Green has become the new trendy colour for all industries, but painting the town green is not as easy as it sounds. Supplying the construction industry with sustainable solutions is not only based on delivering more green or environmentally-friendly products. A golden, or should a person say “green” thread needs to connect all the dots, from the manufacturing of the product to the supply chain and lastly the final product introduced to the market.
Walls & Roofs takes a closer look at the concrete and cement industry, and how this industry implements green principles.
Riding the green wave
According to the Cement and Concrete Institute (C&CI), it has become common practice to make an unsubstantiated or misleading claim about the environmental benefits of products. “The Cement and Concrete Institute recognises the importance of validating claims concerning the greenness of concrete with integrity and scientific evidence,” the institute states on its website.
To prove its point, the institute commissioned InEnergy Africa to determine the C02 emissions of the most commonly used constituent materials in concrete like cement, aggregate, water, fly-ash, ground-granulated blast-furnace slag and admixtures. The investigation also included aspects such as the processes of production of both precast and ready-mix concrete. InEnergy was also requested to develop a model to allow users to determine the CO2e (equivalent) from the production of a cubic meter of concrete using various materials. The C&CI says that developing the model was the next logical step in the South African cement manufacturer’s commitment to the responsible manufacturing of cement.
Manufacturers have been using waste tyres in kilns since 1990. The use of waste tyres in kilns reduces the percentage of CO2 per giga-joule of energy consumed by approximately 11%, while the burning of tyres results in curbs on ash emissions. “The cement producers have managed to boost production while decreasing the use of finite raw materials,” says the C&CI.
The C&CI says the industry has grown by leaps and bounds to become more environmentally conscious. The introduction of modern technology such as the fitting of bag house filters and electrostatic precipitators further reduced particulate emissions. “Other emissions are being reduced by the use of pre-calciners and pre-heaters. With this world-class technology in place, the producers have already reached 50% of the target set by the Department of Minerals and Energy, which calls for a 15% reduction of energy consumption by 2015.”
Green products becoming more popular
Sustainable cement products are becoming more popular with large clients such as SANRAL and Eskom. “These clients are moving towards durability specifications and away from only specifying strength in an attempt to achieve durable concrete,” the C&CI states.
According to the Institute, material specifications now play a critical role to reduce the embodied energy in a building. “With the adoption of the Green Star rating in South Africa, materials need to be factored in terms of measurable emissions, energy and finite material consumption,” says the C&CI. “Buildings must now be constructed with longer lifespans in mind with the emphasis on durability, and then retrofitting rather than demolishing.”
Adding green solutions to the mix
The C&CI says the use of admixtures in concrete is a sure way to adapt to sustainable principles. Admixtures result in a reduction of cement and water content in mixes. The use of cement extenders such as fly-ash, ground granulated blastfurnace slag (ggbs) and silica fumes together with admixtures have been standard practice in the concrete industry for many years. “Initially such techniques were only used to reduce costs, but manufactures soon found that it also has an effect on improving the durability and sustainability of concrete,” says the C&CI.
According to the Institute, precast products such as hollow-core slabs also reduce the volume of in-situ concrete substantially, while the use of the new generation of permeable concrete pavers form part of a responsible water management and safety programme by getting water off the surface of a road and letting it get back into the groundwater. “Self-compacting concrete in sustainable developments allows for architectural shapes and forms previously regarded as impossible.”
The Institute is also excited about new research that is producing exciting data on the re-absorption of carbon dioxide by hardened concrete. A Danish study has found that 50% of the volume of concrete will be “carbonated” over 70 years of any building’s service life. “This sponge effect makes concrete a more green choice than previously thought, emphasising how global sustainability can be achieved with concrete,” the C&CI adds.
Charlene Lamb, country communications manager of Lafarge Industries in South Africa, says the use of fly-ash creates a significant benefit to the environment because it conserves natural resources as landfill disposal and dumping is no longer required. “By adding fly-ash, the concrete has ultimately higher strength and is more durable because of its contribution to the chemical resistance of the properties of the materials used,” she adds.
She says fly-ash partially displaces the production of other concrete ingredients. “Fly-ash can replace cement and/or can be used as a sand replacement, especially in concrete products. These different applications result in a reduction of clinker-based material, therefore less greenhouse gas emissions.”
