Strategies for decarbonising residential buildings in ahmedabad quantifying consumption of cement, steel & bricks & associated co₂ emissions by 2050

Abstract

The urban areas have received increasing attention as key areas that can accelerate and upscale climate action. Several Indian cities are witnessing a huge demand for residential buildings and consequently the demand for energy-intensive building materials. Adopting a bottom-up methodology, this study develops a methodological framework for estimating the material demand for cement, steel, and bricks from residential structures in Ahmedabad by 2050. The study adopts mixed methods. Estimated Material Demand (EMD) for 2050 is derived based on the total constructed floor area (CFA) calculated and the quantity of material consumption per sqm. The total constructed floor area is calculated based on the floor space estimation technique which includes shares considering housing types, unit sizes, and building heights. A mix of trend analysis using data from the last 50 years (1965-2015) and forecasts for various building typologies in Ahmedabad by 2050 has been used to estimate future floor space. The quantitative research was further strengthened by conducting semi-structured interviews with sixteen specialists, including building contractors, developers, and structural engineers. Three future scenarios are analysed until 2050 using AIM/Enduse, a bottom-up technology optimization model. Scenarios differ in their demand technology and energy assumptions. The study uses scenarios for analysing decarbonisation strategies for cement, steel, and bricks. Based on the IPCC AR6 framework, four decarbonisation strategies to quantify CO₂ emissions from building materials (cement, steel, and bricks) have been adopted for the study. The strategies considered for the study are Energy efficiency, clean technology, circular Economy, and sufficiency. Based on parameter assumption, these strategies are categorized into two broad categories: supply-side intervention which relies on energy efficiency and cleaner technologies, and demand-side interventions which consider parameters such as reduce and recycle strategies based on CE principles and sufficiency parameters. This study assesses three alternative future scenarios for India from 2015 through 2050 as follows: 1. Baseline Scenario (BLS). 2. Energy Efficiency and Clean Technology Scenario (EECTS). 3. Circular Economy and Sufficiency Scenario (CESS). BLS scenario is taken as the reference scenario which follows the updated India’s Nationally Determined Contribution (NDC) and targets to reduce CO2 emission. Energy Efficiency and Clean Technology (EECTS) aims to reduce climate impacts through responsible production as the primary focus by optimizing the use of low-carbon fuel and technology. AIM End-use model which is an optimisation simulation model is been used for the study to understand and forecast the potential GHG emission reduction. Circular Economy and Sufficiency Scenario (CESS) focuses on reducing demand strategies and the use of recycled products and reducing the demand for materials manufactured from virgin minerals. The primary goal of this scenario is to reduce the use of conventional materials to combat resource scarcity against huge material demand to cater residential sector in the long term, where it is assumed that 70% of the projected units are yet to be built.Based on estimated cement, steel, and bricks demand for Ahmedabad, CO₂ emissions by 2050 are estimated to reach 102.2 million tons for cement, 52.7 million tons for steel, and 23.2 million tons for bricks. Analysis shows that both scenarios have high mitigation potential and would contribute significantly to CO₂ emission reductions. The study highlights a change in residential building types with a decline in single-storey independent houses to a more multi-storey apartment by 2050. The study quantifies material consumption at the city level. If current trends continue, 5.32 million new housing units will be needed by 2050 resulting in a demand of 45.62 million tons of cement, 13.32 million tons of steel, and 150.5 million tons of bricks. The production of estimated material demand would result in 177.8 MtCO2 from cement, steel, and bricks. The material impact as a result of growing affluence clearly comes out in the results of this study. Such a methodology could also be replicated in other contexts. The results from the study would be helpful to government authorities and policymakers in fostering resource efficiency and advocate responsible production and consumption of building materials. The results of the study call for a fundamental shift in the current development pattern.