Using compost/wood chip material as biofiltration media

SINCE 1995, the city of Brownsville, Texas has operated a composting facili ty at its municipal landfill receiving steady deliveries of shrubbery, hedg e and palm tree trimmings as well as other woody materials and organic feed stocks from homeowners and food processors. About 450 tons/year of manure a nd hay bedding from the Gladys Porter Zoo in Brownsville are also composted . Municipal staff and Brownsville Public Utility Board Staff have collaborate d with researchers in the Environmental Engineering Department of Texas A&M University-Kingsville to come up with a program designed to optimize produ ction of a high quality compost product designed for many horticultural app lications. The city has also hired the A&M-Kingsville researchers to evalua te the wood residues left after screening operations for use in biofiltrati on of contaminated air streams. Biofiltration is a promising control technology for processes that emit lar ge off gas volumes with relatively low concentrations of contaminants. Whil e the compost product produced at the Brownsville landfill has valuable pro perties for use in biofiltration applications, it is known that specially p repared biomass support media (such as wood mulch) improve performance and have a lower pressure drop than just soil or compost in biofiltration appli cations. The larger size mood chip residues left alter compost screen proce ssing at Brownsville have several characteristics that could make them idea l for use as support and biofiltration media. The economic advantages of biofiltration for the capture of odor-causing an d volatile organic compound (VOC)emissions are well known. It requires mode rate capital investment and low operating costs, generates nonhazardous by- products, and can handle a wide range of VOCs and other input compounds for treatment. Once a biofilter has begun steady state operation, little maint enance is required. Long-term maintenance typically includes maintaining th e moisture level and monitoring pH and nutrient loadings. Biofiltration med ia can last from two to five years.