Techniques for Nitrogen Management in Municipal Solid Waste Composting

Though it has been around for centuries, composting is becoming increasingly important today in research and in practice for its environmental benefits. Nitrogen plays a central role in the composting process and in many of the applications of compost, but despite the relevance of this topic it has not been thoroughly studied in municipal solid waste (MSW) composting. Improved management of nitrogen in compost could benefit water quality, in areas suffering from non-point nutrient runoff due to conventional fertilizers; waste management, for the organic fraction of the municipal waste stream; and agriculture, for which compost is currently too nutrient-poor to be commercially viable as fertilizer on a large scale. In this project, possible methods for engineering the MSW composting process to yield a product richer in organic nitrogen have been identified through tests in aerated, pilot-scale reactors. Compost batches run with traditional methods tended to yield a product that was low in organic nitrogen, with high nitrogen losses often observed. These results were consistent with previous research that has shown traditional MSW compost to be relatively poor for agricultural use. However, some of the process modifications were successful in conserving organic nitrogen. These included (1) the inclusion of shredded office paper as a feedstock, (2) the collection of compost leachate, and (3) the addition of strong acid or acid-loaded clay. The results of this study suggest future experiments to develop methods for producing better MSW compost.