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English summary

The main purpose of this project is to document whether animal manure contains quantities and types of chemicals leading to unacceptable environmental impacts when the manure is spread on farmland. Furthermore, the project compares the impact of chemicals from animal manure with the impact of using sewage sludge. The reason for doing the project is that this topic has been debated for quite a long time and that knowledge is very limited.

One of the many areas studied is whether the different types of farms (pig farms, cattle farms and organic cattle farms) differ in their way of using chemicals, whether chemicals end up in animal manure thus in theory polluting farmland. This project has exclusively focussed on slurry. Information was also needed on whether small and large farms differ in their use of chemicals and the impact of chemicals on their land. Finally an assessment was made describing whether the consumption pattern and behaviour in relation to chemicals reflect the content and environmentally offensive substance in slurry.

Chemicals ending up in slurry may originate from many different sources, the most important being detergents, disinfectants and udder ointments. There are also other sources and types of chemicals which have not been analysed in this project, e.g. drug residues.

A comparison between small and large farms shows no clear difference – neither as regards the farms´ stated consumption of agents or the contents of the analysed slurry samples – nor is there any difference in 30 slurry contents between farms with large and modest chemical consumption. When the farms involved in this project was selected, data were not available on the contants of chemicals contained in the products used on the farms where the slurry samples were to be taken out.

When comparing the different types of farms (pig farms, cattle farms and organic cattle farms), there is neither any distinct difference in terms of consumption pattern for chemicals nor any statistical difference in the contents of chemicals in the slurry. LAS and PAH were found in all 30 slurry samples, traces of NPE in 5 samples and DEHP in 11 samples. When estimating the environmental impact on farmland based on the analyses, it is evident that the conventional cattle farms had the highest average LAS impact whereas NPE, DEHP and other phthalates had the highest impact on organic cattle farms. The PAH impact was the same and highest on the both types of cattle farms. However, it should be noted that the level was low, that the generally low concentrations measured lead to high uncertainties and that individual farms within one type of farms may carry great weight. In the aggregate, this makes the conclusion very uncertain. Based on the analyses there is no indication that slurry from any of the individual farms has any critical contents of chemicals.

If the requirements concerning the spreading of environmentally offensive substances in sewage sludge (cf. the Danish Sewage Sludge Order) are to be considered normative of acceptable spreading on farmland, the conclusion is that the impact from slurry is very low. If compared with the contents of environmentally offensive substances spread on farmland, the contents of slurry are also very low on average. A former study [1] of two cattle slurry samples, so far used to characterise the impact level of slurry, showed higher contents of environmentally offensive substances than the present study. So this study must be very poor at characterising the impact level of slurry.

When the soil impact is calculated on the basis of the stated consumption of the farms as well as the suppliers’ stated and estimated sales of agents, a somewhat different picture is emerging. There is thus a large difference between somewhat higher consumption-based contents and the analysed LAS and NPE values. The cause of this difference has not been clarified but the report states various possible explanations. It is normally assumed that these substances are not degraded under anaerobic conditions, presumably existing in slurry, but degradation in slurry has not yet been investigated. As the slurry had an average age og 4-6 months at the time of sampling, degradation, if any, may influence the quantifiable contents.

In the products used, NPE often contains 8, 12 or 20 ethoxy groups. As it is assumed that no substantial NPE degradation is taking place in slurry during storage, it is possible that only a minor part of the original NPE is converted to nonylphenolic substances with 0, 1 or 2 ethowy groups (NP, NPEO1 and NPEO2) included in the chemical analyses. So it is considered uncertain whether the measured NP an NPE concentrations approximate to the total concentration of nonylphenol substances in animal manure. On the basis of the analyses the calculations of NPE impact on farmland are considered very uncertain.

Even on the basis of the consumption-related contents the LAS, phthalate and PAH contents of slurry are not problematic compared to the requirements of the Danish Sewage Sludge Order – nor after the year 2000. However, realistic worst case calculations of NPE content show that we cannot preclude the possibility that some farms will not meet the requirements for sewage sludge after the year 2000. As NPE is considered to have undesirable environmental qualities [1], efforts should be made to phase-out this substance. The analysis material does not indicate that the worst case situation occurs but the material is relatively scanty and thus not necessarily fully representative of slurry in general.

The project shows that contrary to expectation some of the chemicals analysed are found in slurry on farms where substances containing the chemicals involved have not been used. So on this background some chemicals does not exclusively originate in the sources analysed, like for instance detergents and disinfectants.

Furthermore, this project has identified a wide range of other chemicals used in farming but not included in the analyses carried out. On the basis of the environmental qualities an toxicity classes of the substances an A, B and C score system has been worked out for all the chemicals used, graduating the chemicals to be either undesirable in animal manure (A-substances), substances whose use should be limited in order to avoid substantial environmental impacts (B-substances) and substances which are not considered to have environmental impact if used in the ordinary way (C-substances).

By far the majority of the chemicals used on farms is expected not to have a character or to occur in slurry in quantities which make their use alarming. However, some of the chemicals used have been identified as A-substances whose application should be limited as much as possible. The A-substances are mainly found in udder ointments.

The application of A-substances can be limited by attaching labels to the products, providing the farm manager with guidance and information but a strategy focussing on phasing-out or replacement should be preferred. However, this presupposes that alternative products and methods are available. The questionnaires filled in by the farmers involved show that the use of chemicals and the farmers’ behaviour in the livestock houses differ a great deal. So today it should be possible to use more or less chemical-free solutions in some areas.

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