Combining dynamic life cycle assessment and net ecosystem exchange through the framework of biobased materials and products-life cycle assessment (BBM-LCA): application to polylactic acid

Abstract

Biobased products can achieve carbon negativity by storing biogenic carbon in the technosphere through circular loops. Quantifying these benefits requires quantitative assessment tools such as life cycle assessment (LCA). However, the LCA of biobased materials is not straightforward due to the complexity of addressing agroecosystem carbon dynamics and the timing of emissions. The aim of this research is to apply the novel framework of biobased materials and products-life cycle assessment (BBM-LCA) to the example of polylactic acid (PLA) to show how it can address biogenic carbon and timing issues of emissions by combining net ecosystem exchange (NEE) and dynamic LCA. BBM-LCA adapts two aspects of conventional LCA to estimate the climate impact of biobased products more accurately. First, concerning the absorption of atmospheric carbon during cultivation, BBM-LCA uses NEE to account for all biogenic emissions occurring within the agricultural ecosystem. This means that it is not limited to the absorption of carbon by agricultural crops. Second, concerning the calculation of climate impacts, BBM-LCA adopts dynamic LCA as a time-dependent approach, to generate a time-sensitive global warming potential (GWP). The example of PLA proves that BBM-LCA is an effective instrument for calculating the climate impact of biobased products due to the implementation of a holistic lifecycle approach and a dynamic impact calculation method. BBM-LCA accounts for the carbon sequestration benefits of recycling, recognizing its actual impact over time in multiple lifecycles. This feature makes BBM-LCA preferable over conventional LCA, which struggles to track greenhouse gas (GHG) emissions at different points over multiple years across the multiple lifecycles of recycled products.