Globally, water hyacinth is a known invasive species that predominantly threatens the pillars of sustainability. The cost of controlling these invasive plants is high and many Southern African countries are barely equipped for this liability as the process has to be performed over time. Despite this challenge, there is valuable resource recovery from water hyacinth which can be used to make financial and environmental returns. The visible differences between the control and utilisation methods lie in the definition, recognition, and matching of costs and benefits. Using a rapid appraisal of existing literature, which was analysed using meta-analysis, the current paper is an attempt to discuss the beneficial use of water hyacinth. It is argued in the paper that the economic feasibility of control methods which, on one hand, are used to calculate the economic value of water hyacinth, mainly relies on assumptions whose reliability and sustainability are questionable, thus implying limitations on using this kind of control methods. On the other hand, the costs and benefits of utilising water hyacinth can be quantifiable, making them susceptible to changes associated with time value and sensitivity analysis of possible fluctuations in cashflows. In the context of these annotations, other scholars have argued for the consideration of other utilisation alternatives, among which is included biogas which has been identified as the most viable option because of its potential in diversifying the energy mix, reducing greenhouse gas emissions, and contributing to improved water quality. Given these observations, this paper aims to contribute to policy and research discussions on the fiscal understandings of the material recovery from water hyacinth to promote the adoption of biogas technology. These views are discussed within the broader discourse of the sustainable development goals (SDGs).

Anaerobic digestion has been identified as a feasible fragment of a bioeconomy, yet numerous factors hinder the adoption of the technology in South Africa. Apart from its energy recovery, other nonmarket advantages support the technology. Though it may be challenging to have a price tag, they provide clear added worth for such investments. With a growing energy demand and global energy transitions, there is a need to sustainably commercialise the biogas industry in South Africa. Most studies are at laboratory scale and under specific conditions, which invariably create gaps in using their data for commercialising the biogas technology. The key to recognising these gaps depends on knowing the crucial technical phases that have the utmost outcome on the economics of biogas production. This study is a meta-analysis of the optimisation of anaerobic digestion through methodological approaches aimed at enhancing the production of biogas. This review, therefore, argues that regulating the fundamental operational parameters, understanding the microbial community’s interactions, and modelling the anaerobic processes are vital indicators for improving the process stability and methane yield for the commercialisation of the technology. It further argues that South Africa can exploit water hyacinth as a substrate for a self-sufficient biogas production system in a bid to mitigate the invasive alien plants.

The widespread use of neonicotinoid pesticides, particularly imidacloprid (IMI) and acetamiprid (ACE), has raised environmental concerns due to their persistence and toxicity in aquatic systems. This study investigates the efficacy of copper oxide-modified Musa Parasidiaca peel biochar-supported reduced graphene oxide (Cu/MPBC/rGO) as a novel adsorbent for removing IMI and ACE from aqueous solutions. The synthesized composite was characterized using scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) etc, to elucidate its morphology, surface chemistry, crystallinity, and porosity. Adsorption experiments were conducted to examine the influence of pH, contact time, adsorbent dose and adsorbate concentration. The adsorption kinetics followed the mixed order kinetic model, and the equilibrium data were best described by the Langmuir isotherm, indicating monolayer adsorption. Cu/MPBC/rGO exhibited high adsorption capacities of 62.19 mg g⁻¹ for IMI and 32.78 mg g⁻¹ for ACE. Reusability studies confirmed the material's stability and efficiency over multiple cycles. These findings proved the potential of Cu/MPBC/rGO as an efficient and sustainable adsorbent for the removal of neonicotinoid pesticides from contaminated water.

Water hyacinth is an invasive alien plant with several impacts on the environment, economy and society. The plant’s high degree of proliferation makes its mitigation difficult and sometimes complex. However, existing evidence suggests that water hyacinth is a sustainable substrate for biogas production. Using the pretreatment processes for the optimisation conditions for biogas production from water hyacinth, this study analysed the effects of moisture content (60%, 70% and 75%) on Trichoderma atroviride pretreatment of water hyacinth and the impact of the pretreatment on biogas production. Anaerobic digestion of the water hyacinth process was performed at 35°C for 35 days. The modified Gompertz model was used to analyse and predict the appropriate kinetic variables of the digestion process. Biogas yields from untreated, pretreated-60%, pretreated-70% and pretreated-75% were optimal at 135, 210, 217 and 223.4 mL/g of volatile solids (VS). These results suggest the pretreatment of water hyacinth enhanced the degradability of water hyacinth by breaking down the cell wall structure and facilitating its use by microorganisms. Furthermore, the results also confirmed that the higher the moisture content, the easier the biodegradation rate and, consequently, the higher the biogas yield. The model predicted maximum methane production potential ranging from 91.84 to 201 mL/g VS, and the maximum methane yield rate was within 10.12–15.12 mL/day. The lag phase varied between 2.46 and 6.94 days. The percentage error between experimental and model outcomes for untreated, pretreated-60%, pretreated-70% and pretreated-75% are 17.96%, 16.67%, 14.20% and 4.68%, respectively, while the coefficients of determination of the model varied between 0.905 and 0.975, demonstrating significant reliability on attained factors.