Almost the simplest and lowest tech of all methods, direct timber burial is collection of timber, digging a big pit and burying it at least 2m down.

https://doaj.org/article/1464538b236e41f895961dbef35591a6

BUT it takes land to grow, some more land to bury (with competion for holes by landfills), fuel to harvest and dig, and isn't 'added value productive' so has not seen much market attention compared to other forms of offse. It is really cheap, and might yet see use.