Poor Management of Animal Wastes
Environmental Assessment: Pressure State Response Indicators

The main problems stem from the disposal of manure from animal production systems, introducing high concentrations of nutrients into the environment. In addition there are problems that result from the accumulation of heavy metals, introduced into feeds as trace element supplements or as accidental pollutants. | Pressure State Response Further Reading

The source is a point source of pollutants, however the method of disposal of the wastes can either result in point source pollution where discharge is focused on a specific site, or as a non-point source pollutant where wastes are dispersed across large land areas. For management purposes the fact that there are clearly identified primary point sources of pollutants allows for a degree of regulation that is not possible in open agriculatural systems.

In all cases the end risk is that ground and surface water will be polluted, either directly through discharge or seepage into water systems, or as a result of leeching or run-off from land areas.

Pressure

As with all industrial enterprises, the impact is the result of the scale of the enterprise, the technologies and management systems in place, and most significantly. the number of these activities taking place.

The problem of discharge of wastes is cumulative, the environment has a natural buffering capacity which can absorb a certain level of organic or inorganic pollutants. Once this level is exceeded, then the natural biological and bio-physical processes break down leading to changes in vegetation, habitats and ecosystems.

The problem is compounded by the incremental impacts of different enterprises within indistrial animal production systems, as well as with other activities. This includes, for example, the treatment and discharge of domestic sewage.

Pressure is characterised by:

- The type of enterprise - pig, poultry, ruminant or dairy;
- The scale of the enterprise - small, medium or large;
- The technology used - high, medium or low;
- The method used for waste treatment and disposal;
- The number of similar or comparable enterprises discharging waste - including those from other sectors.

Less directly pressure can be characterised by changes in market demand and alternative supply sources for animal proteins. Future pressure can be predicted on the basis of present patterns of consumption and projected socio-economic and demographic trends, particularly towards more affluent urban patterns of settlement.

State

The state of the environment is characterised by the concentrations of pollutants in soil and surface and groundwater. The key pollutants are excessive levels of N,P and K, and trace elements and heavy metals such as copper, zinc and cadmium.

The impact of excessive levels of pollutants, is in the long term, change in vegetation, habitat and ecosystem. Natural systems will change and these changes will be reflected in changes in species composition. In aquatic systems the end result is eutrophication, on land there is a change in species mix, tending to fewer species tolerant to high nutrient loads and nutrient imbalance.

However, by the time these macro changes have taken place, the problem of high nutrient loading or high heavy metal and trace element loading may have resulted in irreversible damage - or at the very least impacts that will require high cost solutions to reverse. As a result there is a need to assess the state of the environment through the use of indirect indicators.

The usual response is to assess the two ends of the system, the pathway starts at the production site and ends in the waterway. Assessment can take place at source by measuring discharge concentrations of pollutants, or at the sink - the waterbody - by measuring final concentrations of pollutants.

The major problem is then to define what are damaging, or alternatively, acceptable levels of pollution. But thiis will vary according to the downstream requirements of the system, water quality for industry may have fairly low requirments, while discharge for ecosystem functioning may be higher than for industry but less critical than supplies used for drinking water.

In addition to the need to define the downstream use of water, care must be taken in seasonal variataions in discharge, and possibly more critically dilution whithin the water body.

State indicators are characterised directly by:

- Presence or loss of indicator species - vegetation and microfauna;
- Gross changes in ecosystem or habitat;
- Presence and concentration of pollutants in the water body or soil.

However it is also common to use indirect indicators related to the regulatory mechanisms:

- Concentration of pollutants in discharge waters;
- Volume of manure discharged to waste tanks, spread on farm land or discharged direct into water ways;

Response

The control of pollution from industrial animal production systems, as with most other industrial activities relies largely on legislation of acceptable levels of discharge, and then some form of monitoring and policing to ensure that these guidelines are adhered to.

The two approaches to regulation can be characterised as follows:

- Specification of acceptable levels of discharge for listed pollutants, implying that non-listed pollutants are acceptable; or
- Specification for acceptable levels of discharge of pollutants, implying that only those pollutants specified may be discharged.

Either way regulation relies on defining "acceptable levels". However, this will vary according to the total number of enterprises undertaken within the catchment, and the characteristics of the catchment. Regulation will therefore have to be subject to ammendment as the impact of acceptable discharges are monitored within the water body and on the land - evaluated by the State Indicators.

Response is characterised by:

- Regulations, and ammendment of regulations to specific local requirements;
- Specification of acceptable technologies;
- Monitoring effort by regualting agencies;
- Prosecution or other interventions by regulatory agencies.

One common problem with regulation of animal production systems is that they are often classified as "farm enterprises", with the implicit assumption that agricultural activities are non-point sources of pollution. Regulations may need to be brought in line with major industrial enterprises or with municipal agencies.

Further Reading:

UNESCO/WHO/UNEP 1996. Water Quality Assessments E&FN Spon 2-6 Boundary Row, London SE1 8HN UK.

CAST. 1996. Summary: Integrated Animal Waste Management. http://www.cast-science.org/anwa_is.htm. or view as Acrobat file. Council for Agricultural Science and Technology, 4420 West Lincoln Way, Ames, IA 50014-3447, USA. cast@cast-science.org.

> > [Livestock & Environment Toolbox Home]