3. Results
Four months of composting yielded approximately 3m3 of material, resulting from the decomposition of the
initial 10 m3, indicating a 70% reduction in volume. Stabilisation tests after two months of composting indicated that
the compost product was stable. Autoheating showed the difference between the inside and outside Dewar flask to
be less than 10ºC, which corresponds to a degree of maturity classified as V. This indicates that the compost was
totally stable and that most of the biodegradable material had already been transformed [18]. The degree of stability
was 66.7%, which suggests that more than half of the total organic matter was resistant.
The germination index in the compost was 81.1%, which according to Zucconi et al. [13] indicates the absence of
phytotoxic substances or their presence in very low levels.
The final compost was adequate for use as organic fertilizer, particularly in regard to the NPK content, which was
greater than 4% cumulatively. Unfortunately, the C/N ratio was greater than 20, which is considered high in current
legislation [19] and should be corrected in the future (Table 2).
Salinity was also high (Table 3), mainly due to the saline content in the fish waste products (Table 1). The NH4
+
and el K+ ions are primarily responsible for this. If the compost is to be used as a substrate, recommended salinity
should not surpass 0.65 dS/m in a 1:5 extract [20]. However used as a fertilizer or soil amendment, salinity would
not be of concern.