Ian Riley, WCA, and Matthias Mersmann, KHD, discuss the role of alternative fuels in the cement sector’s journey to net-zero.
Global Cement (GC): How would you describe the use of alternative fuels (AF) in cement in 2023?
Ian Riley (IR): There’s a huge difference seen in AF use due to different waste regulations in different countries. If you have no waste regulations, it is nigh on impossible to make alternative fuels work, except in very special cases.
However, that’s not the whole story, as there are some structural differences too. If we take the two largest cement producers, China and India, both have made some progress with waste regulations, but AF use is still low. In China this is because waste generation per-capita is an order of magnitude below cement capacity per-capita, which is abnormally high compared to elsewhere. There is simply not as much waste available per tonne of cement produced. India, with a cement sector 10 times smaller than that of China, is in a similar position, as are countries like Indonesia and Vietnam. This is shown as light colours below.
In contrast, many more developed economies, particularly in Europe, generate much more waste and have far smaller cement sectors, as shown by the darker colours below. This means that wastes are more abundant and more likely to be funnelled into recycling and re-use, enabling far greater proportions of AF in their cement sector.
GC: What are the best levers to pull to go from excess waste to high AF use?
Matthias Mersmann (MM): The first step is to make landfilling expensive, as has been done across much of Europe, as well as clamp down on dumping. Where the waste then goes from there depends on the local situation. Some countries will develop strong waste collection and recycling systems to ensure that the resources are reused.
Generally, we should always reduce first, reuse second and then recycle. Then, when materials cannot be recycled easily, governments should look at energy recovery. Cement kilns are ideal for this, as they use the calorific content and the inert content, unlike Waste-to-Energy (WtE), and there is an in-built counter-flow filtration within the preheater. Cement is one of the lowest-cost man-made materials, in which fuel represents around 40% of production costs, so AF can help to reduce bills too.
IR: The case of China is instructive as to the path that quite a lot of countries are taking. Landfill was very cheap in China 25 - 30 years ago. However, it became harder to find new sites for landfill, due to a lack of available land. Landfill prices rose and the central government promoted incineration, an approach popular in Europe at that time. All the time the landfill was still filling up, so there was also encouragement for cities to recycle.
However, after a while, the public became aware that the incinerators emitted dioxins and generated toxic bottom ash, so it became difficult to build incinerators too. It was much cheaper - and more ecologically sound - to dispose of waste in a cement kiln. More and more waste is now heading to cement kilns as a result. Hopefully other countries will be able to navigate these transitions speedily and successfully, avoiding some of the pitfalls that other countries have fallen into.
GC: Where are the next countries where waste processing and AF will come in?
MM: KHD is at the forefront of this, dealing with requests from all over the world. At the moment, there is significant movement in North Africa, particularly Egypt. Even Saudi Arabia, famed for its oil, is now keen to install AF systems. However, the most notable country - right now - is still China.
GC: How is biomass changing the AF picture?
MM: Biomass has a special position within AF because its biogenic content means that its CO2 emissions are not counted within emissions frameworks, as they were absorbed from the atmosphere recently. However, its use in the cement sector is still limited by local availability. Anything over 200-300km away from the plant starts to become uneconomic and environmentally less beneficial, due to the transport emissions.
In the future, biomass use will increase. However, for cultivated biomass production, there is a logical threshhold to use. It is not possible to replace all of the fuels with biomass. There simply is not enough space in the world. Earlier investigations on the surface requirements for cultivated biomass sufficient to cater 100% of the fuel requirements of a cement plant in Germany have shown that this strategy is not feasible - and it creates conflict with the eligible demands for nutrition as well.
As an equipment manufacturer, biomass has some awkward characteristics compared to municipal solid waste (MSW). It is often very moist. Even a piece of wood that feels dry to the touch can be 30 - 40% water by weight. This is even worse when we have food waste or meat and bone meal. Such materials require very long retention times, leading to a number of novel combustion technologies in recent years. Remember that we enjoy lighting a fire at home in part because we don’t have to put new logs on every few seconds.
IR: When people think biomass, they imagine homogeneous rice husks or peanut shells that are fairly benign. When I worked in China, the MSW used at Holcim’s plants included kitchen waste, with up to 50% moisture. Burning this is a problem in itself, but the handling and storage of this material is also a significant challenge. The leachate that comes from rotting vegetables and chicken carcasses is extremely corrosive. It eats through the steel structure of the building that’s supposed to be housing it. So, not all biomass is the same!
GC: Is AF, including biomass, just a stepping stone to a point where the cement industry relies on CO2 capture, lower clinker factor and other approaches to decarbonisation?
