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Comparison of recycling and incineration of PET bottles

This project has been commissioned by Infinitum AS, the corporation that runs the deposit recycling scheme for beverage containers in Norway. The study is closely connected to previous work documented in the report “LCA of beverage container production, collection and treatment systems” (Raadal et al., 2016a) and supplemented memo (Raadal et al., 2016b). The systems and major assumptions are based on these above mentioned documents.

The main goal of the study is to compare the environmental impacts of a consumers’ choice to whether: a) use Infinitum’s deposit system in order to recycle their PET bottles; or b) dispose of their PET bottles together with their residual waste to incineration. The systems are analysed using a waste treatment model (Raadal, et al. 2009, Nakatani, 2014), represented by the cases recycling (8% material loss) and incineration, taking into account the avoided burdens from recycling and energy recovery (from incineration), respectively.

Furthermore, a parallel system setup is modelled in order to investigate whether the results will be affected when including multiple recycling loops in the system boundaries. The systems are analysed using a production and waste treatment model, taking both production and waste treatment of the required volume of PET bottles into account. The aggregated environmental impacts of a potential closed loop (bottle-to-bottle) system for PET (8% material loss) and a system without recycling are analysed. Both systems start with a number of virgin PET bottles necessary to distribute 1 000 l of beverages. For every recycling loop, the system without recycling must complement new virgin PET bottles.

The major conclusion is that Infinitum’s recycling system clearly outperforms incineration for the assessed environmental impact categories: Climate Change, Cumulative Energy Demand (CED) and Fossil Resource Depletion. The benefit from recycling increases linearly with the collection rate.

On an annual basis (about 600 million litres beverage distributed by PET bottles), the Climate Change benefit from Infinitum’s recycling system (when assuming 100% collection rate) compared to Incineration are 94 000 tonnes and 70 000 tonnes CO2-equivalents, respectively, dependent on whether district heating or heat from oil is assumed to be replaced by heat from incinerated PET. These reduction potentials correspond to the annual emissions from about 64 000 and 48 000 passenger cars, respectively. When using Infinitum’s existing collection rate (87%) for PET, the annual Climate Change benefit is 81 000 tonnes CO2-equivalents (assuming district heat to be replaced by heat from incinerated PET). A collection rate of 87% corresponds to a potentially saving of 17 000 tonnes virgin PET production per year.

Corresponding annual results for the Infinitum system with 100% collection rate for Cumulative Energy demand (CED) show avoided use of 288 GWh and 294 GWh primary energy, respectively, dependent on whether district heating or heat from oil is assumed to be replaced by heat from incinerated PET. This corresponds to about 27 % of the annual consumption of district heat related to Norwegian households. When using Infinitum’s existing collection rate (87%) for PET, the annual avoided use of primary energy is 251 GWh (assuming district heat to be replaced by heat from incinerated PET).

For Fossil Resource Depletion, the benefit of using the Infinitum system with a collection rate of 100% varies between 268 GWh and 354 GWh fossil primary energy, dependent on whether heat from incinerated PET is assumed to replace average district heating or heat from oil. These reduction potentials correspond to 25% and 33%, respectively, of the annual consumption of district heating in Norwegian households. When using Infinitum’s existing collection rate (87%) for PET, the annual avoided use of primary energy is 308 GWh fossil primary energy (assuming heat from incinerated PET to replace district heating).

The results are also given per bottle in order to compare the environmental impacts of the consumers’ choice to whether recycle or dispose of their PET bottles together with their residual waste to incineration. When taking 100% collection rate into account, the Climate Change benefit of using Infinitum’s system is 0.178 kg and 0.135 kg CO2-equivalents per bottle (when district heat and heat from oil are assumed replaced by heat from incinerated PET, respectively). The figure for 87% collection rate is 0.151 kg CO2-equivalents per bottle (district heat assumed replaced). Corresponding results for CED are 0.546 kWh and 0.557 kWh avoided primary energy per bottle for 100% collection rate, while the figure for 87% collection rate is 0.475 kWh per bottle. When also including the feedstock energy in the avoided primary energy potential, the benefit from Infinitum’s system versus incineration (for 100% collection rate) increases to approximately 1 kWh per bottle.

A parallel system has been analysed using a production and waste treatment model in order to investigate whether the results will be affected when including multiple recycling loops. The environmental impacts are calculated for a bottle-to-bottle system for PET and a system without recycling which is assumed to provide equal amount of PET bottles for beverage distribution as the bottle-to-bottle system. Both systems start with a number of virgin PET bottles necessary to distribute 1 000 l of beverages. For every recycling loop, the system without recycling must complement new virgin PET bottles. The conclusion is that the difference in environmental impacts between the recycling and incineration systems remains the same whether one take multiple recycling loops or not into account. The reason for the equal results from the two models is that the difference in environmental loads between the systems increases proportionally according to the amount of PET material being recycled. Hence, the difference per kg PET bottle or per 1000 litres distributed beverage remains the same. This is supported by Geyer et al. (2015), who also conclude as follows: «A robust recycling system must ensure a steady supply of recyclable feedstock and an equal demand for the resulting secondary outputs, but that is not enough. An environmentally successful recycling system must also make sure that the secondary resources displace their primary competitors».

As documented in this and earlier studies (Raadal et al. 2016a and b), Infinitum’s recycling system provides a steady supply of PET recyclables with the required quality in order to replace virgin PET bottle grade material. Hence, it fulfils two of the three above-mentioned important criteria for providing a robust and environmentally successful recycling system. It is thus up to stakeholders, authorities and other parts of the PET bottle value chain to secure that the third criterion (ensure a sufficient demand for recycled PET) also is fulfilled, e.g. by providing efficient incentives.

 

 

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