Green Economy in the Cement Industry Part 8 : A Comprehensive Approach and the Role of Biomass

Efforts to reduce or lower CO2 in the cement industry continue to develop with various methods to achieve adequate targets. The global target is to achieve Net-Zero Emissions by 2050 while intermediate targets depend more specifically on the cement industry itself, for example, there is a cement industry that targets to reduce its emissions by 35% with a 1990 baseline in 2025 and then to more than 40% in 2030. This can practically be translated into a reduction in CO2 emissions in cement production from around 800 kg CO2/ton of cement, to 520 kg/ton of cement in 2025 and less than 475 kg/ton of cement in 2030. To achieve this target, the industry must create a roadmap that refers to the latest climate solutions in the cement industry, so that it is easier to achieve based on science (Science-Based Targets / SBT).

While the motivations for reducing CO2 emissions are similar across the world, progress is not uniform across regions. Europe is the fastest region to move forward due to its readiness, supported by a number of factors, including:
• Regulations that prioritize efficient resource use and promote a circular economy.
• Economic incentives to switch to cleaner fuels, which in many cases result in negative energy costs.
• Greater market acceptance of blended cement and consumer demand for low-carbon products.
• Significant government support for research and testing of cleaner technologies.
• Carbon emissions regulations, which result in a predictable carbon price.

Efforts to reduce CO2 emissions in cement plants directly or directly related to cement production are focused on three things, namely the use of alternative fuels or renewable energy or low-carbon fuels, reducing emissions from the calcination process and the use of cement additives (supplementary cementious material / SCM) or lowering clinker factor. While indirect efforts can be done by using electricity from renewable energy for the operation of the cement plants.

Technically or technologically in achieving the target of reducing CO2 emissions in the cement industry, the alternative energy sector or more specifically biomass fuel is in third place. This is because the largest source of emissions in cement plants or around 60% comes from the calcination process (clinker production), while combustion or related to fuel is only around 40%. This is so that carbon capture or CCS (Carbon Capture and Storage) in an effort to achieve emission targets is ranked first, then clinker substitution with additives or SCM (Supplementary Cementious Material) is in second place, and the use of alternative fuels including biomass is in third place. CCS technology is still expensive so that its implementation is still constrained, so that in practice it has not been done much but clinker substitution and the use of alternative energy including biomass are easier to do, so many cement plants have done it.

If efforts to become net zero emissions in coal-fired power plants can be done by converting their fuel to 100% biomass, then in cement plants it cannot be done by simply replacing the fuel with biomass because the main source of carbon emissions in cement plants is in their clinker production. So if a cement plant does this, the percentage of CO2 that can be reduced is only a maximum of 40%, meaning that CO2 emissions from the calcination process (clinker production) of 60% still occur. The use of clinker for cement production can be reduced so that CO2 emissions from clinker production can be reduced. That is why in cement plants the use of SCM for clinker substitution, the ratio or portion must also be increased. But of course it is impossible to reduce clinker production to zero or eliminate the calcination process and replace it entirely with SCM (lowering clinker factor) to reduce the 60% CO2 emissions.

This is so that the higher the ratio of clinker to cement produced (C/S), the greater the CO2 emissions produced and vice versa. China has the lowest ratio of clinker to cement (C/S) in the world today, which is 0.58, while a number of areas in other countries have the highest C/S ratio of up to 0.89, namely in the United States. While in Europe 0.77, then in India 0.68, in Latin America 0.71 and the global average is 0.76. It can also be understood that China uses SCM with the highest portion compared to countries in the world. That is why to achieve net zero emissions in cement plants, CCS (carbon capture and storage) equipment need to be added.

About CCS (carbon capture and storage) a number of innovations are being developed so that this technology is cheaper and easier to apply to cement plants. This also includes increasing the efficiency of CO2 capture, the use of new generation non-aqueous solvents, and cheaper modular technology. The transformation of captured CO2 into new marketable products is also the next focus.

The use of alternative fuels with high biomass content is highly recommended for cement plants to reduce CO2. But in reality, there are usually still a number of obstacles during its implementation so that it is even difficult to increase the ratio. These obstacles include the availability, quality and quantity of biomass waste, logistics and supporting infrastructure, market dynamics, the economics of the price of biomass waste-based fuels and a number of limiting technical factors related to the characteristics of the biomass fuel. A number of agricultural or plantation biomass wastes such as rice husks, palm kernel shells, cashew nut shells and olive seeds have also been used as biomass fuels in cement plants. Obtaining a supply of biomass fuel in sufficient volume, standard quality and continuous / sustainable is very important for cement plants to support the reduction of CO2 emissions. And basically there is no choice for cement plants to avoid climate problems, so what must be done is to respond to it with real action.  

