Cement manufacture causes environmental impacts at all stages of the process.
All cement, whether slag cement or Portland cement, starts off as solid chunks of material which are then ground into a fine powder.
Slag cement is called “green” for one reason only: the solid base material is a recycled industrial waste product of the steel smelting process. As such, slag cement is not fired in ultra high temperature kilns, which is the process for Portland cement modules. The high temperature kilns are a key producer of greenhouse gases on a global scale hence the claim that slag cement is “green.”
But to say that slag cement is less polluting than Portland cement does not make it “green.” First, slag is full of heavy metals and chemicals from the steel smelting process. Second, the dust from storing and grinding cement is known to harm and even kill people, animals and plants. Third, the plan to ship slag and clinker halfway across the world requires dirty diesel-powered ships, both wasteful and polluting.
TOXINS — Slag cement contain toxins from the steel smelting process such as hexavalent chromium, the toxin that poisoned Hinckley, CA. Of further concern for Vallejo residents, the slag that would be shipped to Vallejo would not go through any screening process, so it could contain any number of harmful heavy metals and chemicals, potentially even radioactive waste. Orcem plans to ship from China, which is notoriously lax in its industrial processes, and Japan, which has been found guilty of improperly disposing of Fukushima radioactive waste. Who is to say what would arrive in Vallejo?
HARMFUL DUST — The dust from storing slag and Portland clinker, and from the cement grinding process is harmful to humans, animal and plant life.
DIESEL POLLUTION — Shipping slag and Portland clinker halfway around the world to grind it here is not green. The diesel fuel used for ocean-going vessels coming in and trucks going out is dirty…
It should be noted that Orcem plans to mill Portland cement in addition to slag cement – a fact which they try to evade by saying they would only do so based on “market conditions.” Given that Stockton has a slag cement plant farther along in the process, chances are the local cement market is competitive. So, for all their claims to be interested in “green” cement, Orcem also wants to produce the dirty Portland cement it is supposed to replace. chances are the local cement market will be highly competitive. For all their claims to only manufacture “green” cement, Orcem can also produce standard Portland cement. Orcem’s cement is a wolf in green clothing. It’s not green.