The industrial metabolism of plastics : analysis of material flows, energy consumption and CO2 emissions in the lifecycle of plastics

摘要

This thesis deals with the question: Which are promising options for decreasing material consumption, energy consumption and CO2 emissions in the lifecycle of plastics?udThe research described in this thesis mainly focuses on measures that change the material system, i.e. measures that change the pattern of material flows through society.udBy conducting an integral analysis of material flows, energy consumption and CO2 emissions in the lifecycle of plastics, it is possible to compare different measures at different stages in the life-cycle of a material or product, up and down the product-chain. In this thesis measures to replace feedstocks (changing production routes) are compared with measures for using alternative plastic types (material substitution) and measures for using alternative processes for plastic waste management (increasing materials recycling). A calculation method is developed and used to estimate the impact of the different measures on greenhouse gas emissions and fossil fuels consumption over the whole lifecycle of plastics.ududThe research that underlies this thesis leads to the following conclusions:ud* Changes in steamcracker feedstocks (ethane, LPG, gasoil and naphtha) only marginally influence total fossil fuels and feedstocks consumption and CO2 emissions. Higher reductions can be achieved by using new processing routes that use biomass as feedstock, like biomass flash pyrolysis and the methanol-to-olefins process combined with methanol production from biomass. Especially a combination of these two routes turns out to be capable of inducing large reductions.ud* Because substitution potentials between different plastic types are limited and differences in energy use and CO2 emissions for producing different plastic types are relatively small, no large reductions are to be achieved by substitution between plastics types (unless this would enable product changes increasing material efficiency).ud* Landfilling and incineration of plastic waste do not allow simultaneous reductions in fossil fuels and feedstocks consumption on the one hand and CO2 emissions on the other hand. Although it is a cheap and relatively easily applicable option, increasing the share of waste incineration is no valuable option, because it largely increases overall CO2 emissions.ud* Largest reductions of CO2 emissions and fossil fuels consumption by measures aiming at enhanced waste management are achieved by increasing the contribution of mechanical recycling, selective dissolution or blast furnace injection. Effort should be made to clear away the obstacles that limit the share of mechanical recycling, by developing appropriate blending and separation techniques.ud* We estimate that structural changes in the lifecycle of plastics in The Netherlands can lead to a reduction in the consumption of fossil fuels of up to 60% and a CO2 emission reduction of up to 30%. These reductions can be achieved by large scale use of biomass as feedstock for the production of plastics, possibly combined with an increased share of plastic waste recycling. Realisation of these options would, however, be accompanied by a cost increase of the total plastics lifecycle of about 20%.