Just in time for the holidays, researchers in the United Kingdom have developed a new technology that they say could process 100 percent of household plastics -- including gift wrap -- instead of the 11 percent that is recycled there now.
Why is only a small percentage of municipal plastic waste truly recycled?
It is only plastic drink bottles that can be recycled in a commercially-viable way at present; their main advantage being the ease with which they can be extracted from the rest of the waste. At the other end of the spectrum, plastic films are almost impossible to pick out and the only practical solution is to ship them to the Far East for manual sorting. Then, because of the low density of plastic objects, you end up shipping a lot of volume and little weight, which is not economically or environmentally sensible. Therefore, if you cannot sort out the different types of plastic at present, then you cannot reuse them and you must either burn them for their calorific value or put them to landfill. In the UK, this results in only 11 percent of household plastic waste being recycled.
How did you discover a method that could recycle many different plastics at once?
At Warwick, we have been looking at pyrolysis using fluidized beds as a technique for converting various kinds of biomass to valuable chemical feedstock. It occurred to us that the difficulties in handling biomass are similar to those of municipal waste. For instance, how 'dirty' the input material is, how mixed it is and how it varies from one batch to the next. We therefore thought of municipal plastics of which we had seen only a minority was being recycled. We also knew that in order to reprocess plastics there needs to be accurate control of the temperature in the reaction vessel, which is difficult when the input material is of mixed composition. We had solved this for biomass by using a fluidized bed and thus realized this should work for mixed plastics. A fluidized bed uses hot sand as the heat source - because sand has a high heat capacity it stays at the same temperature when you introduce materials into it.
What are the environmental benefits of this technique?
This solves the problem of transporting low-density plastic materials. The output of the process can be optimized to produce high-density liquids and solids which can be viably transported and further processed to separate out the different plastic species in the same way as crude oil is distilled. We believe that no plastics will need to go to landfill, the carbon footprint of reprocessing plastic is reduced and less oil needs to be converted to plastic feedstock.
How could this affect the way local communities recycle plastic?
There still remains the need to separate out plastic from the rest of the waste. But now, any plastic can be collected -- including the tubs and films that normally you are asked not to put in with other plastics. This will make community collection simpler and allow more material to be captured. In addition, the technique increases the value of plastic waste and therefore, like aluminum cans, communities and charities could profit financially by becoming part of the reprocessing stream.
What's the next step for this work?
To fully prove the technique, we now wish to build a full-scale municipal demonstrator unit at a civil amenity site to handle 10,000 tons of mixed municipal plastic per [year]. We believe public money will be available to help fund a collaborative project with commercial companies. This is most likely to come from the European Eco-Innovation scheme, the call for which will open in April 2011. We would welcome the interest of potential collaborators for this project.
Photo: Kevin Marks
This post was originally published on Smartplanet.com