Biomethane Potential of Selected Organic Waste and Sewage Sludge at Different Temperature Regimes

Ewa Neczaj,Anna Grosser,German Smetana

doi:10.3390/en14144217

Abstract

Sewage sludge (SS) generation and its management still pose a problem in many countries. Anaerobic co-digestion (AcD) of SS with grease trap sludge (GTS) and organic fraction of municipal sewage waste (OFMSW), which are two easily biodegradable substrates, may improve biogas production and AcD kinetics. Algae biomass (AB) of the species Undaria pinnatifida can be the third co-digestion component that may also affect the AcD performance. The aim of the study was therefore to evaluate the performance of mesophilic and thermophilic SS batch AcD with OFMSW, GTS as well as AB through biochemical methane potential (BMP) assay in relation to cumulative specific biogas (YB) and methane yields (Ym). Three kinetic models were applied within the scope of the kinetic study. Results of the study showed that the mixture containing SS, GTS and AB brought the most noticeable improvements in Ym compared to other studied mixtures and in respect to standalone SS digestion, the improvement amounted to 88.37% at mesophilic temperature (260.83 ± 15.02 N mL CH4/g-VSadd and for standalone SS 138.47 ± 4.70 N mL CH4/g-VSadd) and 71.09%, respectively, at the thermophilic one (275.66 ± 4.11 N mL-CH4/g-VSadd and for SS standalone 161.13 ± 13.11 N mL-CH4/g-VSadd).

Highlights

With an increase in the global population, the energy demand has induced thorough search for alternative energy sources, in particular, renewable sources
Five types of batch co-digestion mixtures were evaluated during a period of four weeks at mesophilic and thermophilic operational temperatures
The selection was based on the fact that one of the challenges in the anaerobic stabilization of algae is the possibility of inhibition process by releasing ammonia [39]

Summary

Introduction

With an increase in the global population, the energy demand has induced thorough search for alternative energy sources, in particular, renewable sources. One of the examples of such a renewable energy source, has been under constant examination for quite some time due to its positive effect on the environment, and it is utilized as a substitute to “inexhaustible” fossil fuels, i.e., reduction of greenhouse gas emissions—. The dependency of mankind on fossil fuels is deemed to be the major contributor to that global environmental problem [1,2]. Biomass is a sustainable renewable energy source that is characterised by its availability and safety in the application, and one of the examples of such an application is anaerobic digestion (AD) [3,4]. The final stage yields digested residuals as well as biogas—a valuable energy product. The biogas is rich in energy and is a mixture of principally methane (CH4 ), carbon dioxide (CO2 ) as well as traces of other gases in small amounts such as hydrogen sulphide (H2 S) and carbon monoxide (CO) [5]

Objectives

Methods

Results

Conclusion