M e r c u r y E m i s s i on s

M e r c ur y a nd ot h e r e m i s s i ons f r om pow e r pl a nt s ha ve b e e n s t udi e d e xt e ns i ve l y by t he

U ni t e d S t a t e s E nvi r onm e nt a l P r ot e c t i on A ge n c y ( E P A )

. I n f a c t

, t hr ough t he f e d e r a l C l e a n A i r

A c t a m e ndm e nt s o f 199 0, C ongr e s s r e qui r e d E P A t o c onduc t a t h o r ough s t udy of a i r e m i s s i ons

, i nc l udi ng m e r c ur y, f r om pow e r pl a nt s

. E P A c o m pl e t e d t he s t udy a nd c onc l ude d t he f ol l ow i ng

r e ga r di ng m e r c ur y e m i s s i ons :

• “ M e r c u r y i n t he a i r i s a gl oba l pr obl e m

. W hi l e f os s i l f ue l

- f i r e d pow e r pl a nt s a r e t he

l a r ge s t r e m a i ni ng s our c e of hum a n

- ge ne r a t e d m e r c ur y e m i s s i ons i n t he U ni t e d S t a t e s

,

t he y c ont r i but e onl y a s m a l l a m ount ( a bout 1 pe r c e nt ) of t ot a l a nnua l m e r c ur y e m i s s i ons

w or l dw i de

. ” *

• “ R e c e nt e s t i m a t e s of a n nua l t ot a l gl oba l m e r c ur y e m i s s i ons f r om a l l s our c e s

- - bot h

na t ur a l a nd hum a n

- g e n e r a t e d

- - r a ng e f r om r oughl y 4,400 t o 7,500 t ons pe r ye a r

. H um a n

- c a us e d U .S

. m e r c ur y e m i s s i ons a r e e s t i m a t e d t o a c c ount f or r ough l y 3 pe r c e nt of

t he gl oba l t ot a l

, a nd U .S

. c oa l

- f i r e d pow e r pl a nt s a r e e s t i m a t e d t o a c c ount f or onl y a bout

1 pe r c e nt

. ” *

• “ T he U ni t e d S t a t e s i s l e a di ng a n e f f or t w i t hi n t he U ni t e d N a t i on s E nvi r onm e nt

P r ogr a m m e t o c r e a t e a pr ogr a m t ha t w oul d e s t a bl i s h pa r t ne r s hi ps de s i gne d t o he l p

de ve l opi ng c ount r i e s r e d uc e m e r c ur y e m i s s i ons .” *

• “ E P A ha s c onduc t e d e x t e ns i ve a na l y s e s on m e r c ur y e m i s s i ons f r om c oa l

- f i r e d pow e r

pl a nt s a nd s ubs e que nt r e gi ona l pa t t e r ns of de p os i t i on t o U

. S

. w a t e r s

. T hos e a na l ys e s

c onc l ude t ha t r e gi ona l t r a ns por t of m e r c ur y e m i s s i on f r om c oa l

- f i r e d po w e r pl a nt s i n t he

U .S . i s r e s pons i bl e f or

ve r y l i t t l e of t he m e r c ur y i n U .S . w a t e r s .” *

• “ U .S

. c oa l

- f i r e d pow e r pl a nt s e m i t m e r c ur y i n t hr e e di f f e r e nt f or

m s : oxi di z e d m e r c u r y ( l i ke l y t o de pos i t w i t hi n t he U .S .) ; e l e m e nt a l m e r c ur y, w hi c h t r a ve l s hundr e ds a nd

t hous a nds of m i l e s be f or e de pos i t i ng t o l a nd a nd w a t e r ; a nd m e r c ur y t ha t i s i n pa r t i c ul a t e

f or

m .” *

• “ [ A ] t m os phe r i c m e r c u r y f a l l s t o E a r t h t hr ough r a i n, s now a nd dr y de pos i t i on a nd e nt e r s

l a ke s

, r i ve r s a nd e s t ua r i e s

. O nc e t he r e

, i t c a n t r a ns f or

m i nt o, m e t hyl m e r c ur y, a nd c a n

bui l d up i n f i s h t i s s ue ” a nd “ A m e r i c a ns a r e e xpos e d t o m e t hyl m e r c ur y pr i m a r i l y by

e a t i ng c ont a m i na t e d f i s h. ” *

* A l l quot e s a r e f r om E P A ’ s w e bpa g e f ound a t ht t p: / / w w w .e pa .gov/ a i r / m e r c ur yr

ul e / ba s i c .ht m

L as B r i s as E n e r gy C e n t e r

T he L a s B r i s a s m a i n bo i l e r t e c hnol ogy i s i nhe r e nt l y l ow e r i n m e r c ur y e m i s s i ons t ha n

ot he r m or e c onve nt i ona l boi l e r de s i gns

. C i r c ul a t i ng F l ui d i z e d B e d ( C F B ) boi l e r s ha ve a l ow e r

e xha us t or f l ue ga s t e m pe r a t ur e

. T hi s l ow e r t e m p e r a t ur e c a us e s m e r c ur y c om p ounds t o c onde ns e

i n t he e xha us t s t r e a m a n d a l l ow s pot e nt i a l m e r c ur y e m i s s i ons t o be c a pt ur e d by s e ve r a l e m i s s i on

c ont r ol de vi c e s t ha t w i l l be “ dow ns t r e a m ” of t h e m a i n boi l e r s

.

