- The numbers are wrong Archived Message
Posted by mack
on August 3, 2019, 12:30 pm, in reply to "Eco sustainability in Singapore"
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'[..]40,000 cu metres of concrete = 80,000 tonnes - each tonne equivalent to one tonne CO2 emissions.' I'm not defending this nonsense, but it might pay to get the facts straight. Each tonne of cement produced exhales ~0.9t of Co2 in the process. Cement is but a portion of concrete. It is mostly sand and aggregate with cement as the binding agent. The proportion of cement in 1t of concrete is ~0.15. Also, there are many types of concrete design for different applications. There are structural grade lightweight designs that can deliver m3 weight/density of ~1.4t per tonne and in some cases with good insulation quality. It's all in the choice of aggregate combined with mix ratio; whether entrained or entrapped air, water and cement content. In construction, if you want to have an accurate energy budget, then you need to account for the embodied energy in all the materials used and then the energy used to transport them to site and then the energy to actually put them together. You also need to account for a proportion of the embodied energy in the machinery used in the process as well as the fuel used to make them work. Yes, cement is a particularly heavy producer of Co2 in manufacture, but steel is worse at ~1.8 tonnes Co2 per tonne. Only then can you say, with some certainty, that we're ####ed if we carry on like that. |