Zumar M.A. Bundhoo

Current status of solid waste management in small island developing states: A review

This article reviews the current status of waste management in Small Island Developing States (SIDS) and the challenges that are faced in solid waste management. The waste generation rates of SIDS were compared within the three geographic regions namely Caribbean SIDS, Pacific SIDS and Atlantic, Indian Ocean, Mediterranean and South China (AIMS) SIDS and with countries of the Organisation for Economic Co-Operation and Development (OECD). Only Pacific SIDS had a waste generation rate less than 1kg/capita/day. The waste generation rates for the three SIDS regions averaged 1.29kg/capita/day while that for OECD countries was at a mean value of 1.35kg/capita/day. The waste compositions in the different SIDS regions were almost similar owing to comparable consumption patterns while these differed to a large extent with wastes generated in OECD countries. In SIDS, the major fraction of MSW comprised of organics (44%) followed by recyclables namely paper, plastics, glass and metals (total: 43%). In contrast, MSW in OECD countries consisted mainly of recyclables (43%) followed by organics (37%). This article also reviewed the other functional elements of the waste management systems in SIDS. Several shortcomings were noted in the process of waste collection, transfer and transport namely the fact of having outdated collection vehicles and narrow roads which are inaccessible. Among the waste management practices in SIDS, waste disposal via landfilling, illegal dumping and backyard burning were favoured most of the time at the expense of sustainable waste treatment technologies such as composting, anaerobic digestion and recycling.

Promising Unconventional Pretreatments for Lignocellulosic Biomass

This article has been retracted.

Ultrasound-assisted biological conversion of biomass and waste materials to biofuels: A review

Ultrasound irradiation has been gaining increasing interests over the years to assist biological conversion of lignocellulosic biomass and waste materials to biofuels. As such, this study reviewed the different effects of sonication on pre-treatment of lignocellulosic biomass and waste materials prior to biofuel production. The mechanisms of ultrasound irradiation as a pre-treatment technique were initially described and the impacts of sonication on disruption of lignocellulosic materials, alteration of the crystalline lattice structure of cellulose molecules, solubilisation of organic matter, reducing sugar production and enzymatic hydrolysis were then reviewed. Subsequently, the influences of ultrasound irradiation on bio-methane, bio-hydrogen and bio-ethanol production were re-evaluated, with most studies reporting enhanced biofuel production from anaerobic digestion or fermentation processes. Nonetheless, despite its positive impacts on biofuel production, sonication was found to be energetically inefficient based on the lab-scale studies reviewed. To conclude, this study reviewed some of the challenges of ultrasound irradiation for enhanced biofuel production while outlining some areas for further research.

Anaerobic Digestion of Vegetable Wastes Using Biochemical Methane Potential Assays

Solid wastes generation is a major problem in Mauritius in terms of wastes disposal with vegetable wastes representing 40–46 % the organic waste stream by mass. This study focused on the anaerobic digestion (AD) of vegetable wastes using biochemical methane potential (BMP) assays to assess the performance of AD processes in treating these wastes in a sustainable manner. 2,000 mL plastic bottles were used as anaerobic digesters for the assays and the vegetable wastes comprising of carrots, potatoes, cabbage and beetroots were ground and seeded with inoculum in a ratio 4:1 (volume basis). The inoculum used was mature sludge taken from an anaerobic digester treating cattle wastes. The inoculated substrates were then fed in the digesters, purged with N2 and sealed with rubber septum. The AD process was allowed to run over a hydraulic retention time (HRT) of 20 days. Results showed a total solids (TS) reduction of 62.1 %, volatile solids (VS) reduction of 66.4 % and COD reduction of 64.9 % which demonstrated effective degradation of the substrates during the digestion process. The biogas yield was 0.360 L/g VS fed and this value was in agreement with published data. These results hence showed that vegetable wastes can be effectively treated by AD. The next phases of the study consist in investigating the AD process of wastewater treatment sludge and the effects of sonication on AD of vegetable wastes and sludge, with special emphasis on process parameters.