Part III POPs-free/POPs alternatives – overview and case studies
PCBs have been used in closed applications as dielectric fluids in transformers and capacitors, heat transfer fluids and as hydraulic lubricants (primarily in the mining sector).
Open applications of PCBs have included sealants, paints, speciality coatings, pesticide extenders, plasticizers, adhesives, dedusting agents, cutting oils, flame retardants and carbonless copy paper. Open uses were phased out in the early 1970s.
Since widespread production bans in the late 1970s and early 1980s alternatives have been substituted for all uses of PCBs. Substitution of PCBs has, however, not always been based on an adequate assessment of the alternatives.
PCB-Alternatives in closed applications
Some alternatives which were used to replace PCBs include polychlorinated terphenyls (PCTs), alkyl-substituted chlorodiphenyls and PCNs. These substitutes are also persistent and PCN has been evaluated as POPs by the POP Reviewing Committee. The historic substitution of PCB is therefore an example highlighting the need for a better evaluation and an environmentally sound substitution of POPs.
Alternatives to PCBs in closed applications have been evaluated by The Nordic Council of Ministers and those they considered to be less hazardous than PCBs are listed in table 15 below (Norden 2000).
The major use of PCBs was as dielectric fluids. The most frequently used alternatives for transformers are mineral oils, silicone oils and ester fluids (both synthetic and natural). Mineral oils, silicone oils and ester-based materials all are preferable from an environmental perspective. Natural ester based dielectrichas become available which is less costly and has the added advantage that, like the synthetic esters, it is entirely biodegradable. Alternative engineering designs such as encapsulated transformers equipped with air cooling have been recommended for PCB substitutes that are not biodegradable.
Technology to replace PCB oil with alternative oils in larger transformers, called retro-filling, is available. However, most transformers contain a variety of components, including materials that retain the PCB-oil, such as wood. Depending on the size and structure of the transformer this increases the time taken to effectively empty the transformer and replace the oil. In some cases it may be necessary to carry out several retro-filling operations over several months. If all the PCB-containing oil is not removed there will be a gradual leaching of residual PCBs from the porous components which will contaminate the new oil (Norden 2000).
Replacement oils offered on the market today are all suitable for use in electrical equipment. But they may not be suitable for a particular use, e.g. transformers used in certain conditions. Transformers with an expansion chamber outside the transformer can accommodate temperature changes. In this kind of transformers it is possible to use oil with a relatively high coefficient of thermal expansion. In sealed transformers the replacement oil must have the same thermal expansion coefficient as the original oil (Norden 2000).
Alternative fluids used for retro-filling are mineral oils, silicone fluid and ester materials – both synthetic and natural. Synthetic ester materials are more expensive but are well established replacements with good properties. Natural ester based dielectrichas become available which is less costly and has the added advantage that, like the synthetic esters, it is entirely biodegradable. The fluid has marked technical advantages over many other alternatives including: no de-rating factor after conversion; good electrical properties; and suitable for up-grading oil transformers to become classified as less flammable.
Mineral oils have a greater flammability than PCB oil but in many environments this risk is not an over-riding factor and the necessary fire safety performance can often be achieved. Also silicone oil is used in transformers. The transformers are then designed to match the properties of silicone oil. It will therefore be necessary to modify existing transformers to take account of these different properties, and particularly the thermal expansion coefficient, if silicone oils are used as replacements for PCBs (Norden 2000).
Table 16: Alternatives to PCB in closed application (NORDEN 2000)
The Arctic Council initiated a project on the phase-out of PCB use and the management of PCB-contaminated wastes in the Russian Federation (www.amap.no). The Multilateral Co-operative Project on Phase-out of PCB Use and Management of PCB contaminated Wastes in the Russian Federationwas initiated in 1998 under the Arctic Council's Action Plan for Elimination of Pollution in the Arctic. In the project, costs are calculated for more environmentally sound solutions, including a feasibility study with an evaluation of alternative dielectric fluids for use in larger capacitors and transformers. Two alternatives were recommended: AZI-3 (1,1-phenyl xylyl ethane or PXE or S oil) and DON (mixture of 70-75% of mono-benzyl-toluene and 20-25% of dibenzyltoluene). Further testing of AZI-3 was recommended since the toxicity and the environmental properties of this compound were unknown. These alternatives can be based on Russian raw materials and production technology, and they could potentially keep costs in an acceptable range. The utilisation of the vacant process facilities and a part of existing equipment substantially reduces costs. The technology of storage and filling of transformers have been slightly adjusted due to combustibility of the applied liquid dielectrics and fire safety measures have been intensified. Technologies involving the production of power capacitors and transformers may be applied without any updating. Capacitors and transformers using the alternative dielectric fluids have got electric properties and service life comparable with units filled with PCB and will be less expensive to dispose in an environmentally sound manner (AMAP 2003).
 AMAP (2003) PCB in the Russian Federation: Inventory and Proposals for Priority Remedial Actions. Executive Summary of the report of Phase 1: Evaluation of the Current Status of the Problem with Respect to Environmental Impact and Development of Proposals for Priority Remedial Actions of the Multilateral Cooperative Project on Phase-out of PCB Use, and Management of PCB-contaminated Wastes in the Russian Federation. AMAP Report 2000:3
Alternatives in open applications
There is currently no comprehensive compilation on the alternatives available for PCBs in open applications (sealants, paints, ink, lubricants, waxes, adhesives, surface coatings, insulating material, pesticides, dyes, condensate form pipelines, plasticizers). As alternatives have now been used for more than forty years their technical suitability for all applications is no longer an issue. However it is not known to which extent environmental performance of the alternatives has been assessed and there is no compilation what alternatives are used. One major substitute of PCB in open application were/are chlorinated paraffins (e.g. in sealants, paints, flame retardant). Currently short chain chlorinated paraffins (SCCP) is evaluated by the POP Reviewing Committee for listing in the Stockholm Convention and has been listed in the Long-Range Transboundary Air Pollution Convention.
 UNEP Chemicals (1999), Guidelines for the Identification of PCBs and Materials Containing PCBs, http://www.chem.unep.ch/Publications/pdf/GuidIdPCB.pdf.