Projections for Indonesia's Future Waste Management: Production of RDF and Biochar Enriched Compost

Photo taken from here

The MSW problem is a concern in a number of areas currently. This is because MSW, apart from being a serious environmental problem, also has an impact on social problems. The public is starting to become more aware of this MSW problem, especially for urban communities who no longer have land to pile up or burn their MSW and what's more, final disposal sites are no longer able to accommodate the MSW produced by these communities. Flooding, groundwater pollution, air pollution are some of these environmental problems which, if not addressed, will cause a number of serious environmental problems. Public awareness regarding waste should be getting better day by day, and various efforts should be made to overcome it.

One of the composting unit in Indonesia

Currently the central government and regional governments are working hard to overcome the waste problem namely this MSW. Despite hard efforts, generally only a small portion of the MSW can be handled and most of it is still accumulating and accumulating so that it continues to pile up. An example is the current MSW problem in Jakarta, the capital of Indonesia namely with an average daily waste volume of 7,500 tons/day, only around 1,000 tons per day can be processed. With the RDF production unit at Bantar Gebang TPST, with raw materials of 2,000 tons of waste per day originating from 1,000 tons of new MSW and 1,000 tons of old waste (landfill mining), approximately 700 tons/day of RDF is produced. So with only 1,000 tons/day of new waste that can be processed, that means only 13% of the total daily waste volume. Meanwhile, conditions in a number of regions in Indonesia are also almost the same.

 

Future MSW processing must be able to process the 100% of MSW or have zero waste. Apart from that, the MSW processing product must also have useful and economic value. One of them is large capacity RDF and compost production. Almost all organic waste can be composted, while non-organic waste, especially plastic, can be made into RDF. Other waste such as iron, glass, ceramics and metals are separated first so that it does not interfere with the RDF and compost production process. RDF is commonly used as an alternative fuel, especially in cement plants. However, with high chlorine content, the use of RDF in cement plants needs to be limited.

Sometimes the distance between RDF production and the cement plant makes transportation costs expensive and RDF products become uncompetitive. This means that RDF needs to be compressed into RDF pellets. By increasing the density of RDF into pellets, apart from saving transportation costs, it will also make handling, storage and use easier. Meanwhile, biochar can be added to compost to improve its quality. Biochar is added during the composting process and later there will be more nutrients contained in the compost. Biochar with its micro pores will be used as a place to store these nutrients. Apart from that, biochar is used as a carbon sink / carbon sequestration and can survive in the soil for hundreds or even thousands of years. This also has the potential to provide additional income from carbon credits. Biochar production by pyrolysis will also produce heat energy which can be used for drying waste in RDF production and pyrolysis of organic materials.

Green Economy in the Cement Industry Part 5 : Increasing Production and Reducing Emissions

Increasing production capacity but simultaneously reducing CO2 emissions (carbon dioxide, the dominant greenhouse gas) sounds contradictory / paradoxical. It is indeed like that in passing. However, with a decarbonization or CO2 removal (CDR) program, efforts to reduce emissions can be done while increasing cement production. How big the target of reducing emissions and increasing cement production will depend on how much decarbonization efforts are made. The greater the reduction in emissions, the more expensive it will usually be. This is why efforts to reduce emissions while increasing production must also be carried out in stages with certain strategies.

Cement plant is an industry that contributes to an increase in CO2 of more than 6% globally. However, there is something unique about this cement industry, namely that most of the CO2 emissions produced do not come from fuel use, but from the calcination process. The percentage of CO2 produced from the calcination process reaches around 60%, while from fuel use it is only around 40%. The fossil fuels commonly used in cement industries are coal and petcoke, both of which are the two fossil fuels that pollute the air the most. In fact, in a number of areas cement plants are the largest coal users. Cement plants close to oil refineries will use more petcoke.

Decarbonization programs or efforts to reduce CO2 emissions that can be carried out in cement plants include increasing energy efficiency, using clinker substitute materials, using alternative/renewable energy, and using CCUS (Carbon Capture Utilization and Storage). With these characteristics, total decarbonization in the cement industry cannot be carried out by using only the best efficiency technology or by simply replacing the fuel. Meanwhile, the use of clinker substitutes and CCUS is very important among other technologies to achieve near-zero emissions in cement production.

