Is the compost from Philadelphia's Organic Recycling center suitable for vegetable gardening?
Answer
Compost made in municipal facilities is generally safe to use for vegetables. Small amounts of material collected from the road may make it into the compost, but if properly diluted with garden soil, the effect from these materials should be minimized. Also, composting raises the temperature of the material and mixing of the compost should dilute any bad material significantly.
Commercial sources of compost often purchase excess compost from manicipalities and test it, finding it satisfactory. If residents found anything unsatisfactory, they would complain and officials would take corrective action. Small amounts of salts and chemicals like arsenic are in soil having little bad effects on plants or vegetables. Lead has been reduced significantly in gasoline and should not be a problem. Also, worms in the soil process a lot of organic material and are not harmed by materials in compost. My standard soil mix for potted plants uses mumicipally prepared compost with no noticably bad effects.
If you still have concerns, blend the compost in well with garden soil and use 25% or less of compost in the soil. You can have the compost tested by a commercial firm, but I hardly think that is necessary.