Hiilineutraali polttoaine

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Hiilineutraali polttoaine tarkoittaa sellaista polttoainetta, jonka tuotanto ja käyttö yhdessä eivät lisää ilmakehän hiilidioksidia, samoin kuin hiilineutraalius yleensä tarkoittaa mitä tahansa järjestelmää, jonka toiminta ei lisää ilmakehän hiilidioksidia.[1][2][3][4][5][6][7] Jos polttoaineen tuotannon ja käsittelyn kaikissa vaiheissa on hyödynnetty hiiletöntä tai hiilineutraalia energiaa, tuotettu polttoaine on hiilineutraalia.[8] Hiiletön polttoaine on eräs mahdollisuus oikaista hiilineutraalin polttoaineen tuotannossa. Ellei polttoaine itsessään sisällä hiiltä, ei hiilen hankkimisesta tule ongelmaa.[9]

Hiilinegatiivisuudella tarkoitetaan hiilidioksidin poistamista ilmakehästä ja hautaamista. Hiilineutraalit polttoaineet ainoastaan korvaavat fossiilisten polttoaineiden käyttöä ja siten voivat vähentää hiilipäästöjä.[10][11]

Puu on poliittisella päätöksellä nimetty hiilineutraaliksi polttoaineeksi.[12][13] Toisaalta puun hiilineutraalius on kyseenalaistettu, johtuen keruu- ja jatkojalostusmenetelmissä kulutetusta energiasta.[14][8][15] Samoin kuin puu, myös biokaasu luokitellaan hiilineutraaliksi pääasiassa raaka-aineen uusiutuvuuden ansiosta.[16] Myös muuhun biomassaan sovelletaan vastaavaa raaka-aineen kiertoon perustuvaa luokittelua.[17][18]

Polttoaineen hiilineutraaliutta ei voi suoraan päätellä polttoaineen kemiallisesta koostumuksesta. Tuotettu polttoaine voi olla hiilidioksidipäästöjen kannalta erittäin hiili-intensiivinen, mikäli tuotantoon tarvittava vety tuotetaan maakaasusta ja prosessissa tarvittava lisäenergia hankitaan polttamalla kivihiiltä tai muuta fossiilista polttoainetta. Vaikka vety onkin kemialliselta koostumukseltaan hiiletön ja muutenkin päästötön polttoaine, suurin osa maailman vedyntuotannosta perustuu maakaasun käyttöön raaka-aineena.[19] Bioetanolikaan ei ole täysin hiilineutraali käytössä olevilla tuotantoprosesseilla.[20] Vety olisi muuten monessa mielessä ideaalinen polttoaine, mutta sen energiatiheys tilavuuteen suhteutettuna on huono, ja siksi vedyn sijasta on haettu muita vaihtoehtoja.[21]

Vähähiilisillä polttoaineilla kuten maakaasulla voidaan saavuttaa suhteellinen hiilipäästöjen vähennys verrattuna runsashiilisiin polttoaineisiin, mutta päästövähennysten tavoitteiden kasvaessa vähähiiliset polttoaineet eivät riitä ratkaisuksi.[22] Monet vähähiiliset polttoaineet auttavat hyvin rikkipäästöjen vähentämisessä, mutta esimerkiksi laivateollisuudelle asetettu tavoite 50 % vähennykseen kasvihuonekaasujen päästöissä ei toteudu pelkästään vähähiilisen polttoaineen avulla.[23]

Hiilineutraaleja polttoaineita

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Puhtaasti tuotetut hiilettömät polttoaineet ovat hiilineutraaleja:[24][25]

Puhtaasti tuotetut biopolttoaineet ovat hiilineutraaleja:[7][38][25][30]

Vedestä ja ilmakehästä kerätystä hiilidioksidista syntesoidut polttoaineet ovat hiilineutraaleja:[24][43][44][29][34]

Luonnossa kasvava biomassa sellaisenaan, kerättynä ja ilman kemiallista jalostusta katsotaan myös hiilineutraaliksi polttoaineeksi:

Hiilineutraalien polttoaineiden taloudellisuus

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Fossiilisten polttoaineiden käytön yleistyminen on perustunut niiden helppoon saatavuuteen ja suhteellisen pieniin kustannuksiin. Fossiilisten energialähteiden asema kuitenkin vähitellen muuttuu. Vaihtoehtoisilla polttoaineilla on omat pulmansa. Hiilidioksidi ei olekaan synteettisten polttoaineiden valmistuksessa enää harmillista jätettä vaan raaka-ainetta.[50] Biopolttoaineiden valmistuksessa on noussut kysymyksiä biomassan riittävyydestä ja energiakäyttöön kasvatettavan biomassan kuluttamasta pinta-alasta. Mahdollisuus tarvittavan hiilidioksidin keräämiseen suoraan ilmasta on katsottu vaihtoehdoksi.[51][52] Öljyriippuvuudesta vapautuminen edellyttää kuitenkin vaihtoehtojen kehittämistä, ja fossiilista lähteistä riippumattomat hiilineutraalit polttoaineet näyttävät johdonmukaisilta vaihtoehdoilta.[53] Synteettisten polttoaineiden avulla on mahdollista vähentää taloudellista riippuvuutta öljyntuottajista.[54] Vaikka synteettiset polttoaineet eivät olekaan olleet kilpailukykyisiä vapailla markkinoilla, niiden kustannukset ovat laskeneet.[55] Hiilineutraalin synteettisen polttoaineen muuttumista kilpailukykyiseksi voi nopeuttaa myös kasvattamalla päästömaksuja.[56] Bioenergia kilpailee synteettisten polttoaineiden kanssa, mutta jälkimmäisiin ei tarvita paljon pinta-alaa.[57][58]

