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energy_isere a écrit :C'est Gilles qui a l' interpretation correcte.
Tu entre 1 unité d'energie avant la raffinerie, tu en sort 0.917 à la pompe, le rendement est : sortie/entrée = 0.917/1 = 0.917 , et en % ca fait 91.7 %. ca correspond à 8.3 % de pertes (essentiellement l'energie thermique necessaire au craquage)
et si tu sortais 1 unité d'energie à la pompe alors ton rendement serait de 100%. pas de pertes. Mais ca on ne sait pas le réaliser.

Yéyé a écrit :

energy_isere a écrit :C'est Gilles qui a l' interpretation correcte.
Tu entre 1 unité d'energie avant la raffinerie, tu en sort 0.917 à la pompe, le rendement est : sortie/entrée = 0.917/1 = 0.917 , et en % ca fait 91.7 %. ca correspond à 8.3 % de pertes (essentiellement l'energie thermique necessaire au craquage)
et si tu sortais 1 unité d'energie à la pompe alors ton rendement serait de 100%. pas de pertes. Mais ca on ne sait pas le réaliser.

C'est pas en ressortant la même équation bancale qu'on comprend mieux, elle s'applique toujours aussi mal aux autres chiffres présents sur le document de l'Ademe !

Remplace le 0,917 du gas-oil par le 2,05 de l'éthanol et dis moi à quoi correspond le résultat !!!

USA: Le charbon vole au secours du bioéthanol

Sous l'effet de l'augmentation du prix du gaz naturel, les opérateurs des usines de bioéthanol songent de plus en plus à se convertir au charbon pour leurs besoins énergétiques. Pour l'instant, seules 4 des 100 usines d'éthanol en production aux USA recourent à cette énergie fossile, mais selon certains spécialistes, cette tendance devrait s'imposer pour les 190 installations en cours de construction ou en projet.

La conversion au charbon des installations de production d'éthanol aurait des conséquences négatives sur la performance environnementale du biocarburant. En effet, la conversion en éthanol de la matière première, le maïs, est déjà très consommatrice en énergies fossiles, au point que certains scientifiques vont jusqu'à contester sa rentabilité énergétique.

En matière d'émissions de gaz à effet de serre, le biocarburant issu des usines fonctionnant au charbon offrirait un bénéfice réduit par rapport au biocarburant issu d'un procédé au gaz naturel (-19% de réduction d'émissions par rapport aux carburants conventionnels contre -38%).

L'EPA envisage de relâcher les contraintes réglementaires pesant sur les émissions des polluants réglementés par le Clean Air Act émanant des usines de bioéthanol. Le maximum actuel de 100 tonnes par polluant et par an passerait à 250 tonnes par an (maximum s'appliquant déjà aux installations de production d'éthanol destinées aux autres usages).

Ce projet, véritable encouragement au recours au charbon, est fortement soutenu par un collectif du Congrès, ainsi que par la Renewable Fuel Association qui mettent en avant la nécessité de faciliter un développement rapide du marché et des capacités industrielles en bioéthanol. Dans la phase émergente de cette nouvelle industrie prétendent-ils, il convient de privilégier la croissance aux innovations technologiques sur le procédé.

Les opposants à cette nouvelle réglementation objectent que le marché des biocarburants a doublé en 4 ans aux USA et que des technologies prometteuses sont déjà disponibles pour s'affranchir de toute énergie fossile dans la conversion du maïs en éthanol.

Une usine du Nebraska utilisant de la biomasse animale comme base énergétique réaliserait d'ores et déjà un gain de -70% par rapport à l'essence sur les émissions de gaz à effet de serre, se rapprochant ainsi des gains escomptés pour l'éthanol issu des matériaux cellulosiques (-88%).

Rivers of unwanted wine to turn into biofuel

Up to 510 million litres of this year's surplus wine will be made into bioethanol that can only be used as biofuel or industrial alcohol, the European Commission announced on Wednesday.

French winemakers have been given a quota of 150m hectolitres of table wine and 150m of quality wine, while Italians can sell 250m of quality and 10m litres of table wine for what the EU calls "crisis distillation."

Greek and Spanish winemakers have also asked the EU to to buy their unwanted wine, and are awaiting a response.

