Fluff®: a unique municipal solid waste processing by-product

Summary

A pulp-like material called Fluff® has been produced by a solid waste processing technology developed, patented by Bouldin &Lawson, Inc., 2000 and deployed in the US to facilitate rapid separation, volume reduction and conversion of municipal waste into a sterile organic pulp. The process separates the organic fraction of municipal garbage from the recyclable materials, grinds up the garbage, separates ferrous metals, and then sterilizes it using a hydrolyser with high temperature and pressure steam to break molecular bonds and destroy pathogens (Bouldin &Lawson, Inc., 2000). When hydrolysis is complete, one of the end products is a colourless, odourless, aggregate cellulose pulp. The material is then dried and the organic pulp, called Fluff, is separated from the recyclable glass, metal, and plastic constituents by air classification. The sand-like granular fluff is useful as a soil amendment because of its organic base and relatively high nitrogen content. If not utilized as soil amendment the Fluff by-product can still be landfilled at a 30-75% reduction in volume. The Fluff material has been used successfully after composting as topsoil replacement in the horticulture industry (Croxton et al, 2004) however it may also be an effective soil amendment before composting to improve soil physical and chemical properties (Torbert et al, 2007).

The Fluff by-product has been analysed for nutrient components and it has been found to have significant nutrient concentrations that would serve as an organic fertilizer source. Fluff has a near neutral pH, a C:N ratio around 30, and research indicates it decomposes slowly (Busby et al, 2007). Fluff has also been analysed for heavy metals, semi-volatile and volatile organic compounds. The analysis detected 9 heavy metals, 3 semivolatile and 3 volatile organic compounds. Due to the volatile chemical nature and rapid turnover in the environment, the detected organic compounds pose very little risk at concentrations found in the Fluff, especially when incorporated into the topsoil. In comparing metal concentrations in Fluff to the biosolids ceiling limits, it was found that all Fluff metal concentrations were at least an order of magnitude below their respective ceiling limits (Torbert et al, 2011). The Fluff metal concentrations were used to calculate maximum annual and cumulative application rates, where lead (Pb) was found to be the contaminant of primary concern. Annually this limit would be reached with an application rate of 229 t/ha. The maximum cumulative Fluff application rate was found to be 4587 t/ha, or 20 repeated applications at the maximum annual limit (Torbert et al, 2011).

The Fluff is unique in both origin and physical attributes when compared to other soil amendments. Studies have been conducted to evaluate the use of Fluff as a soil amendment to successfully rehabilitate damaged military training lands in the US (Torbert et al, 2007), which often lack of sufficient topsoil, organic matter, and nutrients required for successful rehabilitation (Busby et al, 2006, Busby et al 2010). The non-composted Fluff® was incorporated into a sandy loam soil at Fort Benning Military Reservation, GA on two sites: a moderately degraded and a highly degraded soil. The Fluff was added at rates of 0, 18, 36, 72 and 143 t/ha to assess the effects on soil properties for two growing seasons. Fluff reduced the level of soil bulk density and increased soil concentration of carbon (C) and nitrogen (N). The results of the study indicated that the application of non-composted organic amendment to highly acidic, degraded soils would improve soil conditions and provide a healthier soil environment for plant establishment. The improved conditions were most prominent on the more highly degraded soil, indicating that the more degraded the soil the higher the potential benefit from the addition of organic amendments (even non-composted organic amendments).

Because the Fluff material is derived from the organic component of household waste, a major portion of which is cellulose, it has properties offering potential utilization in dust suppression. Due to the high cellulose content of Fluff it shares similar dust control properties with commercially produced lignosulfonates (by-product of paper industry) extensively used in the US for dust control on un-surfaced county roads (Gebhart and Hale, 1996). The textural characteristics and pore space of Fluff make it an ideal candidate for use as a dust control agent alone or in combination with other dust control compounds.