Hiilineutraalien polttoaineiden tuotannon teknisiä edellytyksiä

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Hiilineutraalit polttoaineet eivät itsessään ole energialähteitä vaan niiden tuotantoon tarvitaan taloudellisesti edullisia ja hiilettömiä primäärienergialähteitä.[29] Tässä varsinkin ydinenergian kehityksen ja lisärakentamisen merkitys korostuu.[59] Ydinenergia on periaatteessa hiilineutraalia ja käytännössäkin lähes hiilineutraalia.[60] Neljännen sukupolven ydinreaktoreiden oletetaan parantavan hiilineutraalien polttoaineiden tuotannon tehokkuutta ja kilpailukykyä.[24] Erityisesti neljännen sukupolven reaktoreiden korkea lämpötila, energianmuunnoksen korkea terminen hyötysuhde ja turvallisuus tekevät ydinenergiasta tärkeän tekijän hiilineutraaleiden polttoaineiden tuotannossa, alkaen kilpailukykyisestä vedyn tuotannosta esimerkiksi korkean lämpötilan elektrolyysissä.[61][62][63][64][65][66][67] Ydinfuusioon perustuva fuusioenergia nähdään myöhemmän tulevaisuuden mahdollisuutena.[68] Verrattuna ydinenergiaan, uusiutuvien energialähteiden kilpailukyky perustuu pieneen laitoskokoon ja nopeaan rakentamisen aikatauluun.[69]

Biomassan käyttökelpoisuus energiantuotannossa korostuu. Biomassalla on luontaisesti edullisia ominaisuuksia:[38]

  1. Biomassa on kotimaista, mikä on merkittävää omavaraisen energiantuotannon ja öljyriippuvuudesta vapautumisen kannalta.
  2. Biomassa on hiilineutraali hiilen ja energian lähde.[70][71]
  3. Biomassa on yhteensopiva fossiilisten polttoaineiden infrastruktuurin kanssa.

Biopolttoaineiden tuotannossa tarvitaan raaka-aineeksi ja energialähteeksi vain biomassaa.[72][40][39][41] Perinteisen biopolttoaineen tuottamisen sijasta biomassaa voidaan kohdella pääasiassa hiilineutraalina hiilen lähteenä, jolloin biomassan sisältämää hiiltä ei tuhlata, ja huomattava osa tarvittavasta energiasta tulee muista lähteistä.[70][73][74]

Hiilineutraalien synteettisten polttoaineiden valmistuksessa tarvitaan:[75][76]

  • Hiilineutraalia energiaa
  • Hiilineutraalia hiilidioksidia
  • Hiilineutraalia vetyä

Ilman sisältämä hiilidioksidi kelpaa myös hiilen lähteeksi polttoaineen valmistuksessa.[71] Mahdollisimman välitöntä polttoaineen tuottamista ilmasta kerätystä hiilidioksidista on kehitetty.[77][78][79][80][46][52][81][45][82][83] Hiilidioksidi siirtyy keräyslaitteistossa suoraan virtaavaan liuokseen, joka siirretään putkia pitkin erotukseen.[84] Hiilivetypolttoaineen tuottamista ilman hiilidioksidista suoraan auringonvalolla on myös kehitetty.[85] Uudella katalyytillä on siinä ratkaiseva merkitys.[86][48][87]

Hiilineutraalien polttoaineiden tulevaisuudennäkymiä

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Huoli fossiilisten polttoaineiden riittävyydestä ja ympäristövaikutuksista ovat johtaneet ponnisteluihin hiilineutraalien polttoaineiden kehittämiseksi.[1] Vaihtoehtoisia hiilineutraaleja polttoaineita kehitettäessä aivan uusien prosessien käyttöönotossa ilmenee teknisiä ja taloudellisia epävarmuuksia. Esimerkiksi mikrolevien hyödyntäminen polttoaineiden tuotantoon on edistynyt odotettua hitaammin.[88][89][90][91]

Hiilidioksidin kerääminen ilmasta synteettisten polttoaineiden tuotantoon on ollut kehitysponnistelujen kohteena.[46][44] Kerätystä hiilidioksidista voidaan valmistaa metanolia ja siitä edelleen useita muita polttoaineita.[47] Samoin hiilettömät polttoaineet kuten vety ja ammoniakki nousevat vaihtoehdoiksi. Näiden tuottamiseen kuluu runsaasti energiaa, jonka tulee olla hiilineutraalia.[28] Entistä parempien katalyyttien kehittäminen tehostaa synteettisten polttoaineiden tuotantoa.[86][87] Laivateollisuuden suunnitelmat hiilineutraalien ja hiilettömien polttoaineiden käyttöönottamiseksi ovat pitkällä.[30] Hiileen pohjautuvien mutta hiilineutraalien synteettisten polttoaineiden odotetaan yleistyvän, sillä niille ovat kuluttajat ja jakeluverkostot valmiina olemassa.[92]

Metsän biomassaan perustuvien biopolttoaineiden hiilineutraaliutta on arvosteltu sen vuoksi että metsät uusiutuvat hitaasti, ja välittömät hiilidioksipipäästöt tuotettua energiaa kohti ovat jopa suuremmat kuin kivihiilellä.[93][94]

