Westbury was one of six cement plants forced to fit selective non-catalytic reduction (SNCR) to meet tighter emissions limits on nitrogen oxides (NOX) and hydrogen chloride (HCl) (ENDS Report 370, pp 15-16 ).
Since 28 December 2005, cement plants that co-incinerate waste have to meet a NOX limit of 800 milligrams per cubic metre and an HCl limit of 10mg/m3. Wet process kilns - such as Westbury - have a derogation on NOX of 1,200mg/m3 until 1 January 2008.
Lafarge intended to use water cooling to reduce NOX emissions and sodium bicarbonate to reduce HCl, but both failed to meet the limits.
Lafarge could have avoided the situation by ceasing to burn tyres temporarily. But was not required to do so by the Agency because it would have increased the site’s NOX emissions from 1,400 to 2,000mg/m3.
Lafarge finished installing SNCR using urea injection and a calcium hydroxide-based HCl reduction system in December.
Agency inspector Tim Loveday said he is confident the system can achieve compliance, although monitoring is needed to demonstrate this.
The Agency said no other cement plants have experienced significant difficulties complying with the Directive.