Composting of waste paint sludge containing melamine resin as affected by nutrients and gypsum addition and microbial inoculation

Melamine formaldehyde resins have hard and durable properties and are found in many products, including automobile paints. These resins contain high concentrations of nitrogen and, if properly composted, can yield valuable products. We evaluated the effects of starter compost, nutrients, gypsum and microbial inoculation on composting of paint sludge containing melamine resin. A bench-scale composting experiment was conducted at 55 °C for 91 days and then at 30 °C for an additional 56 days. After 91 days, the composts were inoculated with a mixed population of melamine-degrading microorganisms. Melamine resin degradation after the entire 147 days of composting varied between 73 and 95% for the treatments with inoculation of microorganisms compared to 55–74% for the treatments without inoculation. Degradation was also enhanced by nutrients and gypsum additions. Our results infer that large scale composting of melamine resins in paint sludge is possible.

► Melamine resin in waste paint sludges could be efficiently composted at bench scale.
► Melamine resin degradation after 147 days of composting was 73–95% complete.
► Nutrients, gypsum and melamine-degrading microorganisms increased composting rate.
► Melamine degradation products first increased and then decreased in the compost.
► Final compost was enriched in nitrogen and other essential plant nutrients.