The cement industry has made major strides to reduce its environmental footprint in recent years and industry leaders, such as the UK’s Lafarge Tarmac, are paving the way with investment in innovative new technologies to improve sustainability across the entire supply chain.
A major breakthrough has been the development of waste derived fuels (WDF), which are increasingly replacing the use of fossil fuels such as coal and petcoke as the main source of energy in cement kilns.
Lafarge Tarmac has pioneered the use of WDF across a number of its cement manufacturing plants in the UK, including 100% biomass carbon neutral content fuels such as processed sewage pellets (PSP) and meat and bone meal (MBM), partially carbon neutral fuels such as waste tyres and solid recovered fuel (SRF), and non-biomass fuels such as waste derived liquid fuel (WDLF) and recycled fuel oil (RFO).
The evolution of waste derived fuels
Waste derived fuels were first used in the industry as far back as the 1970s during the oil crisis. However, such initiatives were short-lived as the networks to collect and process waste were non-existent and landfill was the widely accepted home for waste. In the mid-1990s, Lafarge Tarmac successfully piloted the use of alternative fuels at Cauldon and Dunbar, where shredded tyres were used to replace proportions of petcoke and coal to create a lower-carbon energy source.
Since then, while fossil fuels continue to be the main source of energy in Lafarge Tarmac’s cement kilns, these are increasingly being replaced by WDF. A 29% substitution rate was recorded in 2011. In 2013, when the latest sustainability report was published, Lafarge Tarmac reported a major reduction in the amount of coal used to make 1 t of cement, which fell from 87 kg to 83 kg in 2011.
In the last three years, the company’s Aberthaw cement plant in South Wales has been at the forefront of developing its use of WDF as a more sustainable energy source. While MBM had been used in the cement kilns at Aberthaw to replace coal since 2005, in 2011 Lafarge Tarmac announced plans to extend this by applying to the Environment Agency for a dual-fuel permit to use waste tyres and SRF simultaneously. This was the first time ever that a UK company had applied for a permit for two types of WDF to be used at the same time.
Ahead of applying to the Environment Agency for permission to trial the use of used tyres and SRF, Lafarge Tarmac undertook a comprehensive consultation with local communities around the Aberthaw plant. The aim of this consultation programme was to ensure that all local stakeholders were given the opportunity to assess the facts about sustainable waste derived fuel and the company’s plans to use them at Aberthaw, with the hope of gaining community support for the application.
Lafarge Tarmac was granted a permit allowing the use of dual-fuel WDF. Following this period of proactive engagement with the local community, the permit was granted to allow the dual WDF to be used in just eight weeks. However, achieving the permit was just the start of the process for actually implementing the dual-WDF. The Aberthaw plant, as with other cement plants, continued to undergo an intensive emissions monitoring programme, which involved reporting emissions to Natural Resources Wales. Data was captured by the second and submitted to the public records to ensure that no negative emissions were recorded from the operations during and after the burning of the waste tyres and SRF in the cement kiln. This process continues today as per Lafarge Tarmac’s permit requirements for burning WDF.
Lafarge Tarmac also undergoes an even deeper assessment every six months to test the levels of heavy metals and traces of dioxins in its emissions. Since the introduction of the waste derived fuels back in 2005 and through 2012, no negative change in the emission profile of the plant has been recorded.
In order to ensure a reliable, consistent and legitimate source of waste fuels and specifically tyres, Lafarge Tarmac created Sapphire Energy Recovery. Among many other services, this operation collects tyres from retailers and scrap yards and sorts, checks and cleans them before delivery to the plants. To reduce the environmental impact of the transport and ensure a reliable supply, Sapphire Energy Recovery endeavours to source from regions surrounding the plants, so waste tyres used at Aberthaw, for example, come from South Wales and southwest England. With the development of SRF plants by waste operators it is envisaged that SRF will be supplied as the infrastructure is built from within South Wales.
The benefits of using WDF
The use of WDF is playing an important role supporting the government in reducing UK carbon emissions (80% by 2050) and the move towards a low carbon economy, as well as helping to reduce carbon emissions supporting government targets and ‘recovering’ large volumes of waste that would have otherwise been destined for landfill.
Finally, using WDF complements other wider Lafarge Tarmac sustainability initiatives, including its water footprinting programme. Using coal as fuel significantly increases water usage. Lafarge Tarmac’s endeavours to replace coal with WDF such as used car tyres have primarily served to reduce the carbon footprint of its cement products and manufacturing operation – but with an additional environmental benefit of helping to reduce its water footprint.
Given that water resources in the UK are under huge pressure, this is a major benefit of WDF and their increasing use across the business has played a significant role in helping the company to reduce its demand on external water supplies by an impressive 69%, equivalent to 6500 litres of water per day. At the Aberthaw plant, use of potable water sources has been reduced by 39%.
Using WDF to make cements
In addition to using WDF in the manufacturing process, the blending of waste residue ash in cements is another recent innovation by Lafarge Tarmac. As a result of Aberthaw’s location just 1 km from RWE nPower’s South Wales power station, in 2013 the cement manufacturer launched a unique partnership with the energy company to recycle ash, a byproduct of electricity production.
Lafarge Tarmac has developed a process to refine and separate the ash supplied from the power station to produce a specialist material, Celtic Ash, which can be blended in the manufacturing process to produce lower-embodied carbon cements. The recycling of this ash, which would have otherwise gone to landfill, is another major sustainability initiative by Lafarge Tarmac at Aberthaw.
Written by David Shenton, National Environment Manager, Lafarge Tarmac Cement and Lime, UK. This is an abridged version of the full article, which appeared in the June 2014 issue of World Cement. Subscribers can view the full article by logging in.
Read the article online at: https://www.worldcement.com/europe-cis/28052014/pioneering_waste_derived_fuel_use_252/