If We Don’t Cut Emissions, Creating Carbon Sinks is Irrelevant

The concentration of CO2 in the atmosphere is already high so it must be reduced to save the earth. Efforts to reduce the concentration of CO2 in the atmosphere apparently cannot simply absorb CO2 from the atmosphere (carbon capture and storage). Maximizing the absorption of atmospheric CO2 but on the other hand CO2 emissions continue to increase, it will be very difficult (read: impossible) to reduce the concentration of CO2 in the atmosphere, let alone to a certain target agreed upon by the global community. So what makes sense is that CO2 emissions are not increased again so that the concentration does not increase further and existing CO2 is reduced to a certain level as targeted.

In practice, the production of wood chips and wood pellets as carbon neutral renewable fuels will complement each other with biochar. Wood chips and wood pellets do not add CO2 emissions and biochar absorbs CO2 as a carbon sink (carbon sequestration) or carbon negative. The application of biochar as part of carbon capture and storage (CCS) is currently developing the fastest compared to other CO2 reduction efforts (CDR / Carbon Dioxide Removal). Biochar leads in CDR credits in the voluntary carbon market (VCM), namely with more than 90% globally in 2023 as stated in the cdr.fyi database. From this data, it is estimated that at least 350 thousand tons of biochar have been produced globally in 2023 with an estimated 600,000 units or more of CDR credits (Carbon Credit).

And as in Europe, namely in 2023 there are a total of 48 new biochar plants, installed and operating, although 7 plants are closed, but a total of 41 biochar plants or an estimated total of 171 biochar plants are operating. And in 2024 there are an estimated 51 new biochar plants in Europe or in 2024 the total number of biochar plants is estimated to grow to more than 220 units. In terms of biochar volume, there is an estimated increase of 75,000 tons in 2023 and in 2024 the increase in production to 115,000 tons. Electricity production with 100% biomass fuel and equipped with carbon capture and storage (CCS) devices will also absorb CO2 or carbon negative, but this method is expensive and slow to develop. While biomass and coal cofiring because the cofiring ratio is small, efforts to reduce CO2 emissions are not too significant but cofiring is indeed the easiest entry point for using renewable energy in , especially in the energy or power generation sector (coal power plants). And in the end, creating a carbon sink, but the emission source is not reduced (cut), then it is the same as a lie or an irrelevant effort.

Green Economy in the Cement Industry Part 6: Clinker Substitution in Cement Plants

Substituting clinker with additives or SCM (Supplementary Cementious Material) plays a major role in efforts to reduce CO2 emissions in cement plants. This clinker substitution is ranked second after carbon capture or CCS (Carbon Capture and Storage) in efforts to reduce CO2 emissions or decarbonization in the cement industry. This is because the largest CO2 emissions in cement plants are not from combustion or related to fuel but in the calcination process. CCS technology is still expensive so its implementation still faces many obstacles, but clinker substitution is easier to do, so many cement plants are already doing it. 

In the cement industry, all fuel use and around 60% of electricity use is used for clinker production starting from grinding raw materials, fuel preparation and cement kilns. The higher the clinker to cement ratio, the higher the electricity and fuel used for each ton of cement produced. The clinker to cement ratio can be reduced if less clinker is used in cement production or more additional materials or SCM are added to the clinker. This also means that substituting clinker with SCM can significantly reduce energy use (electricity and fuel) for each ton of cement produced. 

China currently has the lowest clinker to cement ratio in the world, namely 0.58, while a number of areas in other countries have the highest ratio, up to 0.9. It can also be understood that China uses the highest portion of SCM compared to countries in the world. The most commonly used SCMs today are fly ash, ground granulated blast-furnace slag (GGBFS) and ground limestone. Meanwhile, other SCMs such as pozzolan and calcined clay have the potential to be used in the future.

Fly ash comes from by-products or waste from coal-fired power plants. Decarbonization of coal power plants is also continuing to be carried out, namely by cofiring coal with biomass, but this is being done in stages so that fly ash production will still be large for a while. Fly ash from coal-fired power plant waste is very useful in cement production because it reduces the clinker to cement ratio, thereby reducing energy requirements for cement production or in other words reducing the carbon footprint of cement products. Meanwhile, GGBFS comes from iron and steel plant waste. Not all iron and steel plants produce GGBFS waste, this is because it depends on the type of furnace used. Only plants that use blast furnaces - basic oxygen furnaces (BF - BOF) can produce GGBFS, while those that use electric arc furnaces (EAF) cannot. Around 70% of iron and steel plants in the world currently use the BF – BOF process so as to produce quite a lot of GGBFS, even in China more than 90% use this BF – BOF process. Decarbonization in the iron and steel industry is marked by the switch from BF – BOF to EAF which results in the availability of GGBFS. However, the process is running slowly and gradually, so that for a while the amount of GGBFS will be available and can reduce the carbon footprint of cement production.

