Koolstofdioxide als bron voor de volgende generatie brandstoffen: een nieuw perspectief op het klimaatprobleem
Dinsdag 8 november 2016, president Donald Trump wordt ingehuldigd tot 58ste president van de Verenigde Staten in New York city. De benoeming van Trump betekende niet enkel een verandering voor het Amerikaanse politieke landschap, maar luidde ook een nieuw tijdperk in voor het globale milieubeleid. Waar zijn voorganger Barack Obama weergaloos inzette op het gebruik van hernieuwbare bronnen voor de energieproductie maakt het beleid van Trump een ferme ommezwaai: méér fossiele brandstoffen en minder milieubudget. De boodschap is duidelijk: “… we could use a little bit of that good old Global Warming …” (Trump, 2017). Maar wat betekent deze beslissing voor onze luchtkwaliteit en het klimaatprobleem, en welke rol speelt koolstofdioxide (CO2) hierin?
Global Warming en koolstofdioxide: Fake news of niet?
Vandaag de dag is iedereen wel bekend met de hot, letterlijk, topic “global warming”. Door de verbranding van aardgas, steenkool en olie voor de energieproductie komen schadelijke verbrandingsgassen in de lucht terecht. Hierdoor vermindert de luchtkwaliteit en neemt de temperatuur op aarde toe. Deze temperatuurstijging zorgt er niet enkel voor dat de ijskappen in de Noordpool smelten, maar zorgt ook voor lange periodes van droogte, waardoor men in sommige werelddelen al in hongersnood leeft. Het is ook de reden dat je cornetto ijsje in de zomer rapper smelt. Het is dus dichter bij je bed dan je denkt. De grootste boosdoener in dit verhaal? CO2.
Maar CO2 is lang niet het enige gas dat vrijkomt bij de verbranding van fossiele brandstoffen, dus waarom is men hier zo op gefocust? De reden hangt verbazingwekkend genoeg samen met de hoeveelheid waterdamp in onze atmosfeer. Alle gassen in onze atmosfeer nemen namelijk straling op, en alle straling bevat energie. Net zoals je eten opwarmt van de stralen van je microgolf, warmen de gassen in onze atmosfeer door hetzelfde proces op. Waterdamp is het dominante gas in onze atmosfeer, en neemt ook het meeste van de straling op.
Bepaalde types straling worden echter niet opgenomen door waterdamp, en hebben dus geen invloed op de temperatuur van onze planeet. Waar waterdamp deze types straling doorlaat, neemt CO2 deze straling juist op. Hierdoor wordt extra straling omgezet in warmte waardoor onze planeet onnodig opwarmt. Door de voortdurend groeiende wereldbevolking, digitalisering van onze wereld, en ontwikkeling van derdewereldlanden neemt de energievraag exponentieel toe. Er worden dus veel meer fossiele brandstoffen verbrand, waardoor er ook alsmaar meer CO2 in onze lucht terecht komt. Hierdoor blijft de temperatuur dus toenemen.
Om op een duurzame manier aan de stijgende energievraag trachten te voldoen, zet men de laatste jaren ferm in op hernieuwbare energiebronnen zoals wind- en zonne-energie. Deze vormen van energieopwekking gebruiken de zon en de wind om energie op te wekken zonder hiervoor fossiele brandstoffen te verbruiken. De oplossing is echter niet zo eenvoudig: de productie van windturbines en zonnepanelen is namelijk nog steeds afhankelijk van fossiele brandstoffen. Dikwijls komen bij de productie ervan zelfs schadelijke gassen vrij. Daarbovenop vermindert de hoeveelheid CO2 in onze atmosfeer hierdoor niet, waardoor het klimaatprobleem dus ook niet weggaat.
Als we echt een halt willen toeroepen aan dit klimaatprobleem, en ook indirect het energieprobleem, dan moeten er twee dingen gebeuren : (1) het teveel aan CO2 in onze atmosfeer moet verminderen, en (2) we moeten alternatieve energiebronnen voorzien die geen extra CO2 in onze lucht uitstoten.
Van vijand naar vriend : de toekomst van koolstofdioxide in de energiesector
De aandachtige lezer merkt het dus al op : CO2 is de vijand in dit verhaal. Maar wat als we dit probleem vanuit een ander perspectief bekijken. Wat als we stoppen met CO2 als de vijand te zien, maar in de plaats deze als oplossing behandelen. CO2 kan namelijk dienen als een koolstofbron voor de productie van alternatieve brandstoffen. Het omzetten van CO2 in alternatieve brandstoffen kan dus in één klap het klimaat- en het energieprobleem oplossen.
Waarom wordt dit dan nog niet gedaan vraag je je nu af? De reden hiervoor is simpel: CO2 is een uiterst stabiele molecule. Het omzetten van dit gas in alternatieve brandstoffen vereist gewoonweg meer energie dan men ooit uit deze brandstoffen kan winnen. Gelukkig voor ons klimaat bestaan er katalysatoren. Dit zijn molecules die door hun unieke chemische samenstelling de energie van een reactie drastisch kunnen verlagen. Door het gebruik van de juiste soort katalysatoren is het dus wel mogelijk om CO2 efficiënt om te zetten in nieuwe brandstoffen.
Om dit te bereiken moet men begrijpen hoe dit proces in zijn werk gaat. CO2 kan namelijk niet door elk type katalysator omgezet worden. Door de samenstelling van de katalysator echter aan te passen, en hiermee de interactie met CO2, kan men een maximale omzetting creëren. Strontium titanaat blijkt door zijn gunstige samenstelling een beloftevolle kandidaat te zijn, en hierop is mijn onderzoek dan ook gefocust. De uitdaging bestaat er vervolgens in om met zo min mogelijk katalysatoren, zoveel mogelijk CO2 om te zetten. Dit kan men realiseren door de katalysatoren zeer klein te maken, tot een miljoen keer kleiner dan een zandkorrel. Dit noemt men nanokatalysatoren. De reden waarom we deze katalysatoren zo klein maken heeft te maken met het aantal reacties die tegelijk kunnen doorgaan. Indien men een bus volstopt met voetballen, en een tweede bus vol met pingpongballen, dan zal de tweede bus veel meer ballen in één keer kunnen vervoeren. Hetzelfde geldt voor de katalysatoren. Door deze materialen zodanig klein te maken kunnen er veel meer reacties tegelijkertijd doorgaan, waardoor de omzetting dus enorm toeneemt.
Nanokatalysatoren kunnen dus een oplossing bieden voor ons klimaat- en energieprobleem. De eindstreep is echter nog niet in zicht. Vooraleer we CO2 efficiënt kunnen omzetten, dient er nog heel wat onderzoek verricht te worden. Waar mijn onderzoek al een goede stap in de juiste richting is. Het is bizar om te denken dat deze kleine katalysatoren een dergelijk grote impact kunnen hebben op het klimaat- en energieprobleem. Zoals Neil Armstrong (1969) het ooit zei voor de maanlanding, kan het misschien ook ooit voor nanokatalysatoren gezegd worden: “ … one small step for man, one giant leap for mankind”.
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