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Mauriziogio

Sono cascato su wikipedia per caso cercando la mia città su internet. Ho trovato la descrizione su en.wikipedia e poi ho scoperto la versione italiana. La cosa più bella di wiki? Una pagina a caso. Per ora sto traducendo argomenti quasi a caso da en.wikipedia. Per ora ho tradotto:

Una beuta piena di jet fuel ottenuto dalle alghe

Algae fuel o algal biofuel è un combustibile alternativo che usa le alghe come fonte.[1] Molte aziende e agenzie governative stanno finanziando studi per ridurre i costi di investimento e operativi per rendere la produzione di combustibile dalle alghe economicamente conveniente.[2]

Come i combustibili fossili, i combustibili da alghe e gli altri biocarburanti rilasciano CO2 nell'atmosfera una volta che vengano bruciati, ma al contrario dei combustibili fossili, rilasciano CO2 rimossa recentemente dall'atmosfera per mezzo della fotosintesi dalla crescita delle piante o delle alghe. La crisi energetica e la crisi mondiale del cibo, hanno aumentato l'interesse nell'agricoltura (fattorie di alghe) per la produzione di biodiesel e altri biocarburanti utilizzando terreni in cui l'agricoltura tradizionale non è favorevole. Fra le caratteristiche più interessanti del combustibile da alghe c'è la possibilità che possano essere coltivate con minimi apporti di acqua fresca,[3][4] possono essere prodotte utilizzando acque ad alta salinità e acque reflue, il combustibile prodotto ha un alto punto di infiammabilità,[5] è biodegradabile e relativamente poco impattante sull'ambiente in caso di sversamenti accidentali nell'ambiente.[6][7] Le alghe costano di più, per unità di massa, della altre coltivazioni di seconda generazione per la produzione di bio carburanti a causa degli alti costi di investimento e di gestione,[8] ma per contro dichiarano produzioni di combustibile da 10 a 100 volte maggiori per unità di superficie utilizzata.[9] Il Dipartimento dell'Energia degli Stati Uniti stima che se le il combustibile da alghe dovesse sostituire per intero la produzione di combustibile da petrolio, verrebbero occupati circa 40'000 chilometri quadri che rappresenta soltanto lo 0.42 % del territorio degli stati uniti o metà della superficie dello stato del Maine, che comunque è meno di 1/7 dell'area dedicata alla coltivazione del mais negli Stati Uniti nel 2000.[10]

Secondo quanto comunicato dal capo della Algal Biomass Organization, il combustibile da alghe potrà raggiungere la parità con il prezzo del petriolo a partire dal 2018 se verranno garantiti aiuti fiscali.[11] Comunque, nel 2013 l'amministratore delegato della Exxon Mobil Rex Tillertson ha dichiarato l'intenzione di spendere fino a 600 milioni di dollari nei 10 anni seguenti a seguito della Joint venture con Syntethtic Genomics del 2009, Exxon è uscita dopo 4 anni (e 100 milioni di dollari) quando è stato chiaro per loro che il mercato delle alghe probabilmente era ancora a 25 anni dalla fattibilità commerciale.[12] D'altra parte, Solazyme[13] e Sapphire Energy[14] hanno iniziato la vendita di biocombustibile da alghe nel 2012 e 2013, rispettivamente, e Algenol ritiene di iniziare la produzione commericiale nel 2014.[15]

Storia modifica

Ne 1942 Harder e Von Witsch sono stati i primi a proporre che le microalghe poitevano essere allevate come fonte di lipidi per l'alimentazione o come combustibile.[16][17] Dopo la seconda guerra mondiale, sono iniziate ricerche scientifiche negli Stati Uniti,[18][19][20] Germania,[21] Giappone,[22] Regno Unito,[23] e Israele[24] sulle tecniche di coltura e ingegnerizzazione di coltivazione su larga scala di alghe, selezionandop particolarmente il tipo Chlorella. Contemporaneamente, H. G. Aach ha dimostrato che la Chlorella pyrenoidosa poteva essere indotta attraverso privazione di azoto ad accumulare lipidi fino al 70% del proprio peso secco.[25] Stante il fatto che la necessità di sostituire i combustibili fossili diminuì dopo la seconda guerra mondiale, gli studi si concentrarono sull'utilizzo delle alghe come cibo ed in alcuni casi come sistemi di trattamento delle acque di scarico.[26]

L'interesse dell'applicazione delle alghe ai biocarburanti è risalito durante l'embargo seguente alla crisi del canale di Suez e la seguente levitazione dei prezzi del petrolio degli anni 1970, portando il dipartimento dell'energia degli stati uniti ad iniziare il Programma sulle Specie Acquatiche nel 1978.[27] Il Programma sulle Specie Acquatiche spese 25 milioni di dollari in 18 anni con l'obiettivo di sviluppare un combustibile liquido per i mezzi di trasporto ottenuto dalle alghe che potesse avere un prezzo competitivo con i derivati del petrolio.[28] Il programma di ricerca si concentrò sulla coltivazione di micro-alghe in laghi aperti, sistemi che hanno bassi costi di realizzazione ma sono vulnerabili alle contaminazioni e disturbi ambientali come variazioni di temperatura ed invasioni biologiche. 3,000 culture di alghe furono collezionate attraverso tutti gli Stati Uniti e selezionati per le caratteristiche peculiari di alta produttività, contenuto di lipidi e tolleranza alle variazioni di temperatura e le più promettenti inserite nella collezione del Solar Energy Research Institute (SERI) a Golden, Colorado per futuri studi.[28] Tra le scoperte più rilevanti del programma fu che la crescita rapida e la produzione di lipidi erano mutuamente esclusive, dato che la prima chiedeva la presenza di molti nutrienti mentre la seconda scarsezza di nutrienti.[28] Il rapporto finale suggeriva che l'ingegneria genetica forse sarebbe riuscita questa limitazione naturale delle alghe e che la specie ideale potrebbe variare per stagione e posizione[28] Anche se è stato dimostrato che produzione su larga scala di alche per la produzione di biocarburanti in laghi all'aperto era possibile, il programma fallì per il costo che non era competitivo con il petrolio, specialmente con il prezzo del greggio che crollò negli anni 1990. Anche nel caso del miglior scenario, è stato stimato che il petrolio da alghe costa fra i 59 e 186 dollari per barile,[28] mentre il petrolio costava meno di 20 dollari per barile nel 1995.[27] Alla fine nel 1996 il programma venne chiuso per ristrettezze del budget statale.[28]

Altri contributi alle ricerche sui biocarburanti sono arrivati indirettamente da progetti che si concentravano su altre applicazioni delle culture di alghe. Per esempio nei anni 1990 l'Istituto Giapponese per le Tecnologie Innovative per la Terra (RITE) implementò un programma di ricerca il cui obiettivo era quello di sviluppare sistemi di cattura della CO2 per mezzo di micro-alghe.[29] Anche se l'obiettivo non era la produzione di energia, diversi studi del RITE dimostrarono che le alghe potevano crescere utilizzando i gas di scarico di impianti di produzione di energia elettrica come sorgente di CO2,[30][31] una nota importante per lo sviluppo di ricerche sui biocombustibili da alghe. Altro lavoro sulla raccolta di idrogeno, metano o etanolo dalle alche, come pure l'utilizzo come supplemento nutrizionale e composto farmaceutico hanno aiutato i ricercatori impegnati nella produzione di biocarburanti dalle alghe.[26]

