‘How agricultural waste materials can reduce cost of building’
22 August 2022 | 2:50 am
The Raw Material Research and Development Council (RMRDC) has advocated the full utilization of various agricultural wastes and by-products as substitutes for imported materials to reduce
The Raw Material Research and Development Council (RMRDC) has advocated the full utilization of various agricultural wastes and by-products as substitutes for imported materials to reduce the cost of housing and boost the construction of infrastructures.
This was disclosed to journalists by the Director-General of the council, Prof. Hussaini Doko Ibrahim, recently.
The building and construction industry is one of the most important sectors of any given economy.
Globally, the value of the building and construction sector is expected to grow from $34 trillion in 2021 to $85.1 trillion in 2025.
In Nigeria, with the abundant availability of basic building materials, such as clay, laterite, stone, lime, agro-industrial waste, wood/timber, granite, and various types of sand, including glass sand in their natural state, the contribution of this sector to the GDP is expected to be higher and more significant.
However, the sector contributes only 30 per cent of the GDP, which is far less than 70 per cent recommended by the World Bank.
The World Bank has estimated that Nigeria would need to invest $3 trillion in infrastructure to reduce the deficit the country.
According to the National Integrated Infrastructure Master Plan (NIIMP), the Federal Government has initiated a 30-year infrastructure plan with a target date of 2043. The plan aims to bring Nigeria’s infrastructure stock to 70 per cent of GDP level.
As of now, construction projects in Nigeria are driven by both the government and private investors. The government provides key infrastructure such as roads, bridges, dredged waterways, ports, and railways via full government financing, multilateral development banks (MDBs), and bilateral creditors.
Due to the increasing cost of key infrastructure projects and dwindling government financing, the use of public-private partnerships PPPs as a tool to finance projects has also become imperative.
Likewise, the government has obtained Senate approval to secure about $22 billion in external loans for key infrastructure projects in the National Integrated Infrastructure Master Plan.
Based on the proposed share of investment across critical sectors in Nigeria, the housing sector is expected to account for 11 per cent of this fund, while transportation will account for 25 per cent of infrastructure investments.
With Nigeria’s population growing at a rate of over 2.5 per cent yearly, and an expected population of 400 million people by 2050, the NIIPM is expected to mitigate the current housing deficit of 17 million houses by building a minimum of 700,000 houses per year instead of the current 2,000 houses being built on an annual basis.
To facilitate and increase activities in the sector, financing and mortgage lending have been instituted in Nigeria as several financial institutions, including the Nigerian Mortgage Refinance Company, have increased their capacity in the affordable housing market through the provision of loans and advances of over $3.4 billion to customers.
However, the building and construction industry has several challenges.
Approximately 60 per cent of the total cost of a construction project is spent on materials. The majority of electrical items, roofing, windows, sanitary wares, pipeline, etc, are mostly imported with only a few notable construction materials manufacturers operating in the country.
Studies conducted by the Raw Materials Research and Development Council (RMRDC) showed that between 2010 and 2015, Nigeria spent N13.6 trillion on the importation of raw materials, especially building materials, that could have been sourced locally if some more rigorous work had been put into the country’s import substitution strategy.
Statistics also show that Nigeria, in 2016, spent about another N5.89 trillion on the importation of similar raw materials, thus bringing the total sum spent on the importation of raw materials and finished products into the country within the seven-year period to N19.5 trillion.
The costs of building materials have increased significantly. For example, a bag of cement, which is valued at Ν1,350.00 in 2006, goes as high as Ν1,850.00 in 2009 depicting about 37 per cent increment. The price rose to Ν2,000.00 in 2012.
This year 2022, the cost of cement is about N4000 per bag, which is about 100% increment, compared to 2012 prices. This may be due to the increasing cost of cement production which is driven by the cost of energy. Energy accounts for about 40% of the total cost. Each ton of cement requires about 60-130 kg of fuel oil or its equivalent, depending on the cement variety and process used.
One of the major ways the country can reduce the high cost of conventional construction materials such as concrete, cement and steel, is to promote the use of alternative construction materials.
At the global level, different solid wastes that are generated in large quantities, are now being used as a full or partial replacement for conventional materials in many developed countries.
For instance, ashes from industrial and agricultural wastes, such as fly ash and rice husk ash are used as a pozzolan to partially replace cement in concrete production.
Apart from a reduction in cost, this initiative is being promoted as the production of cement and steel has significant environmental consequences. Production of cement has contributed immensely to climate change and global warming as it accounts for approximately 7% of the anthropogenic CO2 emissions worldwide.
Among the SCMs are agricultural wastes such as rice husk ash (RHA) which contains amorphous silica similar to what is found in most natural pozzolanic materials. RHA concrete has shown superior performance over normal concrete.
Closely allied with this is sugar cane straw ash (SCSA) which also exhibits the same chemical and physical properties as the RHA. The performance of concrete containing a fraction of SCSA as a substitute for cement has been extensively investigated. Recycling SCSA in this form will be able to rescue the environment from the pollution caused by the huge amount of sugar cane straw produced annually.
Research also shows that the structural behaviour of reinforced palm kernel shell concrete (PKSC) has a lower density (24% of normal concrete), increased compressive strength (14% higher), with a lower modulus of elasticity and flexural strength which were 33% and 15% of normal weight concrete (NWC) respectively.
“In addition,” he said, “bamboo is used as reinforcing material. The compressive strength of bamboo is two times higher than that of concrete, while the tensile strength is close to that of steel. Bamboo fibre has shear stress that is higher than wood. Bamboo is considered one of the building materials that are very strong with a tensile strength of more and less than 28,000N per square inch, compared to steel which is 23,000 N per square inch.
“Furthermore, bamboo releases oxygen into the air, an ability that cannot be performed by industrial materials like steel, plastic and concrete. For these reasons, bamboo has been widely known as a sustainable building material.”
He said another non-conventional material that has not been explored maximally is tyre rubber. Studies have shown that the strength properties of concrete mixed with crumb rubber as a partial replacement for cement have good skid and abrasion resistance.
“Harnessing these abundant local non-conventional materials that are widely available in Nigeria will not only assist in mitigating the greenhouse emission, but it will also substantially reduce the cost of building materials,” he said.
Likewise, based on the research carried out at the Raw Materials Research and Development Council, limestone is now being used for the finishing of buildings in Nigeria.
The Council has also developed alkyd resin from local sources for the production of paints. One of the major problems constraining the utilization of locally available wood in the building and construction sector is that wood processors find it difficult to season wood to about 12 per cent moisture content or below.
This problem has largely been solved by the development of wood seasoning kilns by RMRDC in collaboration with Scientific Equipment Development Institute, Enugu and Falcon Nigeria Limited, also based in Enugu.