Page 254 - New Trends in Eco efficient and Recycled Concrete

222 New Trends in Eco-efficient and Recycled Concrete

Therefore, it is important to consider the possible trade-offs, that is, a shift in
burden from one life cycle stage to another or one type of impact to another
(Manfredi and Pant, 2011), between the different management options and future
application uses.
The trade-off in impacts and benefits surrounding different management options
for CDW have been thoroughly researched. Several attempts have been made to
calculate the environmental impact related to the CDW management. Craighill and
Powell (1999) applied a LCA methodology to evaluate the environmental, social
and economic impacts of the CDW management options. The authors concluded
that CDW reuse, especially on-site, had the lowest overall impact, followed by a
combination of reuse and recycling, with landfill being the least desirable option.
However, the results have been questioned because of some methodological short-
comings (Tiruta-Barna et al., 2007).
Blengini (2009) conducted a cradle-to-grave LCA of the end-of-life scenarios
after the demolition of a building. Recycling aggregates fostered 83% in energy
savings and an 82% reduction in greenhouse gas emissions. However, when consid-
ered within the life cycle, the environmental benefits dropped to reductions around
19% and 10% for energy use and greenhouse emissions, respectively. Later on,
Blengini and Garbarino (2010) assessed the environmental impact produced in the
recycling operations of inert materials in Italy. The authors justified the environ-
mental gains of the recycled aggregates by the avoided burdens of CDW landfilling
and natural aggregates transport supply. This environmental credit amounted to
14 kg CO 2-eq /t and 250 MJ/t energy powered by nonrenewable sources. Therefore,
all impact categories, except for the human toxicity potential, were lower for the
recycled materials. Nevertheless, the exclusion of the two mentioned environmental
credits still resulted in comparatively better results for the recycled aggregates in
impact categories such aquatic and terrestrial ecotoxicity, land occupation, global
warming, nonrenewable energy consumption and mineral extraction.
Ortiz et al. (2010) compared three Spanish CDW management settings (landfill-
ing, recycling and incineration) for two different streams: surplus of construction
materials (stone, metals, timber, plastic and others) and packaging residues (timber,
plastic and paper and cardboard). Because of the avoided impacts of the recovered
materials, recycling was the most environmentally friendly scenario in terms of
global warming and was preferable to landfilling or incineration except for the
impact categories covering terrestrial ecotoxicity, freshwater ecotoxicity and eutro-
phication. Despite higher global warming potential impacts than landfilling, inciner-
ation was identified as the second best CDW management option. Contrarily,
Mercante et al. (2012) observed for a Spanish scenario that the environmental sav-
ings lay with the recycling of plastics, metals, aggregates, cardboard and wood for
all the impact assessment categories except for the one related to global warming.
However, Mercante et al. (2012) acknowledge that a lot depends on the type of
recycling plant that is studied. It was also found that the processing of concrete has
a higher environmental impact than the processing of mixed CDW due to higher
power requirements in the grinding stage.