A review on strategies to optimize metabolic stages of anaerobic digestion of municipal solid wastes towards enhanced resources recovery

Abstract

Recently, there are increased efforts by municipals and researchers to investigate the potential of utilizing municipal solid wastes (MSW) for resources recovery. In many parts of developing countries, MSW is mostly collected for disposal with little emphasis on resources recovery. However, the MSW has high organic and moisture contents, and are suitable substrates for anaerobic digestion (AD) process to recover biogas for energy and digestate which can be used as fertilizers or for soil amendments. Resources recovery from the AD process consists of four metabolic stages; hydrolysis, acidogenesis, acetogenesis, and methanogenesis. These metabolic stages can be affected by several factors such as the nature of substrates, accumulation of volatile fatty acids, and ammonia inhibition. In this review, different optimization strategies towards resources recoveries such as pre-treatment, codigestion, trace elements supplementation, optimization of key parameters and the use of granular activated carbon are discussed. The review reveals that the currently employed optimization strategies fall short in several ways and proposes the need for improvements.

Two-stage banana leaves wastes utilization towards mushroom growth and biogas production

“…Therefore, the biomass compositions of the banana leave analyzed in this study fall within acceptable limits for the fungal treatment. The pH in anaerobic digestion process for untreated and treated BL were 7.90 ± 0.02, and 7.40 ± 0.00, respectively, and were within acceptable ranges for the AD process (Richard et al 2019). According to Vögeli et al (2014), substrates with more than 60% VS are suitable for resources recovery such as biogas production.…”

Methane Production from Confectionery Wastewater Treated in the Anaerobic Labyrinth-Flow Bioreactor

“…Due to the high organic content of confectionery effluents, the new construction of the anaerobic reactor is suitable to treat such kinds of sewage. Anaerobic digestion takes place in four metabolic phases (hydrolysis, acidogenesis, acetogenesis, and methanogenesis), and each of them requires specific conditions for a smooth and efficient run [62,63]. The most popular reactors used in full-scale to treat confectionery sewage are single-stage tank biogas reactors, such as UASB and EGSB reactors, in which all phases of anaerobic digestion are conducted in parallel in one digestion chamber.…”

Life cycle analysis of potential municipal solid wastes management scenarios in Tanzania: the case of Arusha City

“…The avoided emissions resulting from producing chemical fertilizers (N, P 2 O 5 , and K 2 O) as a result of composting and digestate recovery in SN-2 and SN-3 affected mostly human toxicity impact making SN-3 much better than SN-1, whereas SN-2 remained the most favored scenario in this category. Further comparisons of the economic estimates of each scenario were made based on the economic costs given in Table 8 [7]. From the computation, the Scenario SN-2 was found to have a low economic cost of 47 USD t − 1 , followed by Scenario SN-1(54 USD t − 1 ) and SN-4 (70 USD t − 1 ).…”

“…The difference in results is due to many factors including data used, decision to include or not to include equipment which causes emissions, system boundaries considered in the analysis and local conditions of the concerned study area [6]. Also, MSW in developing countries has high organic content and lower calorific values as compared to the wastes in developing countries [7], and as such previous studies in developed countries cannot be generalized in sub-Saharan Africa where LCA studies are limited. In Tanzania specifically, the LCA applications for MSW decision making are yet to be applied and there is no single study on LCA on MSW that have been published in a peer-reviewed journal.…”