Qualitative and quantitative characterization of municipal solid waste and the unexploited potential of green energy in Tunisia

Feeding controls H2S production in situ in high solid anaerobic digestion

In this study, a high frequency monitoring method was used to assess how semi-continuous feeding affects H2S production in high solid anaerobic digestion. The results showed that H2S characteristics at a monitoring frequency of 1 point/3 h were different to that of 1 point/24 h, its concentration decreased from 3449 ± 227 mg/m3 at 0 h to 298 ± 45 mg/m3 at 3 h. H2S concentration was negatively correlated with volatile fatty acids (VFAs), and oxidation reduction potential (ORP). 72-82% of H2S reduction in the first 3 h resulted from the introduction of O2 during feeding, and 18-28% of that was closely related to the production of a large quantity of soluble acidic matter, such as VFAs. A more accurate H2S release model was established according to the content of VFAs. Totally, this study implies that feed carrying air is a promising method for in situ control of H2S production in anaerobic digestion.

Waste to Energy in Developing Countries—A Rapid Review: Opportunities, Challenges, and Policies in Selected Countries of Sub-Saharan Africa and South Asia towards Sustainability

Daily per capita waste generation will increase by 40% and 19%, for developing and developed countries by 2050, respectively. The World Bank estimates that total waste generation is going to triple in Sub-Saharan Africa (SSA) and double in South Asia (SA) by 2050. This article conducts a rapid review and aims to demonstrate the current waste management scenario and the potential of waste to energy generation in the developing world, focusing on SSA and SA. Although many review articles related to waste to energy (WtE) in developing countries are available in the literature, a rapid review particularly focusing on countries in SSA and SA is rarely seen. An analysis of different WtE generation technologies, and current waste management practices in developing countries in SSA and SA are also presented. The analysis shows that about three-fourths of waste is openly dumped in developing countries of SSA and SA. In terms of waste composition, on average, about 48.70% and 51.16% of waste generated in developing economies of SSA and SA are organic. Opportunities to convert this waste into energy for developing countries are highlighted, with a case study of Bangladesh, a country in SA. Major challenges regarding the waste to energy (WtE) projects in the developing world are found to be the composition of waste, absence of waste separation scheme at source, ineffective waste collection method, lack of suitable WtE generation technology in place, lack of financial support and policies related to a WtE project, and absence of coordination between different governmental institutions.

Potential of windrow food and green waste composting in Tunisia

Solid waste management and disposal is one of the most significant challenges facing urban communities around the world. There is a wide range of alternative waste management options and strategies available for dealing with the notable increase in the waste stream. Composting is one of the most viable and efficient waste treatment options in terms of the reduction in the negative effects from the application of organic waste to soil. The experimental research aimed to examine the potential of producing compost from different organic waste streams in Tunisia. Two experimental windrow piles made from cooked and uncooked food and garden wastes were initiated and temporally monitored. The composting process was controlled in terms of temperature and moisture. Sampling was carried out over the period of the composting process. All of the collected samples were analyzed in terms of their physical, chemical, and biological properties; pH, C:N ratio, nitrification index (NI), microbiological tests, respiration activity (AT4), and heavy metal content. The quality of the final product was determined and compared with Tunisian and German standards. The findings demonstrated a significant reduction in the initial C:N ratio to about 15 by the end of the process. Additionally, the results showed that the compost produced appeared to be stable and was deemed to be class V finished compost; the NI was found to be around 1, while the AT4 was estimated to be lower than 6 mg O2/g TS. Regarding the heavy metal content, the final products were characterized as having a lower concentration than those values set by Tunisian and German standards.

