Influence of lime on struvite formation and nitrogen conservation during food waste composting

• Interaction between lime and struvite mediated nitrogen conservation was studied.
• N loss was reduced by 38% through struvite formation in presence of lime.
• 2.25% lime addition is effective in controlling acidity and struvite formation.
• Nitrogen fixed in struvite decreased when the lime dosage increased.

This study aimed at investigating the feasibility of supplementing lime with struvite salts to reduce ammonia emission and salinity consequently to accelerate the compost maturity. Composting was performed in 20-L bench-scale reactors for 35 days using artificial food waste mixed with sawdust at 1.2:1 (w/w dry basis), and Mg and P salts (MgO and K2HPO4, respectively). Nitrogen loss was significantly reduced from 44.3% to 27.4% during composting through struvite formation even with the addition of lime. Lime addition significantly reduced the salinity to less than 4 mS/cm with a positive effect on improving compost maturity. Thus addition of both lime and struvite salts synergistically provide advantages to buffer the pH, reduce ammonia emission and salinity, and accelerate food waste composting.