A seguito della sospensione del Programma sulle Specie Acquatiche nel 1996, ci fu un periodo di relativa quiete nella ricerca. Altri vari progetti sono stati finanziati dal Dipartimento dell'Energia, Dipartimento della Difesa, Fondazione Nazionale delle Scienze, Dipartimento dell'Agricoltura, Laboratori Nazionali, finanziamenti statali e privati come pure in altri stati.[27] Più recentemente, la crescita del prezzo del petrolio negli anni 2000 ha fatto crecere l'interesse ed i finanziamenti federali sono cresciuti,[27] numerosi progetti di ricerca sono stati creati in Australia, Nuova Zelanda, Europa, Medio Oriente, e altre parti del mondo,[32] e una nuova ondata di compagnie private sono entrate in campo.[33] Nl novembre 2012, Solazyme e Propel Fuels fecero la prima vendita diretta di combustibile derivato dalle alghe,[13] e nel marzo 2013 Sapphire Energy iniziò la vendita di biocarburanti a Tesoro.[14]

Combustibili modifica

Le alghe possono essere convertite in numerosi tipi di combustibili, a seconda della tecnica e della parte della cellula utilizzata. I lipidi, o parte oleosa della biomassa delle alghe, può essere estratta e convertita in biodiesel attraverso un processo simile a quello utilizzato per ogni olio vegetale, o convertito in raffinerie in sostituto di combustibili derivati dal petrolio. Alternativamente o seguendo l'estrazione dei lipidi, il contenuto di carboidrati delle alghe può essere fermentato in bioetanolo o butanolo.[34]

Biodiesel modifica

  Lo stesso argomento in dettaglio: Biodiesel.

Biodiesel è un gasolio derivato da lipidi animali o vegetali (olii e grassi). Studi hanno mostrato che alcune specie di alghe possono produrre il 60% o più del loro peso secco in forma di combustibile.[25][28][35][36][37] Per il fatto che le cellule crescono in un mezzo acquoso, dove hanno facile accesso all'acqua,CO2 e nutrienti disciolti, le microalghe sono capaci di produrre grandi quantitativi di biomassa e olio sia in laghi ad alta efficienza che in fotobioreattori. Questo olio può essere convertito in biodiesel che può essere utilizzato nelle automobili. La produzione locale di micro-alghe e seguente trasformazione in biodiesel può produrre vantaggio per le comunità rurali.[38]

Dato che non devono produrre composti strutturali come cellulosa per le foglie, stelo o radici e dato che possono crescere fluttuando in un ambiente ricco di nutrienti le micro-alghe possono crescere più velocemente delle specie terrestri. Inoltre possono convertire in olio una frazione maggiore della loro biomassa che le specie tradizione, per esempio 60% invece che il 2/3% dei semi di soia.[35] La produzione per unità di area di olio da alghe è stimato essere fra 6,58 e 15,3 kg/m²/anno, a seconda del contenuto di lipidi, che è da 10 a 23 volte maggiore della seconda più alta produttice che è la palma da olio che vale 0,66 kg/m²/anno.[39]

Il Programma del Dipartimento dell'Energia sulle Specie Acquatiche, 1978-1996, si concentrò sulla produzione di biodiesel da micro-alghe. Il rapporto finale suggerì che il biodisel poteva l'unica strada percorribile per cui si poteva produrre abbastanza combustibile per sostituire il tradizionale gasolio.[40] Se il biodiesel ottenuto dalla algheandasse a rimpiazzare la produzione attuale di 1,1 miliardi di tonnellate del gasolio di origine fossile sarebbe necessario mettere a cultura un totale di 230'000 km² (un quadrato di 480 km di lato), che è altamente vantaggioso rispetto ad altri bio-carburanti.[41]

Biobutanolo modifica

  Lo stesso argomento in dettaglio: Butanol fuel.

Il butanolo può essere ottenuto dalle alge o dalle diatomee utilizzando una bioraffineria alimentata da energia solare. Questo combustibile ha unadensità di energia che è minore del 10% rispetto alla benzina ma maggiore sia dell'etanolo che del metanolo. In molti motori a benzina si può utilizzare il butanolo al posto del tradizionale combustibile senza modifiche. In molti test il consumo di butanolo è simile a quello della benzina e quando mescolato con la benzina stessa fornisce prestazioni migliori e resistenza alla corrosione che l'etanolo o dell'E85.[42]

Lo scarto verde che risulta dall'estrazione dell'olio dalle alghe può essere utilizzato per la produzione di butanolo. Inoltre, è stato mostrato che le macro-alghe possono essere fermentate dal batterio Clostridia e trasformato in butanolo e altri solventi.[43]

Biobenzina modifica

La biobenzina è benzina prodotta da biomassa. Come la benzina prodotta tradizionalmente contiene fra 6 (Esano) e 12 (Dodecano) atomi di carbonio e può essere utilizzata in motori a combustione interna.[44]

Metano modifica

Il metano,[45] il principale costituente del gas naturale può essere prodotto dalle alghe con vari metodi, Gassificazione, Pirolisi e digestione anaerobica. Nella gassificazione e nella pirolisi il metano è estratto ad alta temperatura e pressione. La digestione anerobica[46] è un metodo diretto che prevede la decomposizione delle alghe in componenti semplici seguito dalla trasformazione in acidi grassi per mezzo di microbi come il batterio acidificante seguito dalla rimozione di tutte le parti solide e aggiunta finale di batteri metanogenici che rilasciano una miscela di gas contenente metano. Molti studi hanno dimostrato che la biomassa di micro-alghe può essere convertita in biogas per mezzo di una digestione anerobica.[47][48][49][50][51] Inoltre, volendo aumentare il bilancio energetico complessivo delle coltivazioni di micro-alghe, è stato proposto di recuperare l'energia dalle masse di scarti di biomasse, utilizzando la digestione anerobica per la produzione di metano e da questo generando energia elettrica.[52]

Etanolo modifica

Il sistema Agenol che è commercializzato dal BioFields di Puerto Libertad, Sonora, Messico, utilizza l'acqua di mare e scarti industriali per produrre etanolo. L'alga Porphyridium cruentum ha dimostrato la capacità di produrre etanolo per la sua capacità di accumulare grandi quantità di carboidrati.[53]

Hydrocracking per produrre combustibili per trasporto tradizionale modifica

  Lo stesso argomento in dettaglio: Vegetable oil refining.

Le alghe possono essere usta per produrre "gasolio verde" (anche conosciuto come gasolio rinnovabile, petrolio vegetale idro-trattato)[54] per mezzo di un processo di idrocrackin che rompe le molecole in catene di idrocarburi più corte utilizzabili in motori diesel.[55][56] Esso ha le stesse proprietà chimiche del gasolio di origine fossile[55] e questo comporta che non necessita nuovi motori, nuovi oleodotti o infrastrutture per distribuirlo od usarlo. Deve però essere ancora prodotto a costi competitivi con il gasolio tradizionale.[54]

Jet fuel modifica

  Lo stesso argomento in dettaglio: Aviation biofuel.

