We all try to be greener today
More specifically sawdust from treated wood. Up until only a few years ago, most wood used for external structures (such as playground and railroads) were treated with pressure treated preservatives such as Chromated Copper Arsenate or
2. Biodegradable products
All compostable products are biodegradable, but not all biodegradable products are compostable. Biodegradable only means that a product breaks down into smaller versions of itself over time, not that it can be used for fertilization. Unless a biodegradable product states that it is compostable it needs to be sorted properly.
3. Dryer Lint and sheets.
Unless you wear only organic materials, your dryer lint is made up
Walnut trees release a chemical called juglone which is toxic to some vegetables and plants, such as tomatoes so it is best to avoid composting anything related to walnuts in case you want to use the resulting compost with susceptible veggies.
5. Greasy Food Containers