by
Dr. A.G. de Moor
Veterinary Inspector of Public Health,
Inspector of Veterinary Service,
V/H Staatstoezicht
Kon. Julianaplein 3, The Hague, Netherlands
| Summary | Résumé |
| The paper examines briefly the dangers to public health that can arise out of the recycling of wastes for use as animal feeds and, secondarily, fertilizers for grazing land. Taking the Netherlands as an example in the absence of well-developed Legislative provisions in most other countries, it indicates how the legislator can provide a framework for government policy and action in this field. Under proper control by the authorities, rendering plants can play an important role in the recycling of animal wastes, yielding a good end-product without endangering public health. In the Netherlands this activity is governed by a series of laws enacted between 1919 and 1970. Extensive research is currently being carried out on the recycling of animal manures for use as feeds. Good results have been reported with respect to feed efficiency, growth and feed conversion, and residue levels in the end-product are generally acceptable, but many countries, in response to public opinion, prohibit such uses. The Netherlands have established a special Biological Residues Surveillance Programme to monitor the presence of harmful bacteria and residues in feeds, animal organs and end-products, etc. and to intervene actively when contamination is detected. Veterinary public health services should be actively concerned with programmes for animal waste disposal and recycling, particularly since they are in an ideal situation to observe, coordinate or initiate developments in this field. The use of domestic sludges as fertilizer within limits of 1 ton DM/ha/year on grassland and 2 tons DM/ha/year on arable land has been found acceptable from a public health point of view. Industrial sludges have an excessive heavy-metal content, but more research is needed to establish the incidence of these residues in the end-product, and to determine whether their levels can be reduced through application of surface-water pollution legislation. While, in the Netherlands, waste disposal is currently regulated mainly from the point of view of environmental protection, the legislation can also provide the framework for action in the recycling of municipal wastes, as opposed to industrial wastes. | L'auteur examine brièvement les risques que peut faire courir à La santé publique le recyclage des déchets, utilisés comme aliments du bétail ou accessoirement comme engrais pour les pâturages. En se fondant sur L'expérience acquise aux Pays-Bas (La plupart des autres pays manque de textes juridiques appropriés), il indique comment Le législateur peut influer sur la politique et l'action gouvernmentales dans ce domine. Convenablement guidés par les autorités. Les foundoirs peuvent jouner un rôle important dans le recyclage des déchets animaux, fournissant un produit final satisfaisant qui ne menace pas la santé publique. Aux Pays-Bas, cette activité est régie par un certain nombre de lois promulguées entre 1919 et 1970. Des recherches approfondies se pour suivent sur le recyclage des déjections animales aux fins de l'alimentation du bétail. On a obtenu bons résultats en ce qui concernel'efficacité protéique des aliments, la croissance des animaux et le taux de conver sion. La concentration de résidus dans les produits finals étant en général acceptable toutefois, sous la pression de l'opinion publique, de nombreux pays interdisent de telles utilisations. Les Pays-Bas ont instituté un programme spécial de surveillance continue des résidus biologiques pour contrôle la présence de bactéries et de résidus nocifs dans les aliments du bétail, les organes des animaux et les produits finals, etc. et pour intervenir rapidement en cas de contamination. Les services de la santé publique vétérinaire devraient s'intéresser activement aux programmes ayant trait á l'utilisation et au recyclage des déchets animaux, étant, donné qu'ils se trouvent dans une situation idéale pour observer, coordonner ou entre-prendre des activités dans ce domaine. On a estimé qu'il était acceptable du point de vue de la santé publique, d'utiliser les boues ménagères comme engrais jusqu'à concurrence d'une tonne de matière sèche par hectare et par an sur les pâturages et de deux tonnes sur les terres arables. Les boues industrielles ont une teneur excessive en métaux lourds, mais il faut poursuivre les recherches pour évaluer les effets de ces résidus dans les produits finals et déterminer si leurs taux peuvent etre réduits par la mise en oeuvre d'une législation sur la pollution des eaux de surface. Alors qu'aux Pays-Bas l'évacuation des déchets vise essentiellement à assurer la protection de l'environment, la législation peut également fournir des orientations pour le recyclage des déchets municipaux par opposition aux déchets. |
Resumen
En este trabajo se examinan brevemente los peligros para la salud pública que pueden derivar del reciclaje de residuos para su utilización como piensos y, secundariamente, como fertilizantes de los pastizales. Dado que en la mayoría de los paises no existe una legislación de utilidad controlada, se toma como ejemplo los Países Bajos y se indica el modo en que el poder legislativo puede crear un marco para que el gobierno adopte una politica y medidas en este sector.
