Bioconversion of Baltic Seaweeds into Organic Compost

Abstract

Purpose: Large quantities of green seaweeds, resulting from the eutrophication, are cast ashore on the beaches of Baltic Sea (Poland). There is a necessity to collect this biomass and dispose in a cost-effective and environmental-friendly method. In the present paper, preliminary study on the possibility of composting of Baltic algae is described. After 8 weeks, algal compost and compost extract were produced. The obtained bio-products are expected to enhance plant growth and crop yield since seaweeds are known to be rich in macro- and microelement nutrients, amino acids, vitamins and plant growth promoting substances. Methods: The obtained compost and compost extract were characterized in terms of the content of micro- and macroelements and toxic metals. The phytotoxicity of products were then biologically evaluated in germination tests on garden cress (Lepidium sativum) and radish (Raphanus sativus). In the control group, both plant species were watered with distilled water. After the experiment, dry weight of the cultivated plants was measured. Moreover, yield and the content of and micro- and macronutrients in plants was determined. Results: Results showed that there were no phytotoxic effects in both cases and the addition of compost and extract increased the plant growth. The difference in weight for both plants between the examined groups was insignificant. The biomass of plants fertilized with the algal compost and extract was biofortified in micro- and macroelements (in particular B, Fe, Cu, Zn, Ca, K, S). Conclusions: According to these results, composting is a useful technology both to solve waste disposal problems and to produce a valuable organic fertilizer. This could help to reduce the use of chemical fertilizers and improve physicochemical properties of the soil and to increase the plant growth.