The fruit processing industries are concentrated in southern Europe. Most of them are small and medium size and they generate considerable amount of fruit residues. Manufacturers of fruit juice usually dispose of their fruit residues in a number of different ways.
The most common option for making use of fruit residue is as animal feed. However, the high moisture content of fresh residues results in high transportation costs, while the high biodegradability levels limit their use as fresh feed in the surrounding areas. In that case, it is preferable to process anaerobically the residues in order to generate biogas, compost, electricity and heat in adjacent anaerobic digestion plants for example.
Alternatively, and taking into account the above mentioned disposal options and their limitations it is best practice for the fruit juice manufacturers to dispose of their fruit residues by attempting to follow the order of priority cascade as listed below:
- Recovery of valuable products whenever feasible e.g. production of pectin, fine chemicals and/or multifunctional food ingredients.
- Use of the fruit residues as animal feed taking into account availability and requirements of local livestock or interest raised by animal feed producers.
- Use of the fruit residues as anaerobic digestion co-substrate in on-site anaerobic digestion plants, or in adjacent anaerobic digestion plants or considering the construction of a new anaerobic digestion plant together with other producers of organic residues suitable for anaerobic digestion process.
The availability of local options affects significantly the disposal way chosen. Additionally, technical aspects, such as the presence of essential oils in orange residues, namely D-limonene, should be carefully taken into account by the anaerobic digestion plant managers, since the co-digestion with other organic waste prevents the inhibition caused by limonene.