Year	Tonnes
1968	3.667
1981	7.334
1982	3.667
1983	3.667
1984	3.667
1985	3.667
1986	3.667
1987	3.667
1988	7.334
1989	7.334
1990	7.334
1991	7.334
1992	7.334
1993	11.001
1994	11.001
1995	11.001
1996	11.001
1997	11.001
1998	11.001
1999	11.001
2000	11.001
2001	11.001
2002	11.001
2003	11.001
2004	11.001
2005	11.001
2006	11.001
2007	11.001
2008	11.001
2009	11.001
2010	11.001
2011	11.001
2012	11.001
2013	11.001
2014	11.001