The organic matter of municipal waste can be recovered in its entirety.
However, only a small amount of all generated is collected separately, and furthermore not all waste collected in containers for organic matter are actually organic matter. Thus, about one quarter of collected organic matter is not recovered, in other words it is not transformed into compost, due to the presence of inappropriate materials.
During the process called composting, organic matter is transformed into compost, a fertilizer that can be used both for gardening and for agriculture and public works. This is possible thanks to the action of microorganisms that under certain conditions of temperature, moisture and oxygenation organic matter decomposes . This is a biological or anaerobic (in the presence of oxygen) decomposition.
The main problem with this process are the odours generated during the treatment of organic matter (the resulting compost does not smell), for such reason having one close to home is not very accepted. In addition, we find the need to previously separate the non-organic material collected in containers designated for organic matter.
In the year 2009 in Catalonia there were 21 composting plants that treated just over 340 thousand tons of organic matter, while in 1998 the number of plants was 7 and the amount of waste treated barely exceeded 35 thousand tons.
Table 5. Composting plants for the organic fraction of municipal waste in Catalonia in 2009
Source: Compiled from Catalan Waste Agency
Figure 15 shows the proportion of organic fraction of selectively collected waste versus total waste generated in the 41 counties of Catalonia in 2009. In 25 of these counties the organic fraction was less than 10% of the total, while values are between 10% and 20% in 14 more counties. It only slightly exceeds the threshold of 20% in the counties of Segarra and Pla d'Urgell. Despite the obvious improvements compared to the year 1998, the over 340 thousand tons of organic matter collected separately in 2009 for the whole of Catalonia only amount to 8.1% of the total municipal waste generated in Catalonia. Unfortunately, much of the organic fraction of waste continues to be disposed of by sending it either to a landfill or to a waste incineration plant.
Figure 15. Selectively collected organic fraction compared to the total waste generated in Catalonia (2009)
Source: Saladié (2011)