The world is abuzz with great emphasis on the use of natural materials birthed from the womb of Earth. These materials are visually enticing, naturally available to extract and most importantly, provide value to any space or use. However, not all of the natural materials are sustainable since it is the process and the length of its procurement can change how one views the material used.
Embodied Energy Problem | Natural materials
Each material or service created consumes energy and time in the process known as the embodied energy of the material. Most natural materials available around us are processed and put out in the world to use.
However, some natural materials consume copious amounts of energy for their extraction. The extraction of these materials involves a lot of labour and machinery. One of the prime examples of such a case is quarrying of stones like marble, sandstone, laterite and so on.
As per documentation titled “Environmental performance of building materials: Life Cycle Assessment of a typical Sicilian marble (Marzia Traverso & Gianfranco Rizzo & Matthias Finkbeiner, 2009),” average Sicilian marble consumes 2030 MJ per cubic meter. Despite consuming such voluminous energy, it also generates a large number of scraps or damaged blocks when compared to other rocks like sandstone, limestone etc. The energy expended upon these materials is undeniably high, impacts the environment and human health directly, just for the luxury of few.
Some materials on Earth have forever changed the way buildings are constructed now. Materials like cement, glass and many others in its process of creation make up for large CO2 emissions.
In a study conducted in 2016, the cement manufacturing industry generated 2.2 billion tonnes of CO2, accounting for 8% of global emissions. The interesting fact is that more than half of it arises during calcination, which occurs when the limestone is processed to make cement. The generation of CO2 further increases during construction, where it starts curing and generates more carbon dioxide.
Extraction of stones of any kind is dependent on its availability in Earth, which will sooner or later deplete off the face of Earth. Majority of resources available on Earth are bound to finish once used up. With no limestone, manufacturing cement is not possible.
Extraction of metals and metallurgy is also energy-intensive. Although the ability to reuse and recycle is better than earlier materials, the energy consumption for making it fit-for-use is massive. It takes 200 MJ to produce one kilogram of aluminium and 20 MJ for manufacturing one kilogram of steel. Whereas, it takes 5% of original embodied energy for recycling aluminium and 20% for recycling of steel, which is 10 MJ per kg aluminium and 4 MJ per kg steel. To put things into perspective, 1 litre of petrol generates 8.5 MJ of energy, covering a distance of 12.7 kilometres (7.9 miles). Its equivalent is burning nearly 5 litres of petrol to get one kilogram of aluminium. Without stating the numbers of carbon emissions, it is easy to assume the harmful impact it causes to us every day.
Alternatives | Natural materials
Almost every problem that came our way, we have had various solutions that can supplement our requirements while staying relevant to the urban context. Some materials have shown the capabilities to stand through the force of time and has done throughout human history, albeit with limitations. Whereas other materials hold tremendous potential, making it viable for execution in places of extreme weather condition. It happens to be that in this case, the solution is just around us.
Throughout human history, we have learnt well from our surroundings to use materials that are mouldable. Structures made from mud have been some of the most common occurrences throughout the world. Many in rural settings still practice mud architecture. In some cases, mud buildings were also an architectural icon which changed the perception of mud as material to something progressive, even genius. The best thing about rammed earth bricks and products is that it has an embodied energy of 0.05 MJ per kg (Source: EDGE Materials Embodied Energy Methodology & Results Report Version 2.2). In comparison to earlier materials, it is more logical to use rammed earth bricks or members for as many constructions as possible, especially for smaller projects.
For tensile members, bamboos are some of the best materials to opt. Well treated bamboo ply has an embodied energy of 22 MJ per kg ( a visual life cycle analysis by Michiel Kulik, TU Delft, 2013) which is slightly more than the value of recycled aluminium. But bamboo’s life cycle involves absorbing CO2 from nature and giving out oxygen, which is a redeeming quality for it. This list of materials also includes cross-laminated timber, where studies have proven that using CLT for construction utilises 46.5% less energy than concrete.
(Source – A Comparison of the Energy Saving and Carbon Reduction Performance between Reinforced Concrete and Cross-Laminated Timber Structures in Residential Buildings in the Severe Cold Region of China Haibo Guo, Ying Liu, Yiping Meng, Haoyu Huang, Cheng Sun and Yu Shao)
This article is a mere teaser to a world full of newer discoveries that can change the way we look at natural materials and make the right choices for our future generations. Sustainability is the journey to a world friendlier to our Mother Earth. With that in mind, we proceed.