Katso myös

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Lähteet

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Viitteet

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  1. ↑ a b Muradov & Veziroğlu, 2012. s. vii. Lainaus: "There is a growing consensus that in order to maintain the present standard of living and establish an environmentally sustainable energy future, new approaches to managing energy resources and fuels have to be developed and implemented. Concerns over an insecure energy supply and the adverse environmental impact of carbonaceous fuels have triggered considerable efforts worldwide to find carbon-free or low-carbon alternatives to conventional fossil fuels. In particular, it is understood that many existing challenges can be solved in conjunction with the development and implementation of carbon-neutral energy systems (i.e., systems that do not increase atmospheric CO2 concentration)."
  2. ↑ a b Europaeus, 2014. s. 20. Lainaus: "Puuperäinen biomassa vähentää kuitenkin hiilidioksidipäästöjä verrattuna esimerkiksi hiileen, koska puubiomassa on hiilineutraali polttoaine. Hiilineutraali polttoaine ei tuota ilmakehään ylimääräisiä hiilidioksidipäästöjä, koska se vapauttaa palaessaan saman verran hiilidioksidia kuin puu on kasvaessaan sitonut."
  3. ↑ Brown, Cameron, 2018. Lainaus: "Carbon Neutral: Refers to achieving net zero carbon emissions by balancing a measured amount of carbon released with an equivalent amount sequestered or offset, or buying enough carbon credits to make up the difference."
  4. ↑ Kozak, 2018. Lainaus: "In all of these cases, any fuels created would be carbon-neutral, in that burning them would release no extra atmospheric carbon dioxide (provided that the energy used to synthesize and refine them comes from carbon-free sources). And unlike other forms of bio-derived fuel, such as ethanol created from corn or sugar cane, it doesn’t require scarce resources like fresh water for its production. If successfully implemented, these technologies could carve out a space for internal combustion in a world that seems increasingly intent on reducing emissions and embracing and/or imposing renewable energy standards."
  5. ↑ The Climate Examiner, 2018. Lainaus: "When combusted, these synfuels just emit back into the atmosphere what had earlier been drawn down, making the fuel carbon-neutral."
  6. ↑ Gable, 2018. Lainaus: "Carbon neutral is a term used to describe carbon-based fuels that when burned will not increase carbon dioxide (CO2) in the atmosphere. These fuels neither contribute to nor reduce the amount of carbon (measured in the release of CO2) into the atmosphere."
  7. ↑ a b c Gable, 2018. Lainaus: "Pure biofuels such as biodiesel, bio-ethanol, and bio-butanol are carbon neutral since plants absorb the C02 released by being burned."
  8. ↑ a b Muradov & Veziroğlu, 2012. s. 207. Lainaus: "If the energy used to gather, process, and convert the biomass into transport fuel is provided by a carbon-free or carbon-neutral source, the biofuel will be carbon neutral."
  9. ↑ Brown, Cameron, 2018. Lainaus: "Zero Carbon: This is a case when no carbon was emitted from the get-go, so no carbon needs to be captured or offset."
  10. ↑ The Climate Examiner, 2018. Lainaus: "We can make synthetic fuels, and if they displace fossil fuels, then we are reducing emissions but we are certainly not going carbon negative."
  11. ↑ Brown, Cameron, 2018. Lainaus: "Negative Emissions: Refers to a number of technologies, the objective of which is the large-scale removal of carbon dioxide from the atmosphere."
  12. ↑ a b Science, 2018. Lainaus: "Weighing in on a fierce, long-standing climate debate, the head of the U.S. Environmental Protection Agency (EPA) in Washington, D.C., said yesterday the agency will now define wood as a “carbon-neutral” fuel for many regulatory purposes."
  13. ↑ a b Vieno, 2011. s. 52. Lainaus: "Suomen metsät kasvavat enemmän kuin niitä hakataan, näin on tapahtunut 60-luvulta lähtien. Aktiivinen metsätalous ja metsien käytön lisääntyminen mahdollistavat tavoitteiden mukaisen uusiutuvan raaka-aineen käytön lisäyksen jatkossa. Metsät ja metsämaa toimivat hiilinieluna ja -varastona kestävän metsätalouden ja hyvän metsänhoidon ansiosta. Hiilinielut hidastavat ilmakehän hiilidioksidipitoisuuden kasvua ja hillitsevät siten ilmastonmuutosta. Energiakäytössä puun päästökerroin on nolla, koska on poliittisesti sovittu, että puu on hiilineutraali polttoaine. Metsät sitovat hiiltä kasvaessaan ja vapauttavat sitä hajoamisen, palamisen ja lahoamisen yhteydessä. Metsikkö toimii siis elinkaarensa aikana vuoroin hiilinieluna ja -lähteenä. Luonnontilaisessa metsässä hiilinieluvaikutus kuitenkin päättyy metsikön kasvaessa täysikasvuiseksi."
  14. ↑ a b Science, 2018. Lainaus: "But many environmental groups and energy experts decried the move, arguing the science is far from settled on whether wood is a climate-friendly fuel."
  15. ↑ a b Anttila & Rönkkönen, 2017. s. 51. Lainaus: "Puun polttaminen ei juurikaan lisää ilmakehän hiilidioksidipitoisuutta, koska hiili vaan kiertää ilmakehän ja biomassan välillä. Puu on lähes hiilineutraali polttoaine poikkeuksena puuta käsiteltäessä käytettävät polttoaineet, joita käytetään puuta kerättäessä, kuljettaessa ja käsiteltäessä."
  16. ↑ a b Santala, 2018. s. 24. Lainaus: "Biokaasu on varteenotettava polttoaine, sillä se on uusiutuva energianlähde. Biokaasun jalostuttua biometaaniksi, voidaan sillä korvata fossiilisia polttoaineita. Biokaasun katsotaan olevan hiilineutraali polttoaine uusiutuvuutensa ansiosta. Biometaania voidaan käyttää suoraan omalla moottorilla tai polttokennon raaka-aineena. Päästöt tällä polttoaineella ovat vähäiset ja sen aiheuttama meluhaitta on huomattavasti vähäisempi kuin nestemäisillä aineilla."
