Anaerobic dehalogenation of cfc gases in landfill environment. Batch studies

19 1. INTRODUCTION Blowing agents (BA) for insulation foam in home appliances as refrigerators and freezers have been usually halocarbons having very high global warming or ozone depletion potentials. After their cycle of life, which lasts normally 10 – 15 years, in many countries most of the appliances are shredded and disposed into landfills. For the next decade it is expected that only in the U.S. 8 millions of fridges per year will be disposed off (3). This means that 4000 tons of CFC-11 (Trichloro- Fluoro-Methane, the most used BA in the last 20 years, also called FREON-11) will be released in the atmosphere, assuming that 500 g of CFC-11 per fridge is lost (3). There is the interest in data about the fate of the BAs, because many environmental assessments of household refrigerators don’t take into account the degradation processes taking place in landfills, which could play a not negligible role in attenuating the polluting potential of BAs’’ (1, 2, 3). Peter Kjeldsen, Charlotte Sheutz and co-workers carried out studies about the release of the gases from the shredded foams, in order to know the release rates and the factors influencing them (3). The other side of this research has been a data collection about degradation processes affecting BAs in landfill environment. The potential of anaerobic (methanogenic) bacteria to degrade blowing agents under landfill condition was tested in several batch and column studies focusing on both degradation rates and mass balance (2). The degradation rates of some BAs were found to be correlated with the number of chlorine atoms attached to the carbon. The products of the degradation of CFC-11 are HCFC-21, HCFC-31 and HFC-41. ‘’A complete degradation of CFC-11 to HFC-41 would lead to emission of a compound from landfills with zero ozone depletion potential and very low global warming potential’’ (2). However, considering just the gaseous products, more than 70% of the stoichiometric amount was missing (2). The hypothesis of defluorination, i.e. the rupture of the carbon-fluoride bond, as last step in the CFCs degradation, has been done. This hypothesis can be proved thanks to a recovery of free fluoride in the matrix where degradation occurs. Furthermore, an accurate recovery of fluoride in simulated landfill conditions (batch or column studies) could lead to a more exhaustive mass balance of the CFCs degradation process. ‘’The integrated evaluation of the fate of halocarbons contained in foam waste disposed in a landfill, carried out by P. Kjeldsen and co-workers, extended a