Fate and Effects of Silicone Polymer During the Composting Process

Abstract

Silicone (polydimethylsiloxanes, or PDMS) fluids are widely used in industrial and consumer products, and may find their way into municipal biosolids that are eventually applied to the land. In soil PDMS breaks down into dimethylsilanediol which is then either volatilized or biodegraded. Since biosolids are often composted prior to land application, this paper investigates fate and effects of PDMS in compost. PDMS (0,3, or 30g) was added to 180g of matured compost and incubated at 58°C for six weeks. Some treatments also had 180g of wood ash and/or additions of 15g of alfalfa every two weeks. Releases of CO, from all treatments were identical to their respective controls (no PDMS), indicating no effects from these extremely high PDMS levels on the composting process. Wood ash caused an initial delay in CO, release after which results were similar to treatments without wood ash. After six weeks, PDMS was unchanged in molecular weight and concentration, indicating that it will be transferred intact, after composting, to the land where it can degrade in the presence of soil.

Leaching and Biodegradation of Darocur 1173 used as a Photo-Initiator in the Production of Photocrosslinked Silicone Acrylates

“…However, when the coatings, silicon oil or Darocur were used as sole carbon sources, almost no biogas production was observed, indicating that these substrates were almost not biodegraded under anaerobic conditions. This result confirmed the information from previously published studies [11,22,23]. It could be explained by the possible need of O 2 in the initial steps of biodegradation, as described for example in the biodegradation of lignin [24] or poly-aromatic hydrocarbons studies [25] where aerobic bacteria and fungi were mostly responsible of biodegradation.…”

Life Cycle of Silicone Polymer, from Pilot-Scale Composting to Soil Amendment

“…These events are explained by the rapid consumption of fresh organic matter in the early stages of composting, followed by decreased activity as the more stable organic materials remain (Diaz et al 1993). No effects by the PDMS were noted on the compost operations, which was expected because our previous paper showed no effects of much higher levels (14%) of PDMS on composting of fresh plant material (Smith et al 1998). The maturing of the composts is also reflected in their chemical analyses.…”

“…Sludges, finished composts, and compost-amended soils were extracted with tetrahydrofuran (THF) and analyzed for PDMS and potential breakdown products us- Lehmann, D. M. Smith, R. Narayan, G. E. Kozerski, f. R. Miller ing Gel Permeation Chromatography interfaced to an Inductively Coupled Plasma (GPC-ICP) according to the methods in our previous paper (Smith et al 1998).…”

“…A previous study used a standardized ASTM test in which extremely high levels (14%) of PDMS were mixed with a mature compost product and incubated in 2-liter bottles at 60°C for 6 weeks (Smith et al 1998). Although the PDMS did not degrade under these conditions, it also did not interfere with C0 2 generation from freshly added alfalfa.…”

Bioremediation of Heavy Metals and Organic Toxicants by Composting

“…Silicone polymers from industrial and consumer products may enter into municipal sewage sludge. A silicone polymer (polydimethylsiloxane) did not degrade during composting but did not appear to interfere with composting [103]. Silicone polymers are reported to degrade readily in soils [104].…”