Feasibility of OFMSW co-digestion with sewage sludge for increasing biogas production at wastewater treatment plants

Abstract

Sweden has the ambition to increase its annual biogas production from the current level of 1.9 to 15 TWh by 2030. The unused capacity of existing anaerobic digesters at wastewater treatment plants is among the options to accomplish this goal. This study investigated the feasibility of utilizing the organic fraction of municipal solid waste (OFMSW) as a co-substrate, with primary and waste-activated sewage sludge (PWASS) for production of biogas, corresponding to 3:1 ratio on volatile solid (VS) basis. The results demonstrated that co-digestion of OFMSW with PWASS at an organic loading rate of 5 gVS l −1 day −1 has the potential to increase the biogas production approximately four times. The daily biogas production increased from 1.0 ± 0.1 to 3.8 ± 0.3 l biogas l −1 day −1 , corresponding to a specific methane production of 420 ± 30 Nml methane gVS −1 during the laboratory experiment. Co-digestion of OFMSW with PWASS showed a 50:50 distribution of hydrogenotrophic and aceticlastic methanogens in the digester and enhanced the turnover kinetics of intermediate products (acetate, propionate, and oleate). Practical limitations potentially include the need for sludge dewatering to maintain a sufficient hydraulic retention time (17 days in this study), as well as additional energy consumption for mixing due to an increased sludge apparent viscosity (from 1.8 ± 0.1 to 45 ± 4.8 mPa*s in this study) at elevated OFMSW-loading rates.

Optimizing the co-digestion supply chain of sewage sludge and food waste by the demand oriented biogas supplying mechanism

“…For example, Mattioli et al (2017) took the co-digestion technology of a sewage plant in Rovereto, Italy, as a case example; the results showed that the organic loading rate (OLR) could be doubled without any process difficulties, and the increased biogas yield could satisfy 85% of the plant’s energy demand. Similar conclusions have also been drawn by Björn et al (2017) , who proved that co-digestion with food waste has the potential to increase biogas production by approximately four times. Similar techno-economic studies can also be found in Glivin et al (2018 , 2019b ), Lamidi et al, 2019 and Walekhwa et al (2014) .…”

The Enhancement of Energy Efficiency in a Wastewater Treatment Plant through Sustainable Biogas Use: Case Study from Poland

“…The share of co-substrate in the feedstock was maintained at the level from 6.2 to 21.2% and it depended on the amount of sewage sludge (Figure 8). The dosing of co-substrate should be constantly controlled due to the possibility of biogas composition deterioration (increase the CO 2 content) and operational problems, especially during the dewatering of digested sludge [55,75]. It is assumed that the share of additional substrates for co-digestion with sewage sludge should not exceed 30% [76].…”

Exploiting the unwanted: Sulphate reduction enables phosphate recovery from energy-rich sludge during anaerobic digestion

“…The ability to use the energy-rich methane in a combined heat and power (CHP) unit for electricity and heat production quickly allowed the transition of AD from a waste treatment technology to an integrated system for renewable energy recovery. Different organic waste streams, such as animal manure (Holm- Nielsen et al 2009), waste activated sludge (Appels et al 2008), the organic fraction of municipal solid waste (Hartmann and Ahring 2006) have been valorised through AD, either as such or through co-digestion with other waste streams (Björn et al 2017, Mata-Alvarez et al 2011). In the framework of the current transition from "wasteto-energy" to "waste-to-resource", the recovery of nutrients, in addition to energy, has become more and more pressing to (1) safeguard natural resources and (2) ensure long-term economic viability of the AD process.…”