EN­ERGY RE­COV­ERY: SMARTMANAGEMENT OFWASTE

Waste to en­ergy plants smart al­ter­na­tives for man­ag­ing waste, says David de Lara, Mid­dle East coun­try man­ager, ACCIONA In­dus­trial

Utilities Middle East - - FINAL WORD -

Man­ag­ing the thou­sands of tonnes of waste that towns and cities pro­duce ev­ery day is one of the most im­por­tant chal­lenges in or­der to pre­serve our en­vi­ron­ment.

In the case of solid waste, this is a triple chal­lenge: firstly to re­duce the quan­tity of this waste; se­condly, to re­use the high­est pos­si­ble per­cent­age of the waste pro­duced; and lastly to re­cy­cle any waste that can­not be reused. It is known as the “3R” rule, an ini­tia­tive that started in Ja­pan in 2002 and ad­vo­cated by the G8 Sum­mit in June 2004, to glob­ally pro­mote a so­ci­ety that re­cy­cles and uses re­sources and ma­te­ri­als ef­fi­ciently.

Land­fill has been the tra­di­tional method for treat­ing waste that was tech­ni­cally im­pos­si­ble to re­cy­cle, or for which the cost of re­cy­cling out­weighed the ben­e­fits. Ac­cord­ing to a re­cent study con­ducted by the Abu Dhabi Cen­tre for Waste Man­age­ment, the amount of waste in UAE av­er­aged 4.892 mil­lion tonnes per year.

Land­fill sites oc­cupy large tracts of land with a sig­nif­i­cant im­pact on the en­vi­ron­ment and the land­scape; while the bio­gas and the large amount of leachates they pro­duce (liq­uids that fil­ter into the sub­soil and can en­ter sur­face or ground­wa­ter) pose an ob­vi­ous risk of pol­lu­tion. Con­se­quently, new tech­nolo­gies have been de­vel­oped to pre­vent th­ese neg­a­tive im­pacts, which fo­cus on “en­ergy re­cov­ery” plants, also known as “Waste to En­ergy” plants or W2E.

Th­ese plants ther­mally treat the waste, through com­plete ox­i­da­tion, in or­der to re­lease the en­ergy con­tained in it, to pro­duce elec­tric­ity, heat or a com­bi­na­tion of the two. There are even new tech­nolo­gies in de­vel­op­ment that aim to pro­duce to com­mer­cially valu­able chem­i­cals from the waste.

W2E plants com­prise a se­ries of fa­cil­i­ties with spe­cific func­tions in or­der to con­vert waste into en­ergy via a multi-stage process. The waste ar­rives at the re­cep­tion and stor­age zone where it is weighed, un­loaded and stored. Since the plants op­er­ate 24 hours a day through­out the year, suf­fi­cient waste must be stored to en­sure un­in­ter­rupted op­er­a­tions at all times.

An­other fa­cil­ity, which is typ­i­cal within an en­ergy re­cov­ery plant, is the me­chan­i­cal waste clas­si­fi­ca­tion zone, where waste is clas­si­fied by size, den­sity or type of ma­te­rial.

Plants that re­ceive a sig­nif­i­cant amount of or­ganic waste also have a bi­o­log­i­cal treat­ment zone. Two types of pro­cesses are gen­er­ally used: com­post­ing to pro­duce com­post (or­ganic fer­tiliser) and anaer­o­bic di­ges­tion, which pro­duces a bio­gas that can be used for elec­tric­ity or can be washed to pro­duce nat­u­ral gas.

The waste is burnt in com­bus­tion fur­naces at tem­per­a­tures in ex­cess of 850º C in or­der to pre­vent diox­ins form­ing. The by-prod­uct of this com­bus­tion is slag, which can be used as a con­struc­tion ma­te­rial. The heat pro­duced by the fur­naces is con­verted into steam in the boil­ers, which are es­pe­cially de­signed to col­lect the ash gen­er­ated by the com­bus­tion. The steam drives the tur­bines to pro­duce elec­tric­ity or heat.

The un­ques­tion­able ben­e­fits of en­ergy re­cov­ery pro­cesses based on ur­ban waste have led to the re­gional ex­pan­sion of this ap­proach: The Abu Dhabi Na­tional En­ergy Com­pany, TAQA, de­vel­oped a fa­cil­ity near the sea port in Mus­saf­fah that has an an­nual ca­pac­ity of 1 mil­lion tonnes of solid waste which can be con­verted into 100 MW of en­ergy, suf­fi­cient to power around 20,000 Abu Dhabi homes.

Also, the Abu Dhabi Fund for De­vel­op­ment (ADFD) ap­proved a con­ces­sion­ary loan to Emi­rates Waste to En­ergy Com­pany (EWEC) for the de­vel­op­ment of the W2E fa­cil­ity in Shar­jah, UAE. Once the first phase of op­er­a­tions be­gins by 2020, the plant will be able to con­vert 2,000 met­ric tonnes of mu­nic­i­pal solid waste per day to pro­duce 60MW of power. The UAE aims to be one of the lead­ing coun­tries in the GCC to achieve the high­est rate of solid W2E man­age­ment.

ACCIONA In­dus­trial, one of the di­vi­sions of ACCIONA in­fra­struc­ture with pres­ence in the UAE since 2008 and in the re­gion since 1993, is driv­ing sus­tain­able de­vel­op­ment in the in­dus­trial sec­tor. We are fo­cus­ing our strat­egy on in­creas­ing our port­fo­lio of re­new­able en­ergy projects and work­ing to­wards clean and com­pet­i­tive tech­nol­ogy all over the world and the GCC re­gion.

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