  17. ↑ a b TVO, 2011. s. 15. Lainaus: "Ydin-, tuuli- ja vesivoima aiheuttavat vähiten hiilidioksidipäästöjä koko elinkaaren aikana. Biomassan katsotaan olevan hiilineutraali polttoaine, sillä sen poltossa vapautuva hiilidioksidi sitoutuu takaisin luontoon kasvien kasvuvaiheessa."
  18. ↑ Muradov & Veziroğlu, 2012. s. 28. Lainaus: "Biomass, although considered as a carbon-neutral source, is also a significant source of CO2 emissions via a variety of fermentations, gasification, and combustion processes."
  19. ↑ Roberts, 2018. Lainaus: "If the electricity comes from fossil fuels, the CO2 comes from a fossil fuel exhaust stream (i.e., from the geosphere), and the hydrogen comes from steam reforming of natural gas (as roughly 95 percent of hydrogen does today), the resulting fuel is extremely carbon-intensive."
  20. ↑ Salo, 2017. s. 3. Lainaus: "CO2 palautuu luonnon normaaliin kiertokulkuun. Bioetanoli tuottaa uutta hiilidioksidia ilmakehään vain 20% bensiinin tuottamasta määrästä."
  21. ↑ Dolan, 2017. s. 623. Lainaus: "Due to the low energy density of hydrogen gas, it may be more useful to bind the hydrogen in fluid chemical compounds that are easy to handle. These synthetic fuels are also known as XtL-fuels, meaninc conversion of substance X to liquid."
  22. ↑ Brown, Trevor, 2018. Lainaus: "The shipping industry is beginning to recognize the mathematical impossibility of achieving its GHG emission reduction targets using fossil-based fuels, even “low-carbon” fuels like LNG."
  23. ↑ Brown, Trevor, 2018. Lainaus: "Relative to the IMO’s target of a 50% reduction in GHG emissions, fossil-derived fuels like LNG, LPG, and methanol offer very little opportunity. (However, they are excellent for achieving the IMO’s 2020 sulphur caps)."
  24. ↑ a b c d Muradov & Veziroğlu, 2012. s. 57. Lainaus: "Recently, new developments in the nuclear reactor technology showed a potential to significantly expand the role of nuclear energy as a carbon-neutral energy source. In particular, the Generation IV reactors (GEN-IV Initiative) have the goals of improving economics, safety, reliability, and security (including proliferation resistance) of the reactors and the fuel cycle. Most importantly, the Generation IV reactors would significantly expand the range of technological options for producing carbon-neutral fuels such as hydrogen and synthetic fuels and improve the sustainability of the nuclear source to meet the needs of present and future generations."
  25. ↑ a b c d e f g h i Muradov & Veziroğlu, 2012. s. 72. Lainaus: "Several options are technically feasible and currently are under different stages of development, including the use of
    • Electricity produced from carbon-free primary sources
    • Non-carbon-bearing fuels, such as hydrogen and ammonia
    • Fuels that are less carbon intensive than conventional petroleum-based fuels (e.g., synthetic liquid hydrocarbons [SLH], substitute NG, methanol)
    • Biofuels (biodiesel, bioethanol, biobutanol, “green” gasoline, etc.)"
  26. ↑ Muradov & Veziroğlu, 2012. s. 75. Lainaus: "Hydrogen is considered an ultimate carbon-neutral fuel provided it is produced from water and carbon-free primary energy sources."
  27. ↑ a b Leighty, lokakuu 2012. s. 17–19.
  28. ↑ a b c Leighty, marraskuu 2012. s. 1. Lainaus: "We must soon “run the world on renewables” but cannot, and should not try to, accomplish this entirely with electricity transmission. We need to supply all energy, not just electricity, from diverse renewable energy (RE) resources, both distributed and centralized, where the world’s richest RE resources – of large geographic extent and high intensity – are stranded: far from end-users with inadequate or nonexistent gathering and transmission systems to deliver the energy. Electricity energy storage cannot affordably firm large, intermittent renewables at annual scale, while carbon-free gaseous hydrogen (GH2) and liquid anhydrous ammonia (NH3) fuels can: GH2 in large solution-mined salt caverns, NH3 in surface tanks, both pressurized and refrigerated."
  29. ↑ a b c Bosch, 2017. Lainaus: "Technically speaking, it is already possible to manufacture synthetic fuels. If the electricity used is generated from renewables (and thus CO2-free), such fuels are carbon-neutral and very versatile. The hydrogen (H2) that is initially produced can be used to power fuel cells, while the fuels created following further processing can be used to run combustion engines or aircraft turbines."
  30. ↑ a b c d Brown, Trevor, 2018. Lainaus: "By 2050, DNV GL predicts that 39% of the global shipping energy mix will consist of “carbon-neutral fuels,” a category that include ammonia, hydrogen, biofuels, and other fuels produced from electricity."
  31. ↑ a b Brown, Trevor, 2018. Lainaus: "DNV GL forecasts that the shipping industry will achieve the IMO’s “ambitious” targets. It predicts steep emissions reductions, with the lion’s share due to the use of carbon-neutral fuels like ammonia and hydrogen."
  32. ↑ Leighty, marraskuu 2012. s. 4. Lainaus: "NH3 contains no carbon; has physical properties similar to propane; liquefies at ambient temperatures at about 10 bar or at -33 degrees C at 1 atmosphere. Liquid ammonia has over 50% more volumetric energy than liquid hydrogen; more than twice the volumetric energy of hydrogen gas at 700 bar."
