Contents - Previous - Next

Response: Technology and policy options

Technologies. Most technologies that reduce greenhouse gas emission are typical examples of win-win situations. They are being used because they make economic sense and their benefit is an added benefit.

Savanna improvement, as well as forestation, can lead to substantial permanent CO₂ sequestration. Recent findings by CIAT scientists (Fisher, et al., 1995) show that, by introducing improved pastures (Andropogon) with a much larger root system in the Colombian savannas can fix up to 50 tons of CO₂ per hectare, which is comparable with the 50 to 100 tons per hectare that forest plantations can store. Increased production thus leads also to lower CO₂ levels, and provides a "win-win" situation.

To reduce methane emissions, improved breeding, veterinary care, better feeds and improved feeding technologies are the main weapons, although these technologies are usually not employed for their environmental benefits but for increasing profitability. Improvements in animal productivity have two beneficial effects. They direct a greater proportion of feed energy to the production of useful products (milk, meat, draft power, offspring), and thus reduce methane emissions per unit of product. In addition, they lead to reductions in the herd size required to meet a given production level.

More specifically, improvements in nutrition through mechanical and chemical feed processing, or through strategic supplementation, can drastically reduce methane emissions. Chopping, and alkali and urea treatment of low digestible straws, improve digestibility. When fed to ruminants, these options may decrease methane emissions in the order of 10 to 25 percent in normally poorly fed animals. Strategic supplementation is another option. Critical nutrients, such as nitrogen and essential minerals can be provided, through molasses/urea multi-nutrient blocks and bypass protein techniques (Box 5.9). Substantial increases in animal productivity can be achieved in tropical areas with chronic feed constraints. Here, methane emissions can be reduced by 25 to 75 percent per unit or product. Productivity may also be enhanced through the use of production enhancing agents such as bovine somatrotropin and anabolic steroids, for which emission reductions of 5 to 15 percent have been demonstrated.

There are promising techniques for recovering methane from manure, thereby not only reducing emissions but providing a source of energy, for example for generating on-farm electricity. Large, confined animal operations make such techniques profitable. The slurry effluent can be used as animal feed, as aquaculture supplements, and as crop fertilizer. In addition, managed anaerobic decomposition reduces the environmental and human health problems often associated with manure management. The controlled bacterial decomposition of the volatile solids in manure reduces the potential for contamination from run-off, significantly reduces pathogen levels, removes most noxious odours and retains the organic nitrogen content of the manure.

The primary approaches for recovering this methane include the following:

• Covered lagoons. Manure solids are washed out of the livestock housing facilities with large quantities of water, and the resulting slurry flows into an anaerobic primary lagoon. The anaerobic conditions result in significant methane emissions, particularly in warm climates. Placing an impermeable floating cover over the lagoon and applying negative pressure recovers the methane which can be used as fuel or to generate electricity. This is specially interesting for developed countries (Box 5.10).

• Digesters. Large and small scale designs exist. Large scale digesters are engineered vessels into which a mixture of manure and water is placed. The retention time of the manure is about 20 days. The digester is heated to about 60 °C and the gas drawn off and used for energy. Large dairy and pig farms, with high energy requirements, typically find these systems to be cost effective. Small scale digesters typically do not include heating and are therefore only appropriate for warm climates. They are relatively simple to build and operate, require little capital investment, and the recovery of high quality fertilizer from digesters can be an important benefit where cost of commercial fertilizers are high.

• Policies. The identification of specific policies to reduce greenhouse gas emissions are complex. Ideally, they are part of an overall development process driven by the need to improve productivity. Technologies which enhance productivity, improve root biomass for carbon sequestration and nutrition, and for recycling methane for energy, are likely to be the most effective and should be promoted through education and training. While some of these technologies are profitable and improve the environment at the same time, others, such as urea treatment, are not always adopted by farmers because of high input costs, which are often not off-set by increases in productivity alone.

An important issue is how to reward the adoption of techniques which reduce greenhouse gases. If the additional benefit of greenhouse gas reductions could be captured by farmers, adoption rates could be much higher. For example, while valuation mechanisms for CO₂ are still in an early stage of development, Brown et al., (1993), estimating the damage from a doubling of atmospheric CO₂ in terms of global warming at 1 percent of Gross World Product, arrive at a price of US$ 10 per ton of CO₂ trapped. This would mean that the above mentioned improvement of South American savannas with Andropogon could be valued at US$ 500 per hectare. International arrangements are required beyond those of the Global Environment Facility (GEF) to achieve such transfer mechanisms.

A number of donor agencies are implementing projects, where reduction of methane emission is an explicit objective and its degree of achievement has an impact on project approval. Policies may be directed to establish regulations to limit, or ban, lagoon manure storage, or to impose methane recovery. In some countries governments favour the establishment of facilities to recover methane through direct subsidies on the construction of such facilities (California, Denmark). However, the most important determinants for the adoption of these technologies are the price and availability of energy, which largely influence the profitability of these systems. For large-scale facilities, energy requirements for heating, for example, may be high and the high costs of commercial energy may induce investment into methane recovery, whereas for small-scale operations it is often lack of infrastructure and energy supply that make its establishment profitable, as in, for example, remote areas with no electricity. The use of methane as a regenerative source of agriculture is thus determined by the larger picture of fossil energy supply and national policies in that regard. Some OECD countries have started favouring the use of regenerative energy vis-à-vis fossil sources and create corresponding price incentives.

The emission of greenhouse gases is subject to the UN Framework Convention on Climate Change. The agreement, now signed by more than 150 countries, became legally binding in March 1994, and many signatories have voluntarily agreed to stabilize their carbon dioxide emissions at 1990 levels by 2000. The agreement is targeted at the other trace gases with which livestock production can be associated, i.e. methane and nitrous oxide. However, to minimize climate change from greenhouse gases, much more specific international agreements are required and efforts must be made to respect them.

Processing of livestock products

Environmental challenges
State and driving forces
Technology and policy options

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 wastewater. 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:

• to raise technology levels and increase knowledge on waste prevention, use of by-products and waste treatment;
• to strengthen institutions to establish and enforce environmental regulations; and
• to develop infrastructure to linking rural-based production and processing to growing urban markets.

State and driving forces

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-product because a higher proportion of the animal is usually consumed.

Table 5.8: Potential waste emissions of a red meat slaughterhouse.

Source: Verheijen et al., 1996.

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 deponed 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 beam-house operations, tanning and finishing. Hides are usually tanned twice. For the first step, mineral or vegetable tanning is practiced. 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 big-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.

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.

Table 5.9: Typical values of waste characteristics produced by different animal processing industries.

Contents - Previous - Next