Waste compaction is the process of compacting waste, reducing it in size. Garbage compactors and waste collection vehicles compress waste so that more of it can be stored in the same space. Waste is compacted again, more thoroughly, at the landfill to conserve valuable airspace and to extend the landfills life span. A side effect of this is that important items, like evidence in a crime, may be difficult to recover from the garbage. Due to reduced oxygenation, biodegradation of organic waste is also slowed.