Batch and semi-continuous anaerobic digestion of food waste in a dual solid–liquid system

The hybrid anaerobic solid-liquid (HASL) system is a modified two-phase anaerobic digester for food waste treatment. To enhance the performance of anaerobic digestion in the HASL system, thermal pre-treatment (heating at 150°C for 1 h) and freezing/thawing (freezing for 24 h at−20°C and then thawing for 12 h at 25°C) were proposed for food waste pre-treatment before the anaerobic digestion. Both processes were able to alter the characteristics and structure of food waste favoring substance solubilization, and hence production of methane. However, there was no net energy gain when the energy required by the pre-treatment processes was taken into account.

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Digestion of frozen/thawed food waste in the hybrid anaerobic solid–liquid system

Waste Management ◽

10.1016/j.wasman.2007.05.021 ◽

2008 ◽

Vol 28 (9) ◽

pp. 1654-1659 ◽

Cited By ~ 25

Author(s):

O. Stabnikova ◽

X.Y. Liu ◽

J.Y. Wang

Keyword(s):

Food Waste ◽

Liquid System ◽

Solid Liquid

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A comparative study of anaerobic digestion of food waste in a single pass, a leachate recycle and coupled solid/liquid reactors

Water Science & Technology ◽

10.2166/wst.2003.0073 ◽

2003 ◽

Vol 47 (1) ◽

pp. 319-324 ◽

Cited By ~ 5

Author(s):

H.L. Xu ◽

J.Y. Wang ◽

H. Zhang ◽

J.H. Tay

Keyword(s):

Anaerobic Digestion ◽

Food Waste ◽

Methane Content ◽

Anaerobic Sludge ◽

Methane Fermentation ◽

Two Phase ◽

Single Pass ◽

Digestion Process ◽

Solid Liquid ◽

Methanogenic Phase

A single pass reactor (R1), a leachate recycle reactor (R2) and a coupled solid/liquid bioreactor (R3-Rm) for anaerobic digestion of food waste were comparatively investigated in terms of digestion process and treatment efficiency. The coupled solid/liquid bioreactor is an enhanced two-phase system and distinctive from a traditional two-phase process with an upflow anaerobic sludge blanket (UASB) reactor as the methanogenic phase and a circulation of treated leachate between the acidification and methanogenic phases. In comparison with R1 and R2, R3-Rm enhanced the digestion process and increased the methane content of biogas. 100% of the R3-Rm methane yield was from the methanogenic phase with average methane content of 71%. The significant enhancement was also confirmed by the removal of 79% of total organic carbon (TOC), 60% of volatile solids (VS) and 80% of total COD in 12 days running of R3-Rm. However, no active methane fermentation was detected in R1 and R2 during 60 days operation. The results in this laboratory-scale study show that the rapid accumulation of volatile fatty acids (VFAs) due to the rapid acidification of food waste inhibits the development of effective methane fermentation in single pass and leachate recycle reactors. The coupled solid/liquid bioreactor is more efficient in converting food waste into methane and carbon dioxide.

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Semi-continuous anaerobic digestion of food waste using a hybrid anaerobic solid-liquid bioreactor

Water Science & Technology ◽

10.2166/wst.2003.0247 ◽

2003 ◽

Vol 48 (4) ◽

pp. 169-174 ◽

Cited By ~ 10

Author(s):

J.-Y. Wang ◽

H.-L. Xu ◽

H. Zhang ◽

J.-H. Tay

Keyword(s):

Anaerobic Digestion ◽

Solid Waste ◽

Food Waste ◽

Biogas Production ◽

Continuous Operation ◽

Methane Content ◽

High Rate ◽

Uasb Reactor ◽

Two Phase ◽

Solid Liquid

A hybrid anaerobic solid-liquid (HASL) bioreactor was developed to enhance food waste conversion. The HASL bioreactor is a modified two-phase anaerobic digestion system with a solid waste reactor and a high-rate anaerobic wastewater reactor, which was a UASB reactor. In this study, the methanogenesis in the UASB reactor was investigated under a semi-continuous operation of the food waste digestion system. The HASL process, including 7 days of start-up and 23 days of semi-continuous operation followed by 6 days of batch operation, was commenced by loading 2.8 kg of shredded food waste. During the semi-continuous operation, 0.2 kg of the same waste was loaded daily. The leachate from acidification phase, i.e., solid waste reactor, remained acidic (pH 4.9-5.5) and high in total VFA (TVFA), 9,500-11,500 mg/L, and COD (8,000-11,800 mg/L) levels. In the methanogenesis phase, i.e., UASB reactor, effective TVFA and COD removals (88 ± 5% and 85 ± 7%, respectively) were obtained, while the methane content was 71%. At the end of operation, about 78% of VS added in the HASL bioreactor was removed, while TOC and total COD reductions were 78% and 79%, respectively. The results showed that the use of UASB reactor in the semi-continuous HASL system can enhance the methanogenesis process and increase the methane content in biogas production.

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A hybrid anaerobic solid–liquid system for food waste digestion

Water Science & Technology ◽

10.2166/wst.2005.0521 ◽

2005 ◽

Vol 52 (1-2) ◽

pp. 223-228 ◽

Cited By ~ 9

Author(s):

J.Y. Wang ◽

H. Zhang ◽

O. Stabnikova ◽

S.S. Ang ◽

J.H. Tay

Keyword(s):

Food Waste ◽

Methane Production ◽

Anaerobic Treatment ◽

Liquid System ◽

Ammonia Removal ◽

Total Removal ◽

Two Phase ◽

Satisfactory Performance ◽

Volatile Solids ◽

Solid Liquid

A hybrid anaerobic solid – liquid (HASL) system was developed to enhance food waste bioconversion in comparison with the conventional two-phase anaerobic digester. The advantages of the HASL system were the higher efficiency of methane production and smaller volume of effluent from the system. The biogas, which was generated from the methanogenic phase, had an average methane content of 71–72%. Total removal of volatile solids consisted of 78–80%. The HASL system can be operated in both batch and semi-continuous modes with satisfactory performance. The addition of a submerged biofilter for ammonia removal to the HASL system further enhanced the performance of anaerobic digestion. Methane production in the enhanced HASL system was increased by 26% in comparison with the HASL system without submerged filter. This paper describes the development of the enhanced HASL system for anaerobic treatment of food waste.

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