Effect of Carbon/Nitrogen Ratio, Temperature, and Inoculum Source on Hydrogen Production from Dark Codigestion of Fruit Peels and Sewage Sludge

Lirio María Reyna-Gómez,Armando Robledo-Olivo,Carlos Eduardo Molina-Guerrero,Juan Manuel Alfaro,Arquímedes Cruz-López,Santiago Iván Suárez Vázquez

doi:10.3390/su11072139

Abstract

This paper studies the use of fruit peel biomass and waste sludge from municipal wastewater treatment plants in the metropolitan area of Monterrey, Mexico as an alternative way of generating renewable energy. Using a Plackett–Burman experimental design, we investigated the effects of temperature, inoculum source, and the C/N (Carbon/Nitrogen) ratio on dark fermentation (DF). The results indicate that it is possible to produce hydrogen using fruit peels codigested with sewage sludge. By adjusting the C/N ratio in response to the physicochemical characterization of the substrates, it was revealed that the quantities of carbohydrates and nitrogen were sufficient for the occurrence of the fermentation process with biogas production greater than 2221 ± 5.8 mL L−1Reactor and hydrogen selectivity of 23% (366 ± 1 mL H2·L−1Reactor) at the central point. The kinetic parameters (Hmax= 86.6 mL·L−1, Rm = 2.6 mL L−1 h−1, and λ = 1.95 h) were calculated using the modified Gompertz model. The quantification of soluble metabolites, such as acetic acid (3600 mg L−1) and ethyl alcohol (3.4 ± 0.25% v/v), confirmed the presence of acetogenesis in the generation of hydrogen.

Highlights

The energy needs of economic activities have increased exponentially in the last few years, whereas fossil fuel reserves have diminished
This paper describes an exploratory study of dark codigestion using fruit peels (FP) with sewage sludge (SS) generated from a municipal wastewater-treatment plant
The physical and chemical characteristics of the FP are essential for the design and operation of anaerobic digesters, because they will affect the production of biogas and the stability of the dark fermentation (DF) process

Summary

Introduction

The energy needs of economic activities have increased exponentially in the last few years, whereas fossil fuel reserves have diminished. The production of H2 from biological processes that involve organic waste is an important area of opportunity in the production of bioenergy [11,12] In such cases, the H2 produced is called biohydrogen. Biohydrogen can be generated through various processes, a number of investigators have described the fundamentals of the biological production of H2 using photolysis or dark fermentation (DF). The latter is considered a simpler method and has the advantage of using municipal, agricultural, and industrial wastes as starting materials [13,14,15,16]

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Results

Conclusion