Pittsburgh residents will have a chance to pick up free mulch and compost next month, thanks to the city’s Department of Public Works. DPW’s Environmental Services will distribute the materials at the Pittsburgh Zoo & PPG Aquarium overflow parking lot on May 2 and May 9, from sunup to sundown. The mulch is made from Christmas trees collected at the end of last year’s holiday season. This year, 845 trees collected across the city were chipped into natural mulch instead of being sent to a landfill.