4. Discussion
4.1. Ammonia-N:Nitrate-N ratio
To stabilize carbon, composting can occur at such a rapid rate that sometimes phytotoxins remain in the compost and must be neutralized before using in high concentrations or in high-end uses. This step is called curing. Typically, ammonia is in excess with the break-down of organic materials resulting in an increase in pH. This combination results in a loss of volatile ammonia (it smells) (De Guardia et al., 2010 and Zeng et al., 2012). Moreover, the total ammoniacal nitrogen can be immobilized as organic nitrogen, accumulated in the compost, emitted as ammonia and/or converted into nitrate and then molecular nitrogen through nitrification and denitrification, respectively. Therefore, during the composting process, nitrogen can be kept in the solid matrix, lost through leaching or released as ammonia, nitrous oxide or molecular nitrogen in exhaust gases.