A s a ge ne r a l m a t t e r

, m e r c ur y c a n be e m i t t e d i n f l ue ga s i n e i t he r a ga s e ou s or pa r t i c ul a t e

f or

m

. T he r e du c e d C F B f l ue ga s t e m pe r a t ur e ( de s c r i be d a bov e ) w i l l r e s ul t

, t hr oughc onde ns a t i on

, i n a gr e a t e r pr opor t i on of m e r c ur y i n pa r t i c l e f or

m a nd l e s s m e r c ur y a s a ga s

. T he

s c r ubbe r e m i s s i on c ont r o l s ys t e m w i l l a l s o s e r ve t o c onde ns e m e r c ur y c om pounds a nd, t oge t he r

,

t he s e f e a t ur e s o f t he L a s B r i s a s de s i gn w i l l c ons i de r a bl y e nha n c e m e r c ur y c o l l e c t i on by t he

f a

br i c f i l t e r p a r t i c ul a t e c ont r ol

. M e r c ur y i n t h e pa r t i c ul a t e f o r

m i s r e m ove d ve r y e f f i c i e nt l y ( upw a r ds of 99% ) by t he f a

br i c f i l t e r c ont r ol ( s om e t i m e s r e f e r r e d t o a s a “ ba ghous e ” ) pr opos e d

by L a s B r i s a s

.

F i na l l y, w hi l e a f a

br i c f i l t e r w i l l s e r ve t o a bs o r b s om e of t he ga s e ous e l e m e nt a l m e r c u r y,

L a s B r i s a s i s not s t oppi ng w i t h t hi s m e t hod of c ont r ol a nd i s pr opos i ng t he m os t a ggr e s s i ve

m e t hod of m e r c ur y c ont r ol c om m e r c i a l l y a va i l a bl e

. T he pr opos e d a c t i va t e d c a r bon i nj e c t i on

s ys t e m ( A C I ) w i l l de l i ve r pow de r e d a c t i va t e d c a r bon i nt o t he f l ue ga s t o a bs or b t he ga s e ous or

va por i z e d m e r c ur y f r a c t i on. A f t e r t he c a r bon a ds o r bs t he ga s e ous m e r c ur y f r om t he f l ue ga s

, i t i s

c a pt ur e d by t he hi ghl y e f f i c i e nt f a

b r i c f i l t e r w i t h t he ot he r pa r t i c ul a t e m a t t e r

.

L as B r i s as E m i s s i o n s M od e l i n g

W hi l e t he r e i s no f e de r a l or s t a t e a m bi e nt a i r qua l i t y s t a nda r d e s t a bl i s he d f or m e r c ur y, t he

T e xa s C om m i s s i on on E nvi r onm e nt a l Q ua l i t y ( T C E Q ) ha s e s t a bl i s he d a n E f f e c t s S c r e e ni ng

L e ve l ( E S L ) f or m e r c ur y t ha t i s ut i l i z e d i n e va l ua t i ng a ny pot e nt i a l i m pa c t f or a pr opos e d

f a c i l i t y. T C E Q e xpl a i ns t ha t “ E S L s

, e xpr e s s e d i n t e r m s of m i c r ogr a m pe r c ubi c m e t e r ( μ g/ m 3)

or

pa r t s p e r bi l l i on by vol um e ( ppbv) i n a i r

, a r e us e d t o e v a l ua t e pot e nt i a l f or

e f f e c t s t o oc c ur a s a

r e s ul t of e xpos ur e t o c onc e nt r a t i ons of c ons t i t ue nt s i n t he a i r ” a nd “ E S L s a r e ba s e d on da t a

c onc e r ni ng he a l t h e f f

e c t s

, odor / nui s a nc e pot e nt i a l

, a nd e f f

e c t s on ve ge t a t i on. ” T C E Q doe s

e s t a bl i s h E S L s a s a m bi e nt a i r qua l i t y s t a nda r d s but

, a c c or di ng t o t he a ge nc y pr ot oc ol s

, “ i f

pr e di c t e d o r m e a s ur e d a i r bor ne l e v e l s of a c ons t i t ue nt [ s uc h a s m e r c u r y] do not e xc e e d t he

s c r e e ni ng l e ve l

, a dv e r s e he a l t h or w e l f a r e w oul d not be e xpe c t e d t o r e s ul t ” a nd “ [ i ] f a m bi e nt

l e ve l s of c ons t i t ue nt s i n a i r e xc e e d t he s c r e e ni ng l e ve l

, i t doe s not ne c e s s a r i l y i ndi c a t e a pr obl e m

, but a m or e i n

- de pt h r e vi e w i s c onduc t e d. ”

L a s B r i s a s pr e l i m i na r y a i r di s pe r s i on m ode l i ng

, a t t he e m i s s i on r a t e s pr opos e d i n t he

pe r m i t a ppl i c a t i on i ndi c a t e s t ha t m e r c ur y e m i s s i ons f r om t he pr oj e c t w i l l be l e s s t ha n 1% of t h e

E S L

. T hus

, m e r c ur y e m i s s i ons f r om t he pr oj e c t w i l l not e ve n a ppr oa c h t he a m bi e nt

c onc e nt r a t i on c ons i de r e d by t he T C E Q t o w a r r a nt a c l os e r r e vi e w

.