The best scenario for increasing production and reducing emissions can be done by using much higher energy efficiency improvements using commercially available technology, using more aggressive fuels to low carbon or even carbon neutral fuels, using higher rates of clinker substitute materials. and adopting a higher portion of commercially available CCUS technologies.

And it's worth noting that all suggested improvements in these best-case scenarios can be achieved by implementing technologies that are already commercially available and most of them should also be cost-effective. As for CCUS, while the technology is commercially available, implementation requires large investments that demand higher financial incentives or carbon prices. However, on the other hand, CCUS has the largest contribution to CO2 reduction, followed by the use of clinker substitutes and the switch to low-carbon or even carbon-neutral fuels. And the use of efficiency-enhancing technology has the smallest contribution to reducing CO2 emissions. This is mainly because process-related emissions from calcination account for around 60% of total CO2 emissions and are not related to energy use.

Green Economy in the Cement Industry Part 4

 

The cement plants apart from being an industry that utilizes or processes waste such as slag and fly ash so that a circular economy pattern is formed, is also an industry that destroys waste by using it as fuel. RDF (Refuse Derived Fuel) from municipal solid waste (MSW) is an alternative energy source that is widely used by the cement industry, especially in the manufacture of clinker. In addition to helping overcome environmental problems in the form of environmental pollution from city waste, the use of RDF  also helps reduce carbon emissions or is part of the effort to decarbonize. Related to addressing environmental problems, alternative fuels such as used tires which are chopped into tire chips and plastic are also often used. In addition to these alternative fuels, biomass waste such as agricultural waste and livestock waste are also being used. The biomass waste is 100% renewable fuel, so it is more compatible and environmentally friendly. The use of agricultural waste such as rice husk and camel manure is an example of the use of this biomass waste, for more details, read here.

By operating at high temperatures, the cement plant can function as an effective waste destroyer. In this regard, a DRE (Destruction Removal Efficiency) test is required which must meet a very high score or nearly 100% (99.9999%) to be able to carry out the waste destruction activity. The failure to reach this value is due to the insufficiently high temperature, so the consequence is that not all facilities in the cement plant are able to destroy or burn the waste, only burners in kilns that operate above 1200 degrees Celsius can do it, which technically is waste or alternative fuel also has its own feeding point.

Apart from the power failure, cement plant operations can stop due to blocking. The blocking clogs the cyclone on the preheater and calciner. The main cause of blocking occurs is due to the sulfur content, especially from coal and petcoke or alternative fuels that have a high sulfur content such as tires (tyre chips, the sulfur then reacts with the alkali to form compounds that easily stick to the walls of the cyclone or even the kiln. This means that the percentage of sulfur needs to be limited. And the second cause of blocking is chlorine, which also reacts with alkali so it easily sticks to the walls of the equipment, but the difference is blocking because chlorine occurs at a lower temperature, so it sticks to the top of the cyclone. This means that the percentage of chlorine also needs to be limited.

Based on the conditions mentioned above, the use of alternative fuels, especially from renewable materials, is important, moreover, renewable fuels such as biomass have very low sulfur content, as well as chlorine, but certain alternative fuels must be calculated carefully, especially sulfur and chlorine content. , so no blocking occurs. Meanwhile, fossil fuels such as coal and petcoke apart from being cons of decarbonization efforts also turn out to be the main cause of blocking. This means that the use of fossil fuels must be further reduced.

Green Economy in the Cement Industry Part 3

Fly ash is a byproduct or waste of coal power plants. Like slag, fly ash is also an additive or supplement (SCM/supplementary cementious material) in cement production. The difference is that fly ash is very fine so it doesn't need to be refined anymore and can be mixed directly with clinker and gypsum. Every ton of fly ash used prevents about 1 ton of carbon dioxide (CO2) from escaping into the atmosphere. This is in line with the green economy or decarbonization as a climate solution effort for the industry.

Unloading fly ash

As the same with slag, the chemical content of fly ash also influences the quality of the cement produced, for example certain regions or countries have requirements for grade 120 alumina in the slag. Cement with a certain quality can be designed with the use of these additives. In the current era, apart from technical factors such as mechanical strength or cement adhesion, microstructure, durability and so on, and economic factors, environmental friendly product factors are also a concern or have their own positive image. Circular economy in the form of utilizing waste from other industries to become raw materials for this industry, also occurs in the cement industry. And basically the cement industry besides being able to process waste is also a waste destroyer.

