Page 134 - Materials Chemistry, Second Edition

130 6. Life cycle thinking for sustainable development in the building industry

Steel
Particulate matter formation
Cement(nonconcrete use)
lonizing radiation Concrete
Metal depletion Wood
Brick
Photochemical oxidant...
Sand
Terrestrial ecotoxicity Gravel
Lime
Freshwater ecotoxicity
Glass
Marine ecotoxicity Ceramic tiles
Human toxicity
Marine eutrophication
Freshwater eutrophication
Fossil depletion
Terrestrial acidification
Climate change
0.00 0.10 0.20 0.30 0.40 0.50
FIG. 6.3 Environmental impact indicators associated with the production of building material used in 2015, using
the ReCiPe method, normalized to global indicators in 2000 (Nv, cf. Eq. 2) (Huang et al., 2018a).

are illustrated in Fig. 6.3 (the 13 highest of the 18 environmental indicators are presented).
Overall, the most severe environmental impacts are found to be human toxicity, fossil fuel
depletion, global warming, and metal depletion, emphasizing that greenhouse gas emissions
should not be the sole focus of research on environmental impacts of building materials.
In general, cement, steel, concrete, and bricks are the key contributors to the environmental
impacts of building materials. The contributions of some materials are due to their high use
(e.g., concrete, sand, gravel, and brick). Other materials have disproportionate contribution to
various impacts despite their comparatively low use by mass (cf. Fig. 6.2). Steel is the most
prominent example, but also lime, glass, and wood. Cement stands out as a material whose
high contribution to impacts is a combination of both high usage and high impacts per kg.
Tracing the sources of these key environmental indicators, human toxicity is primarily
caused by heavy metals (including arsenic, cadmium, zinc, lead, etc. (Huijbregts et al.,
2000)) emitted in the mining and manufacturing processes of cement, concrete, and bricks.
Fossil depletion is mainly caused by the large demand for coal, petroleum, electricity, and
natural gas in the manufacturing process of steel, brick, gravel, and cement. The largest con-
tributions to global warming come from steel and cement production and each account for
around 25% of total impact from building materials (Fig. 6.4).
Global warming burdens originate in the large energy consumption during the production
processes of steel, cement, and concrete (Guo et al., 2016; You et al., 2011; Dodoo et al., 2009)
and in the chemical reactions of clinker production for cement manufacture (Y€ ucel, 2013).
Thus, reducing the energy use and using less CO 2 -intensive energy sources in steel and lime
production are presumably the most effective approaches. Whereas in the case of concrete,
gravel, and bricks, the focus should be on reducing consumption or looking for substitute