According to her, Lafarge uses fly-ash in many of its products as it is of great benefit to the manufacturing process as well as being more beneficial for the environment. “It can either be used in the raw mix preparation (providing valuable Al2O3) for clinker manufacturing or as a constituent in Portland fly-ash or Pozzolanic cements.”
The triple bottom line
The C&CI is convinced that sustainability is not only about embodied energy and CO2 emissions. “A balance needs to be achieved between economic, social and environmental factors. This concept is often referred to as the triple bottom line.”
According to the C&CI, concrete has a number of inherent characteristics that contribute towards achieving sustainability, whether it is for the benefit of the owner, the developer or the designer. “All things considered, concrete is virtually unequalled in combining its many unique qualities and attributes to make it the responsible choice in construction materials, balancing all the elements for increased sustainability.”
The C&CI says the energy-efficiency and thermal mass qualities of concrete also increases sustainability. “Case studies can already prove that the recyclability of concrete makes it a very attractive option as a construction material.”
Green agreement signed to support cement industry
The Association of Cementitious Material Producers (ACMP) has signed a partnership agreement with the Swiss-based World Business Council for Sustainable Development (WBCSD) for sustainable development cooperation in the cement industry. Harmke Immink, a director of Promethium Carbon said “The South African cement sector’s experience makes it well placed to contribute based on the historic GHG (Green House Gas) record keeping and calculations. Successful partnerships such as this promote transparency and build capacity for GHG accounting and reporting.
Dr Dhiraj Rama, executive director of the ACMP, said this reflects the mutual wish of companies in this industry to cooperate. “The cooperative agreement would ensure transfer of knowledge in both ways. It is noteworthy that South Africa is already one of the leaders in the world in terms of extending cement, thereby reducing the use of limestone, a non-renewable resource.”
Dr Rama says that, on the other hand, there is much experience internationally with regards to the use of alternative fuels and resources to substitute energy sources such as coal. He said the ACMP has just finalised the South African cement sector’s sustainability report, which provides a broad overview of trends for the past three years. “It also reflects the trends of CO2 emissions since 1999. We believe this report provides a platform to collaborate with international partners to inform our future response.”
He adds that, based on 2010 data, half the CO2 emissions in the cement industry came from raw material clinker while coal represents about 40% and electricity about 7%.
According to him, the industry has shown a decrease in greenhouse gas (GHG) emissions from 1990 to 2010, meaning less use of limestone, coal and electricity. The ratio of tons of CO2 produced to tons of clinker used has also shown a decline. “The overall benefit is that the major players in the cement industry have agreed to sustainable development in their industry, leading the way for other industries to follow, which will benefit both local manufacturers and consumers,” says Dr Rama.
Green Star SA rating
Francois Retief, technical manager at the Green Building Council of South Africa, says that within the Green Star SA rating system, projects are rewarded for significantly reducing the quantity of Portland cement used within their project. This can be achieved through the use of industrial waste products or oversized aggregate.
According to him, the manufacturing process of cement has a large carbon footprint. “We reward projects that use concrete mixes that incorporate industrial waste products like fly-ash or slag as a replacements for cement. Recycled aggregates that are used in place of natural aggregates also count in their favour in terms of achieving the Concrete credit in the Green Star SA rating system,” he states.
He also adds that the intent of the credit is for the project to be assessed, based on the impact it has on the environment in terms of embodied energy and resource depletion associated with concrete. “It all depends on the percentage reduction in cement achieved by substituting industrial waste products or oversized aggregate, and also the percentage of recycled aggregate used as opposed to natural aggregate.”
Reducing CO2 emissions
Lafarge, one of the industry leaders in manufacturing cement, is on board with integrating green principles in their manufacturing process. Lamb says they are an avid supporter of the preservation of the planet, sustainability and innovation.
According to Lamb, the company has been extending its cement products with fly-ash for several years “The term extension refers to using less clinker in the clinker-manufacturing process as it is a main contributor to greenhouse gasses because of the decarbonisation of limestone,” says Lamb. “Making less clinker also saves energy, which again reduces CO2 emissions with the most electricity in South Africa produced through the burning of fossil fuel.” In addition, Lafarge is committed to optimising its fossil fuel (coal) used to fire the kiln, which contributes to reduced emissions from the plant.
NPC CIMPOR based in Kwazulu Natal and who are part of the international cement group CIMPOR, fully supports the concept of sustainable development as a means of ensuring that economic, environmental and social concerns underlying its operations are treated on an equal footing. The group continuously works towards a sustainable future.