La crescita del prezzo del combustibile da motori aeronautici ha aumentato la pressione sulle compagnie aeree,[57] creando un incentivo per la produzione di combustibile avio da alghe. L'Associazione Internazionale del Trasporto Aereo, per esempio supporta la ricerca, sviluppo di combustibili da alghe. L'obiettivo della IATA è che i suoi membri utilizzino il 10 % dei combustibili da origini alternative entro il 2017.[58]

Prove sono state eseguite con biocombustibile avio da Air New Zealand,[59] Lufthansa, e Virgin Airlines.[60]

Nel febbraio 2010, l'Agenzia per la Ricerca di Progetti Avanzati della Difesa (DARPA) annunciò che i militari stavano per iniziare la produzione su larga scala di combustibile avio a alghe coltivate in laghi. Dopo l'estrazione a 2$ per gallone, l'olio viene raffinato a 3$ per gallone. La produzione su larga scala di 50 milioni di galloni è prevista per il 2013, con la possibilità di costi di produzione ancora più bassi potrebbe essere più conveniente del combustibile di origine fossile. Il progetto, gestito da SAIC e General Atomics, è previsto che produca 1000 galloni di combustibile per acro all'anno da alghe coltivate in laghi.[61]

Specie modifica

La ricerca di alghe per la produzione in massa di combustibili si concentra principalmente in micro-alghe (organismi capaci di fotosintesi che hanno diametro minore di 0,4 mm fra cui le diatomee e i cyanobatteri) come all'opposto le macro-alghe. La preferenza verso le micro-alghe è stata principalmente per la loro inferiore complessità, alto tasso di crescita e alto contenuto di olio (per alcune specie). Comunque alcune ricerche sono state condotte anche sulle alghe di dimensioni maggiori probabilmente per la loro disponibilità.[62][63]

Al 2012 i ricercatori in molte aree del mondo hanno iniziato ad analizzare le seguenti specie per la loro capacità di produttori ad alta capacità di olio:[64][65][66]

Il quantitativo di olio prodotto dalle alghe varia molto. Di seguito le varie specie e i range di produzione olio:

  • Ankistrodesmus TR-87: 28–40% peso secco
  • Botryococcus braunii: 29–75% ps
  • Chlorella sp.: 29% ps
  • Chlorella protothecoides(autotrophic/ heterothrophic): 15–55% ps
  • Cyclotella DI- 35: 42% ps
  • Dunaliella tertiolecta : 36–42% ps
  • Hantzschia DI-160: 66% ps
  • Nannochloris: 31(6–63)% ps
  • Nannochloropsis : 46(31–68)% ps
  • Nitzschia TR-114: 28–50% ps
  • Phaeodactylum tricornutum: 31% ps
  • Scenedesmus TR-84: 45% ps
  • Stichococcus: 33(9–59)% ps
  • Tetraselmis suecica: 15–32% ps
  • Thalassiosira pseudonana: (21–31)% ps
  • Crypthecodinium cohnii: 20% ps
  • Neochloris oleoabundans: 35–54% ps
  • Schizochytrium 50–77% ps[69]

Inoltre visto il suo alto tasso di crescita la Ulva[70] è stata studiata come combustibile per l'utilizzo come combustibile nel ciclo SOFT , (SOFT significa Solar Oxygen Fuel Turbine), un ciclo chiuso per la generazione di potenza adatto all'utilizzo in zone aride e sub-tropicali.[71]

Coltivazione delle Alghe modifica

  Lo stesso argomento in dettaglio: Culture of microalgae in hatcheries.
 
Photobioreactor from glass tubes
 
Design of a race-way open pond commonly used for algal culture

Le alghe crescono più velocemente delle specie terrestri, e possono produrre centinaia di volete di più olio che altre specie come colza, palma, o jatropha.[39] Visto che le alghe hanno un ciclo di raccolta di 1-10 giorni, la loro coltivazione permette molti raccolti in un tempo molto limitato, una strategia molto differente rispetto alle piante annuali.[36] Inoltre, le alghe possono crescere su terreni inutilizzabili per coltivazioni terrestri, inclusi terreni aridi o terreni con salinità troppo alta, minimizzando la competizione con l'agricultura tradizionale.[72] Molte ricerche sulla coltivazione delle alghe si sono concentrate sulla crescita delle alghe in costosi ma puliti fotobioreattori o in laghi aperti che sono economici da mantenre ma esposti alla contaminazione.[73]

Sistemi a circuito chiuso modifica

La mancanza delle strutture necessarie per la produzione in massa di alghe ha impedito la diffusione della produzione di massa di alghe per la produzione The lack of equipment and structures needed to begin growing algae in large quantities has inhibited widespread mass-production of algae for biofuel production. Maximum use of existing agriculture processes and hardware is the goal.[74]

Closed systems (not exposed to open air) avoid the problem of contamination by other organisms blown in by the air. The problem for a closed system is finding a cheap source of sterile CO2. Several experimenters have found the CO2 from a smokestack works well for growing algae.[75][76] For reasons of economy, some experts think that algae farming for biofuels will have to be done as part of cogeneration, where it can make use of waste heat and help soak up pollution.[77][78]

Photobioreactors modifica

Most companies pursuing algae as a source of biofuels pump nutrient-rich water through plastic or borosilicate glass tubes (called "bioreactors" ) that are exposed to sunlight (and so-called photobioreactors or PBR).

Running a PBR is more difficult than using an open pond, and more costly, but may provide a higher level of control and productivity.[36] In addition, a photobioreactor can be integrated into a closed loop cogeneration system much more easily than ponds or other methods.

Open pond modifica

 
Raceway pond used for the cultivation of microalgae

Open-pond systems for the most part have been given up for the cultivation of algae with especially high oil content.[79] ManyTemplate:Who believe that a major flaw of the Aquatic Species Program was the decision to focus their efforts exclusively on open-ponds; this makes the entire effort dependent upon the hardiness of the strain chosen, requiring it to be unnecessarily resilient in order to withstand wide swings in temperature and pH, and competition from invasive algae and bacteria. Open systems using a monoculture are also vulnerable to viral infection. The energy that a high-oil strain invests into the production of oil is energy that is not invested into the production of proteins or carbohydrates, usually resulting in the species being less hardy, or having a slower growth rate. Algal species with a lower oil content, not having to divert their energies away from growth, can be grown more effectively in the harsher conditions of an open system.[36]

Some open sewage-ponds trial production has taken place in Marlborough, New Zealand.[80]

Algal Turf Scrubber modifica

 
2.5 acre ATS system, installed by Hydromentia on a farm creek in Florida

The algal turf scrubber (ATS) is a system designed primarily for cleaning nutrients and pollutants out of water using algal turfs. ATS mimics the algal turfs of a natural coral reef by taking in nutrient rich water from waste streams or natural water sources, and pulsing it over a sloped surface.[81] This surface is coated with a rough plastic membrane or a screen, which allows naturally occurring algal spores to settle and colonize the surface. Once the algae has been established, it can be harvested every 5–15 days,[82] and can produce 18 metric tons of algal biomass per hectare per year.[83] In contrast to other methods, which focus primarily on a single high yielding species of algae, this method focuses on naturally occurring polycultures of algae. As such, the lipid content of the algae in an ATS system is usually lower, which makes it more suitable for a fermented fuel product, such as ethanol, methane, or butanol.[83] Conversely, the harvested algae could be treated with a hydrothermal liquefaction process, which would make possible biodiesel, gasoline, and jet fuel production.[84]

