Enhanced Production of Biogas Using Biochar-Sulfur Composite in the Methane Fermentation Process

Abstract

The methane fermentation of organic waste is one way to minimize organic waste, which accounts for 77% of the global municipal waste stream. The use of biochar as an additive for methane fermentation has been shown to increase the production potential of biogas. Sulfur waste has a potential application to synergistic recycling in a form of composites with other materials including biochar. A composite product in the form of a mixture of biochar and molten sulfur has been proposed. In this experiment, additions of the sulfur−biochar composite (SBC) were tested to improve the fermentation process. The biochar was produced from apple chips under the temperature of 500 °C. The ground biochar and sulfur (<1 mm particle size) were mixed in the proportion of 40% biochar and 60% sulfur and heated to 140 °C for sulfur melting. After cooling, the solidified composite was ground. The SBC was added in the dose rate of 10% by dry mass of prepared artificial kitchen waste. Wet anaerobic digestion was carried out in the batch reactors under a temperature of 37 °C for 21 days. As an inoculum, the digestate from Bio-Wat Sp. z. o. o., Świdnica, Poland, was used. The results showed that released biogas reached 672 mL × gvs−1, and the yield was 4% higher than in the variant without the SBC. Kinetics study indicated that the biogas production constant rate reached 0.214 d−1 and was 4.4% higher than in the variant without the SBC.

Keywords: biochar; biogas; methane fermentation; sulfur.

Figure 1

Procedure to produce biogas and SBC mixture to test the potential of biogas production.

Figure 2

The biochar from applewood chips (left, upper corner); sulfur (right, upper corner); SBC (bottom)—samples located in the Petri ditches with the diameters of 15 cm.

Figure 3

Graph of biogas growth curves over time for the control sample—digestate (I), digestate + substrate (IKW), and for digestate + substrate + SBC (IKW + SBC).