Exploring beneficial uses of Ecklonia maxima waste residue

Abstract

The rise in technological advancements has brought about an increase in industrial production, this in turn has caused a surge in consumerism, with waste being generated at an increasing rate in a linear economy system. The increase in waste generation has resulted in pressures on landfill sites and economic resources being directed to the management of these landfills. To address the adverse impacts associated with the disposal of waste and to divert waste away from landfilling, the South African government has developed legislation, strategies and regulations towards implementing the waste management hierarchy, with specific focus on the beneficial use of waste and achieving a circular economy. The aim of this research was to explore the potential beneficial uses of Ecklonia maxima waste residue generated by a seaweed processing company based in South Africa. This was achieved through a mixed methods approach. In summary, the physico-chemical properties of Ecklonia maxima waste residue were determined; the possible beneficial uses of Ecklonia maxima waste residue were identified and ranked to identify the most preferable use of the waste residue; and the optimal conditions of the most preferred identified beneficial use, were ultimately, evaluated. Laboratory analysis of the waste residue, supported by literature review, indicated the presence of nutritional elements in the algae waste residue (nitrogen: 2.18%, potassium: 5.58%, phosphorus: 0.35%, and organic matter: 63.26% (based on dry mass)). These characteristics of the waste residue make it potentially suitable for beneficial use in the production of animal feeds and aquaculture; the food sector; biogas production; use as a soil conditioner or compost additive; as well as potential reprocessing of the waste residue in production processes of the seaweed processing company (after enzymatic hydrolysis). Based on a ranking process (which applied criteria such as suitability of algae waste residue composition for beneficial use, compliance of the beneficial use within the South African legal framework, economic viability, energy efficiency, business advantage, and compatibility of the beneficial use with existing formulations) enzymatic hydrolysis for reprocessing was identified as the most preferred beneficial use for the algae waste residue. The research, finally, evaluated the optimal conditions for the enzymatic hydrolysis of algae waste residue for the purposes of reprocessing. Different enzyme- and pre-treatment combinations were tested to determine the combination which would yield the highest concentration of total soluble organic matter and total sugars. Residues pre-treated with peracetic acid, generally yielded higher concentrations of total organic matter and total sugars, than residues treated with sulphuric acid, or those without any pre-treatment. The enzyme combination of Celluclast + Viscozyme yielded the highest concentration of total organic matter and sugars. An in-depth analysis of the E. maxima waste residue is critical in exploring all the potential beneficial uses. Future laboratory analysis should include the full profile of all the complex carbohydrates in the residue. More research should be conducted in assessing the suitability of the waste residue in relation to its inclusion in the food manufacturing sector. Finally, process optimisation of enzymatic hydrolysis for reprocessing purposes is recommended.