The Science & Technology
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Wednesday 6th September 2017

Charikleia Spathi

article posted 15 June 2017

Dr Charikleia Spathi (Hara) joined Sheffield Hallam University in 2016 as a Postdoctoral Research Fellow in Glass and Ceramics, based in the Materials and Engineering Research Institute (MERI). She holds a PhD in Resource Efficiency and Sustainable Built Environment from Imperial College London. Her current research aims to develop lower-energy routes to commercial soda-lime glass manufacture through changes in the raw materials balance. She has solid knowledge of materials science and waste valorisation with demonstrated ability to turn research results into exploitable products. She particularly enjoys working at the interface between academia and industry.

Utilisation of food and biomass ash by-products in mainstream coloured container soda-lime-silica glass production
Charikleia Spathi* a, Teig Coulbeck a,b, Robert Ireson b & Paul A. Bingham a

This work developed resource efficient routes to produce coloured container glass through modifying composition mixtures of feed materials. To this extent, the production of green (Cr2O3-doped) container soda-lime-silica glass using food and biomass ash by-products was investigated. The waste streams used included: eggshell, seashell and biomass ash, all sourced domestically in the UK and found in sufficient quantities to fully or partially replace current glassmaking raw materials. The named by-products represent sources of valuable 'urban-mined' minerals having appropriate chemical make-up and consistency, requiring no extensive processing prior to use in glass manufacture. Recent scientific work on the use of such wastes in glass and glass-ceramics production also provides evidence of the proof-of-concept, a prerequisite for subsequent industry involvement [1, 2].

The key objective was to maximise the content of identified by-products in the proposed glass batch recipes in order to achieve the benchmark oxide composition for green container glass. The latter was determined after discussions with key UK glass manufacturers and it is representative of contemporary glass formulations. Through large-scale glass melting experiments (1kg glass produced), it was established that commercial container glass oxide compositions can be attained with the use of by-products with significant decrease in the volumes of standard quarried minerals. Given, increased transition metals concentration in biomass ash samples, the material was solely considered for the production of green container glass. Eggshell and seashell resources were, hence, also used in the production of coloured glass to allow comparisons between glass samples. In the case of eggshell and seashell by-products, provided free of any impurities and/or organic contaminants by suppliers, it was demonstrated that full substitution of limestone was possible. When biomass ash was used, it was found that iron silicate, a raw material currently used in coloured container glass production, can be fully replaced as biomass ash represented an alternative source for iron. The ash sample used in this study also provided alkali metals, which are known for promoting melting of glass formulations [3].

Key glass properties measured included: a) density, b) optical properties, c) dilatometric softening point, d) liquidus temperature, e) chemical durability and f) viscosity-temperature relationships based on the work of Lakatos [4]. For all glass formulations containing a waste material, glass properties were comparable to those of baseline container glass.

In conclusion, based on experimental findings, there is significant potential to exploit the mineral content of food and biomass ash by-products to substitute depleting naturally sourced materials used in mainstream glass making. This can deliver associated productivity and energy consumption benefits to the UK glass sector, which currently generates 2 Mtonnes of CO2, and can help the industry meet the decarbonisation roadmap targets as described in [5].


1. Danewalia, S.S., Sharma1, G., Thakur, S. & Singh, K. (2016) Agricultural wastes as a resource of raw materials for developing low dielectric glass-ceramics. Scientific Reports, 6, Article number: 24617.
2. Cornejo, I.A., Ramalingam, S., Fish, J.S. & Reimanis, I.E. (2014) Hidden treasures: Turning food waste into glass American Ceramic Society Bulletin, 93 (6), pp. 24-27.
3. Day, D.E. (1976) Mixed alkali glasses - Their properties and uses. J. Non-Cryst. Solids, 21, pp. 343-372.
4. Lakatos, T. (1976) Viscosity-temperature relations in glasses composed of SiO2–Al2O3–Na2O–K20–Li2O–CaO–MgO–BaO–ZnO–PbO–B2O3. Glastekn. Tidskr., 31 (3), pp. 51–54.
5. British Glass Manufacturers’ Confederation (2014) A Clear Future: UK glass manufacturing sector decarbonisation roadmap to 2050.XED


a Materials & Engineering Research Institute, Sheffield Hallam University, Sheffield S1 1WB
b Glass Technology Services Ltd., Sheffield S35 2PY