This review analyses the main challenges of the process of food waste composting and examines the crucial aspects related to the quality of the produced compost. Although recent advances have been made in crucial aspects of the process, such composting microbiology, improvements are needed in process monitoring. Therefore, specific problems related to food waste composting, such as the presence of impurities, are thoroughly analysed in this study. In addition, environmental impacts related to food waste composting, such as emissions of greenhouse gases and odours, are discussed. Finally, the use of food waste compost in soil bioremediation is discussed in detail.

There is actually a common consensus in using biological technologies for the treatment of organic wastes. For instance, composting is used for aerobic biological stabilisation of organic wastes. The amount of materials and the variety of wastes composted are increasing. However, composting is inherently a process generating gaseous emissions. Greenhouse gases (GHG) such as carbon dioxide, methane and nitrous oxide from compost are of special relevance for global warming. Although a part of these gases is inherent to the process, another important part can be abated by low-cost biological technologies such as biofiltration and its variations. This article reviews the emission of GHG from composting gases, from detection and measurement to minimisation and abatement. Special emphasis is given to the measurement of GHG to obtain reliable emission factors for the different composting technologies. These factors will help to compare different waste treatment options based on overall analysis tools such as life cycle assessment. A specific chapter is related to carbon and nitrogen dynamics in the composting matrix, and their consequences on the production of carbon and nitrogen gases. Finally, we present a review of the best available practices to minimise the GHG emissions from composting and the final treatment of composting off-gases.

Composting of several organic wastes of different chemical composition (source‐separated organic fraction of municipal solid waste, dewatered raw sludge, dewatered anaerobically digested sludge and paper sludge) was carried out under controlled conditions to study the suitability of different biological indexes (oxygen uptake rate, respirometric index, and respiratory quotient) to monitor the biological activity of the composting process. Among the indexes tested, oxygen uptake rate (also referred to as dynamic respirometric index) provided the most reliable values of microbial activity in a compost environment. On the other hand, values of the static respirometric index measured at process temperature, especially in the early stages of the composting process, were significantly lower than those of the dynamic index, which was probably due to oxygen diffusion limitations present in static systems. Both static and dynamic indexes were similar during the maturation phase. Static respirometric index measured at 37°C should not be used with samples obtained during the thermophilic phase, since it resulted in an underestimation of the respiration values. Respiratory quotient presented only slight variations when changing the process temperature or the waste considered, and its use should be restricted to ensure aerobic conditions in the composting matrix.