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24 September, 2018 - 20:28 By Kate Sweeney

Fuel for thought as Cranfield University academics address plastics issue

Scientists at Cranfield University are looking at upcycling plastics into base compounds for manufacturing, or for liquid fuels to substitute fuels produced directly from crude oil. Mining landfill sites for previously discarded plastics to recover valuable chemicals and liquid fuels is a major basis of research at the institution.

Cranfield researchers are working to understand the potential recovery of valuable chemicals from plastic-containing waste which is not currently recycled – diverting low-grade plastic waste from landfill to produce chemicals for use in manufacturing or as liquid fuels.

Dr Stuart Wagland, Senior Lecturer in Energy & Environmental Chemistry at Cranfield, said: “There are a number of potential advantages in recovering materials from closed landfill sites. These sites are a long-term environmental burden, requiring careful monitoring and management, with evidence showing that nearby groundwater can be affected. Enhanced landfill mining will effectively reduce this burden, recover valuable materials and enable the use of land for redevelopment.”

“In this project, we are looking at upcycling plastics into base compounds for manufacturing, or for liquid fuels to substitute fuels produced directly from crude oil.”

Previous work at Cranfield has highlighted that plastic recovered from landfill is not typically suitable for conventional recycling routes. Work is now underway to apply pyrolysis, an advanced thermal treatment process, to produce base chemicals for use in manufacturing or as liquid fuels.

There are over 20,000 landfill sites across the UK. Plastics within closed household waste landfill sites account for around 15-20 per cent of the total waste. However the value and viability of reclaimed plastics is not clear as it is typically low-grade and difficult to recycle economically. Enhanced landfill mining is an emerging area that aims to recover value from such excavated solid waste, a process known as ‘upcycling’.

The concept of enhanced landfill mining is promoted through the European Enhanced Landfill Mining Consortium, (EURELCO), which Cranfield is a founding member of.

Maximum value is sought through excavating the waste, recovering value from materials (e.g. rare earth elements, secondary raw materials)and  energy-rich commodities (plastic, textiles, paper and card) and by being able to use the resulting land space for further development.

Understanding the potential for secondary raw material recovery was explored in a recent project funded by the European Union under the Horizon 2020 programme (SMART GROUND). The use of plastics for direct energy conversion is one option, however, work at Cranfield is seeking to develop more valuable products which would have a greater impact by substituting the use of fuels and chemicals derived from crude oil. 

Driving the future

Due to the under capacity of suitable refuse plants in the UK, more than three million tonnes of potential refuse-derived fuels (RDF) are currently exported each year. The university says that locally sourced sustainable alternatives to fossil fuels are crucial as the UK, and the rest of the world, seeks to develop safe waste management and energy security.

Through its research, Cranfield aims to support the production of high value materials from wastes which would otherwise destined for landfill or as use as direct energy conversion – or power from incineration.

Partnering with Syngas Products and WestAfricaENRG, the research team will demonstrate that RDF and wastes containing low-grade plastic materials, which are currently rejected by material recycling facilities (MRF), can be used in a town-scale pyrolysis plant. 

Developed by Syngas Products, the plants produce energy, alongside affordable and high-quality liquid fuels, for use as base chemicals in manufacturing. By adding additional processing to the existing Syngas Products technology for waste processing, this ‘upcycling’ approach could be a commercially viable option to solve both the low-grade plastic waste issues and dependency on fossil fuels for transport.

Dr Stuart Wagland, Senior Lecturer in Energy & Environmental Chemistry at Cranfield said: “RDF material is energy-rich and represents a loss-of-resource once it leaves the UK. Similarly, substantial quantities, around 340,000 tpa, of rejected and mixed low-grade plastics from UK MRFs are produced each year, as the market for recovering and recycling this material is not commercially viable. 

“Our research to date shows that through smaller-scale advanced thermal treatment, pyrolysis in this case, products can be recovered in addition to the energy and power.

“To ensure the UK is at the forefront of flexible ATT (advanced thermal treatment) processes we are developing a business case for the commercialisation of the liquid fuels and chemical products in both the UK and internationally. 

“ATT processes are not necessarily rivals with conventional energy from waste technology – combustion, larger-scale facilities play a key role in diverting waste from landfill. However, town-scale advanced thermal treatment facilities are key to developing a diverse and flexible resource management future in the UK.”

In Nigeria, the electricity connection is sporadic and unreliable, which is typical across many developing countries. Therefore, there is a necessity to rely on costly diesel back-up generators. There are low levels of landfill diversion, however, WestAfricaENRG is amongst the more progressive companies and has built and operates a 280,000 tpa MRF in Lagos - the first in West Africa. 

If rolled-out across Nigeria, the outputs of the waste pyrolysis would provide a 'greener' fuel for the generators, security of power supplies and reduce the reliance on pure fossil-fuels, in addition, stimulate the development of more MRFs in Nigeria.

Cranfield says that there is a significant availability of plastic-containing mixed waste streams in the UK and in Nigeria, yet further development is needed to demonstrate ATT on a community scale and to outline a pathway to commercialisation of liquid fuel outputs.

They hope that the knowledge gained from this research could reduce transportation emissions by siting technology locally at a small modular scale, where the waste arises or where there is a need for fuel. It could prevent the use of fossil fuels by utilising the energy from non-recyclable waste, improve security of supply and provide a low cost and sustainable fuel, avoiding the volatility of the oil and gas industry.

• IMAGE: © Can Stock Photo / gyn9988

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