Breakdown of natural toxins in hemlock and yew during composting
18th November 2010
A field experiment to determine whether, and to what extent, coniines in hemlock plant material and taxoids in yew plant material degrade over the duration of a PAS100-compliant commercial green waste composting process.
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Composts are most commonly made from plant materials, which could include species such as yew and hemlock. Recent research has highlighted a lack of understanding around the breakdown of some of the naturally-occurring toxic compounds in these species during composting.
This project measured target compounds in hemlock and yew before and during a commercial PAS 100 composting process.
The compounds measured in yew (taxine A and taxine B) were degraded to below the limits of detection after 65 days. Of the compounds measured in hemlock, coniine concentrations had decreased by 64 % after 20 weeks, while coniceine decreased to below the limit of detection after 5 weeks.
Given the likelihood of degradation before and during composting, as well as the likely dilution of yew and hemlock in typical compost feedstocks, the toxic compounds present in yew and hemlock are expected to pose a negligible risk to livestock grazing on compost-treated fields.
