Op I'm usually all for supporting dils in awful situations with their mils because it nearly destroyed my marriage and my in laws have been the only problems in my life since met dh.
My beautiful dm isn't with us anymore and never spent a single Xmas with my dc and never met them.
I'd have loved a Mil I could happily share the joy of my dc with but she's bitter, negative, uses presents as a weapon, will play the dc off agaisnt each other, she's funny about food, and cleaning and is just a miserable night mare to be around.
I guess my point is... This is a large issue to you but is it really important in the grand scheme of work things. I wish this is the worst thing my Mil did so we could spend Xmas with her.
I also find it really unfair that your going through her bin!
Nearly everyone has something that they feel passionate about but we don't all feel passionate about the same things which is good. Because we all care about different things that means cat charities get support, cancer charities... Some people care about disabled access, others about people with downs syndrome.
You care about recycling and the environment (and I hope to god you don't have a bloody real fire or log burner like my neighbours).
That's your passion and whilst I totally understand you want to save the planet.. I'm with you! But your Mil really isn't sending us all down the swanee. You need to re direct your frustration to China say every time she annoys you, tweet something to big businesses etc.
And enjoy the fact you do have a sweet lady who is caring enough to buy presents for your dc!