There are three major advantages of ATS over other systems. The first advantage is documented higher productivity over open pond systems.[85] The second is lower operating and fuel production costs. The third is the elimination of contamination issues due to the reliance on naturally occurring algae species. The projected costs for energy production in an ATS system are $0.75/kg, compared to a photobioreactor which would cost $3.50/kg.[83] Furthermore, due to the fact that the primary purpose of ATS is removing nutrients and pollutants out of water, and these costs have been shown to be lower than other methods of nutrient removal, this may incentivize the use of this technology for nutrient removal as the primary function, with biofuel production as an added benefit.[86]

 
Algae being harvested and dried from an ATS system

Fuel production modifica

After harvesting the algae, the biomass is typically processed in a series of steps, which can differ based on the species and desired product; this is an active area of research.[36]

Dehydration modifica

Often, the algae is dehydrated, and then a solvent such as hexane is used to extract energy-rich compounds like triglycerides from the dried material.[1] Then, the extracted compounds can be processed into fuel using standard industrial procedures. For example, the extracted triglycerides are reacted with methanol to create biodiesel via transesterification.[1] The unique composition of fatty acids of each species influences the quality of the resulting biodiesel and thus must be taken into account when selecting algal species for feedstock.[36]

Hydrothermal Liquefaction modifica

An alternative approach called Hydrothermal liquefaction employs a continuous process that subjects harvested wet algae to high temperatures and pressures—350 °C (662 °F) and 3 000 libbre per pollice quadro (21 000 kPa).[87][88][89]

Products include crude oil, which can be further refined into aviation fuel, gasoline, or diesel fuel. The test process converted between 50 and 70 percent of the algae’s carbon into fuel. Other outputs include clean water, fuel gas and nutrients such as nitrogen, phosphorus, and potassium.[87]

Nutrients modifica

  Lo stesso argomento in dettaglio: Algal nutrient solutions.

Nutrients like nitrogen (N), phosphorus (P), and potassium (K), are important for plant growth and are essential parts of fertilizer. Silica and iron, as well as several trace elements, may also be considered important marine nutrients as the lack of one can limit the growth of, or productivity in, an area.[90]

Carbon dioxide modifica

Bubbling CO2 through algal cultivation systems can greatly increase productivity and yield (up to a saturation point). Typically, about 1.8 tonnes of CO2 will be utilised per tonne of algal biomass (dry) produced, though this varies with algae species.[91] The Glenturret Distillery in Perthshire, UK – home to The Famous Grouse Whisky – percolate CO2 made during the whisky distillation through a microalgae bioreactor. Each tonne of microalgae absorbs two tonnes of CO2. Scottish Bioenergy, who run the project, sell the microalgae as high value, protein-rich food for fisheries. In the future, they will use the algae residues to produce renewable energy through anaerobic digestion.[92]

Nitrogen modifica

Nitrogen is a valuable substrate that can be utilized in algal growth. Various sources of nitrogen can be used as a nutrient for algae, with varying capacities. Nitrate was found to be the preferred source of nitrogen, in regards to amount of biomass grown. Urea is a readily available source that shows comparable results, making it an economical substitute for nitrogen source in large scale culturing of algae.[93] Despite the clear increase in growth in comparison to a nitrogen-less medium, it has been shown that alterations in nitrogen levels affect lipid content within the algal cells. In one study[94] nitrogen deprivation for 72 hours caused the total fatty acid content (on a per cell basis) to increase by 2.4-fold. 65% of the total fatty acids were esterified to triacylglycerides in oil bodies, when compared to the initial culture, indicating that the algal cells utilized de novo synthesis of fatty acids. It is vital for the lipid content in algal cells to be of high enough quantity, while maintaining adequate cell division times, so parameters that can maximize both are under investigation.

Wastewater modifica

  Lo stesso argomento in dettaglio: Wastewater treatment facility.

A possible nutrient source is waste water from the treatment of sewage, agricultural, or flood plain run-off, all currently major pollutants and health risks. However, this waste water cannot feed algae directly and must first be processed by bacteria, through anaerobic digestion. If waste water is not processed before it reaches the algae, it will contaminate the algae in the reactor, and at the very least, kill much of the desired algae strain. In biogas facilities, organic waste is often converted to a mixture of carbon dioxide, methane, and organic fertilizer. Organic fertilizer that comes out of the digester is liquid, and nearly suitable for algae growth, but it must first be cleaned and sterilized.[95]

The utilization of wastewater and ocean water instead of freshwater is strongly advocated due to the continuing depletion of freshwater resources. However, heavy metals, trace metals, and other contaminants in wastewater can decrease the ability of cells to produce lipids biosynthetically and also impact various other workings in the machinery of cells. The same is true for ocean water, but the contaminants are found in different concentrations. Thus, agricultural-grade fertilizer is the preferred source of nutrients, but heavy metals are again a problem, especially for strains of algae that are susceptible to these metals. In open pond systems the use of strains of algae that can deal with high concentrations of heavy metals could prevent other organisms from infesting these systems.[72] In some instances it has even been shown that strains of algae can remove over 90% of nickel and zinc from industrial wastewater in relatively short periods of time.[96]

Environmental impact modifica

In comparison with terrestrial-based biofuel crops such as corn or soybeans, microalgal production results in a much less significant land footprint due to the higher oil productivity from the microalgae than all other oil crops.[97] Algae can also be grown on marginal lands useless for ordinary crops and with low conservation value, and can use water from salt aquifers that is not useful for agriculture or drinking.,[77][98] Algae can also grow on the surface of the ocean in bags or floating screens.[99] Thus microalgae could provide a source of clean energy with little impact on the provisioning of adequate food and water or the conservation of biodiversity.[100] Algae cultivation also requires no external subsidies of insecticides or herbicides, removing any risk of generating associated pesticide waste streams. In addition, algal biofuels are much less toxic, and degrade far more readily than petroleum based fuels.[101][102][103] However, due to the flammable nature of any combustible fuel, there is potential for some environmental hazards if ignited or spilled, as may occur in a train derailment or a pipeline leak.[104] This hazard is reduced compared to fossil fuels, due to the ability for algal biofuels to be produced in a much more localized manner, and due to the lower toxicity overall, but the hazard is still there nonetheless. Therefore, algal biofuels should be treated in a similar manner to petroleum fuels in transportation and use, with sufficient safety measures in place at all times.

Studies have determined that replacing fossil fuels with renewable energy sources, such as biofuels, have the capability of reducing CO2 emissions by up to 80%.[105] An algae-based system could capture approximately 80% of the CO2 emitted from a power plant when sunlight is available. Although this CO2 will later be released into the atmosphere when the fuel is burned, this CO2 would have entered the atmosphere regardless.[98] The possibility of reducing total CO2 emissions therefore lies in the prevention of the release of CO2 from fossil fuels. Furthermore, compared to fuels like diesel and petroleum, and even compared to other sources of biofuels, the production and combustion of algal biofuel does not produce any sulfur oxides or nitrous oxides, and produces a reduced amount of carbon monoxide, unburned hydrocarbons, and reduced emission of other harmful pollutants.[106] Since terrestrial plant sources of biofuel production simply do not have the production capacity to meet current energy requirements, microalgae may be one of the only options to approach complete replacement of fossil fuels.

