[hansarne]

It's correct that lignin is used as a fuel, here's one source of it. ~98 is burnt. "currently most of the lignin produced from paper industry is burned as low-value fuel to generate electricity and heat (Luo and Abu-Omar, 2017) and only less than 2% is used for producing specialty chemicals ..." https://www.sciencedirect.com/science/article/abs/pii/S09266...

[civilized]

I wonder what makes it a low value fuel. If it has a lot of carbon per energy released, it may be better to bury it than burn it.