruction of aquatic ecosystems. It also damages potable water quality. Typical values of the waste water are given in Table 5.9. However, huge variations have been found, due to large differences in scale and management practices of each factory or plant. The quantity of water used during the process is of major importance, with high water use related to high emission values.

Table 5.9 Typical values of waste water characteristics produced by different animal processing industries.
Operation Expressed per BOD SS Nkj-N P
Red meat slaughterhouses ton LWK 5 5.6 0.68 0.05
Red meat packinghouses ton LWK 11 9.6 0.84 0.33
Poultry slaughterhouses ton LWK 6.8 3.5
Tanneries ton raw hide 100 200
Dairies (consumption milk) ton milk 4.2 0.5 <0.1 0.02

In theory the production of waste water does not necessarily lead to environmental problems if the density of animal product processing is low enough to guarantee low concentration of pollutants in the receiving water bodies. However, if compared to European target values for urban waste water discharge (e.g. 25 mg BOD, 10-15 mg N and 1-2 mg P per litre), waste loads are excessive at even low quantities of animal products processed. For example, the 5 kg BOD per ton Liveweight Killed would require the enormous amount of 200,000 litres of water (5,000,000 mg divided by 25 mg/l) to get it down to EU standards.

Air pollution and solid waste result in minor problems compared to waste water production. Air pollution is mainly related to fossil energy use in all three types of processing. Significant amounts of volatile organic compounds are emitted by the leather industry. Solid waste may result in hygiene problems, particularly with slaughterhouses but, in principle, these are relatively easy to solve. An exception is chromium containing leather waste, which must be disposed in special dumping grounds.

Technology and policy options

Technology. Technologies exist to significantly reduce emissions from processing plants. The problem is one of cost and corresponding incentive and regulatory framework. Because of the high BOD-load in the waste water of tanneries, dairies and slaughterhouses, anaerobic systems are the most suitable waste water purification systems. Simple anaerobic systems could cut the BOD contents by half, while more sophisticated anaerobic systems reach 90 percent BOD-purification. Waste water treatment usually first separates solids from the liquid, followed biological treatment under anaerobic conditions (lagoons). Then, nutrients such as phosphorus are removed by chemical or physical processes such as adsorption, stripping or coagulation. The same process serves to remove the remaining BOD as well as pathogens. In a few developed countries environmental problems have already led to high quality standards being required for discharge water. To meet these standards, a combination of anaerobic and aerobic treatment is required, often coupled with nutrient removal systems.

As most of the air pollution is related to fossil energy consumption, prevention to reduce environmental pollution, is even more important for air pollutants than for waste water. There are methods to treat polluted air, although generally at high cost.

Slaughterhouses. In slaughterhouses, the environmental impact can often be greatly reduced by employing simple technology:

Tanneries. Pollution through waste water can be reduced by cutting down on total water use, for example, by re-using waste water, by introducing new technologies to minimize water use and by reducing the use of chemicals such as lime, salt, sulphide etc. and chromium. Higham (1991) gives more details:

Box 5.11 Regulations induce search for innovative solutions: the case of Tyson Food Inc.
In the state of Arkansas, USA, Tyson Foods Inc. was sued by more than 100 Green Forest residents who contended that their water supply had been fouled by a lack of adequate sewage treatment from chicken processing plants in 1989. Tyson was ordered to pay for property damage, for overloading of the city's water treatment system, and for violating the Clean Water Act. Furthermore, the use of burial pits for dead bird disposal by growers was banned. This resulted in Tyson Foods investing in research and development to remedy the problem.
Tyson Foods subsequently developed a recovery technology that allowed them to recycle proteins, fat and carbohydrates recovered in their water treatment process into nutrients for animal feed. This enabled the company to recycle not only various solids (primarily proteins, carbohydrates, and fats) from its water treatment plants in Arkansas, Oklahoma and Missouri, but also the inedible animal parts from its poultry treatment and pretreatment centres attached to its processing plants. Further, it also enabled the recycling of dead birds from the farms. In order to facilitate the use of this technique, Tyson Foods distributed some 2,000 custom freezers to its growers to aid them in the disposal of dead birds, which were collected and transported to the rendering plant.
Thus, the refinement of the rendering process resulted in a win-win solution, i.e. an improvement of the environment and a profitable solution for Tyson. The ability to recycle by-products is becoming more of a concern as consumers are demanding more processed meat and pet food companies, among others, purchase the processed protein meal and other products for use as high-quality ingredients in various animal rations. The feathers can also be hydrolyzed into a feather meal that can be used as another high protein animal feed ingredient.
Source: Narrod, 1994.

Dairies. Waste can be prevented to a considerable extent by good management practices and use of adequate equipment. While poor management results in waste loads of 3 kg BOD per ton of milk, good management can reduce this to 1 kg. Again, this can be achieved by optimizing the use of water, resulting in lower volumes of waste water, and by recovering solids from the waste water.

Policies. In contrast to many other impacts of livestock production, processing is usually point source pollution and therefore easier to quantify and to control.

Regulations are an essential component in dealing with the environmental impact of processing plants. They may limit or prohibit the use of chromium in tanneries, control the use of CFCs in chilling processes and limit the total BOD output in waste water. In addition, odour and gaseous emission control may be prescribed.

Zoning. For small processing units, a policy of encouraging an even geographical distribution is probably the best approach. Similarly to the industrial livestock production system, specific sites should be identified for industrial processing operations. Because of its bulkiness and perishable nature, milk processing has always been sited close to producers and is less concentrated. A similar trend is starting in the developing countries. However, zoning is dependent on a functioning infrastructure and adequate enforcement of pollution control regulations.

Incentives. Use and processing of by-products depends to a great extent on whether there is a market for a given commodity, on the availability of a practical commercial process for converting the animal by-product into a usable commodity, and on storage facilities for the perishable product and on whether there will be a sufficiently large volume for it to be financially viable. Also here, win-win situations can be found, as shown in box 5.11. Increasing the prices for water and energy can make the use of these resources more efficient and thus reduce the waste load and emissions. Incentive policies may help to stimulate a market, creating selective advantages for by-product use and waste recovery but, as with public incentives in general, should be of short duration and well-targeted.

Institutional instruments. Finally, there is an urgent need to strengthen pollution control and enforcement mechanisms and to establish financial independence of slaughterhouses in the developing world which now, frequently, see all their income going back to the public coffers, without re-investment in maintenance and infrastructure improvements.

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