Microalgae production also includes the ability to use saline waste or waste CO2 streams as an energy source. This opens a new strategy to produce biofuel in conjunction with waste water treatment, while being able to produce clean water as a byproduct.[106] When used in a microalgal bioreactor, harvested microalgae will capture significant quantities of organic compounds as well as heavy metal contaminants absorbed from wastewater streams that would otherwise be directly discharged into surface and ground-water.[97] Moreover, this process also allows the recovery of phosphorus from waste, which is an essential but scarce element in nature – the reserves of which are estimated to have depleted in the last 50 years.[107] Another possibility is the use of algae production systems to clean up non-point source pollution, in a system known as an algal turf scrubber (ATS). This has been demonstrated to reduce nitrogen and phosphorus levels in rivers and other large bodies of water affected by eutrophication, and systems are being built that will be capable of processing up to 110 million liters of water per day. ATS can also be used for treating point source pollution, such as the waste water mentioned above, or in treating livestock effluent.[83][108][109]

Polycultures modifica

Nearly all research in algal biofuels has focused on culturing single species, or monocultures, of microalgae. However, ecological theory and empirical studies have demonstrated that plant and algae polycultures, i.e. groups of multiple species, tend to produce larger yields than monocultures.[110][111][112][113] Experiments have also shown that more diverse aquatic microbial communities tend to be more stable through time than less diverse communities.[114][115][116][117] Recent studies found that polycultures of microalgae produced significantly higher lipid yields than monocultures.[118][119] Polycultures also tend to be more resistant to pest and disease outbreaks, as well as invasion by other plants or algae.[120] Thus culturing microalgae in polyculture may not only increase yields and stability of yields of biofuel, but also reduce the environmental impact of an algal biofuel industry.[100]

Economic viability modifica

There is clearly a demand for sustainable biofuel production, but whether a particular biofuel will be used ultimately depends not on sustainability but cost efficiency. If more energy goes into the fuel than is expelled after combustion, there is no net environmental or economic benefit. Therefore research is focusing on cutting the cost of algal biofuel production to the point where it can compete with conventional petroleum.[36] Also, besides focusing on simply producing biofuel alone, it is also advisable to combine the fuel production with making other export products from the algae, such as fatty acids, colorants, protein, antioxidants, or food for another species (fish, ...) The production of several products from algae has been mentioned as the most important factor for making algae production economically viable. Other factors are the improving of the solar energy to biomass conversion efficiency (currently 3%, but 5 to 7% is theoretically attainable[121])and making the oil extraction from the algae more easy.[122]

In a 2007 report[36] a formula was derived estimating the cost of algal oil in order for it to be a viable substitute to petroleum diesel:

C(algal oil) = 25.9 × 10−3 C(petroleum)

where: C(algal oil) is the price of microalgal oil in dollars per gallon and C(petroleum) is the price of crude oil in dollars per barrel. This equation assumes that algal oil has roughly 80% of the caloric energy value of crude petroleum. As of 29 January (2013), with petroleum priced at $110.52/barrel,[123] algal oil should cost no more than $120 per barrel ($2.86/gallon) in order to be competitive with petroleum diesel. (Note: 1 petroleum barrel = 42 US gallons)

With current technology available it is estimated that the cost of producing microalgal biomass is $2.95/kg for photobioreactors and $3.80/kg for open-ponds. These estimates assume that carbon dioxide is available at no cost.[124] If the annual biomass production capacity is increased to 10000 tonnes, the cost of production per kilogram reduces to roughly $0.47 and $0.60, respectively. Assuming that the biomass contains 30% oil by weight, the cost of biomass for providing a liter of oil would be approximately $1.40 and $1.81 for photobioreactors and raceways, respectively. Oil recovered from the lower cost biomass produced in photobioreactors is estimated to cost $2.80/L, assuming the recovery process contributes 50% to the cost of the final recovered oil.[36] If existing algae projects can achieve biodiesel production price targets of less than $1 per gallon, the United States may realize its goal of replacing up to 20% of transport fuels by 2020 by using environmentally and economically sustainable fuels from algae production.[125]

Whereas technical problems, such as harvesting, are being addressed successfully by the industry, the high up-front investment of algae-to-biofuels facilities is seen by many as a major obstacle to the success of this technology. Only few studies on the economic viability are publicly available, and must often rely on the little data (often only engineering estimates) available in the public domain. Dmitrov[126] examined the GreenFuel's photobioreactor and estimated that algae oil would only be competitive at an oil price of $800 per barrel. A study by Alabi et al.[127] examined raceways, photobioreactors and anaerobic fermenters to make biofuels from algae and found that photobioreactors are too expensive to make biofuels. Raceways might be cost-effective in warm climates with very low labor costs, and fermenters may become cost-effective subsequent to significant process improvements. The group found that capital cost, labor cost and operational costs (fertilizer, electricity, etc.) by themselves are too high for algae biofuels to be cost-competitive with conventional fuels. Similar results were found by others,[128][129][130] suggesting that unless new, cheaper ways of harnessing algae for biofuels production are found, their great technical potential may never become economically accessible. Recently, Rodrigo E. Teixeira[131] demonstrated a new reaction and proposed a process for harvesting and extracting raw materials for biofuel and chemical production that requires a fraction of the energy of current methods, while extracting all cell constituents.

Use of Byproducts modifica

Many of the byproducts produced in the processing of microalgae can be used in various applications, many of which have a longer history of production than algal biofuel. Some of the products not used in the production of biofuel include natural dyes and pigments, antioxidants, and other high-value bio-active compounds.[73][132][133] These chemicals and excess biomass have found numerous use in other industries. For example, the dyes and oils have found a place in cosmetics, commonly as thickening and water-binding agents.[134] Discoveries within the pharmaceutical industry include antibiotics and antifungals derived from microalgae, as well as natural health products, which have been growing in popularity over the past few decades. For instance Spirulina contains numerous polyunsaturated fats (Omega 3 and 6), amino acids and vitamins,[135] as well as pigments that may be beneficial, such as beta-carotene and chlorophyll.[136]

Advantages modifica

Ease of growth modifica

One of the main advantages that using microalgae as the feedstock when compared to more traditional crops is that it can be grown much more easily.[137] Algae can be grown in land that would not be considered suitable for the growth of the regularly used crops.[73] In addition to this, wastewater that would normally hinder plant growth has been shown to be very effective in growing algae.[137] Because of this, algae can be grown without taking up arable land that would otherwise be used for producing food crops, and the better resources can be reserved for normal crop production. Microalgae also require fewer resources to grow and little attention is needed, allowing the growth and cultivation of algae to be a very passive process.[73]

Impact on food modifica

Many traditional feedstocks for biodiesel, such as corn and palm, are also used as feed for livestock on farms, as well as a valuable source of food for humans. Because of this, using them as biofuel reduces the amount of food available for both, resulting in an increased cost for both the food and the fuel produced. Using algae as a source of biodiesel can alleviate this problem in a number of ways. First, algae is not used as a primary food source for humans, meaning that it can be used solely for fuel and there would be little impact in the food industry.[138] Second, many of the waste-product extracts produced during the processing of algae for biofuel can be used as a sufficient animal feed. This is an effective way to minimize waste and a much cheaper alternative to the more traditional corn or grain based feeds.[139]