  33. ↑ Brown, Trevor, 2018. Lainaus: "If ammonia succeeds as the carbon-neutral fuel of choice in the shipping sector, this new demand will be roughly equivalent to 200 million tons of ammonia per year, more than today’s total global production."
  34. ↑ a b c Dolan, 2017. s. 622–623. Lainaus: "Not only can electricity be generated with very high efficiency, but the synthesis chain also becomes viable for inexpensive chemical products such as ammonia and hydrazine for vehicles or petrochemical compounds."
  35. ↑ Dolan, 2017. s. 623–624. Lainaus: "In order to avoid the exploitation of coal&zwsp;–because it is not available or the generation of carbon dioxide is undesirable–&zwsp;atmospheric nitrogen may be used instead of carbon. Here, the synthetic fuel of choice would be hydrazine (N2H4), a liquid fuel with properties similar to benzine (including toxicity). Hydrazine has been used as a rocket propellant for 80 years. Produced by nuclear energy, it becomes an affordable alternative to petroleum products for use in transport."
  36. ↑ Dolan, 2017. s. 624. Lainaus: "Hydrazine combustion is very clean process creating only water and nitrogen. Thus hydrazine may be considered an NtL-fuel: nitrogen to liquid."
  37. ↑ Dolan, 2017. s. 624. Lainaus: "Silanes are the silicon homologs to carbon-based alkanes, which present an StL (silicon to liquid) synthetic fuel option. Starting with heptasilane (Si7H16) they are stable, easy to handle and possess very high energy densities. At combustion temperatures above 1400 °C, where silane burns exothermically with oxygen to water and with nitrogen to silicon nitride (Si3N4), consuming 99 % of atmospheric intake, it is perfectly suitable for hypersonic ramjets or scramjets."
  38. ↑ a b c d e f g Muradov & Veziroğlu, 2012. s. 67–68. Lainaus: "Biomass can be converted to different types of energy. The use of biomass to produce energy (heat, electricity) and fuels (i.e., biofuels such as bioethanol, bio-butanol, biodiesel, “green” gasoline, FT synfuels) has gained a significant interest worldwide recently. Of particular importance are dedicated energy crops, for example, short rotation woody crops, switch grass that are solely grown for production of bioenergy. The surge in biomass-related activities is mainly fueled by three factors, namely, bioenergy is:
    • A domestic resource (which would potentially alleviate the dependence on imported oil)
    • A carbon-neutral source of energy (although CO2 is released during the energy use of biomass: directly or in the form of biofuels, the equivalent amount of CO2 is captured from the atmosphere during its growth, a so-called closed carbon loop)
    • Compatible with the fossil fuel infrastructure (e.g., biomass can be coprocessed with coal, and biofuels can be delivered, distributed, and used in existing engines with minimal changes)"
  39. ↑ a b Gable, 2018. Lainaus: "The most common carbon neutral fuel is biodiesel. Because it is produced from such organically derived resources as animal fats and vegetable oil it can be used to recycle a wide range of waste material."
  40. ↑ a b c d e f Muradov & Veziroğlu, 2012. s. 79. Lainaus: "The term biofuel covers a wide range of gaseous (e.g., biogas, LFG, bio-hydrogen) and liquid (bioethanol, biobutanol, biodiesel, “green” gasoline, etc.) fuels produced from biomass via a variety of fermentative and thermochemical processes."
  41. ↑ a b Gable, 2018. Lainaus: "Bioethanol is ethanol (alcohol) that is produced by the fermentation of plant starches such as grains like corn, sugarcane, switchgrass and agricultural waste. Not to be confused with ethanol that is a by-product of a chemical reaction with petroleum, which is not considered renewable."
  42. ↑ Lukkari, Jukka: Vantaalla tehdään biometaania hiilidioksidista ja vedystä – St1 ja Q Power yhteishankkeeseen Tekniikka & Talous. 27.8.2019. Viitattu 27.8.2019.
  43. ↑ a b c d e Muradov & Veziroğlu, 2012. s. 77. Lainaus: "Due to ever-increasing anxiety over the depletion of liquid hydrocarbon resources, synthetic liquid fuels are in the focus of intensive R&D and commercial activities worldwide. The main driving forces behind these efforts are twofold: the advantages of using existing petroleum-based fuel infrastructure and car engines with minimal changes, and concerns that other alternative fuels (e.g., hydrogen) may not enter the market in the nearest decade or two. The term synthetic fuel typically covers a wide range of liquid, liquefied, and gaseous fuels that could be synthesized from synthesis gas or syngas (H2 –CO mixture): FT hydrocarbons, methanol, synthetic methane (or substitute natural gas [SNG]), dimethyl ether (DME), C2–C5 alcohols, Mobil-gasoline, and others."
  44. ↑ a b c d e Bosch, 2017. Lainaus: "Up until recently, a carbon-neutral combustion engine was the stuff of dreams. Now it may soon become reality. The secret lies in synthetic, or carbon-neutral, fuels, whose manufacturing process captures CO2. In this way, this greenhouse gas becomes a raw material, from which gasoline, diesel, and substitute natural gas can be produced with the help of electricity from renewable sources."
  45. ↑ a b Gable, 2018. Lainaus: "Last year Audi, together with German energy-company Sunfire, announced it was able to synthesize a diesel fuel from water and CO2 that can fuel automobiles."
  46. ↑ a b c d e Roberts, 2018. Lainaus: "Instead of burying the CO2 it captures, Carbon Engineering plans to use it as an input to make synthetic fuels that can substitute for diesel, gasoline, or jet fuel."
