Waste - A Biotechnological System for Production of Value-added products, Bioethanol and Methane from Non-animal Food Wastes

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Resource or Project Abstract

The primary aim of this project was to develop an integrated non-GMO strategy for (i) production of high value products, (ii) generation of bioethanol, and (iii) generation of renewable energy in the form of biogas from vegetable, fruit and confectionery wastes (VFCWs) and source-separated OFMSW. In the project, a range of novel, optimized and low-cost thermostable enzyme cocktails (thermozymes) were developed from generally regarded as safe fungal sources and used as eco-friendly biocatalysts to convert carbohydrate-rich processed and unprocessed vegetable, fruit and cereal residues to soluble sugar rich syrups and fractions rich in other high-value bioactive molecules. Maximum sugar yields were obtained (>66-90% hydrolysis) at 70-80oC with gentle agitation throughout the enzyme treatment process. Other reaction parameters, such as pH, reaction time and moisture content were dependent on the thermozyme cocktailwaste combination. Of the wastes treated, >68-91% of the sugars released were monosaccharides (or simple fermentable sugars). The relative amounts and types of monosaccharides varied depending on the waste (i.e. mixed vegetable waste, mixed breads, carob waste, apple pomace/pulp, mixed fruit residues, mixed cereals/cereal fractions, biodegradable packing, catering waste paper and card, coffee waste, spent tea bags/tea leaves, etc.). The enzyme cocktails and reaction conditions can be readily optimized for a wide variety of waste feedstocks. The results highlighted the low-cost and highly efficient properties of the thermozymes in that very low dosages of enzyme cocktail were required. While enzyme recovery was investigated, the economic advantages of enzyme recovery would be out-weighed by the cost of any recovery system.

The potential of utilising thermophilic digestion in the second stage of the thermozymeanaerobic technology process was clearly proven in this study. Rapid start up of the 9 thermophilic reactor R1 was achieved using mesophilic granular inoculum. In response to increased loading rates, the thermophilic reactor was more susceptible to the build up of intermediate VFAs, however, the thermophilic granules were demonstrated to be more robust than mesophilic granules. During the application of thermozyme hydroysates the thermophilic reactor performed comparably, and during some periods, exhibited superior performance to the mesophilic reactor. Remarkably, the biomass in both reactors retained the capacity to readily degrade sugars which they had not been exposed to for some time. It was found that the application of thermozyme hydrolysate improved the capacity of the reactors to degrade all sugars tested. In contrast to other reports in the literature, thermophilic AD was found to be very stable and not subject to substrate inhibition. In addition, the sugar-rich hydrolysates were shown to be good feedstocks for the production of other bio-fuels such as bioethanol by yeast fermentation, and other highvalue products (e.g. chemical feedstocks and natural antioxidants). A preliminary study was conducted to evaluate key hygiene aspects of the reaction processes with respect to microbial pathogen kill-rates. This study was important to investigate if the thermozyme- AD process could meet the highest environmental and public health standards, thereby ensuring higher value and a greater diversity of end-use for the reaction products. The effects of pre-sanitation at 55oC (temperature for thermophilic AD) and 70oC on the survival of faecal indicator organisms was investigated to assess the efficiency of hygienisation (and/or a treatment step). Sewage sludge was used as substrate with Escherichia coli, Enterococci, Salmonella seftenberg and Clostridium perfringens as test indicator species. While the results represent preliminary findings, at 70oC, both E. coli and S. seftenberg were very susceptible to the increased temperature and could not be detected after <5 min. While the Enterococci counts were markedly reduced after 5 min at 70oC, but remained constant for the remaining 55 min. The results suggest that a longer treatment time at 70oC, or a higher treatment temperature (e.g. 80oC), both of which are compatible with the enzyme technology, may be more appropriate to ensure complete kill-off of the Enterococci and C. perfringens. To protect the thermozyme technology, the source organism(s) and key applications, a PCT has been filed to protect the thermozyme 10 technology, the source organism(s) and key applications. Scale-up of thermozyme production is in progress and plans to develop the combined technologies at pilot scale are envisaged. This study has revealed the potential of the thermozyme-AD technology to provide a simple, efficient and low-cost option for waste management and energy recovery from non-animal food wastes.

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Contact Information for This Resource

Dr. Maria Tuohy
National University of Ireland Galway

Professor Emer Colleran
National University of Ireland Galway

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End of Project Report    ERTDI_Touhy_BioethanolWaste_epr.pdf  (6.43 Mb)

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Author(s)Tuohy, M. Colleran, E.
Title Of WebsiteSecure Archive For Environmental Research Data
Publication InformationWaste - A Biotechnological System for Production of Value-added products, Bioethanol and Methane from Non-animal Food Wastes
Name of OrganisationEnvironmental Protection Agency Ireland
Electronic Address or URL https://eparesearch.epa.ie/safer/resource?id=1147b2fd-24cb-102d-8e25-e9973852f3cf
Unique Identifier1147b2fd-24cb-102d-8e25-e9973852f3cf
Date of AccessLast Updated on SAFER: 2024-07-21

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Tuohy, M. Colleran, E.   "Waste - A Biotechnological System for Production of Value-added products, Bioethanol and Methane from Non-animal Food Wastes". Associated datasets and digitial information objects connected to this resource are available at: Secure Archive For Environmental Research Data (SAFER) managed by Environmental Protection Agency Ireland https://eparesearch.epa.ie/safer/resource?id=1147b2fd-24cb-102d-8e25-e9973852f3cf (Last Accessed: 2024-07-21)


