Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 11 de 11
Filter
Add more filters










Publication year range
1.
Bioresour Technol ; 388: 129726, 2023 Nov.
Article in English | MEDLINE | ID: mdl-37690217

ABSTRACT

Production of volatile fatty acids from food waste and lignocellulosic materials has potential to avoid emissions from their production from petrochemicals and provide valuable feedstocks. Techno-economic and life cycle assessments of using food waste and grass to produce volatile fatty acids through anaerobic digestion have been conducted. Uncertainty and sensitivity analysis for both assessments were done to enable a robust forecast of key-aspects of the technology deployment at industrial scale. Results show low environmental impact of volatile fatty acid with food wastes being the most beneficial feedstock with global warming potential varying from -0.21 to 0.01 CO2 eq./kg of product. Food wastes had the greatest economic benefit with a breakeven selling price of 1.11-1.94 GBP/kg (1.22-2.33 USD) of volatile fatty acids in the product solution determined through sensitivity analysis. Anaerobic digestion of wastes is therefore a promising alternative to traditional volatile fatty acid production routes, providing economic and environmental benefits.

2.
Waste Manag ; 129: 20-25, 2021 Jun 15.
Article in English | MEDLINE | ID: mdl-34020372

ABSTRACT

A novel approach of using two stage anaerobic digestion coupled with electrodialysis technology has been investigated. This approach was used to improving bio hydrogen and methane yields from food waste while simultaneously producing a green chemical feedstock. The first digester was used for hydrogen production and the second digester was used for methane production. The first digester was combined with continuous separation of volatile fatty acids using electrodialysis. The concentrations of carbohydrates, proteins and fats in the prepared food waste were 22.7%, 5.7% and 5.2% respectively. Continuous removal of volatile fatty acids during fermentation in the hydrogen digester not only increased hydrogen yields but also increased the production rate of volatile fatty acids. As a result of continuous VFA separation, hydrogen yields increased from 17.3 mL H2/g VS fermenter to 33.68 mL H2/g VS fermenter. Methane yields also increased from 28.94 mL CH4/g VS fermenter to 43.94 mL CH4/g VS fermenter. This represents a total increase in bio-energy yields of 77.1%. COD reduced by 73% after using two stage anaerobic digestion, however, this reduction increased to 86.7% after using electrodialysis technology for separation of volatile fatty acids. Electrodialysis technology coupled with anaerobic digestion improved substrate utilization, increased bioenergy yields and looks to be promising for treating complex wastes such as food waste.


Subject(s)
Food , Refuse Disposal , Anaerobiosis , Bioreactors , Fatty Acids, Volatile , Hydrogen , Methane
3.
Waste Manag ; 122: 81-88, 2021 Mar 01.
Article in English | MEDLINE | ID: mdl-33494002

ABSTRACT

A novel method to recover VFAs from a continually-fed 100 L food waste bioreactor was developed using industrially applicable methods. The in-situ recovery of VFAs increased production rates from 4 to 35 mgvfa gvs-1 day-1 by alleviating end-product inhibition and arresting methanogenesis, and electrodialysis was able to concentrate the recovered VFAs to 4000 mg L-1. There remains considerable scope to increase the production rates and concentrations further, and the VFAs were recovered in a form that made them suitable for use as platform chemicals with minimal refining. This is the first time that continuous VFA recovery from real-world food waste has been reported at this scale with continual feeding, and represents a promising means through which to produce sustainable platform chemicals. Furthermore the production of VFAs arrests methane production in bioreactors, which is a low value product around which there is a growing concern about fugitive emissions contributing to climate change.


Subject(s)
Food , Refuse Disposal , Anaerobiosis , Bioreactors , Fatty Acids, Volatile , Fermentation , Methane
4.
Bioresour Technol ; 301: 122543, 2020 Apr.
Article in English | MEDLINE | ID: mdl-31927456

ABSTRACT

This research investigated the use of an innovative polytetrafluoroethylene (PTFE) membrane configuration coupled to electrodialysis for the in-situ removal of Volatile Fatty Acids (VFAs) from a mixed culture bioreactor. It was shown that by stacking the PTFE membranes to increase the active membrane surface area, shortened VFA recovery times was seen. The addition of electrodialysis to the PTFE membrane stack enabled the continuous extraction of VFAs from fermentation media whilst retaining essential nutrients and organic compounds in the diluate stream. Ammonium, phosphate and nitrate remained in the diluate chamber and did not cross the PTFE membrane stack. Up to 98% of total VFA recovery was achieved with the PTFE and electrodialysis system. The process was shown to extract from a reservoir of low VFA concentration to a reservoir with a VFA concentration 10 times higher. These results show that the addition of electrodialysis to PTFE provides a robust solution for the in-situ extraction of VFAs from fermentation media within bioreactors to support the demand for sustainable fuels and green chemical feedstocks.


