There are many kinds of lignin, different kinds, and even different parts of the same species are slightly different.

Of course, if you only want lignin, you can extract it from any leaf. But be sure to use the same tree in the future, so that your data can be compared.

And if you write a paper, you can say it is practical, because you use local materials. Reasonable application.

What do you use lignin for, plasticizing?