Toward More Realistic Estimates of Product Displacement in Life Cycle Assessment

Life-cycle assessment (LCA) is one of the most widely
applied methods
for sustainability assessment. A main application of LCA is to compare
alternative products to identify and promote those that are more environmentally
friendly. Such comparative LCA studies often rest on, explicitly or
implicitly, an idealized assumption, namely, 1:1 displacement between
functionally equivalent products. However, product displacement in
the real world is much more complicated, affected by various factors
such as the rebound effect and policy schemes. Here, we quantitatively
review studies that have considered these aspects to evaluate the
magnitude and distribution of realistic displacement estimates across
several major product categories (biofuels, electricity, electric
vehicles, and recycled products). Results show that displacement ratios
concentrate around 40–60%, suggesting considerable overestimation
of the benefits of alternative products if the 1:1 displacement assumption
was used. Overall, there have been a small number of modeling studies
on realistic product displacement and their scopes were limited. Additional
research is needed to cover more product categories and geographies
and improve the modeling of market and policy complexities. As such
research accumulates, their displacement estimates can form a database
that can be drawn upon by comparative LCA studies to more accurately
determine the environmental impacts of alternative products.