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.   

Green Economy in the Cement Industry

The trend of decarbonization, including the low carbon economy, has penetrated various sectors, including the cement industry. Cement is the most common human-made product in the world, consuming about 0.5 tons per person per year. The cement industry is also a significant contributor to greenhouse gases, reaching 21% (IPCC 2014), with these conditions making it one of the biggest contributors to climate change. And because the cement industry has a history as a major contributor to these greenhouse gas emissions, there are opportunities today to reduce emissions significantly through increasing efficiency and innovation in the industry.

Increasing energy efficiency in cement production will reduce the resulting carbon emissions. Even in the cement industry, the use of energy is also slowly starting to be used as renewable energy or alternative energy, including the use of RDF from municipal waste or household waste, which more or less reduces environmental pollution. While in the production aspect the use of additional materials originating from other industrial waste (circular economy) such as slag and fly ash or SCM (supplementary cementious materials) has also been widely used. The addition of these materials depends on the type of cement to be made and aims to reduce the use of clinker because clinker production requires high costs and produces CO2 gas as a result of calcination. 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. In addition, a number of countries also support the production and use of slag cement in order to support environmentally friendly products. The things above also indicate concern for the environment and sustainability is increasing.

In the cement industry, about 50% of emissions come from the calcination process itself, 40% from fuel for heating the kiln, and the remaining 10% from grinding and transport. Inside the calciner, a calcination process occurs, namely the decomposition of CaCO3 into CaO and CO2 and a little MgCO3 into MgO and CO2. Because the calcination reaction is endothermic, high heat is required, so it is equipped with a burner for burning coal utilizing tertiary air from the cooler and hot gas from the kiln. The release of CO2 due to the reaction in the calciner is a crucial environmental issue in the cement industry, the volume of CO2 gas from calcination is much greater than CO2 from burning fuel (coal) or 50% to 40%.

Various types of cement with different qualities often require specific SCM qualities as well. Under these conditions the review is not only general specifications but down to the chemistry of the material. For example slag from a steel plant or Granulated Blast Furnace Slag (GBFS) with a certain chemical content or fly ash but with a low alkaline content or slag from a nickel smelter not suitable for certain types of cement and so on. To obtain specific SCM such as slag and fly ash is closely related to the particular source of slag and fly ash, although in some cases it is possible to add certain materials to obtain the desired chemical composition.

And in the cement industry, emissions are not easily reduced. Emissions from processes cannot be reduced by optimizing or using only renewable energy or alternative energy. In the cement industry, when following the scenarios developed by the International Energy Agency (IEA) or the Intergovernmental Panel on Climate Change (IPCC), it is clear that to reach the limit of 2 C or even 1.5 C, cabon capture and storage / carbon capture and utilization (CCS / CCU) is needed. However, more is needed if the industry is to meet the ambitious goals set by the Paris agreement. The cement industry is particularly challenged by this target because carbon is generated by the energy used in the process and the calcination process itself. Even if energy-based emissions could be eliminated by switching to carbon-neutral fuels, those calcination process emissions would still be present and would require a carbon capture unit (CCS/CCU).

Europe has become a research center for carbon capture and storage (CCS) and carbon capture and utilization (CCU). From a number of carbon capture technologies, amine-based absorption (organic compounds and functional groups whose contents consist of lone-paired nitrogen atoms) is the most advanced carbon capture technology and has been implemented on a commercial scale. Carbon capture technology seems to play an important role in fighting climate change, especially in the cement industry.