2.1. Feedstock and inoculum
Yard waste was obtained in June 2011 from the OARDC Wooster campus and contained leaves and tree branches. The feedstock was oven dried at 40 °C for 48 h in a convection oven (Precision Thelco Model 18, Waltham, MA) to obtain a moisture content of less than 10%, and then ground with a hammer mill (Mackisik, Parker Ford, PA) to pass through a 5 mm screen, and stored in air tight containers until used. Food waste was collected in August 2011 from the feeding hopper of quasar energy group’s liquid anaerobic digester in Wooster, Ohio, USA. The food waste originated from several Wal-Mart grocery stores nearby. The food waste collected was cut and ground up using a standard kitchen blender. Food waste was stored in air-tight buckets at 4 °C in a walk-in cooler until used.