This warning has come from SAC Consulting and SEPA following suggestions there is a link between the use of gypsum, from waste plasterboard and other gypsum-containing wastes, in animal bedding and a number of livestock deaths when mixed with slurries.
The agitation and mixing of manures and slurries in livestock sheds is already known to release hydrogen sulphide. The toxic gas affects the nervous system causing a range of symptoms including discomfort, disorientation, collapse, or sudden death.
As gypsum contains sulphur, mixing it with slurries will increase the total amount of hydrogen sulphide gas produced. However at certain levels the human sense of smell becomes unable to detect the odour and when concentrations reach 700 parts per million the gas can be lethal.
To understand the potential levels of hydrogen sulphide associated with the use of gypsum in animal bedding, SAC Consulting Environment and Design conducted an air quality assessment in September 2012. The assessment aimed to determine whether detectable levels of hydrogen sulphide gas could be found during the removal of farm yard manure from a site where gypsum had been used.
It was found that as soon as the farm yard manure was disturbed hydrogen sulphide gas was detected at levels up to 2705 parts per million, while carbon dioxide readings also increased.
Gavin Hill from SAC Consulting's Farm Rural Business Services said: "No matter what advantages are seen in using gypsum as animal bedding, it is simply not a risk worth taking. Recent tragedies have highlighted the issues that face us and we must take all steps to eliminate the risks."
Gary Walker, principal policy officer, of the Scottish Environment Protection Agency, said: "The results of this study illustrate the dangers associated with the use of waste gypsum in animal bedding. The use of plasterboard, gypsum and gypsum-containing wastes can lead to the production of the highly toxic gas hydrogen sulphide.
"When used in animal bedding, it is likely waste gypsum will produce considerable levels of hydrogen sulphide due to the damp, non-ventilated conditions. In such circumstances, hydrogen sulphide presents a significant risk to animal and human life, as well as the environment, and we would advise against anyone using it for this purpose."
Information from SAC Consulting and SEPA on the use of waste gypsum and slurry can be found at: http://www.sruc.ac.uk/gypsum.