The 3R principle of reduce, reuse and recycle can be used to manage C & D waste. Understanding the sources of C & D waste can help minimise its quantity
The construction of infrastructure projects is rising at an alarming rate in most of the cities of Nepal. Some infrastructures are newly built, some are renovated, and some are built after demolition of old buildings and structures. The waste generated from these construction, renovation and demolition is simply known as construction and demolition (C & D) waste. C & D waste consists of heavy materials like concrete, bricks, metals, asphalts, plastics and woods.
Construction and demolition waste is directly related to the consumption of construction materials, and the waste produced is construction debris. Out of total construction expenditure, construction material comprises 50-60 per cent. More infrastructure activities mean more use of construction material and more waste. The estimation of construction waste either from new construction activity or renovation activity or from complete demolition of a building is a topic of research in the world.
As per the World Bank, C & D waste accounts for over 36 per cent of the total solid waste generated globally, and it is expected to reach 2.2 billion tons per year by 2025.
Different researchers have developed different models to quantify the amount of construction and demolition waste all over the world. Due to high demand of construction materials globally, natural resources are being depleted quickly, which has caused several environmental issues. More use of construction material means more greenhouse gas emission. It also contributes to increasing energy consumption.
In Nepal also, illegal or haphazard extraction of aggregates, stones and sand from the rivers has become a serious problem. It is often heard that sand and gravel mining is mostly illegal, and it is a matter of serious concern from a resource conservation perspective.
Waste from construction comes from a variety of sources. Studies indicate that the main causes of waste are connected to design, operations, material handling and procurement. A few examples of design-related factors are modifications to the design while construction is underway; a designer's ignorance of products; a lack of information in the construction drawings; the selection of inferior items; lack of use of appropriate construction technology; and mistakes in contract agreement documents.
Factors associated with operations include mistakes made my construction workers; carelessness; use of incorrect materials, thus requiring replacement; equipment malfunction; and weather and temperature-related damages. Material handling causes include materials misplaced on the job site, improper site storage and damage during transportation. Procurement-related factors include ordering errors and purchases that don't meet the necessary criteria.
The advanced countries have developed guidelines for the estimation and management of construction and demolition waste. But in developing countries like Nepal, this topic is less discussed. On one hand, the management of solid waste generated from households has been a problem in the major cities of Nepal. On the other hand, construction and demolition waste management is also becoming a problem in Nepal. It is often seen that construction and demolition waste is left in the open on roads or open spaces or illegally dumped at the site. This often causes accidents due to obstructions.
The 3R principle of reduce, reuse and recycle can be used to manage C & D waste. Understanding the sources of C & D waste can help minimise its quantity. As previously indicated, effective design, procurement, material handling and good operational strategies can help minimise the sources of C & D waste. Only use right quantities of materials and reduce the errors in construction as much as possible. If the structure can be saved with retrofitting techniques, the buildings should be preserved where possible rather than dismantling them.
Also, the C & D waste can be reused for various construction purposes if dismantled properly. Also recycled aggregates, bricks, concrete and rebars can be used for construction purpose. Use of recycled products is often more economical can buying new ones, and it gives the required strength.
As construction resources are limited on the earth, recycling improves resource scarcity and depletion of resources. In Nepal, the policy of establishing recycling plants to reuse C & D waste holds great potential. Various nations across the world, including our neighbouring country, India, have established various recycling plants for the better use of recycled products. Our country can also learn from international studies and practices.
People should be made aware about the use of recycled products in construction. Construction builders and contractors can make investments in recycling facilities to use construction and demolitions waste. There should be a cooperative stakeholder collaboration among the local communities, government agencies and construction firms to create and execute efficient waste management plans. This will not only reduce the pressure on landfill sites and prevent open dumping but also improve the aesthetic view of the city.
It will also reduce carbon emissions and energy consumption. Ultimately, it will help in resource conservation and sustainable construction.
Neupane and Koirala are with the Graduate School of Engineering, Mid-West University
