A normalised market trend is a metric used in Life Cycle Assessment when evaluating joint production systems, where multiple products are produced simultaneously from a single activity. This metric represents the trend for the market on which each joint product is sold, divided by (normalised to) the ratio of that joint product output relative to the total output of all joint products from the same joint production activity.
In the context of Life Cycle Assessment, joint production occurs when an activity generates two or more co-products in fixed or variable proportions. Understanding market trends for these co-products is essential for consequential LCA modelling, as it helps determine which products are determining products and which are by-products. The determining product is typically the one for which demand changes will affect the production volume of the entire activity.
However, comparing raw market trends across different joint products can be misleading when the products are generated in different proportions. A product that represents 80% of the joint production output may show a smaller absolute market growth than a product representing only 20% of output, yet the smaller product may be growing faster relative to its production share. The normalised market trend addresses this issue by accounting for each product's proportional contribution to the total output.
To calculate the normalised market trend, one takes the market growth rate (or trend) for a specific joint product and divides it by that product's output ratio within the joint production. This normalisation allows for direct comparison of market dynamics across all joint products from the same activity, regardless of their different production volumes. The joint product with the highest normalised market trend is typically growing fastest relative to its production share and may be the determining product driving the activity's production volume.
This metric is particularly valuable in industries with significant joint production, such as oil refining, meat processing, or chemical manufacturing, where understanding which product drives production decisions is crucial for accurate environmental assessment.