Si las autoridades ejercen una vigilancia adecuada, las fábricas transformadoras pueden desempeñar una función importante en el reciclaje de residuos animales, fabricando un producto final que no ponga en peligro la salud pública. En los Países Bajos estas actividades están reguladas por una serie de leyes promulgadas entre 1919 y 1970.
Se está realizando un amplio programa de investigaciones sobre el reciclaje de estiércoles para utilizarlos como piensos. Se han señalado buenos resultados en cuanto a la eficiencia de los piensos, al crecimiento del ganado y la conversión de los piensos; por otra parte el contenido de residuos en el producto final es generalmente aceptable, pero muchos países, sensibilizados por la opinión pública, prohiben tales usos. Los Países Bajos han establecido un programa especial de vigilancia de los residuos biológicos para vigilar la presencia de bacterias y residuos nocivos en los piensos, órganos animales, productos finales, etc., y para intervenir activamente cuando se detecte contaminación.
Los servicios de veterinaria de salúd pública deben participar activamente en programas de eliminación y reciclaje de residuos de origen animal, particularmente porque están en condiciones ideales de observar, coordinar o emprender actividades en este sector.
El empleo de residuos domésticos como fertilizantes, dentro de los límites de una tonelada de MS/ha/año en pastizales y de dos toneladas de MS/ha/año en tierras de labranza, ha resultado aceptable desde el punto de vista de la salud pública. Los residuos industriales tienen un contenido excesivo de metales pesados, pero se necesitan más investigaciones para establecer la incidencia de estos residuos en el producto final y determinar si pueden reducirse sus niveles aplicando una legislación relativa a la contaminación de las aguas superficiales.
Aunque en los Países Bajos se regula actualmente la evacuación de residuos principalmente desde el punto de vista de la protección del medio, la legislación puede ofrecer también un marco para adoptar disposiciones con respecto al reciclaje de residuos municipales, en cuanto distintos de los residuos industriales.
Since this subject is still new and national legislation is yet rather undeveloped in most countries, the legislative provisions existing in the Netherlands are taken as an example in this paper.
A recent report by two FAO consultants (1) on animal waste disposal concludes that it would be better to speak of animal waste “disposal and utilization” rather than “recycling”. “Recycling” may be a new word, but the concept behind it is not new: what it means is that new and usable products can be made from old, non-usable materials or wastes.
Disposal of the animal itself provides a good example of how fallen animals and slaughterhouse waste have been recycled by renderers for many years and have been transformed into important products suitable for animal feeding.
In this type of animal waste recycling, a good end-product is obtained and there are no public health hazards, subject to proper handling and to good control by the Veterinary Services. Legislative authority for such control is provided by the Public Nuisance Act of 1952 (Hinderwet), the Destruction Act of 1957 (Destructiewet), the Pollution of Surface Waters Act of 1970 (Wet verontreiniging opperulaktewateren) and the Air Pollution Act of 1970 (Wet op de luchtverontreiniging).
The rendering plants themselves are private enterprises governed by the Meat Act of 1919 and the Destruction Act of 1957. These Acts define “destruction” as the destruction of fallen animals and slaughter wastes, their conversion into usable products and the elimination of unsuitable material. They provide for the disposal of rendering products, requiring that they constitute no danger to public health and that useful material is not lost. The destruction and elimination referred to in these Acts are entrusted to the municipal authorities.
Animal manure constitutes another important waste product. In envisaging its use, two major considerations must be borne in mind: 1. The feeding of nutrients recovered from animal excreta implies dangers to animal health, and, through animal products, also indirectly to human health.
2. The utilization of animal manure and sludge on agricultural land creates certain public health hazards which have legal implications. Thus, when cattle are grazed on manured fields, there could be cumulative effects on the animals and indirectly on the end-products of animal origin.
