This week we look at the differing attitudes to alternative fuels (AFs) on each side of the Atlantic. While CEMBUREAU in its 2022 Activity Report has demonstrated the rising level of co-processing in the EU-27 as achieving 52 per cent, in the USA a study by Global Efficiency Intelligence (GEI) has argued that US cement plants may well do better replacing coal and petcoke with natural gas rather than alternative fuels.
Europe is considered the leading proponent of co-processing and the use of AFs. Their use in the EU cement sector has enabled the prevention of 21.2Mt of CO2 being emitted in 2020 alone, claims CEMBUREAU. In the same year, the EU cement sector used approximately 36Mt of waste and by-products in the cement manufacturing process and around 12Mt of this waste were specifically used as AF in clinker production. Several European cement plants even operate at 90-95 per cent AF substitution, virtually eliminating the use of fossil fuels.
North America – slow to increase AF usage
While North American cement producers would likely follow EU developments in this area, an industry report released this week entitled “Emissions Impacts of Alternative Fuel Combustion in the Cement Industry” by GEI may further halt progress in the US to switch to higher AF substitution levels. The report admits that while some 73 per cent of US cement plants currently use some share of AF in their fuel mix, increasing their AF use proved marginal in terms of CO2 abatement. Co-processing of waste oil represented a 1-7 per cent improvement in CO2 abatement, while the co-processing of sewage sludge amounted to a 1-5 per cent improvement in CO2 abatement, according to the GEI study. Co-processing of solid waste and biomass represented just a two per cent reduction in CO2 emission levels when switching from petcoke and coal. However, a switch to natural gas could result in a 2-12 per cent abatement of CO2 in the US cement sector, claims GEI.
SO2 and NOx levels were also considered in the GEI study. It concluded that SO2 levels would potentially see considerable reductions of 16-82 per cent if plastic waste was co-processed. Sewage sludge, MSW and scrap tyres would similarly have a 14-80 per cent potential reduction for NOx if switching from fossil fuels and waste oil had a slightly wider range of 17-87 per cent.
The GEI claims that its main findings suggest that: "The co-processing of alternative fuels, especially waste-derived fuels, will not result in a meaningful reduction in the CO2 emissions of a cement plant, especially if biogenic CO2 emissions are not considered carbon-neutral."
Furthermore, the report warns that “…poor selection of alternative fuels, improper pre-processing and co-processing, or improper substitution rates in the fuel mix can result in negative environmental and health consequences in the form of higher CO2 or non-CO2 air pollutant emissions.”
US co-processing initiatives
Despite the GEI’s study, many businesses do see great potential in growing the US AF market. Geocycle has just announced its processing facility in Cumberland, Maryland, USA to process 75,000tpa of off-specification products for alternative fuels. Potential customers are likely to be the Holcim Hagerstown plant and Argos’ Martinsburg plant in West Virginia.
Meanwhile, Holcim has opened a new whole-tyre co-processing facility at its Alpena cement plant in Michigan. This was a state-supported investment of US$7.4m that will convert up to 22,000tpa of waste tyres to fuel the cement plant and will account for 10 per cent of the plant’s thermal requirement.
In addition, Continental Cement (Summit Materials Inc) has ordered an FLSmidth FUELFLEX® Pyrolyzer, which is being designed to achieve 55 per cent fossil fuel replacement at the Davenport cement plant in Buffalo, Iowa. This project is scheduled to come on-stream in 2024 and is only the second such order following the first FUELFLEX® Pyrolyzer installation at Mannok Cement in Ireland.
Moreover, Holcim’s Holly Hill cement plant in South Carolina has recently set the standard of reaching 100 per cent thermal energy substitution in the USA. Henry González, Holly Hill’s plant manager, said: “I am pleased to tell you that we achieved more than 40 continuous hours of operating at 100 per cent thermal energy substitution rate (TSR) between 30-31 March 2023, in fact on average the month of March was also a record for the plant which achieved 89.7 per cent TSR.”
Summary
Although US cement plants have, on average, a much lower TSR than European cement plants, there has been a general move towards increasing AF usage. Multinationals such as Holcim are likely to carry out similar AF policies worldwide, so further growth in the US AF market can be expected. The choice of fuel will depend on such matters as what equipment is already at the cement plant, the price of AF and availability compared to natural gas and fossil fuels, and the sustainability and decarbonisation strategies being employed at the facility. The achievements made at Holly Hill are likely to act as an incentive for other US cement plants to replicate in the coming years for those that do make the switch to AF.