Subject(s)
Fatty Acids, Volatile , Polytetrafluoroethylene , Bioreactors , Fermentation , Hydrogen-Ion Concentration , Nutrients , Sewage
5.
Bioresour Technol ; 229: 46-52, 2017 Apr.
Article in English | MEDLINE | ID: mdl-28107721

ABSTRACT

Electrodialysis (ED) removed volatile fatty acids (VFAs) from a continually-fed, hydrogen-producing fermenter. Simultaneously, electrochemical removal and adsorption removed gaseous H2 and CO2, respectively. Removing VFAs via ED in this novel process increased H2 yields by a factor of 3.75 from 0.24molH2mol-1hexose to 0.90molH2mol-1hexose. VFA production and substrate utilisation rates were consistent with the hypothesis that end product inhibition arrests H2 production. The methodology facilitated the recovery of 37g of VFAs, and 30L H2 that was more than 99% pure, both of which are valuable, energy dense chemicals. Typically, short hydraulic and solid retention times, and depressed pH levels are used to suppress methanogenesis, but this limits H2 production. To produce H2 from real world, low grade biomass containing complex carbohydrates, longer hydraulic retention times (HRTs) are required. The proposed system increased H2 yields via increased substrate utilisation over longer HRTs.


Subject(s)
Biofuels/analysis , Bioreactors/microbiology , Electrochemistry/instrumentation , Electrochemistry/methods , Fatty Acids, Volatile/biosynthesis , Hydrogen/metabolism , Sucrose/metabolism , Biomass , Carbohydrates/analysis , Fermentation
6.
Bioresour Technol ; 218: 512-7, 2016 Oct.
Article in English | MEDLINE | ID: mdl-27394998

ABSTRACT

The use of electrochemical hydrogen removal (EHR) together with carbon dioxide removal (CDR) was demonstrated for the first time using a continuous hydrogen producing fermenter. CDR alone was found to increase hydrogen yields from 0.07molH2molhexose to 0.72molH2molhexose. When CDR was combined with EHR, hydrogen yields increased further to 1.79molH2molhexose. The pattern of carbohydrate utilisation and volatile fatty acid (VFA) production are consistent with the hypothesis that increased yields are the result of relieving end product inhibition and inhibition of microbial hydrogen consumption. In situ removal of hydrogen and carbon dioxide as demonstrated here not only increase hydrogen yield but also produces a relatively pure product gas and unlike other approaches can be used to enhance conventional, mesophilic, CSTR type fermentation of low grade/high solids biomass.


Subject(s)
Bioreactors , Biotechnology/methods , Carbon Dioxide/chemistry , Hydrogen/chemistry , Anaerobiosis , Biomass , Carbohydrates/chemistry , Electrochemistry/methods , Fatty Acids, Volatile/biosynthesis , Fermentation , Hydrogen-Ion Concentration
7.
Bioresour Technol ; 189: 279-284, 2015 Aug.
Article in English | MEDLINE | ID: mdl-25898090

ABSTRACT

Hydrogen production during dark fermentation is inhibited by the co-production of volatile fatty acids (VFAs) such as acetic and n-butyric acid. In this study, the effectiveness of conventional electrodialysis (CED) in reducing VFA concentrations in model solutions and hydrogen fermentation broths is evaluated. This is the first time CED has been reported to remove VFAs from hydrogen fermentation broths. During 60 min of operation CED removed up to 99% of VFAs from model solutions, sucrose-fed and grass-fed hydrogen fermentation broths, containing up to 1200 mg l(-1) each of acetic acid, propionic acid, i-butyric acid, n-butyric acid, i-valeric acid, and n-valeric acid. CED's ability to remove VFAs from hydrogen fermentation broths suggests that this technology is capable of improving hydrogen yields from dark fermentation.


Subject(s)
Carboxylic Acids/metabolism , Dialysis/methods , Electricity , Fatty Acids, Volatile/isolation & purification , Fermentation , Acetic Acid/metabolism , Batch Cell Culture Techniques , Bioreactors , Butyric Acid/metabolism , Fermentation/drug effects , Hydrogen/metabolism , Hydrogen-Ion Concentration , Poaceae/chemistry , Solutions , Sucrose/pharmacology
8.
Bioresour Technol ; 189: 379-383, 2015.
Article in English | MEDLINE | ID: mdl-25913885

ABSTRACT

Real time measurement of gas production and composition were used to examine the benefits of two stage anaerobic digestion (AD) over a single stage AD, using pelletized grass as a feedstock. Controlled, parallel digestion experiments were performed in order to directly compare a two stage digestion system producing hydrogen and methane, with a single stage system producing just methane. The results indicated that as well as producing additional energy in the form of hydrogen, two stage digestion also resulted in significant increases to methane production, overall energy yields, and digester stability (as indicated by bicarbonate alkalinity and volatile fatty acid removal). Two stage AD resulted in an increase in energy yields from 10.36 MJ kg(-1) VS to 11.74 MJ kg(-1) VS, an increase of 13.4%. Using a two stage system also permitted a much shorter hydraulic retention time of 12 days whilst maintaining process stability.


