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Methane Production Characteristics of an Anaerobic Co-Digestion of Pig Manure and Fermented Liquid Feed
Farida Hanum1,2, Yoichi Atsuta3, Hiroyuki Daimon1,3
1Department of Applied Chemistry and Life Science, Toyohashi University of Technology, Toyohashi 441-8580, Japan.
Abstract:
Methane production characteristics of anaerobic co-digestion of pig manure (PM) and fermented liquid feed (FLF) were investigated in a continuous digester under mesophilic conditions. The experiment followed three phases. PM alone was digested in phase I. In phases II and III, PM and FLF were mixed in a ratio of 95:5 and 90:10 (% v/v), respectively. The specific methane yields (SMYs) during phases I, II, and III were 238, 278, and 326.8 mLCH4·gVS-1-added, respectively. It was due to the effect of balancing the feedstock carbon-to-nitrogen ratio by adding FLF. This improvement can also be attributed to the readily biodegradable compounds in the FLF. The higher SMY obtained in this study showed a positive synergistic effect in the anaerobic co-digestion of PM and FLF. The results also indicate that adding the FLF positively affected and maintained a constant pH level, avoiding volatile fatty acid accumulation and ammonia inhibition in the anaerobic digestion (AD). Thus, this study provides valuable information regarding the usage of unused or wasted FLF as a co-substrate for the practical AD of PM. The production of fermented liquid additives such as FLF to improve the methane production from the AD of PM is a potential novel alternative to food waste recycling in Japan, besides compost and animal feeding.
Insights
Adding fermented liquid feed (FLF) to pig manure (PM) significantly boosts methane production through anaerobic co-digestion. This method improves feedstock balance and stability, offering a novel waste recycling approach.
Area of Science:
- Biotechnology
- Environmental Science
- Renewable Energy
Background:
- Anaerobic digestion (AD) of animal waste is crucial for sustainable energy.
- Pig manure (PM) digestion faces challenges like suboptimal carbon-to-nitrogen ratios.
- Fermented liquid feed (FLF) is an underutilized byproduct with potential as a co-substrate.
Purpose of the Study:
- To investigate the methane production characteristics of anaerobic co-digestion of PM and FLF.
- To evaluate the impact of varying FLF addition ratios on specific methane yields (SMYs).
- To assess the synergistic effects and stability improvements in the AD process.
Main Methods:
- Continuous digester operation under mesophilic conditions.
- Three experimental phases: PM alone, PM:FLF (95:5 v/v), and PM:FLF (90:10 v/v).
- Measurement of specific methane yields (SMYs) and monitoring of process parameters like pH and volatile fatty acids.
Main Results:
- SMYs increased from 238 mLCH4·gVS-1 in Phase I to 278 mLCH4·gVS-1 (Phase II) and 326.8 mLCH4·gVS-1 (Phase III).
- FLF addition balanced the carbon-to-nitrogen ratio and provided readily biodegradable compounds, enhancing methane yield.
- Co-digestion demonstrated a positive synergistic effect, with stable pH and inhibited volatile fatty acid accumulation and ammonia toxicity.
Conclusions:
- Anaerobic co-digestion of PM with FLF significantly enhances methane production.
- FLF acts as a valuable co-substrate, improving AD process stability and efficiency.
- This approach presents a novel and practical alternative for food waste recycling and PM management in Japan.
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