15.12.2020

Waste4ME accomplished comparative Life Cycle Assessment (LCA) for End-Of-Life alternatives applied to household plastic waste. The specific of this type of waste was that it is a rejected stream of waste which was previously treated by means of mechanical recycling and is destined in majority of cases to be incinerated or landfilled. However those two options are not always fully sufficient regarding both waste management technics, lost profit and environmental protection. In the process of work we were estimating pyrolysis potential, comparing to incineration and landfilling, in treatment of such waste.

One more important goal of the research was to define environmental impact and impact to human health of using these waste treatment technologies, their advantages and disadvantages comparing to each other.

Conducting an LCA is also a legal requirement under LAP3 in order to justify one's choice of waste treatment technology. That is why this research is aimed to be used, among others, as an official proof of pyrolysis feasibility in the given conditions.

As pyrolysis is quite broad technology that gives different output we studied its three options:

- The pyrolysis from which the pyrolytic oil output is of no value and thus must be treated in chemical treatment facilities. In this scenario the gas can be used for electricity generation and the heat produced from generating electricity and from the flue gas is recovered. The metals from the pyrolytic ashes are not separated but considered to be equivalent to virgin metal with significant loss in quality;

- The pyrolysis from which the pyrolytic oil output is considered as low quality Heavy Fuel Oil. In this scenario the excess pyrolytic gas can be used for electricity generation and the heat produced from generating electricity and from the flue gas is recovered. The metals from the pyrolytic ashes are not separated but considered to be equivalent to virgin metal with significant loss in quality;

- The pyrolysis from which the pyrolytic oil output is considered as low quality Heavy Fuel Oil. In this scenario the excess pyrolytic gas is considered of naphtha quality. The metals from the pyrolytic ashes are not separated but considered to be equivalent to virgin metal with significant loss in quality.

Regarding incineration and landfilling we used data for the incineration of mixed domestic plastic waste in a typical Dutch waste incineration plant and from which heat is recovered and electricity is generated. The landfilling was used as a worst case scenario. The landfilling site is considered to include gas treatment, leachate treatment, sludge treatment and deposition. For defining pyrolysis results we applied data of the test conducted on our Waste Energy Recovery unit.

The results given following the impact assessment methodology are most interpretable and conclusions can be drawn from the so-called endpoint area of protections, expressed as damage to human health, damage to ecosystems, and damage to resource availability. They show that the environmental performance of the pyrolysis scenarios are overall higher in terms of environmental benefits. For example, assessing damage made to human health, pyrolysis shows proof of better environmental impacts with the exception of pyrolysis type, described above as a first option. This is mainly due to the oil being seen as waste to be treated and its subsequent process emissions. However, when it comes to the damage to ecosystems as well as damage to resources availability, the different pyrolysis scenario are all showing positive, or avoided impacts on the environment. Since incineration also uses a more efficient energy recovery than landfill, it also shows, to a lesser extent, avoided damage to the environment but still has non negligible impact on climate change and freshwater consumption compared to the three pyrolysis scenario. It was found that the landfill scenario do not show any positive impact on the environment when treating the plastic mix. Finally, as expected, the scenario involving Heavy Fuel oil recovery and gas as recoverable naphtha has the most avoided impact to resource availability.

Thereby, as the result, LCA shows that rest stream valorization technologies, be it incineration or pyrolysis have some impact on human health, due to exposure to the pollutants emitted during the energy conversion and recovery. On the other hand, clear benefits arise from the use of the pyrolysis technology, since these alternatives allows for avoided damage made to ecosystems. The pollutants being emitted, the extent of energy and material recovery allows for significant environmental benefits compared to the scenarios of landfilling and incineration.