Composting solid swine manure and lignite mixtures with selected plant residues

Abstract

A study was undertaken to investigate the composting of mechanically separated solid swine manure and ground lignite residues mixtures enriched with rice seed peels and ginned cotton residues. A set of odor-free compost piles, due to lignite addition, was installed, on site, at AFI KARAPATIS SA organic fertilizer factory at Zeli in central Greece. The findings of this study indicated that co-composting of solid swine manure and ground lignite (mixed at a ratio of 1:1 by volume) together with ginned cotton residues and rice seed peels resulted in improved composting and chemical composition characteristics compared to the mixture of solid swine manure and ground lignite alone or enriched with either ginned cotton residues or rice seed peels. Ground lignite, due to its excellent odor- and moisture-absorbing capacities allowed for the successful incorporation of the wet and malodorous swine manure into the compost process. Ginned cotton residues (at a 1:1 mixing ratio by volume) proved to be a bulking agent with excellent ‘insulating behavior’ but with lower composting rates and increased EC and Na values in the final product. Rice seed peels, as C/N amendment, speeded up the compost process and improved the quality characteristics of the final product but showed a very poor ‘insulation behavior’. When both ginned cotton residues and rice seed peels were added to a pile, all adverse effects were removed and best results were obtained (maximum temperature range between 45–55°C for about 20 days and overall compost process of about 85 days with ambient air values below 10°C).