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Access Information For This Resource

SAFER-Data Display URL https://eparesearch.epa.ie/safer/iso19115/display?isoID=131
Resource Keywordsntegrated non-GMO Bioethanol Methane wastes biogas thermostable enzyme cocktails thermozymes sugar carbohydrate
EPA/ERTDI/STRIVE Project Code2001-WMF-LS-7/7
EPA/ERTDI/STRIVE Project ThemeWaste and Resource Management
Resource Availability: Any User Can Download Files From This Resource
Limitations on the use of this Resourcen the event of obtaining access to datasets corresponding to this resource any datasets, data, or information resources being used in a journal article or other means of publication the original authors should be informed of this usage and an appropriate acknowledgement or citation is included within the published article. The EPA advise that this acknowledgement should take one of the following forms dependent upon how heavily the published work relates to the downloaded data: * Co-Authorship(s) for the original author(s)* Written acknowledgement within the body of the article* Written acknowledgement by means of the inclusion of a bibliography entry which clearly cites the original authors.
Number of Attached Files (Publicly and Openly Available for Download): 1
Project Start Date Thursday 1st February 2001 (01-02-2001)
Earliest Recorded Date within any attached datasets or digital objects Thursday 1st February 2001 (01-02-2001)
Most Recent Recorded Date within any attached datasets or digital objects Wednesday 1st February 2006 (01-02-2006)
Published on SAFERTuesday 17th November 2009 (17-11-2009)
Date of Last EditTuesday 17th November 2009 at 14:39:35 (17-11-2009)
Datasets or Files Updated On Tuesday 17th November 2009 at 13:07:22 (17-11-2009)

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Geographical and Spatial Information Related To This Resource

Description of Geographical Characteristics of This Project or Dataset
This project was completely carried out in a laboratory setting. There are no geographical characteristics to the experimental setup.

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Supplementary Information About This Resource

In this section some supplementary information about this resource is outlined. Lineage information helps us to understand why this project was carried out, what policy or research requirements did it fulfil, etc. Lineage is important in understanding the rationale behind the carrying out of a project or the collection of a specific dataset etc. Links to web sites, applications, papers, etc are outlined to provide you with additional information or supplementary reading about the project or dataset

Lineage information about this project or dataset
In Ireland at present most of our recycled MSW is recycled in other countries. Only a small proportion of MSW is recycled in Ireland, and worryingly the percentage recycled in 2004 decreased from 26% to 17% in 2005, i.e. a decrease of 25% on the 2004 figures (EPA, 2006). The core aim of this project is to develop an integrated biological (or biotechnological) strategy for (i) production of high value products (enzymes), (ii) generation of bioethanol, and (iii) recovery of biomass energy in the form of methane gas by AD, from vegetable, fruit and confectionery wastes (VFCWs) and source-separated OFMSW. The project has also facilitated links between national waste management and recovery companies, as well as companies involved in the bioenergy sector. Potential partnerships that will enable scale-up and development of the project are in progress. The project team is also engaged in key outreach and dissemination activities to engage with local communities and school children and to increase awareness on key waste management and recycling issues.
Supplementary Information
While direct anaerobic digestion has been used in waste management strategies for food waste for some time, and while enzymatic conversion of lignocellulose-rich biomass has been well characterized with respect to bioethanol production, to the best knowledge of the authors, this project represents the first report on the combination of a thermostable enzyme treatment step followed by downstream AD to provide a combined solution for reduction in non-animal food waste and production of value-added products, primarily biogas. The relatively simple approach has significant potential to (i) decrease the volume of food waste to landfill and hence fulfil (at least in part) the diversion to landfill targets, (ii) highlight the potential of non-animal food waste as a valuable feedstock for production of bioenergy and key value-added by-products, (iii) pasteurize the sugar-rich feedstock generated by thermozyme treatment, and (iv) decrease AD retention times and bioreactor loading rates.

All chemicals used in the lab were of molecular biology or analytical grade. De-ionised water from the Milli-Rx 20, Millipore system, was used to prepare all analytical solutions.

Other scientists and research experts which were involved in this project:
Dr. Patricia Mulcahy, Head of Development & School of Science IT Carlow, Ireland Tel.: +353 59 9170550,patricia.mulcahy@itcarlow.ie

Dr. Gunnar Liden, Department of Chemical Engineering, University of Lund, Sweden

Tel.: +46 46 2220862,E-mail: Gunnar.Liden@chemeng.lth.se

Prof. Marc Claeyssens,Department of Biochemistry, Microbiology and Physiology, University of Ghent, Belgium Tel.: +32 9 264 5270 E-mail: marc.claeyssens@ugent.be

Key recommendations for future research: A number of key recommendations can be made from the trials involving thermophilic and mesophilic anaerobic digestion. The reactor operational conditions imposed throughout this trial remained unchanged with respect to influent COD concentrations, VLR and HRT. This was in part due to instability in reactor performance as a result of imposing an increased loading rate early in the trial period. However, in order to fully demonstrate the robustness of the proposed two step strategy, further investigations into the comparative stability of mesophilic and thermophilic anaerobic digestion are required. These trials should be carried out using a variety of loading rates and retention times to properly evaluate the potential and stability of thermophilic anaerobic treatment. To more thoroughly investigate the substrate range of the mesophilic and thermophilic biomass, further reactor trials are recommended whereby more complex waste streams incorporating other dimeric and oligomeric carbohydrates are applied to the reactors.
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