Efficient electrokinetic remediation of heavy metals from MSWI fly ash using approaching anode integrated with permeable reactive barrier

During electrokinetic remediation (EKR) of heavy metals (HMs) (Pb, Zn, Cu, and Cd) from municipal solid waste incineration (MSWI) fly ash enhanced by a permeable reactive barrier (PRB), the nearer to the anode, the higher the concentration of H⁺ ions and the greater the remediation effect. Therefore, a potentially new method of PRB-enhanced EKR using an approaching anode (A-EKR + PRB) was studied to help H⁺ ions to quickly migrate to the sample near the cathode. Consequently, the HM leaching and total concentrations were reduced, while an energy reduction of nearly 40% was achieved. The results showed that the best remediation ability was obtained when MSWI fly ash was treated for 16 days at a voltage gradient of 2.5 V/cm, the approaching anode was moved after 4 days, and the PRB contained 10 g of activated carbon. After remediation, the environmental risk analysis showed that A-EKR + PRB reduced all the fractions of HMs, especially the acid extractable and oxidizable fractions, which might have been due to the enhancement of acid dissolution and oxidation by the approaching anode. In addition, the environmental risks of the remaining HMs were reduced, and the results indicated that A-EKR + PRB is an advisable choice for remediation of MSWI fly ash.

Potential of Sustainable Concept for Handling Organic Waste in Tunisia

Nowadays, Tunisia is seeking to implement cost-efficient and sustainable solutions in relation to the treatment of organic waste which, at up to 65%, makes up the largest proportion of total waste generated in the country. Therefore, an efficient tool for decision makers is needed to provide a clear approach about the potential of organic waste as well as the treatment concept, which can be adapted based on technical requirements and local conditions. Results revealed that there is a high variation in terms of the nature of the collected biowaste, which affects the selection of the adopted bioprocess for each geographical zone of the study area. Three main categories of biowaste are produced along the coastline of Tunisia: food waste (FW) (102.543 t/a); green waste (GW) (1.326.930 t/a); and cattle manure (CM) (1.548.350 t/a). Based on the results of similar projects and laboratory-scale research work, anaerobic and aerobic digestion were examined. Regarding aerobic digestion, the monitoring of several physicochemical parameters ascertained that the co-composting of FW and GW at different ratios (GW: FW = 100:0, 75:25, 50:50, and 25:75) allowed the production of a stable and mature compost. A highly qualified end-product was generated from each trial categorized as a finished compost of class V with reference to German Standards of compost. Regarding the anaerobic process, different feedstock mixtures (FW:CM = 0:1, 1:1, 2:1, and 3:1) were prepared to feed semi-continuous anaerobic reactors. However, a significant improvement in the process development was recorded for digesters including a higher fraction of FW, which produced 0.846 LN/kg VSin as the maximum biogas production. Therefore, biological treatments of food waste and different co-substrates seems to be a suitable technique for Tunisia in terms of waste management, environmental, and energy aspects. However, the evaluation of the efficiency of the proposed biological treatments was also verified by a draw-up of a technical and economic feasibility analysis. Although the cost–benefit estimations proved that the profits from both the compost and biogas plants would be very modest, the feasibility of such sustainable projects should not only be evaluated on an economic basis, but also by taking into account socio-environmental considerations including decreasing environmental threats, providing work opportunities, increasing incomes, stimulating public awareness as well as reducing the operating costs linked to landfilling.

Qualitative and quantitative analysis of municipal solid waste in Iran for implementation of best waste management practice: a systematic review and meta-analysis

With the rapid growth of population, development of different industries, and production of several ranges of products, the generation of municipal solid waste (MSW) has been growing significantly in the recent years. However, if MSW is not managed properly, it can greatly contribute to an environmental crisis. In the present study, we aimed to examine the characteristics and quantity of MSW generated in Iran through a meta-analysis and systematic review. The major international and Iranian national databases including Science direct, Scopus, PubMed, Google scholar, and SID and Magiran were searched completely using appropriate keywords to identify the articles that have been published from 2003 up to November 2019 on the topic on interest. Based on the inclusion criteria, a number of 13 papers were found eligible to be reviewed in this study. The results showed that the amount of generated waste per capita in Iran is 839 g/capita/day. Moreover, organic matters, paper and cardboard, plastics, glasses, textiles, rubber, polyethylene terephthalate (PET), metals (ferrous and non-ferrous), wood materials, and other wastes were found to be contributed to 65.85%, 8.79%, 8.39%, 2.73%, 2.74%, 1.18%, 1.07%, 2.83%, 1.20%, and 5.22% of total MSW in Iran, respectively. Due to the high level of organic waste in MSW stream in Iran, composting program is recommended as a practical and beneficial approach. Of note, the recyclable materials include plastic, PET, glass, metals, and paper and cardboard have accounted for 24.05% of total MSW in Iran.