The use of fly ash in cement production is usually limited to 25-35% for technical performance reasons. Meanwhile, GGBFS can be used in larger portions than fly ash or other SCM. Even European standards allow the use of GGBFS up to 95% but in practice it is lower. Other SCMs commonly used are pozzolan and calcined clay. Pozzolan comes from mining, namely from deposits in nature. Pozzolan requires drying and grinding before being used in cement production. The electricity used for crushing (grinding) pozzolan is also almost the same as crushing clinker. Calcined clay can also be used as a substitute for clinker. The initial use of calcined clay with a higher portion causes a decrease in the compressive strength of the cement product produced. However, further developments using a combination or mixture of calcined clay with limestone powder have the potential to substitute up to 50% clinker without affecting the quality of the cement. Calcined clay is produced from the clay calcination process which requires energy, but the energy required is much less than the energy for clinker production. It is predicted that in 2050 by the IEA (International Energy Agency) / WBCSD (World Business Council for Sustainable Development) cement production with the above combination of materials will reach more than 25% worldwide.

It turns out that the use of SCM is not only a substitute for clinker in cement production but also in concrete production. The use of SCM in concrete production is also no less than a substitute for clinker, even in the United States SCM is mostly added during concrete production and not during cement production. A study in the United States estimated that only 5% of SCM was added to cement production and around 13% to concrete production. But basically the addition of SCM to both cement production and concrete production has reduced the carbon footprint or is in line with decarbonization. The problem is that the lack of education regarding the benefits of SCM, especially in concrete production, is a barrier to increasing the use of SCM. Other factors such as the availability of SCM, price and its relation to cement and building quality are also similar barriers. The creation of new standards and codes related to increasing the use of blended cement with SCM and concrete production needs to be developed to transform the current market.

Biochar to Increase the Porosity of Damaged and Marginal Soils

Basically, porous materials will have large surface areas. The more pores, the greater the surface area of the material. Efforts to increase pores or expand the surface can be done in many ways depending on the goal. The type of pores also affects the total surface area and also the use or application of the material. For example, materials that have more micropores will have a larger surface area and have different specific uses than materials that are dominant with medium pores (mesopores) or large pores (macropores). Designing a material so that it is micropore, mesopore or macropore dominant can be done, namely by selecting raw materials and process technology, for example biochar produced from pyrolysis will produce a larger surface area compared to the initial unprocessed biomass.

In land related to use for agriculture or plant cultivation, the aspect of soil porosity or pores is an important aspect. This is mainly related to nutrient and water retention as well as soil aeration. Expanding soil pores will be very useful for improving soil quality so as to support the success of agriculture or plant cultivation. Soil that has more pore space will be able to store large amounts of water and nutrients too. Soil that has a high number of small (micropore) and medium (mesopore) pores will tend to hold water and nutrients more strongly than soil that has many large pores (macropore). And if there is evaporation or use of water by plants or a leaching process occurs in nutrients, then the large pores (macropores) left behind by the water and nutrients will follow the medium (mesopore) and  micropore.

Providing organic material in the form of compost to the soil is generally used to form more micropore spaces. The more micropore spaces that are formed, the more moisture the soil will have. Soil organic matter has more pores than soil mineral particles, which means that the surface area for absorption is also greater. Providing organic material in the form of compost, apart from increasing the number of pores or soil porosity, also reduces the volume weight. This organic material or compost is a source of energy for soil microbial activity, reduces soil volume, improves soil structure, aeration and air binding capacity. Soil with high total pores, such as clay, tends to have a low volume weight, while soil with low total pores, such as sandy soil (coarse texture), tends to have a high volume weight.

Apart from increasing total pores, adding compost also increases soil pH, namely in sandy soil and acidic soil, including entisol, ultisol and andisol and is able to reduce soil exchangeable Al. The increase in pH is due to the process of breaking down the compost. The results of this overhaul will produce basic cations which can increase the pH or release basic cations from the compost into the soil so that the soil is saturated with basic cations. The weathering or decomposition process of the compost will release alkaline cations which cause the soil pH to increase.