IR: AF is certainly an early answer to cement sector decarbonisation, and there is still a lot more that can be done. However, I would not characterise it as a stepping stone. Even if you decarbonise your cement plant entirely, you can still co-process difficult wastes. With biogenic AF, you might even be able to sequester CO2 using cement plants.
Sometimes, we hear that certain markets would be better off ‘skipping’ AF in cement production altogether and heading straight to CO2 capture. This ignores the waste-mitigation benefits of coprocessing. At the same time, cement producers are looking to reduce costs of cement production, in order to be able to free-up resources to run CO2 capture plants.
And remember that SO2 and NOx are also greenhouse gases. NOx emissions are generally lower when we use AF. Avoiding NOx is also important when it comes to ocean acidification and smog in cities.
GC: Is there a risk with falling waste volumes being a target - certainly in the EU - that the price of AF will rise to parity with fossil fuels in the coming decade, negating their cost advantage?
IR: I think that we are some way from that point. That said, investing in something that needs a reliable waste stream is inherently a risk if those waste streams are removed or redirected to other uses.
GC: Are CO2 trading schemes working when it comes to cement sector decarbonisation and AF?
MM: Between 2010 and 2013, I was involved in research by the European Cement Research Academy (ECRA), which showed that the journey to decarbonisation would start in earnest for most technologies above an ETS price of Euro100 - 120/t. We are now, slowly, getting there... The price to emit CO2 is fluctuating at Euro80 - 100/t. I am really keen on this solution, as it relies on market forces to reward the lowest emitters and put pressure on the
big emitters.
The ETS is the solution in the EU and similar approaches exist in other locations. Other countries will develop tax relief schemes that are well-tailored to their markets and others will find solutions that work in their specific situations. On the question of whether these schemes encourage AF use, the answer is less clear.
IR: On top of this, it is clear that many consumers - including local, state and national governments - are now demanding low-CO2 buildings. This means more low-CO2 concrete and low-CO2 cement.
GC: Is it likely that established plants, for example in the EU or North America, will be forced to close due to being unable to decarbonise economically?
MM: When you formulate the question like this, I agree that there is a clear threat to individual plants. I cannot tell you which plants are ‘at risk,’ but they will be those that are presented with logistical challenges. Those far from CO2 sequestration sites will be at greater risk. Those that cannot access sufficient AF / biofuel and / or supplementary cementitious materials will be at greater risk. Smaller plants, or those with limited space may also be threatened.
However, on the macro-scale, I simply don’t buy the proposal made by some that we can have a future without concrete production. There is simply no alternative to concrete for most constructions, and this means in turn, that the cement industry needs to be fully decarbonised... but it will continue to exist and prosper.
IR: The industry will change quite a lot over the next 10 years, especially in terms of reducing the overcapacity that it has been burdened with since the late 2000s. Overall, decarbonisation represents an opportunity for the sector as a whole to rationalise around the most efficient cement producers, not just in terms of production, but also distribution and product mix.
GC: What could be the cost implications of rationalisation?
MM: The cost of cement and concrete will rise, but the whole value-chain will become accustomed to higher prices. But these will be far less significant than detractors say. KHD is currently involved in an EU-funded study to evaluate down-stream price effects of higher cement production costs. This shows that, even if the cement price doubled, it would add just 2% to the overall cost of a major construction project. This is entirely bearable, especially given that prices have already risen significantly in the past 12-18 months. Decarbonisation is not going to kill the cement industry!
GC: Returning to AF, what is the likely trajectory of thermal substitution rates in the future?
MM: The VDZ Roadmap says that the sector must get to 85% AF in order to achieve the targets of the Paris Agreement. Other roadmaps propose comparable substituion rates. They are very ambitous targets! Even Europe, the leading region for AF in 2023, has an average of 40% AF. I think that reaching even this level globally by 2050 represents an enormous challenge.
IR: I think that AF rates might be even lower, around 25% globally. This is not to say that I am less optimistic than Matthias, I just think that AF will play a slightly smaller role in the transition to net zero. This is partly based on a potential lack of waste. While waste volumes are forecast to rise significantly, it isn’t guaranteed that this will be in the right place, at the right time, at the right cost and of the right quality. AF will be part of a patchwork solution to decarbonisation in which many solutions will have a valuable part to play.
GC: Thank you both for your time today.
IR/MM: It was great to talk!
About the interviewees
Ian Riley, CEO of the World Cement Association (WCA). Ian has 18 years’ experience in the cement sector, most recently as country manager for LafargeHolcim (now Holcim) in China in 2008 - 2019.
Matthias Mersmann, Chief Technology Officer at KHD Humboldt Wedag. Matthias has more than 25 years’ of cement sector experience, including an earlier stint KHD and at the modelling and simulation expert aixergee.