Minimization of waste modifica

Growing algae as a source of biofuel has also been shown to have numerous environmental benefits, and has presented itself as a much more environmentally friendly alternative to current biofuels. For one, it is able to utilize run-off, water contaminated with fertilizers and other nutrients that are a by-product of farming, as its primary source of water and nutrients.[137] Because of this, it prevents this contaminated water from mixing with the lakes and rivers that currently supply our drinking water. In addition to this, the ammonia, nitrates, and phosphates that would normally render the water unsafe actually serve as excellent nutrients for the algae, meaning that fewer resources are needed to grow the algae.[73] Many algae species used in biodiesel production are excellent bio-fixers, meaning they are able to remove carbon dioxide from the atmosphere to use as a form of energy for themselves. Because of this, they have found use in industry as a way to treat flue gases and reduce GHG emissions.[73]

Disadvantages modifica

Commercial Viability modifica

Algae biodiesel is still a fairly new technology. Despite the fact that research began over 30 years ago, it was put on hold during the mid-1990s, mainly due to a lack of funding and a relatively low petroleum cost.[32] For the next few years algae biofuels saw little attention; it was not until the gas peak of the early 2000s that it eventually had a revitalization in the search for alternative fuel sources.[32] While the technology exists to harvest and convert algae into a usable source of biodiesel, it still hasn't been implemented into a large enough scale to support the current energy needs. Further research will be required to make the production of algae biofuels more efficient, and at this point it is currently being held back by lobbyists in support of alternative biofuels, like those produced from corn and grain.[32] In 2013, Exxon Mobil Chairman and CEO Rex Tillerson said that after originally committing to spending up to $600 million on development in a joint venture with J. Craig Venter’s Synthetic Genomics, algae is "probably further" than "25 years away" from commercial viability,[12] although Solazyme[13] and Sapphire Energy[14] already began small-scale commercial sales in 2012 and 2013, respectively.

Stability modifica

The biodiesel produced from the processing of microalgae differs from other forms of biodiesel in the content of polyunsaturated fats.[137] Polyunsaturated fats are known for their ability to retain fluidity at lower temperatures. While this may seem like an advantage in production during the colder temperatures of the winter, the polyunsaturated fats result in lower stability during regular seasonal temperatures.[138]

Research modifica

Current projects modifica

United States modifica

  Lo stesso argomento in dettaglio: Algae fuel in the United States.

US universities which are working on producing oil from algae include: Washington State University,[140] Oregon State University, Arizona State University, The University of Arizona, University of Illinois at Urbana-Champaign,[141] University of Michigan[142] University of California, San Diego,[143] University of Nebraska Lincoln, University of Texas at Austin,[144] University of Maine, University of Kansas, The College of William and Mary, Northern Illinois University, University of Texas at San Antonio, Old Dominion University, University of Toledo, Utah State University, New Mexico State University,[145] and Missouri University of Science and Technology.[146][147]

The National Renewable Energy Laboratory (NREL) is the U.S. Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development. This program is involved in the production of renewable energies and energy efficiency. One of its most current divisions are consists the biomass program which is involved in biomass characterization, biochemical and thermochemical conversion technologies in conjunction with biomass process engineering and analysis. The program aims at producing energy efficient, cost-effective and environmentally friendly technologies that support rural economies, reduce the nations dependency in oil and improve air quality.[148]

At the Woods Hole Oceanographic Institution and the Harbor Branch Oceanographic Institution the wastewater from domestic and industrial sources contain rich organic compounds that are being used to accelerate the growth of algae.[34] The Department of Biological and Agricultural Engineering at University of Georgia is exploring microalgal biomass production using industrial wastewater.[149] Algaewheel, based in Indianapolis, Indiana, presented a proposal to build a facility in Cedar Lake, Indiana that uses algae to treat municipal wastewater, using the sludge byproduct to produce biofuel.[150][151]

Sapphire Energy (San Diego) has produced green crude from algae.

Solazyme (South San Francisco, California) has produced a fuel suitable for powering jet aircraft from algae.[152]

Europe modifica

Universities in the United Kingdom which are working on producing oil from algae include: University of Manchester, University of Sheffield, University of Glasgow, University of Brighton, University of Cambridge, University College London, Imperial College London, Cranfield University and Newcastle University. In Spain, it is also relevant the research carried out by the CSIC´s Instituto de Bioquímica Vegetal y Fotosíntesis (Microalgae Biotechnology Group, Seville).[153]

The Marine Research station in Ketch Harbour, Nova Scotia, has been involved in growing algae for 50 years. The National Research Council (Canada) (NRC) and National Byproducts Program have provided $5 million to fund this project. The aim of the program has been to build a 50 000 litre cultivation pilot plant at the Ketch harbor facility. The station has been involved in assessing how best to grow algae for biofuel and is involved in investigating the utilization of numerous algae species in regions of North America. NRC has joined forces with the United States Department of Energy, the National Renewable Energy Laboratory in Colorado and Sandia National Laboratories in New Mexico.[148]

The European Algae Biomass Association (EABA) is the European association representing both research and industry in the field of algae technologies, currently with 79 members. The association is headquartered in Florence, Italy. The general objective of the EABA is to promote mutual interchange and cooperation in the field of biomass production and use, including biofuels uses and all other utilisations. It aims at creating, developing and maintaining solidarity and links between its Members and at defending their interests at European and international level. Its main target is to act as a catalyst for fostering synergies among scientists, industrialists and decision makers to promote the development of research, technology and industrial capacities in the field of Algae.

CMCL innovations and the University of Cambridge are carrying out a detailed design study of a C-FAST[154] (Carbon negative Fuels derived from Algal and Solar Technologies) plant. The main objective is to design a pilot plant which can demonstrate production of hydrocarbon fuels (including diesel and gasoline) as sustainable carbon-negative energy carriers and raw materials for the chemical commodity industry. This project will report in June 2013.

Ukraine plans to produce biofuel using a special type of algae.[155]

The European Commission's Algae Cluster Project, funded through the Seventh Framework Programme, is made up of three algae biofuel projects, each looking to design and build a different algae biofuel facility covering 10ha of land. The projects are BIOFAT, All-Gas and InteSusAl.[156]

Since various fuels and chemicals can be produced from algae, it has been suggested to investigate the feasibility of various production processes( conventional extraction/separation, hydrothermal liquefaction, gasification and pyrolysis) for application in an integrated algal biorefinery.[157]

Other modifica

The Algae Biomass Organization (ABO)[158] is a non-profit organization whose mission is "to promote the development of viable commercial markets for renewable and sustainable commodities derived from algae".

The National Algae Association (NAA) is a non-profit organization of algae researchers, algae production companies and the investment community who share the goal of commercializing algae oil as an alternative feedstock for the biofuels markets. The NAA gives its members a forum to efficiently evaluate various algae technologies for potential early stage company opportunities.

