Mapping the flat glass value-chain: a material flow analysis and energy balance of UK production

Glass is one of the UK’s eight energy-intensive industries. As such, it is under scrutiny to decouple growth in production from greenhouse gas (GHG) emissions. Recycled glass, also known as cullet, requires less energy to melt than primary raw materials in new glass production. The use of cullet thus reduces the energy intensity per unit of output whilst also reducing demand for primary material resources. However, efficient systems for flat glass collection are yet to be established in the UK, resulting in a limited supply of cullet available for the flat glass market and missed environmental opportunities. This study identifies the existing supply-chain inefficiencies in the UK glass industry in three stages. Firstly, the mass flows of materials within the three main glass sectors: container glass, flat glass and glass wool, are mapped from natural resource through to primary application and subsequent end-of-life management based on a reference year of annual production figures. The map is presented in the form of a “Sankey” diagram which draws attention to several opportunities for increasing resource efficiency; namely in the stark contrast in glass collection rates between the flat and container glass industry. Using the data collected on the annual mass flows of materials in the UK flat glass sub-sector, the energy (MJ) and GHG emission (CO2-eq) saving potential of enhanced end-of-life collection methods are assessed, based on three alternative recovery scenarios. These scenarios consider the use of alternative distributions of recovered flat glass cullet in the three primary glass sub-sectors. The emission savings resulting from each recovery scenario are evaluated, based on the estimated tonnage yield of finished flat glass products. It is shown that together with improved manufacturing yield, the reutilization of end-of-life flat glass as cullet in new production could reduce the annual emissions of the UK flat glass value-chain by up to 18.6%. Finally we review the existing barriers to recycling different glass types based on acceptability criteria and available take-back infrastructure, and thus find that the advancement of improved recycling rates will rely on establishing the business opportunity and/or supporting policy for developing efficient systems for flat glass collection.