Open windrow composting of fish waste in Estonia

Abstract

By-catch fish is caught unintentionally during the fishing and is currently thrown back in water bodies to cause the water pollution. Currently fishermen does not have a motivation to bring the by-catch fish to the shore, as it needs to be sorted by fish species, causing fishermen extra work without additional income. Estonian Ministry of Rural Affairs decided to give funding to present study with purpose to find solution to this matter. One possible solution for by-catch fish utilization is to produce high value nutrient rich fertilizer in order to close nutrient cycle and return valuable nutrients into soil. The adaptive study of outdoor windrow composting was conducted with consecutive treatments, rather than simultaneously, in order to make adaptive improvements to the set-up of each consecutive treatment. The consecutive treatments showed that fish waste composting is manageable from a technical perspective, feasible in a temperate climate, and that this type of compost holds high potential as an organic fertiliser or soil improver. Composting process started rapidly and, as required by the EU Commission regulation EU 142/2011, temperatures exceeded 70 h in all windrows. While initial treatments suffered from odours, as well as events inhibitive to the composting process, these disadvantages were successfully avoided in later treatments by adding a biofilter and inoculant from previous composting windrows, as well as lake sediments. Rather than disposing of low-value fish, these can be recycled into stable and nutrient-rich compost on-site, near fishing harbours.