Pond Biofuels Inc.[159] in Ontario, Canada has a functioning pilot plant where algae is grown directly off of smokestack emissions from a cement plant, and dried using waste heat.[78] In May 2013, Pond Biofuels announced a partnership with the National Research Council of Canada and Canadian Natural Resources Limited to construct a demonstration-scale algal biorefinery at an oil sands site near Bonnyville, Alberta.[160]

Ocean Nutrition Canada in Halifax, Nova Scotia, Canada has found a new strain of algae that appears capable of producing oil at a rate 60 times greater than other types of algae being used for the generation of biofuels.[161]

VG Energy, a subsidiary of Viral Genetics Incorporated,[162] claims to have discovered a new method of increasing algal lipid production by disrupting the metabolic pathways that would otherwise divert photosynthetic energy towards carbohydrate production. Using these techniques, the company states that lipid production could be increased several-fold, potentially making algal biofuels cost-competitive with existing fossil fuels.

Algae production from the warm water discharge of a nuclear power plant has been piloted by Patrick C. Kangas at Peach Bottom Nuclear Power Station, owned by Exelon Corporation. This process takes advantage of the relatively high temperature water to sustain algae growth even during winter months.[163]

Companies such as Sapphire Energy and Bio Solar Cells[164] are using genetic engineering to make algae fuel production more efficient. According to Klein Lankhorst of Bio Solar Cells, genetic engineering could vastly improve algae fuel efficiency as algae can be modified to only build short carbon chains instead of long chains of carbohydrates.[165] Sapphire Energy also uses chemically induced mutations to produce algae suitable for use as a crop.[166]

Some commercial interests into large-scale algal-cultivation systems are looking to tie in to existing infrastructures, such as cement factories,[78] coal power plants, or sewage treatment facilities. This approach changes wastes into resources to provide the raw materials, CO2 and nutrients, for the system.[167]

A feasibility study using marine microalgae in a photobioreactor is being done by The International Research Consortium on Continental Margins at the Jacobs University Bremen.[168]

The Department of Environmental Science at Ateneo de Manila University in the Philippines, is working on producing biofuel from a local species of algae.[169]

Genetic engineering modifica

Genetic engineering the algae has been used to increase lipid production or growth rates. Current research in genetic engineering includes either the introduction or removal of enzymes. In 2007 Oswald et al. introduced a monoterpene synthase from sweet basil into Saccharomyces cerevisiae, a strain of yeast.[170] This particular monoterpene synthase causes the de novo synthesis of large amounts of geraniol, while also secreting it into the medium. Geraniol is a primary component in rose oil, palmarosa oil, and citronella oil as well as essential oils, making it a viable source of triacylglycerides for biodiesel production.[171]

The enzyme ADP-glucose pyrophosphorylase is vital in starch production, but has no connection to lipid synthesis. Removal of this enzyme resulted in the sta6 mutant, which showed increased lipid content. After 18 hours of growth in nitrogen deficient medium the sta6 mutants had on average 17 ng triacylglycerides/1000 cells, compared to 10 ng/1000 cells in WT cells. This increase in lipid production was attributed to reallocation of intracellular resources, as the algae diverted energy from starch production.[172]

In 2013 researchers used a "knock-down" of fat-reducing enzymes (multifunctional lipase/phospholipase/acyltransferase) to increase lipids (oils) without compromising growth. The study also introduced an efficient screening process. Antisense-expressing knockdown strains 1A6 and 1B1 contained 2.4- and 3.3-fold higher lipid content during exponential growth, and 4.1- and 3.2-fold higher lipid content after 40 h of silicon starvation.[173][174]

Funding programs modifica

Numerous Funding programs have been created with aims of promoting the use of Renewable Energy. In Canada, the ecoAgriculture biofuels capital initiative (ecoABC) provides $25 million per project to assist farmers in constructing and expanding a renewable fuel production facility. The program has $186 million set aside for these projects. The sustainable development (SDTC) program has also applied $500 millions over 8 years to assist with the construction of next-generation renewable fuels. In addition, over the last 2 years $10 million has been made available for renewable fuel research and analysis[175]

In Europe, the Seventh Framework Programme (FP7) is the main instrument for funding research. Similarly, the NER 300 is an unofficial, independent portal dedicated to renewable energy and grid integration projects. Another program includes the horizon 2020 program which will start 1 January, and will bring together the framework program and other EC innovation and research funding into a new integrated funding system[176]

The American NBB's Feedstock Development program is addressing production of algae on the horizon to expand available material for biodiesel in a sustainable manner.[177]

International policies modifica

Canada modifica

Numerous policies have been put in place since the 1975 oil crisis in order to promote the use of Renewable Fuels in the United States, Canada and Europe. In Canada, these included the implementation of excise taxes exempting propane and natural gas which was extended to ethanol made from biomass and methanol in 1992. The federal government also announced their renewable fuels strategy in 2006 which proposed four components: increasing availability of renewable fuels through regulation, supporting the expansion of Canadian production of renewable fuels, assisting farmers to seize new opportunities in this sector and accelerating the commercialization of new technologies. These mandates were quickly followed by the Canadian provinces:

BC introduced a 5% ethanol and 5% renewable diesel requirement which was effective by January 2010. It also introduced a low carbon fuel requirement for 2012 to 2020.

Alberta introduced a 5% ethanol and 2% renewable diesel requirement implemented April 2011. The province also introduced a minimum 25% GHG emission reduction requirement for qualifying renewable fuels.

Saskatchewan implemented a 2% renewable diesel requirement in 2009.[178]

Additionally, in 2006, the Canadian Federal Government announced its commitment to using its purchasing power to encourage the biofuel industry. Section three of the 2006 alternative fuels act stated that when it is economically feasible to do so-75% per cent of all federal bodies and crown corporation will be motor vehicles.[175]

The National Research Council of Canada has established research on Algal Carbon Conversion as one of its flagship programs.[179] As part of this program, the NRC made an announcement in May 2013 that they are partnering with Canadian Natural Resources Limited and Pond Biofuels to construct a demonstration-scale algal biorefinery near Bonnyville, Alberta.[160]

United States modifica

Policies in the United States have included a decrease in the subsidies provided by the federal and state governments to the oil industry which have usually included $2.84 billion. This is more than what is actually set aside for the biofuel industry. The measure was discussed at the G20 in Pittsburgh where leaders agreed that "inefficient fossil fuel subsidies encourage wasteful consumption, reduce our energy security, impede investment in clean sources and undermine efforts to deal with the threat of climate change". If this commitment is followed through and subsidies are removed, a fairer market in which algae biofuels can compete will be created. In 2010, the U.S. House of Representatives passed a legislation seeking to give algae-based biofuels parity with cellulose biofuels in federal tax credit programs. The algae based renewable fuel promotion act (HR 4168) was implemented to give biofuel projects access to a $1.01 per gal production tax credit and 50% bonus depreciation for biofuel plant property. The U.S Government also introduced the domestic Fuel for Enhancing National Security Act implemented in 2011. This policy constitutes an amendment to the Federal property and administrative services act of 1949 and federal defense provisions in order to extend to 15 the number of years that the Department of Defense (DOD) multiyear contract may be entered into the case of the purchase of advanced biofuel. Federal and DOD programs are usually limited to a 5-year period[180]

Other modifica

The European Union (EU) has also responded by quadrupling the credits for second-generation algae biofuels which was established as an amendment to the Biofuels and Fuel Quality Directives[176]

Companies modifica

  Lo stesso argomento in dettaglio: List of algal fuel producers.

