In order to meet the recent environmental concern specifications of creosote are altered, the B[a]P content is limited and restrictions on the emission of volatile organic compounds (VOC) and higher polyaromatic hydrocarbons (PAH) are expected in some countries. Research has been conducted on an emulsion of a selected tar oil fraction. Using a waterborne formulation opens new perspectives for targetting penetration and retention, waste water recycling, energy saving and overall emission control to water and air. Results are reported on toxic limits, leaching of PAH compounds, ecotox testing and initial trials of pilot plant treatments. Standard laboratory tests show a biological efficacy comparable to standard creosote specifications AWPA and WEIB. Preliminary leaching tests indicate a lower level of total PAH leaching although the initial emission flux is higher than that of the traditional types of creosote. At a target retention of 35 kg/m³ no inhibition of algal growth was noticed, microtox tests demonstrated the high sensitivity of bacteria for organic compounds found in leachates of timber treated with tar oil preservatives. Preliminary treatments on pilot-scale equipment revealed a strongly reduced smell of impregnated timber and a clean surface with a typical dark brown colour.

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