Assessment of mussel processing waste stabilization methods: Crop nutritive value and element composition

Mussel aquaculture generates processing waste (MPW); a source of crop nutrients. Work was conducted to test Ca(OH)2 as a stabilizer to slow MPW decomposition and reduce odour/liquefaction. Parameters were elemental composition of MPW products, and crop performance/nutrient uptake of radish and oat amended with MPW materials. Only 2% (w:w) Ca(OH)2 was needed to stabilize MPW; shown by reduced liquefaction/increased pH. Fresh, liquid fraction, and Ca(OH)2-stabilized contained substantial macro/micro nutrients; composted had less plant-available N. All materials contained potentially phytotoxic elements, but levels were below recommended limits or detection. Fresh MPW acidified soil and reduced radish density; the latter possibly due to products of decomposition. MPW can be a nutrient source if crop damage can be avoided. Composted MPW does not damage crops but has lower nutrient availability. Ca(OH)2 stabilization retains more nutrients from fresh MPW and avoids phytotoxicity.