  47. ↑ a b c Muradov & Veziroğlu, 2012. s. 89. Lainaus: "The second option is technologically advanced since it is based on an industrial process for methanol production (32 millions tons of methanol produced worldwide). If necessary, methanol could be further converted to gasoline according to a commercial methanol-to-gasoline Mobile-process."
  48. ↑ a b ScienceDaily, 2017. Lainaus: "Scientists have paved the way for carbon neutral fuel with the development of a new efficient catalyst that converts carbon dioxide (CO2) from the air into synthetic natural gas in a 'clean' process using solar energy."
  49. ↑ Science, 2018. Lainaus: "As Science contributing correspondent Warren Cornwall reported last year, the forest products industry has long been pushing for the carbon neutral definition in a bid to make wood an attractive fuel for generating electricity in nations trying to move away from fossil fuels."
  50. ↑ Roberts, 2018. Lainaus: "CO2 used for greenhouses has economic co-benefits (i.e., it’s worth money). Same with CO2 used to make fuels, or for enhanced oil recovery, or as an industrial feedstock. In contrast, burying CO2 has no economic co-benefits whatsoever."
  51. ↑ The Climate Examiner, 2018. Lainaus: "Where the challenge with the carbon intensity of biofuels is the land-use change required to produce them. And the land footprint of syn-fuels is about 100 times smaller than biofuels."
  52. ↑ a b Morton, 2018. Lainaus: "Direct Air Capture (DAC) technology pulls carbon dioxide out of the atmosphere and converts the carbon into pellets that can be used to make hydrocarbon fuel that works in traditional engines. A new study details the process, which has been tested over the last three years, and offers some cost-saving solutions that make DAC more economically feasible than ever."
  53. ↑ Gable, 2018. Lainaus: "Our addiction to oil has had dire consequences. It seems that the logical solution would be to develop or discover an alternative carbon-neutral fuel not derived from petroleum."
  54. ↑ Roberts, 2018. Lainaus: "Every country could have access to its own source of what is effectively carbon-neutral oil."
  55. ↑ Morton, 2018. Lainaus: "In 2011, a report by the American Physical Society estimated the process would cost between $600 and $1,000 per metric ton of carbon dioxide. But the new endeavor, from a Canadian company called Carbon Engineering, has developed a DAC method that costs as little as $100 per metric ton."
  56. ↑ The Climate Examiner, 2018. Lainaus: "A low carbon fuel standard (LCFS) is the lynchpin of what makes the business case for us. If we’re producing synthetic fuels at a dollar a litre and fossil fuels are closer to 60 cents or so, to make synfuels competitive, they would need a price on carbon of about $200 a tonne."
  57. ↑ Roberts, 2018. Lainaus: "Now, it may be that some blessed day, later in the century, we will have no more fossil fuel exhaust streams to pull CO2 from, and DAC will compete only with BECCS for sequestration funds. Then it might have a fighting chance; though its carbon capture costs are higher, it requires, Keith estimates, 30 to 100 times less land."
  58. ↑ Morton, 2018. Lainaus: "To bring costs down, the team at Carbon Engineering focused on adapting existing cooling tower technology as the building blocks for the contactors that bring ambient air in contact with the capture solution."
  59. ↑ Muradov & Veziroğlu, 2012. s. viii. Lainaus: "Advantageously, nuclear energy does not inherently involve any direct use of fossil fuels or generation of CO2 or other greenhouse gases. Thus, nuclear energy has the potential to make major contributions to the production of carbon-neutral fuels and energy carriers by providing a major carbon-free source of primary energy."
  60. ↑ Muradov & Veziroğlu, 2012. s. 55. Lainaus: "Nuclear energy is considered an important carbon-free source of energy that could substantially alleviate the potential power shortage problem without disturbing the Earth’s fragile carbon balance."
  61. ↑ Muradov & Veziroğlu, 2012. s. 57–58. Lainaus: "As seen from the Table 1.1, the Generation IV reactors are designed to operate at much higher temperatures than conventional light-water reactors, which would result in a substantial increase in the thermal-to-electrical energy conversion efficiency. U.S. DOE projects that the Generation IV nuclear reactors will be deployed beyond the year 2025 time frame (U.S. DOE GEN IV 2002)."
  62. ↑ Muradov & Veziroğlu, 2012. s. 57 taulukosta 1.1 ilmenee että 1000 °C reaktorin lämpötila mahdollistaa yli 50 % termisen hyötysuhteen.
  63. ↑ Muradov & Veziroğlu, 2012. s. 83. Lainaus: "Nuclear source may provide a significant, but not decisive, share of carbon-free energy, and there is a hope that a widespread implementation of advanced nuclear (e.g., breeder, high-temperature) reactors would provide a means for large-scale production of electricity and carbon-neutral fuels in a reasonable time frame."
  64. ↑ Muradov & Veziroğlu, 2012. s. 212. Lainaus: "Nuclear power can provide the large-scale source of hydrogen at reasonable cost, which is needed to make these visions into a reality."
