It rather depends on what you consider "chemicals". Typically, but perhaps on a larger scale, elemental sulfur is what is used to lower soil pH (make it more acidic). There are pH lowering sulfur products that are OMRI-listed so acceptable for organic growing.
Canadian peat moss is typically quite acidic but not all peat mosses are equally so, so when using peat moss make sure it is an acidic one.
What is the soil pH now? That makes a difference as to what you'd need to use and how much (and whether lowering it is feasible).
This article below on acidifying soil for blueberries in Washington and Oregon may give you some other ideas:
https://catalog.extension.oreg...