Potential of Sustainable Concept for Handling Organic Waste in Tunisia

Abstract

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.

Effects of co-substrates’ mixing ratios and loading rate variations on food and agricultural wastes’ anaerobic co-digestion performance

“…In this light, agricultural residues are considered as attractive co-substrates to be exploited for biological treatments and aerobic and anaerobic processes. Furthermore, based on the availability of agricultural streams in Tunisia as well as the appropriateness of biowastes to enhance FW anaerobic digestion, cattle manure (CM) and wheat straw (WS) are the most pertinent residues to be exploited [28].…”

Effects of Co-substrates’ Mixing Ratios and Loading Rate Variations on Food and Agricultural Wastes’ Anaerobic co-digestion Performance

“…Furthermore, based on the availability of agricultural streams in Tunisia as well as the appropriateness of biowastes to enhance FW anaerobic digestion, cattle manure (CM) and wheat straw (WS) are the most pertinent residues to be exploited (Chaher et al 2020b).…”

“…A particular divergence in terms of food waste (FW) characteristics is marked globally, as it depends on several cultural trends, norms, practices and behaviors that create the difference in terms of FW quantity and quality (Phasha et al 2020). In this matter, Tunisia generates a relatively signi cant amount of FW from different sectors of activity, which promotes its selection as a main substrate for feeding anaerobic reactors (Wa et al 2019) (Chaher et al 2020b).…”

“…In this light, agricultural residues are considered as attractive co-substrates to be exploited for biological treatments, and aerobic and anaerobic processes. Furthermore, based on the availability of agricultural streams in Tunisia as well as the appropriateness of biowastes to enhance FW anaerobic digestion, cattle manure (CM) and wheat straw (WS) are the most pertinent residues to be exploited (Chaher et al 2020b).…”

Upgrading of Food Waste in-vessel Composting Process: Effects of Biochar-rich Digestate Addition

“…Indeed, the recuperation of inorganic materials is frequently ensured by the informal sector 'activity (Wilson et al 2006), while a complete organization is mandatory to handle the high fraction of organic one. As this latter represented more than 50% of the total amount of waste in the developing countries, particularly in the Middle East and North Africa (MENA) region, biowaste recovery was henceforth been assigned as a high-priority (Negm and Shareef 2020;Chaher et al 2020c).…”