Subject(s)
Biotechnology/methods , Hydrogen/metabolism , Methane/biosynthesis , Poaceae/metabolism , Alkalies/pharmacology , Anaerobiosis/drug effects , Bicarbonates/pharmacology , Biofuels , Bioreactors , Fatty Acids, Volatile/biosynthesis , Poaceae/drug effects , Thermodynamics
9.
Bioresour Technol ; 129: 561-7, 2013 Feb.
Article in English | MEDLINE | ID: mdl-23274219

ABSTRACT

Changes in fermenter gas composition within a given 24h period can cause severe bias in calculations of biogas or energy yields based on just one or two measurements of gas composition per day, as is common in other studies of two-stage fermentation. To overcome this bias, real time recording of gas composition and production were used to undertake a detailed and controlled comparison of single-stage and two-stage fermentation using a real world substrate (wheat feed pellets). When a two-stage fermentation system was used, methane yields increased from 261 L kg(-1)VS using a 20 day HRT, single-stage fermentation, to 359 L kg(-1) VS using a two-stage fermentation with the same overall retention time--an increase of 37%. Additionally a hydrogen yield of 7 L kg(-1) VS was obtained when two-stage fermentation was used. The two-stage system could also be operated at a shorter, 12 day HRT and still produce higher methane yields (306 L kg(-1) VS). Both two-stage fermentation systems evaluated exhibited methane yields in excess of that predicted by a biological methane potential test (BMP) performed using the same feedstock (260 L kg(-1)VS).


Subject(s)
Algorithms , Biological Assay/methods , Bioreactors/microbiology , Methane/analysis , Methane/metabolism , Models, Biological , Triticum/microbiology , Computer Simulation , Computer Systems , Fermentation , Gases/analysis
10.
Bioresour Technol ; 99(14): 6325-31, 2008 Sep.
Article in English | MEDLINE | ID: mdl-18226889

ABSTRACT

Hydrogen was successfully produced by fermenting primary sewage sludge which had been both heat treated and digested with a commercially available enzyme preparation. When either heat treatment or enzymatic digestion were not used, no hydrogen was produced during fermentation. Heat treated mesophilic anaerobic sludge was used as an inoculum rather than a pure microbial culture. Fermentation was conducted at pH levels ranging from of 4.5 to 7.0. When fermentation took place at pH 5.5 a peak hydrogen production rate of 3.75 ml min(-1) was observed. At this pH the hydrogen yield was 0.37 mol H(2)mol(-1) carbohydrate, equivalent to 18.14L H(2)kg(-1) dry solids.


Subject(s)
Enzymes/metabolism , Hydrogen-Ion Concentration , Hydrogen/metabolism , Sewage/microbiology , Fermentation
11.
Appl Environ Microbiol ; 69(11): 6758-61, 2003 Nov.
Article in English | MEDLINE | ID: mdl-14602637

ABSTRACT

A new method for the isolation of Cryptosporidium parvum oocysts and Giardia lamblia cysts from biosolid samples has been developed that utilizes sedimentation and immunomagnetic separation. The method was used to recover stained cysts and oocysts (spike organisms) from primary settled sewage sludge, anaerobically digested sewage sludge, and bovine manure. Recovery efficiencies associated with this method were approximately 40 to 60% and were significantly greater than those associated with similar methods based on sucrose flotation (P < 0.001). The recovery efficiency of the sedimentation-based method showed no significant reduction as a result of sample storage for up to 21 days (P > 0.05). Recovery efficiencies were determined by spiking samples with prestained cysts and oocysts, allowing them to be differentiated from those naturally present in the biosolid samples. The prestained cysts and oocysts had been fixed in 5% formalin, and the recovery efficiencies associated with this method may be different from recovery efficiencies for fresh cysts or oocysts.


Subject(s)
Cryptosporidium parvum/isolation & purification , Giardia lamblia/isolation & purification , Immunomagnetic Separation/methods , Oocysts/isolation & purification , Anaerobiosis , Animals , Cattle , Centrifugation, Density Gradient , Cryptosporidium parvum/growth & development , Feces/parasitology , Giardia lamblia/growth & development , Parasite Egg Count , Parasitology/methods , Sewage/parasitology
SELECTION OF CITATIONS
SEARCH DETAIL
...