I haven't seen any data, but coffee grounds seem more similar to straw, which has been used with some success. https://iopscience.iop.org/article/10.1088/1757-

I haven't seen any data, but coffee grounds seem more similar to straw, which has been used with some success. https://iopscience.iop.org/article/10.1088/1757-899X/394/3/032080/pdf https://iopscience.iop.org/article/10.1088/1757-899X/394/3/0...