Soil organic C will also increase with the addition of compost and total N (nitrogen). The more organic matter added to the soil, the greater the increase in organic C in the soil. Compost from animal waste has the lowest C/N ratio compared to compost from plants. Organic materials that have a high lignin content will inhibit the speed of N mineralization and the C/N ratio will be high. In fact, further decomposition of organic matter is characterized by a low C/N ratio. Meanwhile, a high C/N ratio indicates that decomposition has not yet continued or has just started. In this process there is a decrease in carbon / C and an increase in nitrogen / N.

The need for compost on marginal land such as sandy land is also much greater, reaching almost twice as much as on ordinary or standard land. Meanwhile, the need for chemical fertilizer on marginal land is usually less than on normal/standard land. Ideally, using compost at optimal doses will be able to increase plant productivity and preserve the environment.

Unlike compost which will completely decompose, as a soil amendment, biochar can last hundreds of years in the soil. Biochar, which has a large surface area, also has many micropores which increase soil porosity, like compost. Pyrolysis conditions are important in determining the quality of biochar besides the biochar raw material itself. In rough textured soils such as sandy land, biochar will improve water and nutrient retention because its micro pores slow down its release (slow velocity). The quality of biochar is directly proportional to the efficacy of biochar treatment. A number of parameters related to the application of biochar for soil improvement/treatment are also similar to compost, including: soil carbon content and mineralization, soil micro-structural & aggregation, bioavailable nitrogen, and microbial activity & diversity. Almost all biochar is not fertilizer like compost, read more details here, so inoculation (charging) of biochar before application can be done by filling the biochar pores with water containing specific chemical elements or microbes. This will produce rapid positive effects compared to biochar alone. Apart from that, biochar is also used to reduce carbon dioxide (CO2) in the atmosphere as carbon sequestration. This is very much in line with the current problems of climate change and global warming.

Biochar is a heterogeneous substance rich in aromatic carbon and minerals. Biochar is produced from the pyrolysis process (a process where organic material is decomposed at temperatures between 350 to 1000 C with well-controlled conditions of minimal or no oxygen and is widely used for soil amendment). The carbon content for biochar must be above 50%, whereas if pyrolysis products of organic material with a carbon content of less than 50% are not included in the biochar category but are referred to as pyrogenic carbonaceous material (PCM). The organic carbon content of pyrolyzed char fluctuates between the range of 5% and 95%, depending on the raw material and temperature. process used. For example, the carbon content from pyrolysis of chicken manure is around 25%, while from wood it is around 85% and bone is less than 10%. When using mineral-rich raw materials such as sewage sludge or animal waste, the pyrolysis products will contain high ash so that the total pores are smaller.

Apart from that, biochar must also have a molar ratio of H/Corg of less than 0.7 and a molar ratio of O/Corg must be less than 0.4. The molar ratio of H/Corg is an indicator of its degree of carbonization (pyrolysis) and is therefore closely related to the stability of biochar, which is one of the most important characteristics of biochar. This ratio fluctuates depending on the type of biomass used and the conditions of the production process. A ratio value that exceeds 0.7 indicates non-pyrolytic char or inadequate pyrolysis process conditions. Meanwhile, the O/Corg ratio is also used to differentiate it from other carbon products. Specific surface area is also a measure of the quality and characteristics of biochar, and also a control value for the pyrolysis method used. Although a surface area of less than 150 m2/gram can be used in certain cases, it is preferred or preferred if it is more than 150 m2/gram.

With the characteristics above, compost and biochar as well as chemical fertilizers can be used together, even in the composting process biochar can also be added to reduce N organic released into the atmosphere. Apart from increasing the number of micro pores in the soil or increasing the total pores, the nutrients from compost and chemical fertilizers will also be released more slowly (slow release). How slow release the fertilizer can be designed depends on needs, for more details you can read here. When biochar is used properly, it can maximize harvest productivity, improve soil fertility and minimize environmental impacts. Four things need to be considered when applying biochar, namely the right source of biochar, the right location (right place), the right dose (right rate) and the right time. Not all types of soil and plants will produce increased yields from biochar applications, so it is important to know what type of soil produces increased productivity. A soil map can help to identify soil types that have the potential to provide benefits or advantages from the application of biochar. Farmers can consult with agricultural consultants or professionals in the field to help with the selection and application of biochar. 

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.