Life cycle assessment of polymer composite blocks
Another test approach within natural polymer stabilized soil materials focuses on environmental issues. Energy in buildings can be categorized into two types: firstly the energy for the maintenance/servicing of a building during its useful life, namely operational energy (OE) and, secondly, the energy capital that goes into the production of a building using various building materials, named embodied energy (EE). The study of both types of energy consumption is required for the complete understanding of building energy needs. EE of buildings can vary over wide limits depending upon the choice of building materials and building techniques. Reinforced concrete walls, fired
Figure 4.7 (A) Different samples of SEM of wool fiber in the white soil mix (X370);
(B) SEM of wool fiber in the yellow soil mix (X430); (C) SEM of wool fiber in the black soil mix (X430); and (D) SEM of wool fiber in the red soil mix (X370).
clay brick masonry, concrete blocks masonry, bream and block slabs represent common conventional systems forming the main structure of buildings in Spain. Similar building systems can be found in many other developed and developing countries.
Alternative building technologies such as stabilized soil blocks can be used for minimizing the embodied energy of buildings (Venkatarama et al., 2003; Walker et al., 2000; Shukla et al., 2009). Generally, the materials used for the structure of buildings represent more than 50% of the embodied energy in the building (Asif et al., 2007).In this sense, the use of alternative materials, such as mortar/concrete blocks, stabilized soil blocks or fly-ashes, instead of materials with a high embodied energy such as reinforced concrete could save 20% of the cumulative energy over a 50-year life cycle (Huberman et al., 2008). In addition, recycling building materials (Thormark, 2002; Blengini 2009) is essential to reduce the embodied energy in the building. For instance, the use of recycled steel and aluminium confers savings of more than 50% in embodied energy (Chen et al., 2001).
In two recently published studies (Galan-Mann et al., 2015, 2016) a comparison of natural polymer stabilized soil blocks with other traditional building materials was performed. The first of these two works was analyzed through an ecodesign tool for new options for materials used in the construction of structural load-bearing walls (Gaian-Mann et al., 2015). The research aimed to examine the environmental performance of each material alternative assessed: fired clay brick masonry (FC), concrete block masonry (CB), reinforced concrete-based wall (RC), and stabilized soil block masonry (SS)—stabilized with natural fibers and natural polymers. These conventional and new materials with a low level of embodied energy, such as earth blocks, were evaluated from the point of view of their environmental consequences.
In all four materials studied, the LCA phases that most clearly determine the final results are manufacturing and construction. For a three storey building, in the manufacturing process, the embodied energy is between 38 and 51% of the total, and the CO2 emissions range from 44 to 72%. In the construction phase the embodied energy is between 25.5 and 31.8% and the CO2 emissions range from 16.5 to 32%. In terms of the distances (span) between walls, stabilized soil block masonry (SS) obtained much better overall LCA results than fired clay brick masonry (FC) or reinforced concrete wall (RC). When comparing LCA results between stabilized soil block masonry (SS) and concrete block masonry (CB) for all distances between the walls, SS scored worse than CB. The proportion between these values is increased as the building height is increased. The average embodied energy value calculated for SS doubled that obtained for CB. Comparing SS and CB for CO2 emissions showed that these are less relevant as the difference is only 12% SS to CB. The explanation lies in the difference between total wall mass, which is 2—3 times higher for SS than for CB. The difference in final LCA results increases when the span between walls extends. This establishes a relationship to be taken into account, when designing the building structure, between the type and characteristics of the building and the choice of structural material from the embodied energy and CO2 emissions perspective.
Accordingly, in the second of these two works, an environmental perspective comparing various conventional technologies for building walls to others that use new low-impact materials was followed (Galan-Mann et al., 2016). In this case not only embodied energy (EE) but operational energy (OE) was taken into account. In this study three different kinds of parameters in a single case study were implemented: the structural comparison, the material comparison, and the environmental comparison. The last variable included compares the results in two real climate conditions and real scenarios. In order to analyze the influence of the construction materials, several material options for the facade load-bearing walls were studied. The different building construction systems used are BW (Fired Brick Walls), CW (Concrete Block Walls), and SW (Stabilized Soil Walls). All the ACV calculations were done according to a 50-year lifespan of the building. In order to analyze the influence of the OE demand, the building was located in two different Spanish climates. These climates are named Location 1, corresponding to the Mediterranean climate, and location 2, corresponding to the inner continental areas of the peninsula.
If different phases are compared, i.e., both CO2 emissions and cumulative energy demand, the greatest differences among both climates take place in the Construction and Demolition Phases. The results showed the consumption data per m2 and year; they show remarkable differences between SW and BW values of total embodied energy. CO2 emissions for BW rise up to 1.6 times higher in cold climates. For warm climates BW exceeds 1.5 times the values of SW. The OE emissions of the building are higher than the ones associated with the EE for all three materials. Accordingly the OE emissions of the building represent more than 200% of the EE for the SW case. However, for BW OE represents only 130% of EE. Accordingly with these results it could be said that the energy consumed to build houses with brick walls in warm climates represents 165% of the energy invested to erect the same building with stabilized earth walls.