Monday, 8 October 2018
Built Environment has massive impact on Natural Environment. Construction process and construction materials are major contributing factors. Construction materials interact with Embedded Energies Footprint resulting in Global Warming. The interaction between these three elements namely, construction materials, embedded energies footprint and global warming is a complex phenomenon and needs to be understood with clarity while arriving at a conclusion in assessing the exact nature of impact on natural environment. Currently the built environment is a huge consumer of depletable energy resources and is altering the planet’s environment in an irreversible way. Over the span of a building’s life the operational energy rather than the embodied energy of a building is the largest energy consumer.
Assessment of the impact of built environment on natural environment demands systematic analysis. Different types of Infrastructures like Residential and commercial buildings, transportation, roads, bridges, utilities, ports, and railways, private and public construction are essential due to urbanization and include every input and output of the life-cycle stages of the built environment namely; i) raw materials acquisition and processing, ii) manufacturing, iii) construction, iv) operation, v) maintenance, and vi) end-of-life option. However, the construction industry must not only comply with the ever-growing number of environmental legislations but go beyond compliance, proactively internalizing environmental performance in a way similar to that of other industries keeping Sustainable future as the goal.
Studies have shown that building construction with its four phases including Pre Construction, Construction, Operative, maintenance and Recycling phase is energy centric. With rapid urbanization and improved social status there is an increasing trend to consume more energy per capita. This is also reflected in modern construction trends and changing sky lines giving rise to new generation construction materials. Estimates show that about 80 percent of energy gets consumed during the operative and maintenance phase and remaining will get consumed in other phases like construction, demolition, heating, ventilation and Air conditioning phases.
In developing countries like India, infrastructural growth in general and construction industry in specific, demands considerable amount of energy. Recent survey shows industries alone consume about 45% of the total energy generated. Reduction of energy demand during construction phase is mainly due to embodied energy of construction materials. Due to extreme complexity involved in arriving at the exact quantification of energy consumed during the construction phase, reduction strategies are also complex. The entire process in the Life Cycle of a building gives rise to complex interaction phenomena between the Construction Materials, Embodied Energy footprint and Global warming.
To resolve this complexity there is a need to control and prudently use natural resources to shrink the carbon foot print. Meticulous planning of growth and proper understanding of interactions between the three attributes stated above play a vital role for societal sustainability.
Dr. Ajit Sabnis
Monday, 1 October 2018
WHAT CIVIL ENGINEERS SHOULD KNOW ABOUT CLIMATE CHANGE
- Dr. Ajit Sabnis
|Impact of Urbanisation|
Civil Engineers play a vital role in country’s economic development and they participate by way of conceptualizing a project, planning a project, estimation, prepare specifications and bill of quantities, designing, construction, monitoring, quality assurance, material selection, repairs and retrofitting and decommissioning. In a nutshell, they get involved in all the four stages of life cycle of a building.
Construction industry is extremely energy intensive and consume enormous amount of energy in every stage. In a building’s life span of about 60 years, operative and maintenance phase, has a large period and energy consumed during this period is obviously very high, but distributed over a period of 60 years. Energy consumption during this phase is more or less stream lined due to advancements in science and technology. We have efficient gadgets, home appliances, building automation to optimize energy consumption etc. This leaves behind, the construction phase of building’s life cycle, which is very critical from sustainability point of view. Greenhouse gas emissions contributing to global warming and climate change are phenomenal during the construction phase. These result in a phenomena called ‘Carbon Spike Phenomena (CSP)’ which occur in a short period of time as compared to operative and maintenance phase.
Global warming and Climate Change:
The two critical factors that call for immediate attention of all civil engineers and practitioners are: Climate change and Global warming. Climate change generally refers to all the various long term changes in our climate and Global warming refers to the observed warming of our planet due to greenhouse gasses emitted by human activities. Both these are interconnected and lead to one another. Role of civil engineers here is to assess the quantum of greenhouse gasses being emitted by the construction industry and make sustainability and sustainable development inclusive.
In the global energy consumption scenario, buildings, industries, transport and other sectors consume 31%, 27%, 28% and 14% respectively. In case of global greenhouse gas emission scenario, buildings, Industries, transport and other sectors emit 29%, 35%, 22% and 14% respectively. Out of this, 8 to 10% of the total CO2 emission is due to cement manufacturing process. This is mainly due to heating of kiln furnaces up to 1500 deg. C using enormous amount of fossil fuel. Due to this reason, laudably, many cement manufacturers are striving hard to optimize and refine their manufacturing processes. Greenhouse gas emission due to one tonne of manufactured cement varies from 0.65 to 1.0 tonne of CO2 equivalent.
Effect of Urbanisation:
About 70% of Indian population still lives in rural India and looking forward to migrate to towns and nearby cities for better living, better life style, better education, comfort etc. This migration puts enormous pressure on limited landmass, infrastructure available in cities. It is estimated that in the next forty years, India will experience one of the most dramatic transitions in the history of humankind. Population in cities will swell from current 300 million to 700 million-more than double. Mumbai-Nashik-Pune; Delhi region and greater Kolkata, will be the three largest urban concentrations in the world.
Urbanisation has two important relationships in respect of climate change:
Effect of climate change on urbanisation: One of the critical reasons for migration could also be due to climate induced impacts like floods, draughts, storms etc. Population that migrates due to these reasons, termed as ‘Environmental Refugees’, will face different set of problems in urban scenario and also pose complications in terms of housing and other facilities.
Effect of urbanisation on climate change: Other set of population migrating for better lifestyle, better education, comfortable life etc. will adapt and adopt new conditions of urban scenario and start contributing to greenhouse gas emission, adding to global warming.
Global warming and climate change have become existential problem for humanity. We are already experiencing their impacts. More and more dangerous climate impacts are inevitable as we march ahead into the future. Unrestricted GHG emissions will cause more warming and raise the average earth temperature by 5.5 to 6.5 deg. C and raise sea levels by 6 to 7 meters. Existing urbanisation models are not suitable and sustainable at Indian Scale and there are no off-the-shelf alternative algorithms available for India. We need to chart our own path for sustainable growth. Decarbonisation is the only way forward. This is where, Civil Engineers and their role, comes into picture.
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