Evaluation of municipal solid waste compost as a plant growing media component, by applying mixture design

The amount of municipal solid waste (MSW) generated is increasing rapidly in parallel with the increasing size of population. The use of sanitary landfills to dispose of biodegradable wastes is currently restricted by the European Landfill Directive. Moreover, incineration of MSW produces significant amounts of polluting flue gases and toxic solid residues, so that high investments for pollution control in MSW incineration plants are needed. Composting may be a safe and successful strategy for accelerating the decomposition and stabilization of the biodegradable components of biowaste from MSW, for sustainable complete recycling, thereby producing compost that can be used as soil conditioner and/or organic fertilizer. In the present study, municipal solid waste compost from Galicia (NW Spain), obtained on an industrial scale by anaerobic fermentation followed by aerobic stabilization, was characterized and compared with peat and composted pine bark as a component of plant growing media. Due to the high content of salts, the evaluated MSW compost was not appropriated to be used alone as a soil conditioner or organic fertilizer. Mixtures of MSW compost, peat and composted pine bark were evaluated statistically by applying mixture designs and triangular surface. The dependent variables (shoot dry weight of Lepidium sativum and Hordeum vulgare) were adjusted to linear equations, and good statistical parameters for correlation and significance were obtained, allowing accurate description of experimental data. The best results were obtained by mixing MSW compost with composted pine bark, rather than mixing MSW compost with peat.