  65. ↑ Muradov & Veziroğlu, 2012. s. 227. Lainaus: "High-temperature nuclear reactors have the potential for substantially increasing the efficiency of hydrogen production from water, with no consumption of fossil fuels, no production of GHGs, and no other forms of air pollution. Water splitting for hydrogen production can be accomplished via HTE or thermochemical processes, using high-temperature nuclear process heat. In order to achieve high efficiencies, both processes require high-temperature operation. Thus, these hydrogen-production technologies are tied to the development of advanced high-temperature nuclear reactors. High-temperature electrolytic water splitting supported by nuclear process heat and electricity has the potential to produce hydrogen with overall thermal-to-hydrogen efficiencies of 50% or higher, based on high heating value."
  66. ↑ Muradov & Veziroğlu, 2012. s. 383. Lainaus: "While the operating temperature range for different thermochemical cycles varies up to about 2000°C, the moderate temperature thermochemical cycles, which can be performed at 400°C–600°C, are especially attractive because such conditions create more opportunities for combining the cycles with a number of available heat sources such as solar concentrators and Generation IV nuclear reactors, which have been recently under an intense development. Advantageously, conducting the thermochemical cycles at moderate temperatures (sometimes called alternative thermochemical cycles) allows for the use of a wider range of construction materials. This is a critical issue as material selection becomes crucial as operating temperatures are increased."
  67. ↑ Dolan, 2017. s. 623. Lainaus: "The operating temperature of 1000 °C enables highly efficient production of hydrogen from water through combined electrolysis and thermolysis. This method, the HOT ELLY process, was developed for the high-temperature reactor at the Jülich Research Center in Germany. Alternatively, the sulfur-iodine cycle could produce hydrogen at a temperature of only >830 °C."
  68. ↑ Muradov & Veziroğlu, 2012. s. 58. Lainaus: "Nuclear fusion energy is considered a long-term option (most experts agree that, in all likelihood, it will contribute to overall energy supply by the end of this century)."
  69. ↑ Muradov & Veziroğlu, 2012. s. 58–59. Lainaus: "Unlike the 1970s, which saw a real boost in nuclear power in response to the energy crisis, the current global energy field has new dynamic players, for example, solar and wind industries, CCS technologies. These competitors offer the advantage of relatively quick installation, compared with as much as 10 years of construction and $7 billion-plus price tag typical of nuclear power plants installation (Johnson 2010)."
  70. ↑ a b Muradov & Veziroğlu, 2012. s. 85. Lainaus: "Recently, a number of researchers reported on the development of alternative approaches to production of carbon-neutral fuels from biomass, which would allow a significant increase in the yield of SLH per unit of biomass feedstock (Bossel et al. 2005; Shinnar and Citro 2006; Agarwal et al. 2007; Muradov and Veziroǧlu 2008; Forsberg 2009; Zeman and Keith 2008). These approaches, although differing in technical details, have a common idea of SLH production by using biomass as a source of carbon and water as a source of hydrogen with the energy input from non-carbogenic energy sources (e.g., nuclear, solar, wind) (Figure 1.49). According to the reported estimates, this approach would yield three to four times more synthetic fuels, compared to conventional routes of biofuels production (e.g., via gasification, on the unit of biomass energy basis) (Shinnar and Citro 2006; Agarwal et al. 2007)."
  71. ↑ a b Muradov & Veziroğlu, 2012. s. 78. Lainaus: "In order to be considered carbon-neutral fuels, SLH have to be generated from biomass-based feedstocks or CO2 from atmosphere."
  72. ↑ Gable, 2018. Lainaus: "Carbon neutral fuels can help prevent too much CO2 from accumulating in the atmosphere. It accomplishes this when the released carbon is absorbed by plant crops that will help produce tomorrow’s next gallon of a carbon-neutral fuel."
  73. ↑ Muradov & Veziroğlu, 2012. s. 86. Lainaus: "In a recent analytical study, Forsberg (2009) outlined a nuclear-hydrogen-biomass concept as an attractive approach to future carbon-neutral energy systems. The author argues that due to high energy intensity of biomass-to-liquid fuel processes, there would be insufficient amount of biomass to meet U.S. liquid transportation fuel demands. However, with the use of nuclear energy to provide heat, electricity, and hydrogen for processing biomass (especially, cellulosic biomass) to fuels, the production of liquid hydrocarbon-based fuels (e.g., diesel fuel) per unit of biomass could be dramatically increased to the extent that U.S. liquid fuel requirements would be met. The proposed nuclear-hydrogen-biomass system is robust and can be implemented with the current or near-term technologies; in particular, nuclear-powered electrolysis and FT technology could provide a basis for the near-term implementation of the biomass-to-liquid fuels process."
  74. ↑ Muradov & Veziroğlu, 2012. s. 89. Lainaus: "The combination of biomass, non-carbogenic hydrogen, and carbon-free primary energy sources could potentially produce the required quantity of carbon-neutral transportation fuels utilizing a reasonable area of the land surface."
  75. ↑ Roberts, 2018. Lainaus: "Creating synthetic fuels (there are a number of different kinds) involves combining a carbon-based molecule, usually CO2, with hydrogen. Electricity powers the process."
  76. ↑ Roberts, 2018. Lainaus: "The carbon intensity of the resulting fuels depends on the source of all three components: the electricity, the CO2, and the hydrogen."