Research on ensiling and on the drying of manure, especially poultry manure, has facilitated the development of different separation techniques that enable the manure to be used in the solid and liquid states. Research on the possible mixing of dried manures into compound feeds has yielded information on their antibiotic, pesticide and heavy-metal residue contents (see Table 20.1).
The different experiments have shown good results with feed efficiency, growth and feed conversion, and there appear to be no problems with bacteria, pesticides, minerals and antibiotics. However, many countries, including the Netherlands, currently prohibit the presence of a manure component in compound feeding stuffs, not so much for reasons of public health as from a public opinion or aesthetic point of view.
Much research has also been carried out on recycling liquid purified manure in pigs in the form of drinking water, and drinking water from an effluent of an anaerobic lagoon is also being given to fattening pigs (Ames, USA). In these cases, however, some changes in the kidneys, deformation of the lymph nodes and a larger number of leucocytes have been observed.
From a public health point of view it is of interest to know what kind of residues are found in the end-products of animal origin when dried manure or poultry litter is fed to cattle. (2) (3) (4). In US experiments, drug residues have frequently been found in broiler litter, but feeding the litter to cattle resulted in little or no drug accumulation in tissues tested after a 5-day withdrawal period. Only copper was shown to accumulate in the liver, and this should be borne in mind particularly with regard to sheep. In the Netherlands experiments, dried poultry manure was fed as a nitrogen source to fattening young bulls. After slaughter the carcasses were tested for antibiotic and organochlorine pesticide residues. The residues detected were not any larger than in the control groups.
| Domestic sludge (purification plant) | Agricultural sludges | Industrial sludges | Manure | Municipal compost | ||
| organic material | % | 48.0 | 65.0 | 38.5 | ||
| nitrogen | % | 3.08 | 2.51 | 1.00 | ||
| P2O5 | % | 4.39 | 1.58 | 0.85 | ||
| K2O | % | 0.24 | 1.72 | 0.31 | ||
| CaO | % | 4.62 | 1.91 | 2.90 | ||
| MgO | % | 0.35 | 0.79 | 0.38 | ||
| Na2O | % | 0.22 | 0.46 | 0.28 | ||
| Cl | % | 0.21 | 0.93 | 0.26 | ||
| Fe | ppm | 28700 | 860 | 44000 | ||
| Mn | ppm | 830 | 230 | 360 | ||
| Zn | ppm | 1650 | 700 | 5400 | 70 | 1500 |
| Pb | ppm | 250 | 300 | 1050 | 20 | 850 |
| Cr | ppm | 130 | 0 | 2600 | 20 | 200 |
| Cu | ppm | 420 | 100 | 4300 | 14 | 600 |
| Cd | ppm | 8 | 0 | 300 | 1 | 5 |
| Ni | ppm | 30 | 0 | 900 | 4 | 100 |
| Hg | ppm | 10 | 0.1 | 5 | ||
| As | ppm | 10 | 1 | 10 | ||
| Sb | ppm | 10 | 1 | 10 | ||
Source: de Haan, 1976 (7)
These results are encouraging, but nevertheless governments have an important role to play in monitoring the food chain as a whole, not only for reasons of public health, but also for economic reasons, especially as regards exporting countries. The consumer of the end-product should be assured that he has a safe product at a reasonable price. It is relevant in this context to draw attention to the Biological Residues Surveillance Programme, developed in the Veterinary Service in the Netherlands, for cases of Salmonella contaminations and parasites, incidences of pesticides residues, antibiotic residues, hormones, drugs, heavy-metal residues, etc. Basic materials for the compound feeding industries, the feedstuffs themselves, animal organs and fat, and end-products of animal origin are all sampled and examined for the occurrence of residues. The frequency of sampling is dependent on the results obtained. Where contamination is detected, appropriate action is taken to break the cycle. For instance, in cases of Salmonella contamination of feed, decontamination by heating, pasteurization, sterilization and even radiation may be undertaken, although more commonly the feed is pelleted. When high pesticide residues are found, the source of the residues is determined. In the last years, the importation of Argentine pollard pellets, highly contaminated with HCB residues, has been forbidden by law.
The 1975 Joint FAO/WHO Report (5) notes that “safe means of disposal of animal wastes and dead animals are of great importance in countries with newly developing animal industries, as well as in areas with already highly developed specialized industries of this type. They are essential not only for the reasons already stated but also for the control of epizootic infections of the food-producing species themselves including many zoonoses, as well as for the direct protection of consumers of meat and other animal products.”
