Jäätmepõletusel tekkivad tahked ja gaasilised heitmed ning nende mõju keskkonnale Iru jäätmeenergiaploki näitel

Antud lõputöö eesmärgiks oli anda ülevaade jäätmepõletusest Eestis uue ja ainulaadse Iru jäätmeenergiaploki näitel, mis kasutab kütuseks segaolmejäätmeid kuni 220 000 tonni aastas ja võimaldab katta umbes 6% Tallinna elektri- ning 23% pealinna soojuse tarbimisest. Autor püüdis jääda erapooletuks ning tuua välja nii negatiivsed kui ka positiivsed aspektid, kuna eesmärgiks oli seatud ülevaate tegemine ja olulise välja toomine, milleks on jäätmepõletusel tekkinud tahked ja gaasilised heitmed ning olelusringipõhine lähenemine keskkonnamõjudele SEI tehtud uuringu põhjal. Esimese osa moodustas jäätmepõletuse üldine ja põletusprotsessi tehnoloogiline kirjeldus. Teises osas olid vaatluse all tahked heitmed, täpsemalt kolde põhjatuhk, lendtuhk ja suitsugaaside pesujäägid. Vastavalt ohtlike ainete sisaldusele on koldetuhk käsitletav tavajäätmena, lendtuhk ja pesujääk ohtlike jäätmetena. Kuna olmejäätmed pole olemuselt uudsed ja neid on põletatud laias ulatuses ja pikka aega mujal Euroopas ning need ei erine koostiselt oluliselt erinevates kirjandusallikates tooduga, siis ei peaks seoses tuhkadega esinema halbu üllatusi. Kolde põhjatuhka hakatakse kasutama Tallinna Jäätmete Taaskasutuskeskuse prügila katmiseks, eelnevalt tuhka vanandatakse kahe kuu vältel ja eemaldatakse metallid, mis suunduvad taaskasutusse. Lendtuhka kogutakse koos suitsugaaside puhastusjääkidega ning viiakse tsisternveokitega Soome, millega antakse koostööpartnerile jäägid töötlemiseks ja käitlemiseks üle. Kolmandas peatükis käsitleti olulisemaid gaasilisi heitmeid ja nende ohtlikkust ja puhastusmeetodeid. Happeliste gaaside puhul kasutatakse poolkuiva puhastust lubjapiimaga, lämmastikuheitmete vähendamiseks katalüütilist protsessi ammoniaagiga. Viimases osas vaadeldi keskkonna seisukohalt olulisemaid olelusringipõhiseid uuringu tulemusi globaalse soojenemise, hapestumise, veekogude eutrofeerumise ning maapinnalähedase osooni tekke seisukohalt. Olelusringipõhise keskkonnamõjude hindamise uurimustööd analüüsides selgus, et kõikidest võimalikest jäätmete käitlemise alternatiividest on jäätmepõletuse stsenaariumi puhul negatiivsed keskkonnamõjud kõige väiksemad. Seda peamiselt prügilatesse ladestamise määra märgatavast vähenemisest ning kaudse mõju näol asendab jäätmetest toodetud elektri- ja soojusenergia fossiilsetest kütusest saadud energiat.

In the last few years waste incineration has been given a lot of attention, it has been widely covered also in local media because it will bring large changes in the municipal solid waste (MSW) management in Estonia. Public interest has been rather large and there has been wide range of opinions. Iru MSW incineration plant development is good example of how to explain to the public about how the technology works, and what are the possible dangers to the environment and to the health of the population. The Iru plant neighbouring community and other groups of interest were contacted and involved already in the early stages of the project development, mainly through the public hearings. In addition several Environmental Impact Assessment (EIA) studies were ordered to clarify the negative and positive impacts to the surrounding environment. A number of Estonian and English articles have been used as the basis of this thesis, also a set of EIA reports, studies and legislations. The topic was chosen mainly because of the two main reasons. Firstly because the author had a short term contact with the given Iru project, this contributed also to the interest to the waste to energy systems in overall. Secondly the author sees that there are none of such complex overviews written in Estonian and it would be a good chance to introduce the MSW incineration to the Estonian readers as well. The aim of this thesis was to give an overview about the municipal solid waste incineration in Estonia on the basis of the case study of the new Iru waste-to-energy (WtE) plant that will use 220 000 t of MSW per annum and will cover approximately 6% of the electricity and 23% of the heat needs of the capital city Tallinn. The author of this study tried to stay impartial and cover both positive and negative aspects of the produced solid and gaseous wastes and of the life cycle analysis done by Stockholm Environment Institute in Tallinn (SEI). The first chapter of the thesis gave an introductory overview of the MSW incineration technology that is used in the new Iru WtE plant. The second chapter concentrated on the solid wastes: bottom slag, fly ash and air pollution control (APC) residues. Taking into account the concentrations of the harmful chemical compounds and elements it was seen that the bottom slag can be treated as normal waste, but the fly ash and APC residues have to be treated as hazardous wastes. Taking into account that MSW incineration is widely used all across Europe and its composition is quite the same everywhere it can be stated that there should be no bad surprises with the management of the waste ashes also in Estonia. The bottom slag will be used to cover one of the landfills near Tallinn, before using it as a solid cover it will be treated in order to stabilize it chemically, also the metals will be removed for recycling. Fly ash will be collected together with the APC residues and transported in closed tanks to Finland for safe handling and final disposal. In the third chapter most important gaseous wastes, their harmful effects and cleaning methods were studied. Acid gases will be cleaned with semi dry method using lime slurry, nitrogen emissions will be reduced by the catalysis with ammonia. In the last (fifth) chapter an overview of the life cycle analysis was given by the aspects of global warming, acidification, water reservoir eutrophication and formation of the close surface ozone. From this study it was concluded that from all the alternative MSW management scenarios, the most beneficial to the environment would be the Iru MSW incineration. The main positive gain was given by the effect of lowering the rate of landfilling and indirect effect of the produced energy that will replace the more environmentally harmful fossil fuel based energy production.