An evaluation of the phytotoxicity of municipal solid waste during co-composting with different animal manures

Abstract

Composting is a bioxidative process carried out under controlled conditions which utilizes naturally occurring microorganisms for organic waste recycling. In this study, a 60 days cocomposting experiment of different treatment consisting of municipal solid wastes and plant wastes with cow dung, poultry dropping and swine manure were investigated.Compost maturity parameters and phytotoxicity, during co-composting of municipal solid waste (MSW) with different animal manures (3:1 w/w) were evaluated. Four composting treatment set-ups: MSW (control), MSW+Swine Manure (SM), MSW+Poultry Manure (PM) and MSW+Cattle Manure (CM) were prepared and composting carried out for 60 days. Changes in temperature and pH were measured daily while Electrical Conductivity, Organic Matter, Total Organic Carbon, Total Kjedahl Nitrogen, and carbon/nitrogen ratios were assessed at day 0 and day 60. Humification process and phytotoxicity of the treatments were assessed at days 0, 10, 20, 30, 40, 50 and 60, using maize seeds germination bioassays. MSW+PM treatment showed the highest temperature of 63ºC during the thermophilic phase while the control showed the least. The pH at the end of composting in all treatments exhibited alkaline values with MSW+CM showing the highest value of 8.6. Maturity indices showed that there were significant decreases in organic matter, C/N and NH₄+ -N/NO_3^- -N ratios in all the treatments when compared with the control. At the end of   composting, Germination index( GI) values varied from 52.56 to 97.23% with MSW+PM showing the highest germination index (GI?) of 97.23±6.08% followed by MSW+CM and MSW+SM with GI values of 88.4±6.3 and 84.8±5.3% respectively. The germination index indicated that there were significant reductions in the phytotoxicity of the treatments.

 Keywords: Composting, municipal solid waste, phytotoxicity, poultry manure, seed germination test