Yard Waste Composting Facility

Processing
Over 50,000 tons of material is processed annually at the Yard Waste Composting Facility. Yard waste is ground up and moved into long narrow piles known as windrows. In the fall, windrows are comprised primarily of leaves. In the spring, grass is added. The active composting phase requires both leaves and grass. Windrow composting is most effective when the carbon to nitrogen ratio is 25 parts carbon to 1 part nitrogen, the temperature ranges between 130 to 140 degrees Fahrenheit, the moisture is between 45% and 55%, and the oxygen is less than 5%.

Windrow Composting


Windrows are turned using a Scarab windrow turner to accelerate the composting process. Frequency of turning depends on environmental conditions. In general, windrows are turned more frequently during the spring and summer (approximately 2 turns per week). Depending on the weather, the rows of yard waste may require manual watering. Normally, our area receives enough rainfall and temperatures are moderate enough to avoid manual watering. However, in drought conditions or extremely hot weather, watering becomes necessary. The windrow composting process takes approximately 9 months to complete.

The material is then moved to a curing pile where it will continue to decompose for approximately 3 months. Once this process is complete, the compost is spread in a thin layer on the pad to dry.
Next, the material is screened to remove all particles larger than 3/8 inch.

Leafgro


The final product is a dark humus-like material, which is marketed as Leafgro by MES. It is produced in accordance with the Maryland Department of Agriculture regulations and is a great soil amendment. A network of retailers sells the Leafgro. Revenue from the sale of this material is returned to the county to offset the cost of the composting operation.

Food Scrap Composting
Prince George’s County piloted food scrap composting during 2013 utilizing the Gore Cover technology which is an in-vessel aerated pile system with oxygen and temperature monitoring devices.  This technology is designed to create ideal composting conditions within the pile while efficiently trapping odors and other emissions such as dust and volatile organic compounds (VOCs).  This system allows for the processing of a greater volume of yard trim and the inclusion of food scraps on a smaller footprint of area with little energy consumption and creates finished compost within a 30 days.  Utilizing the GORE covered system enables the County to divert food scraps from the landfill increasing the overall recycling rate within the County.

The final product from this process is known as LeafgroGold, a nutrient rich dark humus-like material, marketed by the County’s contractor, the Maryland Environmental Service (MES).  The compost is produced in accordance with the Maryland Department of Agriculture regulations and is a top quality soil amendment.  A network of retailers, found on MES’s website, sells the LeafgroGOLD.  Revenue from the sale of this material is returned to the County to offset the cost of the composting operation.

During 2014, the County increased the Gore Cover system from a three heap pilot project, to a four heap continuous process. The composting of food scraps and yard trim mixed together in the Gore System has been so successful, another expansion to an eight heap system is in process.  Food scraps are accepted from pre and post-consumer entities, including residential, commercial and institutional sectors.