Green Economy in the Cement Industry Part 2

A number of cement plants can do production well by using only limestone and clay raw materials. This is because the material has fulfilled all the oxides needed in the manufacture of the clinker. The oxides needed are CaO (C), SiO2 (S), Al2O3 (A) and Fe2O3 (F). Limestone itself usually has a CaO (C) content of around 90% and 5% SiO2 (S). But the facts on the ground are that many cement  plants require additional materials to achieve the desired oxide composition or commonly called corrective materials. A number of these corrective materials are high grade limestone which has a CaO content of above 95% as C oxide correction, then silica sand for S oxide correction, then kaolin or bauxite for A oxide correction and iron ore or pyrite for F oxide correction.

So in general, currently the materials needed for the production of clinker are limestone, clay, silica sand and iron ore. In its development iron ore can be replaced with slag. The content of Fe2O3 (F) slag is lower than iron ore but the price is cheaper. The slag used mainly comes from the iron and steel industry, commonly known as GBFS or GGBFS. Slag is actually also an additive material that can be added with clinker and gypsum so that it becomes a product (slag) cement. In addition to other slag materials such as fly ash which are also commonly used as a additive, these two materials are commonly called cement supplement materials or SCM (supplementary cementious materials). Fly ash which is very fine does not need to be crushed anymore so it can be mixed directly with clinker and gypsum, while slag from iron or steel industry needs to be crushed again into GGBFS before being mixed with clinker and gypsum. For the need for these additives, in addition to physical aspects such as particle size, chemical aspects, namely slag chemistry and fly ash chemistry, are important parameters that need attention.

The use of SCM such as slag and fly ash above, will reduce the use, especially of fossil fuels. This is because SCM is added to clinker and gypsum so it does not require heat energy. Heat energy itself is needed in the manufacture of clinker, namely in the calciner and rotary kiln. For example, the manufacture of slag cement produces 38% less CO2 emissions than the process for the production of portland cement because less limestone is burned for the production of slag cement than is required for Portland cement. This heat energy currently still uses a lot of fossil fuels and is gradually starting to use renewable energy. Energy derived from biomass such as agricultural waste and animal manure is also starting to be used.

Production of Cow Dung Briquettes / Pellets as Fuel and Bioeconomy

The use of renewable energy is increasing along with global awareness of environmental and climate issues. Materials that used to be considered waste and polluted the environment, now with the concept of zero waste and circular economy, many have been converted into alternative energy or renewable energy. Large industries such as power plants, cement industry and so on have started to use this renewable energy in the framework of CO2 emission reduction or decarbonization programs. This decarbonization program is increasingly popular and is applied to various lines of life. 

As a real example is the cement industry in the UAE, namely Gulf Cement Co., which uses renewable energy from camel dung. From the results of operational trials it was found that every 2 tons of camel dung can replace 1 ton of coal. The use of animal dung as fuel is actually not a new thing for them, from ancestral stories cow dung has been used as heating or fuel, but many have not thought of camel dung. Gulf Cement Co currently uses 50 tons/day of camel dung as fuel. The UAE has a population of around 9000 camels for milk production, racing and beauty contests. Each camel produces 8 kg of manure per day, more or more than the farmer needs. Through a government program, camel breeders collect the camel dung at collection points. 

Cow dung has also been used as an energy source from the United States, Zimbabwe to China. In Indonesia this should also be done. With each cow producing an average of 15 kg of dung per day (about 2 times that of a camel), this is the same as the conditions in the UAE above, the volume of dung is more or more than what farmers need. The excess of this waste becomes an environmental problem and even has to be thrown into rivers and so on. Hundreds of tons of cow dung every day are not utilized in a number of areas in Indonesia, even though the dung can be used as fuel, especially when processed into briquettes or pellets (dried first). Compaction of cow dung into briquettes or pellets aims to obtain uniform size and shape, compactness, ease of storage and use, as well as saving on transportation costs. And to meet the needs of cement factory materials, such as briquettes / cow dung pellets are needed in large quantities, so large capacity production equipment is needed that works continuously. It is estimated that the need for pellets or briquettes is thousands to tens of thousands of tons every month.

In a cement plant there are 2 places that need heat energy: 1. calciner (where the calcination process occurs), 2. Rotary kiln (the heart of the cement factory, where the clinker is made). Renewable energy, such as briquettes or cow dung pellets, will usually be used in calciners with separate feeding points. Meanwhile, in rotary kilns that require higher heat, cement plants generally still use fossil fuels. The gradual use of renewable energy will reduce environmental pollution and accelerate the global decarbonization program. The cement plant itself can be said to be an industry that processes and destroys waste. This is because the cement plant can process waste such as slag and fly ash as an additive to the cement it produces - more details can be read here and also destroys waste, such as using cow dung as the fuel.