CIMPOR’s global focus on sustainability was clearly expressed in 1997 when they joined the World Business Council for Sustainable Development and in 1999 was one of the world’s ten largest cement companies that launched the Cement Sustainability Initiative. CIMPOR’s agenda for action in 2002, which identified six key areas of business activity for progress towards a more sustainable society, included climate protection and the management of CO₂ emissions, the responsible use of raw materials and fuels and emission monitoring and disclosure.
Locally NPC CIMPOR reduces energy consumption by developing the use of alternative fuels, improving energy-efficiency. The company also works towards reducing CO2 emissions by finding more and effective ways to use extenders. They also aim to reduce the use of non-renewable resources. Their overall commitment is illustrated when one reviews the CO2 emissions per ton of cement manufactured to see that NPC CIMPOR’s emissions are well below the industry average.
In 2010 the first load of waste tyres arrived at the Simuma (Port Shepstone) plant for the NPC-CIMPOR Alternative Fuel and Resource Programme, which aims to reduce the environmental impact of the production process while also providing a viable option for the disposal of waste tyres. The ability to source alternative fuels to burn, such as waste tyres, allows a reduction in the dependence on non-renewable resources such as coal.
Sibongile Mooko, general manager of marketing services at PPC, says the company has been measuring its carbon footprint since 1990 and has actively worked to improve the specific carbon footprint of its products by 16% from 1990 to 2010.
According to her, PPC’s investment and process innovation programmes include targets for improving electrical efficiency by 10% and thermal efficiency by 6%, resulting in a further 5% reduction of its carbon footprint by 2017.
She says that PPC also aims to source, either through partnerships or its own development, up to 10% of its electrical energy requirements from renewable and/or alternative sources by the end of 2017. “We are working hard to develop alternative fuel sources for the kilns driving our cement process. These fuel sources will reduce our dependence on coal and further reduce the specific carbon footprint of our products.”
Apart from pursuing an ongoing reduction in the carbon footprint of its products, PPC has also considered the downstream effect of its products on the carbon footprint. “PPC has recently enhanced its products’ performance characteristics, allowing for 15% less cement to be used in concrete, but achieving the same strength. This helps to lower the carbon footprint of concrete and makes it even more effective as an input material for green buildings.”
Finding a green solution
For some time Lafarge has been manufacturing a low emission cement product in Lichtenburg. This is an eco-friendly innovative cement mix that is a popular product choice in the marketplace. “Recently the company started to produce an even lower emission and a slightly more extended cement product at its grinding station in Randfontein,” says Lamb.
NPC CIMPOR’s eco-endorsement is proudly reflected on all packaging, documentation and advertising. This mark is an important reminder of the global and local programmes in place and the company’s progress towards a sustainable future. Look out for the branding on their packaging, “Manufactured using ecologically sustainable materials”, which clearly marks their green products.
Mooko says conventional cement and concrete, the most widely used construction materials in the world, are not likely to see a mass replacement with alternative construction materials in the foreseeable future. “Some of the groundbreaking materials, such as geo-polymers and carbon-negative ‘cements’, are produced on a very small scale and are still in the concept or experimental stage.” She says developments are more likely to be seen in innovative construction methods, recycling and energy-efficient design. “Cement product formulation is continuously evolving to enable durable construction that will enhance user energy-efficiency.”
Benefits of concrete as a green product
According to Mooko, the advantages of concrete for construction include the local availability of cement and aggregates, adequate engineering properties for a variety of structural applications, adaptability, versatility and a relative low cost. “Concrete has an excellent ecological profile compared with other materials of construction. Durability is a key attribute and concrete offers a viable solution for environmentally-responsible design.”
She says concrete has a high thermal mass, which provides natural insulation that can save energy associated with the heating and cooling of buildings. “Thermal mass acts as a heat sink, tempering the internal environment of a building by reducing and delaying the onset of peak temperatures. This keeps a building cooler in summer and warmer in winter,” she adds. According to her, light-coloured concrete paving can reduce summer temperatures in buildings, which is reducing the need for cooling. “The light-reflective properties can also save on the energy cost of lighting.”
Written by Nichelle Lemmer
Full acknowledgement and thanks are given to Lafarge, PPC, NPC CIMPOR, C&CI, and the Green Building Council of South Africa for the information given to write this article.