# Strategies for the Sustainable Management of the Organic Fraction of Municipal Waste
## 1 Introduction  
One of the main problems of municipalities today is the management of the organic fraction of municipal waste, OFMW. the directives established a deadline for the collection and separation of biodegradable municipal waste in 2020, but it is still not possible to achieve that target. The European Union, through Directive 2018/851 [1], modified, among many other aspects, these deadlines, given the low level of compliance of the municipalities, setting December 2023 as the deadline. In a more detailed way, article 22 of this law on bio-waste, Directive 2018/851 [1], states that:  
_\"Bio-waste either be separated and recycled at source, or be collected separately and not mixed with other types of waste\" and also propose to \"encourage the recycling, including composing and digestion, of bio-waste in a way that ensures a high level of environmental protection and generates an output that meets relevant high quality standards\", \"encourage home composing\" and \"encourage the use of materials produced from bio-waste\"._This, coupled with milestones such as limiting municipal waste to a maximum of 10% of landfillable municipal waste by 2035, as well as recycling at least 55% of municipal waste by 2025 and 60% by 2030, make the issue of municipal waste management a priority. Following the specifications given by the regulations and the recommendations issued by the Ministry of Ecological Transition, the main way to manage biowaste is through composting. Composing is an aerobic decomposition of biodegradable waste under controlled conditions and its transformation into humus by the action of micro and macro-organisms, which can be used as a fertilizer in agriculture. Compostable waste refers to a biodegradable waste (also known as green waste or organic waste). In principle, all organic waste of a biological origin is compostable. This includes food leftovers from households, restaurants, canteens, and bars; green waste from gardens and parks; and dirty paper. When we focus on the management of the organic fraction of municipal waste for composting and subsequent use, we can see that there are many wastes managed by municipalities that could be used in the composting process, providing the necessary N and C fractions. Many studies have used _Posidonia ocanica_ ([PERSON] in composting [2], whilst others have also used a mixture of seaweed and fish waste [3,4], seaweed with pruning waste [5], pruning and domestic waste [6], and different mixtures of agricultural and municipal waste [7], to achieve efficient waste management and a circular economy of the municipalities [8]. The characterization of the available raw materials, their seasonality, and volume are, therefore, important factors to consider when defining the management strategy of each municipality. Although these residues can also be destined for use as ruminants feed, some works highlight possible metabolic consequences [9] in high quantities and so a pretreatment is necessary, which, therefore, increases the cost of use. Regarding [10,11], there are different composting systems, with their main objective being to transform waste into a stable and sanitary safe material. Two general types of systems exist: closed and open. In closed systems the waste is processed in reactors. They can be simple or more complex, combining mechanical agitation and forced aeration. They are generally metallic structures, cylindrical or rectangular in shape, where parameters such as aeration, temperature, etc. are kept controlled. These systems enable the initial stages of fermentation to be accelerated. When these stages are finished, the material is removed from the reactor and stored for maturation in the open air or in open warehouses. In general, they are industrial systems with high costs. One of the main advantages of these systems is that they considerably reduce composting surfaces and achieve better control of fermentation parameters and odors, as well as being faster.