With algal biofuel being a relatively new alternative to conventional petroleum products, it leaves numerous opportunities for drastic advances in all aspects of the technology. Producing algae biofuel is not yet a cost-effective replacement for gasoline, but alterations to current methodologies can change this. The two most common targets for advancements are the growth medium (open pond vs. photobioreactor) and methods to remove the intracellular components of the algae. Below are companies that are currently innovating algal biofuel technologies.

Algenol Biofuels modifica

Founded in 2006, Algenol Biofuels is a global, industrial biotechnology company that is commercializing its patented algae technology for production of ethanol and other fuels. Based in Southwest Florida, Algenol’s patented technology enables the production of the four most important fuels (ethanol, gasoline, jet, and diesel fuel) using proprietary algae, sunlight, carbon dioxide and saltwater for around $1.27 per gallon and at production levels of 8,000 total gallons of liquid fuel per acre per year. Algenol's technology produces high yields and relies on patented photobioreactors and proprietary downstream techniques for low-cost fuel production using carbon dioxide from industrial sources.[181]

Blue Marble Production modifica

Blue Marble Production is a Seattle-based company that is dedicated to removing algae from algae-infested water. This in turn cleans up the environment and allows this company to produce biofuel. Rather than just focusing on the mass production of algae, this company focuses on what to do with the byproducts. This company recycles almost 100% of its water via reverse osmosis, saving about 26,000 gallons of water every month. This water is then pumped back into their system. The gas produced as a byproduct of algae will also be recycled by being placed into a photobioreactor system that holds multiple strains of algae. Whatever gas remains is then made into pyrolysis oil by thermochemical processes. Not only does this company seek to produce biofuel, but it also wishes to use algae for a variety of other purposes such as fertilizer, food flavoring, anti-inflammatory, and anti-cancer drugs.[182]

Solazyme modifica

Solazyme is one of a handful of companies which is supported by oil companies such as Chevron. Additionally, this company is also backed by Imperium Renewables, Blue Crest Capital Finance, and The Roda Group. Solazyme has developed a way to use up to 80% percent of dry algae as oil.[183] This process requires the algae to grow in a dark fermentation vessel and be fed by carbon substrates within their growth media. The effect is the production of triglycerides that are almost identical to vegetable oil. Solazyme's production method is said to produce more oil than those algae cultivated photosynthetically or made to produce ethanol. Oil refineries can then take this algal oil and turn it into biodiesel, renewable diesel or jet fuels.

Part of Solazyme's testing, in collaboration with Maersk Line and the US Navy, placed 30 tons of Soladiesel(RD) algae fuel into the 98,000-tonne, 300-meter container ship Maersk Kalmar. This fuel was used at blends from 7% to 100% in an auxiliary engine on a month-long trip from Bremerhaven, Germany to Pipavav, India in Dec 2011. In Jul 2012, The US Navy used 700,000 gallons of HRD76 biodiesel in three ships of the USS Nimitz "Green Strike Group" during the 2012 RIMPAC exercise in Hawaii. The Nimitz also used 200,000 gallons of HRJ5 jet biofuel. The 50/50 biofuel blends were provided by Solazyme and Dynamic Fuels.[184][185][186]

Sapphire Energy modifica

Sapphire Energy is a leader in the algal biofuel industry backed by the Wellcome Trust, Bill Gates' Cascade Investment, Monsanto, and other large donors.[187] After experimenting with production of various algae fuels beginning in 2007, the company now focuses on producing what it calls "green crude" from algae in open raceway ponds. After receiving more than $100 million in federal funds in 2012, Sapphire built the first commercial demonstration algae fuel facility in New Mexico and has continuously produced biofuel since completion of the facility in that year.[187] In 2013, Sapphire began commercial sales of algal biofuel to Tesoro, making it one of the first companies, along with Solazyme, to sell algae fuel on the market.[14]

Diversified Technologies Inc. modifica

Diversified Technologies Inc. has created a patent pending pre-treatment option to reduce costs of oil extraction from algae. This technology, called Pulsed Electric Field (PEF) technology, is a low cost, low energy process that applies high voltage electric pulses to a slurry of algae.[188] The electric pulses enable the algal cell walls to be ruptured easily, increasing the availability of all cell contents (Lipids, proteins and carbohydrates), allowing the separation into specific components downstream. This alternative method to intracellular extraction has shown the capability to be both integrated in-line as well as scalable into high yield assemblies. The Pulse Electric Field subjects the algae to short, intense bursts of electromagnetic radiation in a treatment chamber, electroporating the cell walls. The formation of holes in the cell wall allows the contents within to flow into the surrounding solution for further separation. PEF technology only requires 1-10 microsecond pulses, enabling a high-throughput approach to algal extraction.

Preliminary calculations have shown that utilization of PEF technology would only account for $0.10 per gallon of algae derived biofuel produced. In comparison, conventional drying and solvent based extractions account for $1.75 per gallon. This inconsistency between costs can be attributed to the fact that algal drying generally accounts for 75% of the extraction process.[189] Although a relatively new technology, PEF has been successfully used in both food decomtamination processes as well as waste water treatments.[190]

Origin Oils Inc. modifica

Origin Oils Inc. has been researching a revolutionary method called the Helix Bioreactor,[191] altering the common closed-loop growth system. This system utilizes low energy lights in a helical pattern, enabling each algal cell to obtain the required amount of light.[192] Sunlight can only penetrate a few inches through algal cells, making light a limiting reagent in open-pond algae farms. Each lighting element in the bioreactor is specially altered to emit specific wavelengths of light, as a full spectrum of light is not beneficial to algae growth. In fact, ultraviolet irradiation is actually detrimental as it inhibits photosynthesis, photoreduction, and the 520 nm light-dark absorbance change of algae.[193]

This bioreactor also addresses another key issue in algal cell growth; introducing CO2 and nutrients to the algae without disrupting or over-aerating the algae. Origin Oils Inc. combats this issues through the creation of their Quantum Fracturing technology. This process takes the CO2 and other nutrients, fractures them at extremely high pressures and then deliver the micron sized bubbles to the algae. This allows the nutrients to be delivered at a much lower pressure, maintaining the integrity of the cells.[192]

Proviron modifica

Proviron has been working on a new type of reactor (using flat plates) which reduces the cost of algae cultivation. At AlgaePARC similar research is being conducted using 4 grow systems (1 open pond system and 3 types of closed systems). According to René Wijffels the current systems do not yet allow algae fuel to be produced competitively. However using new (closed) systems, and by scaling up the production it would be possible to reduce costs by 10X, up to a price of 0,4 € per kg of algae.[194]

Genifuels modifica

Genifuel Corporation has licensed the high temperature/pressure fuel extraction process and has been working with the team at the lab since 2008. The company intends to team with some industrial partners to create a pilot plant using this process to make biofuel in industrial quantities.[87] Genifuel process combines hydrothermal liquefaction with catalytic hydrothermal gasification in reactor running at 350 Celsius (662 Fahrenheit) and pressure of 3000 PSI.[195]

See also modifica

References modifica

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