The Biochemical Methane Potential of ProBiotic Scrubber® II
Improving Methane Production in Anaerobic Digesters
Capturing and using methane produced during anaerobic digestion can help wastewater treatment facilities recover energy and offset operating costs.
Methane is a natural component of biogas generated as microorganisms break down organic material under anaerobic conditions. When properly captured and utilized, this biogas can provide a renewable source of energy for wastewater treatment facilities.
Improving anaerobic digester performance and methane yield can therefore increase the energy-recovery potential of the treatment process.
BioLynceus® ProBiotic Scrubber® II (PBII) contains concentrated cultures of live microorganisms designed to support biological wastewater treatment.
The following study evaluated the biochemical methane potential (BMP) of ProBiotic Scrubber® II and compared its performance with anaerobic sludge collected from a monitored research digester.
Biochemical Methane Potential Testing
A serum-bottle BMP test was conducted to compare the methane-producing potential of different anaerobic digester seed sources.
High-strength brewery wastewater was used as the organic substrate, and each treatment was tested in triplicate.
Three treatments were evaluated:
-
GADS: Anaerobic digester sludge at a food-to-microorganism ratio of 1
-
PBS1: ProBiotic Scrubber® II at a food-to-microorganism ratio of 1
-
PBS0.5: ProBiotic Scrubber® II at a food-to-microorganism ratio of 2
The quantity of microbial seed added to each bottle was adjusted according to the treatment ratio.
Each test bottle contained a total liquid volume of 90 mL, including:
A corresponding blank was also prepared for each treatment.
The blanks contained the appropriate microbial seed without brewery wastewater and were used to account for background gas production from the seed material itself.
All test bottles were incubated for 50 days.
Measuring Methane and Biogas Production
During the 50-day incubation period, researchers monitored two primary performance measurements:
Gas production from each treatment was corrected by subtracting the methane and biogas generated by the corresponding blank.
This provided a more accurate estimate of gas production associated with the biological digestion of the brewery wastewater.
Methane Production Results
At the end of the 50-day BMP test, the PBS1 ProBiotic Scrubber® II treatment produced an average methane yield 3.6 mg/g COD higher than the GADS research digester sludge treatment (Figure 1).
The PBS0.5 treatment produced the lowest average methane yield during the study.
The lower methane production corresponded with the smaller amount of microbial biomass used in the PBS0.5 treatment compared with PBS1.
Overall, the PBS1 treatment produced a higher methane yield at Day 50 than the anaerobic research digester sludge under the conditions of this BMP study.
Total Biogas and Methane Yield
Total biogas production provides additional information about anaerobic digestion performance, but methane concentration is especially important when evaluating the energy value of the produced gas.
While total biogas may contain methane, carbon dioxide, and other trace gases, methane represents the primary combustible component used for energy recovery.
For this reason, evaluating both total biogas production and methane yield provides a more complete picture of anaerobic digester performance.
Supporting Anaerobic Digestion and Biogas Recovery
The results of this laboratory study indicate that ProBiotic Scrubber® II has potential as a microbial seed or bioaugmentation product for anaerobic digestion applications.
Under the conditions evaluated, PBII supported methane production from high-strength brewery wastewater and produced a higher Day 50 methane yield in the PBS1 treatment than the research digester sludge.
Bioaugmentation may provide wastewater treatment facilities with an additional tool for supporting:
-
Methane production
-
Organic waste degradation
-
Anaerobic digester startup or recovery
-
Biogas generation
-
Renewable energy recovery
-
Overall digester biological activity
Actual digester performance will depend on factors such as wastewater composition, organic loading, temperature, pH, retention time, microbial populations, and operating conditions.
ProBiotic Scrubber® II for Anaerobic Digestion
BioLynceus® ProBiotic Scrubber® II provides a concentrated source of microorganisms that can be incorporated into biological treatment strategies for facilities evaluating ways to support anaerobic digestion, methane production, and biogas energy recovery.
Figure 1. Averaged methane yield from the GADS (red), PBII (green), and PBS0.5 treatments (purple) at three to five day increments over 50 days.
Biogas Production and Methane Availability
At the end of the 50-day biochemical methane potential (BMP) study, the GADS treatment produced the highest total biogas yield.
However, total biogas production alone does not determine the energy value of the gas. Methane is the primary combustible component of biogas and is therefore an important measurement when evaluating potential energy recovery.
Although the GADS treatment generated more total biogas, it produced a lower methane yield than the PBS1 treatment.
This indicates that a greater portion of the GADS biogas consisted of carbon dioxide and other non-methane gases, while the PBS1 treatment produced more methane under the conditions of the study.
The PBS0.5 treatment produced the lowest total biogas yield during the 50-day testing period.
Higher Methane Yield with ProBiotic Scrubber® II
The PBS1 treatment using BioLynceus® ProBiotic Scrubber® II (PBII) produced a higher methane yield than the GADS research digester sludge treatment.
Because methane provides most of the usable energy in biogas, a higher methane yield can increase the amount of gas potentially available for:
These results highlight the importance of measuring methane yield in addition to total biogas production when evaluating anaerobic digester performance.
Supporting Methane Production During Anaerobic Digestion
The study results suggest that BioLynceus® ProBiotic Scrubber® II has potential as a microbial seed or bioaugmentation product for anaerobic digestion applications.
Under the conditions of this laboratory study, the PBS1 treatment demonstrated:
-
Higher methane yield than the GADS treatment
-
Greater methane availability for potential energy recovery
-
Effective digestion of high-strength brewery wastewater
According to the testing report provided by the Anaerobic Technology Laboratory, measurable differences were observed among the evaluated seed treatments in both total biogas production and methane yield.
Why Methane Yield Matters for Biogas Energy Recovery
Evaluating only the total volume of biogas produced does not provide a complete picture of anaerobic digester performance.
Biogas typically contains primarily:
Since methane is the primary energy-producing component, facilities evaluating wastewater biogas energy recovery should consider both the quantity of biogas generated and its methane content.
The results of this study demonstrate the value of evaluating methane production, total biogas yield, and microbial seed performance together when assessing biological strategies for anaerobic digestion.
