Inexpensive Construction
An inexpensive, three-sided compost bin can be constructed of concrete blocks, discarded pallets (usually free for the asking from local businesses), chicken wire or most any type of building material. Always avoid treated lumber when building your compost bin. Pressure-treated wood, also known as CCA (usually has a greenish tint) contains arsenic, a highly toxic substance. It also contains toxic levels of copper and chromium.
Toxins
Evidence suggests that these toxins leach into the compost from the CCA lumber. The optimal size of a compost pile/bin is 3 feet by 3 feet by 3 feet. This provides the insulation need to maintain sufficient temperatures for more rapid decomposition. Build the bin over soil that has been loosened. This allows worms, bugs and other organisms to migrate upward and aid in decomposition.