Just a week after an alarming report that a banned ozone-depleting chemical is being pumped into the air from somewhere in Asia, researchers claim to have found where some of it is coming from. The substance in question is a chlorofluorocarbon (CFC) called CFC-11, which was once used in refrigerators. Production of CFC-11 was banned in 2006 under the Montreal Protocol, which regulates chemicals that damage the ozone layer. However, on 16 May Stephen Montzka at the National Oceanic and Atmospheric Administration in Boulder, Colorado and his colleagues revealed that the rate of decline in CFC-11 levels had unexpectedly halved since 2012 (Nature, doi.org/cp5g). This suggested someone was making CFC-11, Montzka argued, probably in east Asia. We just dont know what is causing this emissions increase, says Montzka. However, a research paper quietly posted on 7 May, over a week before, may hold some answers. Rather than all of the emissions being due to new and illicit CFC-11 production, some could be coming from the careless recycling of discarded refrigerators in China. So says a team led by Huabo Duan at Shenzhen University in China, which included Reed Miller at Yale University in New Haven, Connecticut. There has been less emphasis globally on the capture of such refrigerants at their end of life, says Miller. China is both the worlds biggest producer and largest consumer of refrigerators and air conditioners. So, the team investigated 50 informal home appliance repair shops in the Shenzen area, which get scrap refrigerators from peddlers and consumers. They also visited seven government-licensed recycling centres in six provinces. The licensed centres aim to capture CFC-11, which was injected into the polyurethane foam insulation of the fridges doors and walls. They do this by breaking up the foam in a low-pressure chamber and separating out the CFC-11, which is then chemically neutralised. The team found the informal repair shops often broke up fridges outdoors, including the CFC-containing foam, and sold the metal off for scrap. Meanwhile, the recycling centres rarely controlled the gas capture process properly. Whats more, the team has not examined the recycling of large commercial chillers, as used in supermarkets. Each chiller could release nearly half a tonne of CFC-11 when decommissioned and replaced, says Miller. Prohibitive replacement costs have resulted in their prolonged use. Miller argues that Chinas fridge recycling problems are a likely contributor to the extra CFC-11 emissions. He wants the Chinese government to devise a subsidy scheme that incentivises peddlers and appliance shops to sell waste fridges on to formal recyclers and for the recyclers to capture the CFCs properly. Its an important study, says Montzka. But he is not convinced that poor recycling can explain the mystery CFC-11 emissions he found. Montzkas research suggested that an extra 13 million kilograms of CFC-11 were being released every year. Millers team estimated that the recycled fridges were emitting less than 1 million kg per year. Thats an order of magnitude less, says Montzka. However, Miller says his teams figure is based on an assumption: that people junk their old CFC-11-containing fridges after just 10 years. If people hold onto older fridges which contain more CFC-11 for 15 years or more, 2.5 million kg of CFC-11 could be released every year. The solution is to feed data on CFC-11 levels in Asia into computer models of air movement, and track the emissions back to their sources, says Michaela Hegglin at the University of Reading in the UK. If the emissions are coming from a broad region, it would suggest recycling is a culprit, whereas a point source would implicate a region, company or industry.
New Scientist, 24 may 2018 ; http://www.newscientist.com/