Anaerobic Co-Digestion of Waste Wafers from Confectionery Production with Sewage Sludge

Abstract

Food waste (FW) is generated in high volumes and is a serious threat to the environment if utilized improperly or left without control. Conventional methods of FW disposal include combustion, landfi lling, aerobic composting, partial recycling, and other ones. Anaerobic digestion (AD) is the most environmentally friendly of all the methods as it is benefi cial to the populace, and food waste is a suitable material for biogas production.Confectionery waste has rarely been utilized by anaerobic digestion (AD) so far. In this paper, the use of waste wafers (WF) in co-digestion with sewage sludge (SS) is proposed for the fi rst time. Annual volumes of production of WW and SS are expressed in hundreds and thousands of tons, respectively. The materials are generated in high amounts and on an ongoing basis, which is a very important factor regarding potential biogas plant investment projects. The objective of this paper was to analyze the AD process of the test substrates in terms of process stability and biogas capacity. The studies have shown that both the waste wafers as the individual material and with sewage sludge (as the co-substrate) are suitable feedstocks for biogas production. The experiments were carried out for the individual material and for a system with a cosubstrate in the form of raw sewage sludge (SS). In both cases, a digested sewage sludge was used as the inoculum. The studies were performed in a laboratory scale using anaerobic batch reactors under controlled (mesophilic) temperature and pH conditions. The highest yields of biogas and methane were obtained for waste wafers (980. ), than for the wafers (WF). The differences in biogas production for the samples were primarily connected with the substrates' composition, including with the content of readily degradable organic compounds and C/N ratio. The combination of waste wafers with raw sewage sludge has appeared to be benefi cial, as evidenced by the results of microbiological and biochemical analyses. The sample WF_SS was

The Use of Lignin as a Microbial Carrier in the Co-Digestion of Cheese and Wafer Waste

“…The efficiency of anaerobic digestion of CE is also comparable with that of food waste from restaurants and canteens [57]. The efficiency of biogas production from confectionery waste or stuffed wafers alone was verified and discussed in detail in earlier publications by Pilarska et al (2018 [14,15]. The co-substrate system with waste wafers and waste cheese was tested for the first time.…”

“…There is a good prognosis for the implementation of this solution in industrial production. The analysis and comparison of the earlier results show that dairy waste proved to be a better co-substrate for waste wafers than sewage sludge [14,25]. and α-amylase immobilization [54].…”

“…They were filled with the batch up to 1 L, which was mixed once a day. The bioreactors were located in a water jacket (4) connected to a heater (1), thanks to which the process could be conducted within the set temperature range (mesophilic conditions) [14,34]. The biogas produced in the process flowed (7) to the tanks (8) freely, where it was stored.…”

“…The physicochemical properties of waste wafers (WF) and digested sewage sludge (inoculum) were characterized in detail by the first author in earlier publications [14,15,25,26]. Generally, WF are characterized by approximately neutral pH, considerable content of total solids (TS) and volatile solids (VS), and a high C/N ratio (see Table 1), which contributes to their high biochemical methane potential (BMP) [15].…”

“…The concentration of ammonium nitrogen (N-NH 4 + ) and light metals does not exceed the critical values [39] for the stability of anaerobic digestion (AD). On the contrary, it favors the development and activity of methanogenic consortia [14,26]. The main advantage of stabilized sewage sludge is its high buffer capacity due to its considerable alkalinity developed in the raw sewage sludge digestion process, where nitrates were reduced to carbonates and hydrogencarbonates (total denitrification) [43].…”