  77. ↑ Business Insights, 2018. Lainaus: "Canadian company Carbon Engineering has designed a plant capable of removing CO2 from the atmosphere and turning it into carbon neutral fuel at a lower cost than existing technology. Though still more expensive than oil, the fuel could soon replace most fossil fuels and cut pollution of the Earth’s atmosphere."
  78. ↑ Business Insights, 2018. Lainaus: "Despite the existence of alternative clean energies, fossil fuels remain the world’s primary energy source. In seeking a greener solution for powering cars, trucks, aircraft and other vehicles, the Canadian company Carbon Engineering has come up with technology capable of producing carbon neutral fuel from carbon dioxide in the air, for a similar price to that of fossil fuel, as reported by Objetconnecté.com."
  79. ↑ Business Insights, 2018. Lainaus: "Capturing carbon dioxide in the air and converting it into fuel is not a new idea. Thanks to a relatively simple chemical process, the carbon dioxide is combined with hydrogen and oxygen and then converted into a fuel generating the same amount of CO2 as that captured, hence its designation as “carbon neutral fuel”."
  80. ↑ Carbon Engineering, 2019. Lainaus: "At Carbon Engineering, we’re commercializing two clean energy technologies that can rapidly accelerate our shift to a net-zero world: our Direct Air Capture technology can deliver large-scale negative emissions by removing carbon dioxide directly from the atmosphere; and our AIR TO FUELS™ technology can significantly reduce the carbon footprint of transportation by creating clean synthetic fuels – made from air, water and renewable power."
  81. ↑ The Climate Examiner, 2018. Lainaus: "Direct air capture in its simplest sense is a technology that processes ambient air, absorbs CO2 and purifies it. The carbon balance—staying neutral or going negative— depends on what you do next."
  82. ↑ Morton, 2018. Lainaus: "Carbon Engineering’s proof-of-concept Direct Air Capture (DAC) plant in British Columbia has been harvesting carbon from the air since 2015."
  83. ↑ Morton, 2018. Lainaus: "Once the carbon is captured and transformed into carbonate ions, it is stored as stable, transportable calcium carbonate pellets in a process similar to one used by water treatment plants to remove excess ions from wastewater. These pellets can then be stored for carbon sequestration or be turned into a wide variety of hydrocarbon fuels in a high-heat thermo-catalytic pathway known as Air to Fuels technology."
  84. ↑ Morton, 2018. Lainaus: "The DAC plant in Squamish harvests carbon dioxide from the atmosphere using giant fans to bring the air into contact with a water-based alkali capture solution, which isolates and stores the carbon dioxide in a process that is chemically similar to the pathway that produces pulp and paper from wood, Keith says."
  85. ↑ Roberts, 2018. Lainaus: "If the electricity comes from renewables, the CO2 comes from the air (i.e., the biosphere), and the hydrogen comes from solar-powered electrolysis, the resulting fuel is extremely low carbon."
  86. ↑ a b Lainaus: "A new efficient catalyst that converts carbon dioxide into synthetic natural gas in a ‘clean’ process using solar energy could pave the way for carbon neutral fuel, Australian scientists say."
  87. ↑ a b ScienceDaily, 2017. Lainaus: "This new catalyst efficiently produces almost pure methane from CO2. Carbon-monoxide production has been minimised and stability is high under both continuous reaction for several days and after shutdown and exposure to air. Importantly, only a small amount of the catalyst is needed for high production of methane which increases economic viability. The catalyst also operates at mild temperatures and low pressures, making solar thermal energy possible."
  88. ↑ Gable, 2018. Lainaus: "These algae can be grown on non-potable water, perhaps even wastewater, in ponds so it is not using arable land or massive amounts of water. While on paper, micro-algae seems like a no-brainer, formidable technical issues have flummoxed researchers and scientists for years."
  89. ↑ Romantschuk, 2011. Lainaus: "Biopolttoaineita voidaan tuottaa levistä, jotka auringonvalon ja hiilidioksidin lisäksi käyttävät jätefraktioita (jätevettä, biojätettä) energian ja hiilen lähteinä. Tavoitteena on hiilineutraali polttoaine, joka uudella tavalla jalostaa jätteet tuotteeksi, eikä kilpaile peltopinta-alasta."
  90. ↑ Gable, 2018. Lainaus: "Algae—specifically microalgae—is a source for a carbon-neutral alternative fuel."
  91. ↑ Gable, 2018. Lainaus: "Microalgae has the ability to produce lipids, which are known as a potential source for biofuels."
  92. ↑ Carbon Engineering, 2019. Lainaus: "The world is transitioning to clean economies and clean fuels. AIR TO FUELS™ technology allows us to produce global-scale quantities of drop-in ready fuels like gasoline, diesel, and Jet-A without the use of crude oil. These fuels are cleaner burning than fossil fuels, can be carbon neutral on a life-cycle basis, can be produced with 100x less land use than biofuels, and are directly compatible with existing infrastructure."
  93. ↑ Tyystjärvi, 2019. Lainaus: "”Keskipitkällä aikavälillä, vuosikymmenien aikaskaalassa, metsät eivät ehdi kerryttää takaisin sitä hiilidioksidin määrää, mikä energiaa tuottaessa vapautuu ilmakehään”, Korhola sanoo tiedotteessa."
  94. ↑ Tyystjärvi, 2019. Lainaus: "”Biopohjaisesti tuotetun energian hiilidioksidipäästöt ovat tuotettua energiamäärää kohden selvästi jopa pahinta ilmastosaastuttajaa, kivihiiltä, suuremmat”, tiedotteessa sanotaan."
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