Sorry for the weak subject line.
Okay, my concern is about my pen cartridge. Let me brag about having the Squire by Baron Fig. It uses a standardized cartridge:
You can grab more refills right through our site, or find any compatible refill that fits the dimensions of a Schmidt P8126.
My issue is about waste and recycling. I will figure out the best, if any, practices for recycling these things. I hate to be defeatist about it, but I mean, I am not going to stop using a pen. It would be more likely I start a cartridge recycling system if one doesn’t exist.
What I am new to is refilling my pens at this level, and I have questions about that. Specifically, what is the rate of writing degradation from low ink?
I noticed my pen stopped writing as boldly or deeply, seeming to output less ink. Ya know, as pens do. But I thought it would run out soon. It just kept on writing, but more and more faded. I could see it from flipping the pages in my notebook, as we approached the current section my writing seemed like it had aged and faded… a nice sentiment on the transient nature and space and time, but I need my fucking pen to work! 
I switched it out, and wow am I glad to have a fresh cartridge. But the refills are metal, and I don’t know how much remains inside. What if I just threw away half the ink?! 
Any insight into how that works, and what the most responsible use of resources is in this scenario? 