Environment |
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Unprocessed rock is product extracted from a quarry after blasting but has not been subject to any cutting, grinding or heat treatment.Consequently, its production results in only 10% of the greenhouse gas emissions compared to competing products like brick, concrete and dimension stone.EnergyEmbodied energy (EE) is the amount of energy that's gone into making and delivering a product. The energy used to make building materials comes mostly from fossil fuels so there is a correlation between the EE of a product and the greenhouse gases emitted due to its production. The data used to make the graphs above come from Victoria University in Wellington in NZ and should be seen as estimates due to variations in the way EE is measured and variationsin the way products are made. The EE value for aggregate or crushed stone is used as a proxy for the EE of unprocessed rock rubble used in building dry-stone walls.
The right-hand graph shows materials which are used to build retaining walls, sea walls or river levees. Comparing MJ/kg is valid for these types of massive structures where the weight of solid material is needed for the structure to perform its design function. Concrete, brick and dimension stone are seen as low embodied energy building materials but it's clear that unprocessed rock is significantly lower on this scale. When comparing materials used to construct the walls of a building then MJ per square metre would be a better comparison. The EE values from Victoria University are in reasonable agreement with another very good resource, the Inventory of Carbon and Energy (ICE) from the University of Bath in the UK. The ICE document has a good introduction to the reasons why there is some error associated with the measurement of EE and the associated greenhouse gas emissions. |
