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Carbon footprint of novel uses of organic wastes for sustainable production of chemicals and materials

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  • Full or part time
    Prof J Smith
    Dr D Vega-Maza
  • Application Deadline
    No more applications being accepted
  • Competition Funded PhD Project (European/UK Students Only)
    Competition Funded PhD Project (European/UK Students Only)

Project Description

There is an urgent global need to develop new and innovative strategies for the sustainable production of chemicals and materials using renewable feedstocks and renewable energy. At present, everyday chemicals and materials (e.g. plastics, pharmaceuticals and fertilisers) are often produced using fossil fuels, both as feedstocks and as a source of energy. Fossil fuels are a finite resource, and their use has a negative impact on the climate. This project is part of a doctoral training programme that aims to train a new generation of researchers, equipped with the skills and knowledge to deliver sustainable production of chemicals and materials from organic waste and to evaluate the environmental and economic impacts of developing such technologies. The research focuses on the conversion of organic waste into chemicals via anaerobic digestion followed by separation and further chemical conversion into a range of products. This project will calculate the carbon footprint of the production of key chemicals by anaerobic digestion compared to traditional chemical production methods combined with traditional uses and treatments of organic wastes. A full life cycle analysis of carbon emissions will be used to estimate the benefits or dis-benefits of new methods compared to traditional approaches.

The organic waste materials used as feedstocks will include agricultural residues, animal manures, sewage, and the organic fraction of municipal solid wastes. Organic waste can be used, with or without pre-treatments, in anaerobic digestion where microorganisms convert the main building blocks (carbohydrates, proteins and lipids) into a mixture of biogas, short chain organic acids, alcohols and new microorganisms. The composition of the anaerobic digestion products depends on the operating conditions of the digesters and on the nature of the feedstock. In general, biogas will be composed of hydrogen, methane and carbon dioxide, the main short chain organic acids will be acetic, propionic and butyric acid, and the main alcohols will be ethanol and butanol. The biogas components will be separated and either used as chemicals, without any further chemical conversion, or used as feedstocks for chemical synthesis which will generate a wide range of other chemicals. For example, the methane in biogas can be compressed and used as fuel, combusted to generate electricity or can be used as feedstock for the synthesis of dimethyl ether (DME), diethyl carbonate (DEC), dimethyl carbonate (DMC) or other substances which can be in turn converted to many chemicals of everyday use, such as plastics (polycarbonate), paints and pharmaceuticals. The carbon dioxide in the biogas will be converted to low-carbon materials suitable for a wide range of industries, replacing current materials which have a large carbon footprint and, via enzymatic kinetics, to important chemicals such as formic acid, methanol and formaldehyde which are currently produced from fossil fuels. The liquid fraction generated by the digester will be made up of water and of short chain organic acids and alcohols. These substances will be separated into individual components, which will then be either used as such as chemicals or be subjected to (electro) chemical synthesis for the production of other chemicals. For example, acetic acid can be used as a solvent or can be used as starting material for many chemical reactions which will produce plastics, paints and many other essential chemicals. Electrochemical oxidation of the liquid-phase products in fuel cells will enlarge the range of substances obtained from this process, for example butanol can be converted to butyric acid, with the simultaneous generation of electricity. The solid fraction effluent from the digester will contain the produced microorganisms and any undigested materials. The solid fraction can then be spread on land as fertiliser, being rich in nitrogen and other essential elements for plant growth, or be used as feedstock for further chemical synthesis, to produce
benzenes and phenols for use in the production of pharmaceuticals or other essential chemicals.

The life cycle analysis of carbon emissions will trace fossil fuel use and carbon emissions throughout this process and compare to the business-as-usual scenario, where wastes are either disposed of (following treatment) or directly used as organic fertilisers. Implications for carbon sequestration in agricultural land and changes in land use will be included in the analysis.

The outputs from the project will be a comprehensive carbon footprint associated with changing to novel uses of organic wastes for sustainable production of chemicals and materials. This information will be of key importance in determining the environmental significance and the sustainability of the new methods developed.

Funding Notes

The 2019-20 maintenance grant for full-time students is £15,009 per annum.

Candidates require an honours degree at 2.1 or above in a subject related to environmental, agricultural or biological science or engineering.

APPLICATION PROCEDURE:
Applications can be completed online: https://www.abdn.ac.uk/pgap/login.php

• Apply for the Degree of Doctor of Philosophy in Biological Sciences
• State the name of the lead supervisor as the Name of Proposed Supervisor
• State ‘Leverhulme CDT in Sustainable Production of Chemicals and Materials’ as the Intended Source of Funding
• State the exact project title on the application form



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