Eskom pours mer­cury into air

Pretoria News Weekend - - NEWS - SHEREE BEGA

TWO of South Africa’s power stations – Lethabo and Ma­timba – were the high­est mer­cury-emit­ting coal power stations in 2015.

“When com­par­ing the amount of av­er­age mer­cury emit­ted per GWh of en­ergy sent out, Ma­timba and Lethabo are the top two ‘mer­cury per GWh’ emit­ting stations, then fol­lowed by Ken­dal, Matla and Tu­tuka.”

This is ac­cord­ing to a new study, Mer­cury Emis­sions from South Africa’s Coal-Fired Power Stations, writ­ten by two Eskom em­ploy­ees, which was pub­lished in the Clean Air jour­nal in Novem­ber last year.

The au­thors, Belinda Garn­ham and Kristy Langer­man, cal­cu­lated the amount of mer­cury emit­ted from each of Eskom’s coal fired power stations based on the amount of coal burnt and the mer­cury con­tent in the coal.

They re­vealed that be­tween 16.8 and 22.6 tons of mer­cury was emit­ted from Eskom’s coal-fired power stations in 2015.

Coal-fired elec­tric­ity gen­er­a­tion plants are the high­est con­trib­u­tors to mer­cury emis­sions in South Africa.

In their pa­per, the au­thors de­scribed how mer­cury was a per­sis­tent and toxic sub­stance that could be bio-ac­cu­mu­lated in the food chain. “Even though mer­cury is present in trace amounts, ex­po­sure in­creases as it ac­cu­mu­lates.”

Trace amounts of mer­cury can be found in coal, mostly com­bined with sul­phur, and can be re­leased into the at­mos­phere upon com­bus­tion.

The au­thors wrote how a ma­jor fac­tor af­fect­ing the amount of mer­cury emit­ted into the at­mos­phere, was the type and ef­fi­ciency of emis­sion abate­ment equip­ment at a power sta­tion.

“Eskom em­ploys par­tic­u­late emis­sion con­trol tech­nol­ogy at all its coal-fired power stations, and new power stations will also have sul­phur diox­ide abate­ment tech­nol­ogy. A co-ben­e­fi­cial re­duc­tion of mer­cury emis­sions ex­ists as a re­sult of emis­sion con­trol tech­nol­ogy.”

They also re­ported a slight de­crease in mer­cury emis­sions from 2011 to 2015, a di­rect link to the qual­ity of coal burnt since 2011, which has de­clined from an av­er­age of 17.9 tons in 2011 to an av­er­age of 16.8 tons in 2015.

“To­tal mer­cury emis­sions are ex­pected to be re­duced by be­tween 6% and 13% over the next 10 years from the im­ple­men­ta­tion of Eskom emis­sion/retrofit plan.”

The au­thors noted how there was lim­ited in­for­ma­tion on the sta­tus of mer­cury emis­sions in African coun­tries “although mer­cury emis­sions in Africa are in­creas­ing due to the rapid eco­nomic devel­op­ment in these coun­tries”.

South Africa signed the Mi­na­mata Con­ven­tion on Mer­cury on Oc­to­ber 2013; “how­ever, there is no leg­is­la­tion re­gard­ing mer­cury at present”.

“South Africa, be­ing the most in­dus­tri­alised coun­try on the con­ti­nent, also has lim­ited in­for­ma­tion on lev­els of mer­cury in re­sources, mer­cury in prod­ucts and mer­cury in emis­sions.

“It’s pre­vi­ously been es­ti­mated that emis­sions of mer­cury as a re­sult of power gen­er­a­tion ac­count for 77% of the to­tal mer­cury emit­ted in SA. This fig­ure, un­less mit­i­gated, is un­likely to de­crease sig­nif­i­cantly as coal is the main source of en­ergy and the de­mand for base en­ergy will in­crease with the in­crease in pop­u­la­tion.”

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