Environmental groups and government advisers agree there is no safe way to dispose of animals slaughtered in the fight against foot-and-mouth.

The government's Environment Agency (EA) has a list of priority disposal methods, of which burning and burial are low down.

BBC News Online examines the pros and cons of each method.

RENDERING

Disposal at authorised and monitored rendering plants is the option most favoured by the EA and environmental groups.

The plants are likely to be highly effective in destroying the virus and existing plants are well equipped to deal with large numbers of carcasses.

Friends of the Earth (FoE) is concerned that the plants are not being used to full capacity.

Tim Williamson, of the National Society for Clean Air and Environmental Protection (NSCA), said rendering was the most favoured option as waste is processed in a controlled industrialised way.

But he said waste being transported to the plant could mean some transport emissions.

INCINERATION

Incineration at authorised and regulated plants is also a preferred option. They would also be highly effective in destroying the virus and carcasses and can cope with large numbers.

Air pollution levels would be similar to buring but can be reduced by filters and enforcing industry regulations.

The toxic ash must also be disposed of after burning and FoE campaigner Adrian Bebb said incinerators create their own cycle of waste.

LANDFILL

The EA has identified 37 suitable UK sites with the appropriate level of environmental protection and control for animal carcass disposal.

FoE favours landfill over burial and burning if the sites are engineered to minimise the risk to groundwater and the wider environment.

Landfills have the potential to pose a long-term threat to water supplies.

BURNING

Burning slaughtered animals is the cheapest, simplest option and often avoids transporting carcasses to other disposal sites.

There is a low risk of transmitting the virus to other livestock.

But government data shows that carcass burning is releasing large amounts of dioxins - highly toxic compounds.

The World Health Organisation has linked dioxins with falling sperm counts, genital malformations and learning difficulties.

The dioxins are likely to result from materials used to light pyres - wooden railway sleepers, coal, and old tyres emit various hazardous substances, including dioxins, PAHs (polycyclic aromatic hydrocarbons), and particulates.

Supervision is also required to ensure combustion is complete.

The NSCA said other fuel types could be investigated. Napalm is one suggestion as it burns at a higher temperature and has been used to destroy anthrax-infected animals.

"Clean" farms fear ash blown from pyres could affect their livestock.

BURYING

Burying slaughtered animals on site at farms is a quick, simple option, but the EA says it poses "significant medium to long-term risks to groundwater from leachate".

Potential pollutants include ammonia, chlorides, phosphates, fatty acids and bacterial contamination.

Metal concentrations in water could increase and affect that water's taste and smell.

Tim Williamson, of the NSCA believes on-site burying is one of the best options if the possibility of infecting water tables can be eliminated. Disposal on site avoids the additional pollution caused by transport to other areas.

Cattle born before 1 August 1996 are not allowed to be buried because of risk from BSE or mad cow disease.