Future vision: carefully storing waste plastics in ‘controlled landfills’

United Kingdom – With volumes of waste plastics rising in the UK as a result of China’€™s import policies, the debate is growing about what to do with them. Landfilling, rather than incineration, might be the better option, suggests Keith Freegard of plastics recycler Axion Polymers.

China’s crackdown on imports of contaminated recyclables is leading to an ever-increasing stockpile of waste plastics worldwide. Tackling this problem waste stream will probably lead to increased incineration of waste to produce energy as the ‘best’ option. But when the carbon produced by that process is taken into account, is it really the best environmental solution? Keith Freegard, director of UK-based Axion Polymers, believes it is not.

‘Creating energy from waste produces between 25% and 30% residual incinerator bottom ash (IBA), which still requires waste disposal or long-term storage,’ he points out. ‘Although generating heat and power from waste sounds appealing, it is inefficient when compared to burning gas in a modern generator system. Burning natural gas also produces fewer emissions and there is nil solid ash waste to dispose of.’

According to Freegard, the carbon release from waste incineration needs to be considered and compared to the alternative methods of generating an equivalent amount of electrical power.

‘Typical energy-from-waste plants have efficiencies of up to 30% for converting feed material into electricity; in contrast, the efficiency of a modern combined cycle gas turbine (CCGT) is typically about 50%,’ he notes. ‘This disparity in efficiencies means that producing 1 MWh of electricity from a CCGT produces just 40% of the CO2 emissions for the same amount of energy made from plastic incinerated at an energy-from-waste plant.’

‘It is true that a best-in-class energy-from-waste plant with integrated heat recovery (ie, a combined heat and power plant) can recover a further 35% of the available energy from the waste fuel; however, this heat could instead be generated by a natural gas boiler that has an efficiency of at least 90%,’ Freegard continues.

‘Even taking this additional heat efficiency into account, a combination of CCGT and boiler still only emits about 65% of the CO2 of the leading energy-from-waste plants.’ Using the CO2 metric alone suggests that it makes more sense to bury large amounts of plastic in a long-term ‘carbon sink’ in the ground and efficiently combust natural gas to satisfy immediate power needs, according to Axion Polymers’ director.

‘However, until world leaders are prepared to transform the taxation on fossil-based fuels in a way that truly reflects the high environmental cost of free carbon release, then this numeric analysis remains an esoteric academic study.’

Landfill rather than ‘sky-fill’

‘Perhaps we should start by calling end-of-life waste incineration technology “sky-fill” to compare it with the alternative landfill disposal route for plastic-rich carbon mass,’ Freegard goes on to suggest.

Increasing incineration capacity also stifles innovation in alternative resource recovery technologies because investment is diverted from developing new processes and towards building huge plants for burning materials to inefficiently create power, he believes.

‘Having first raised the “landfill or incineration” question more than 12 months ago, I still believe that the best environmental option may well be to store the waste plastics in a controlled landfill facility and then to “mine” them back at a later date when new reprocessing capacity becomes available,’ he argues. ‘Effectively acting as a long-term “carbon-sink”, these plastic materials could be extracted for recycling in the future if a new process made this both technically and economically viable at that time.’

Freegard continues: ‘Climate change concerns us all and efforts to control rising global temperatures have included a focus on the uncontrolled burning of fossil fuels in many parts of the world. The huge shift in corporate and national energy habits required to leave fossil fuels in the ground will only happen with a carbon tax placed on the generation of electrical power that is directly linked to the tonnes of CO2 released into the atmosphere per unit of power created.’

‘If that happens, it might then be the time to return to that “mine” of carefully-stowed thousands of tonnes of good plastic and look again at the economics of turning it into new polymer. With a huge carbon tax slapped on burning it, then the economics would probably work. So these plastics may not have to stay in the ground for too long.’