How to account for second life usage of lithium ion batteries in a life cycle analysis?

Question

I am looking to conduct a life cycle analysis (LCA) to investigate the total greenhouse gas (GHG) emission contributions from lithium ion (Li-ion) batteries. The first part of their lifecycle is relatively straightforward. GHGs from raw material extraction, refinement, and cell/pack production (including required energy) are intuitive. The use phase is also somewhat easy to do.

My question is regarding the second life. How does second life application of a Li-ion battery (say... in stationary storage) impact the life cycle emissions? If the battery is used in a stationary storage application, I would imagine this is beneficial to its LCA GHGs. However, how does this mathematically play out? Is it in new battery-manufactured avoidance? Is it in replacement of a more GHG-intensive stationary storage alternative? How do I account for the second life benefit of the battery?

Answer 1

It's important to have a consistent approach towards measuring emissions in this case. Take the approaches below: Approach 1: measurement of the incremental GHG emissions from manufacturing 1 kwh of LiB capacity in this world. Here, the GHG from the upstream steps of extraction, refining, and battery production are included. This 1 kwh is going into an EV, in whose use there is a GHG amount equivalent to the grid emission factor (or whatever relevant EF applies) times the kwh usage / day x life of the EV. Here, you need to subtract the GHG from the ICE vehicle that it is displacing. In its second life, the GHG emissions are negative, and given by the avoided emissions (there is a standard methodology to work that out which you can look up elsewhere).

Approach 2: measurement of the absolute GHG emissions. Here, you repeat the steps in Approach 1 but you don't include the avoided emissions from ICE vehicles nor the avoided emissions in its second life.

I see the output of Approach 1 as being meaningful, while that of Approach 2 serving no practical purpose.