Position Papers
Landfill
The main benefit of oxo-biodegradable is not for plastic waste which gets into landfill, but for plastic waste which gets into the environment, where it will accumulate for many decades.
Not all plastic bags are simply thrown away. Many of them reach landfill only after they have been used as bin-liners or re-used for some other purpose.
Hydro-biodegradable plastics will degrade and emit CO2 in the surface layers of a landfill if there is enough microbial activity. However, in the depths of a landfill, in the absence of air, hydro-biodegradable plastics generate copious quantities of methane, which is a powerful greenhouse gas. Methane is also highly combustible and is a cause of explosions, sometimes affecting housing built on old landfills.
By contrast Oxo-biodegradable plastics fragment and partially biodegrade in the upper layers of the landfill, but the residues are completely inert deeper in the landfill in the absence of oxygen. They do not emit methane at any stage.
Governments are concerned to reduce the amount of waste going to landfill, but oxo-biodegradable plastic waste does not have to be sent to landfill at all. It can be recycled (see above), but the recycling option is not practicable for hydro-biodegradable plastics.
The aim of the EU Landfill Directive 1999 (as amended 2003) is that:
(3) the prevention, recycling and recovery of waste should be encouraged as should the use of recovered materials and energy so as to safeguard natural resources and obviate wasteful use of land;
Oxo-biodegradable plastics would help to achieve these objectives because, they can be recycled and they can be incinerated with high energy-recovery.
Oxo-biodegradable plastic sheet would also reduce the wasteful use of land in a landfill. At present a six to eight inch layer of earth has to be spread over the waste at the end of each day’s work. This is very expensive to do, and it uses up a high proportion of the available space in the landfill pit. Oxo-biodegradable plastic sheeting can now be used as daily landfill covers instead of earth, to cover the waste, and less fuel is burned by the machines employed.
Conventional plastic bags take up more space in a landfill because they trap air, they do not readily disintegrate, and they inhibit the decomposition of their contents in the landfill.
(4) further consideration should be given to the issues of incineration of municipal and non-hazardous waste, composting, biomethanisation, and the processing of dredging sludges;
Oxo-biodegradable plastics can be incinerated with energy recovery.
(12) protective measures [should] be taken against any threat to the environment in the short as well as in the long-term perspective, and more especially against the pollution of groundwater by leachate infiltration into the soil.
Oxo-biodegradable plastics do not cause harmful leachate infiltration
(16) measures should be taken to reduce the production of methane gas from landfills, inter alia, in order to reduce global warming, through the reduction of the landfill of biodegradable waste and the requirements to introduce landfill gas control;
Unlike normal organic waste, and hydro-biodegradable plastics, oxo-biodegradable plastics do not produce methane as they degrade.
The Report on “The impacts of degradable plastic bags in Australia” prepared by ExcelPlas/ Nolan-ITU on 11 September 2003 for the Australian Government noted at 7.3 that:
degradable polymers with starch content have higher impacts upon greenhouse due to methane emissions during landfill degradation and N2O emissions from fertilizing crops. Methane is 23 times more potent for global warming than CO2
degradable polymers manufactured from renewable resources (e.g., crops) have greater impacts upon eutrophication due to the application of fertilizers to land.
1. IPCC (Inter-Governmental Panel on Climate Change) Report page 47 www.ipcc.ch/pub/wg1TARtechsum.pdf