Assessment of Composting Methods for Use in the Green Industry

Abstract

Composting is a common waste management tool for successful reduction of waste materials. Due to increased consumer awareness for compost products and their value to the green industry research is needed to evaluate different compost methods. Composts can be a suitable media component for container-grown plants based on typical physical and chemical properties. The purpose of this study was to evaluate two composting methods of poultry litter (PL) to determine differences in materials destined for use in the green industry. Windrow composting and In-Vessel Digester composting of PL were compared. Composting for both methods began at the same time and were evaluated using temperature logging, moisture analysis, C:N tracking, and quantification of biological organisms such as Salmonella, fecal coliforms, and Enterococci. Results indicated that there were noticeable differences between compost methods in regarding temperature, moisture analysis, and C:N ratios. Both methods produced compost with safe levels of bacteria for human use. At the end of the compost process samples were taken from each of the two methods and compared in plant growth trials for two ornamental crops and a weed germination test. In the first study using Impatiens waleriana ‘Fanfare’ substrate leachates, plant growth indices, and plant dry weights were analyzed at the end of the study to determine which method of composting produced the best overall plants. In this study windrow composted PL out performed in-vessel composted PL. There was a noticeable difference in plant dry weight, substrate leachate, and plant growth indices in substrates comprised of windrow composted PL. In the second study Hemerocallis spp. ‘Pardon Me’ plant growth, substrate leachates, and plant dry weights were analyzed after 10 weeks. Results indicated following the Hemerocallis study that compost produced by windrow method was more suited for container substrate use than in-vessel compost. Plant dry weights for this study revealed that substrates containing windrow composted PL produced larger plants. A weed germination test was conducted in which twelve pots were filled with each compost material and allowed to sit in a climate controlled greenhouse for a total of 6 weeks. Results revealed that both methods are equally suitable at eradicating potential weed seed that are present during the composting process. Results of these studies indicate that windrow composting produced compost more suitable for green industry use. Data revealed that the electrical conductivity and pH levels for in-vessel derived compost might not be suitable for production without pre-plant leaching of salt and pH sensitive plants.