Veterinary public health services should, therefore, be actively concerned with programmes for animal waste disposal and recycling, particularly since veterinary public health is actively and specially concerned with veterinary environmental hygiene.
It is urgen that thorough investigations be undertaken of all proposed methods of recycling or other treatment of animal carcasses, offal and wastes in order that these health risks to man and animals may be minimized.
Veterinary public health services are in an ideal situation to observe, coordinate, or initiate developments in this field and to establish health criteria for substances to be recycled for animal production or other purposes.
Recent research in the Netherlands (6) has shed some light on the possibilities of the use of certain wastes as fertilizers. As a guideline it appears that domestic (but not industrial) sludges may be used on grassland at a rate not exceeding 1 ton DM per hectare and per year; on arable land the rate is increased to 2 tons. Industrial sludges, in addition to having an unacceptable heavy-metal content (see Table 20.1), can also create pesticide residue problems. For example, cows grazed on grass containing 8 ppm dieldrin yield milk containing 2 ppm dieldrin on the fat, whereas the tolerance accepted in the Netherlands for milk and milk products is 0.15 ppm. More research in this field is however needed. It is known that the accumulation of heavy metals is greater in the soil than in the growing plant. The truly relevant factor for the fertilizing of grassland is the amount accumulated by the grazing animals themselves, the public health aspect of the problem being conditioned by the quantities reaching the consumer in end-products of animal origin. Further, it might be possible to decrease the heavy-metals content of industrial sludges through the measures foreseen in the Netherlands Pollution of Surface Waters Act of 1970.
Conclusions
In the Netherlands, the main legal instrument at present for waste disposal is the Public Nuisance Act of 1952, which provides for the prevention of nuisance, danger, or damage by individual “establishments” to their immediate surroundings. The construction, operation and expansion of “establishments” is forbidden except under licences, granted by the municipal authorities, which usually contain requirements for the prevention of environmental pollution. The Destruction Act of 1957 deals with the disposal of a special category of waste: animal material that is for any reason unfit for human consumption (e.g. slaughter waste and animals dead of disease, etc.). A limited number of destructors, each with exclusive responsibility in a given area, is charged with disposal. Waste disposal is thus regulated mainly from the point of view of environmental protection.
Waste disposal legislation can however also provide the framework for government policy and action in the possible recycling and re-use of municipal wastes. In 1973 the Netherlands adopted a Chemical Wastes Act, governing the disposal of chemical wastes and used oil. It enables the authorities to issue regulations defining the substances that are to be considered as chemical wastes and creates a licencing system for storing, treating, processing and destroying them.
For the less hazardous “ordinary” wastes, a Waste Disposal Bill is being prepared. This bill defines the disposal of household waste - as opposed to industrial waste - as a governmental (municipal and provincial) task and makes special provision for the recycling and re-use of waste, in order to reduce the amount of waste.
Like the Chemical Waste Act, it creates a levy system to finance the execution of the Act and measures promoting recycling or effective waste disposal.
References
1. F.A.O. Report Nov. 1975. Olle Swahn and Per Erik Lohm.
2. Instituut voor Veevoedingsonder zoek “Hoorn”, Biureet en gedroogde batterijmest als stikstofbron (eiwitvervanging) voor Vleesstieren: F. de Boer en G.G.H. Hamm.
3. Medicinal Drug Residues in Broiler Litter and Tissues From Cattle Fed Litter: K.E. Webb Jr. and J.P. Fontenot. Virginia Polytechnic Institute and State University, Blacksburg, 24061, J. Anim. Sci. 41 (1975) 4.1212.
4. Recycling Animal Waste as a Feedstuff: A Review by A.N. Bhattacharya and J.C. Taylor, J. Anim. Sci. Vol. 41, No. 5 1975.
5. Technical Report Series 573 WHO, Geneva, 1975. The Veterinary Contribution to Public Health Practice.
6. Zuiveringislib in de Landbouw. Ir. Ch. H. Henkens Bedrijfsontwikkeling 6(1975) 2(februari).
7. S. de Haan: afvalzuiveringsslib als meststof of grondverbeteringsmiddel. Landbouwk. Tijdschr. 1976. 88(1) p 21, 27.