The EU will pay around 130m euros for this year's surplus wine. Last year, more than 180m euros of EU cash went to pay for the distillation of wine for which buyers could not be found.

Turning quality wine into bioethanol may not be the cheapest way of producing biofuel, but it makes use of some of the excess wine that would otherwise go to waste.

Nevertheless, the EU aims to put an end to the practice by cutting the amount of surplus wine produced. Agriculture commissioner Mariann Fischer Boel said: "Crisis distillation is becoming a depressingly regular feature of our common market organisation for wine.

"While it offers temporary assistance to producers, it does not deal with the core of the problem - that Europe is producing too much wine for which there is no market. That is why a deep-rooted reform of the sector is needed urgently."

The EU strategy aimed at cutting waste in the viticulture industry will be unveiled when Mariann Fischer Boel presents her plans for reforming the sector on 22 June.

The plans foresee introducing new production methods to bring down prices and make European wine more competitive on the global market.

A Range of Estimates on Ethanol's Benefits

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By ALEXEI BARRIONUEVO
Published: June 25, 2006

Would using ethanol save energy?

That question, it turns out, is not easy to answer. Ethanol's enthusiasts point to the potential benefits of replacing gasoline with a renewable energy source that they contend will reduce America's reliance on foreign oil and cut greenhouse gases produced by fossil fuels. But the benefits of ethanol, particularly when it is produced from corn, are not so clear cut.

A number of researchers who have looked at the issue have concluded that more energy now goes into making a gallon of ethanol than is contained in that gallon. Others, however, find a net benefit, though most see it as relatively modest.

Those who question whether ethanol is as "green" as advertised say that supporters ignore or downplay the large quantities of natural gas used to produce ethanol, as well as the diesel fuel used to transport it from plants to markets. Moreover, growing corn requires heavy use of nitrogen fertilizers, made from natural gas, and requires extensive use of farm machinery, which burns fuel refined from crude oil.

Given the complexities of the calculations, there is a wide range of estimates of the benefits of ethanol.

On the positive side, analysts at the Agriculture Department concluded in their most recent assessment that ethanol offered a substantial gain, producing a positive output 67 percent greater than the energy inputs. But others who view ethanol favorably are more conservative, with several estimating the net energy benefit at about 20 percent.

David Pimentel, a professor of agriculture and life sciences at Cornell University, is one of several researchers who has challenged the Agriculture Department's conclusion. He has estimated that ethanol requires 29 percent more energy from fossil fuels than it delivers in savings from not using gasoline.

Dr. Pimentel, along with Tadeusz W. Patzek, a civil and environmental engineer from the University of California at Berkeley, published research finding that the Agriculture Department's analysis excluded the energy required to produce or repair farm machinery, as well as the steel and cement used to build the plants.

The Agriculture Department counters by noting that the professors failed to consider the energy benefit of certain ethanol byproducts, including corn oil and corn gluten, and said they were using old farm machinery data.

"They put all the energy on the ethanol," said Roger Conway, director of the department's office of energy policy and new uses.

The Agriculture Department also points to increases in corn yields, and efficiency improvements in the fertilizer and ethanol industries, which add to ethanol's energy benefit.

Dr. Pimentel acknowledged the omissions of some byproducts, saying they might have boosted the energy balance to as much as break even. But he said that even a best-case scenario, using his calculations, did not justify a heavy investment in ethanol. He called the push into ethanol a "boondoggle" motivated by farm-state politics and big profits.

Dr. Pimentel, who first began criticizing ethanol as an energy alternative about 25 years ago, said that he has never been supported by the oil industry. Dr. Patzek has worked as a researcher for an oil company in the past but said that his biofuels research had received no support from the industry.

Several environmental groups that support ethanol concede that the energy savings from corn-based ethanol may be limited, but they say it will serve as a crucial bridge to more efficient sources like switchgrass, a type of prairie grass that could potentially be used to produce ethanol.

The choice of what fuel to use to run an ethanol plant will also play a role in determining its ultimate energy efficiency. In Hereford, Tex., White Energy expects to use natural gas to power its ethanol plant, while another Dallas-based company, Panda Energy International, plans to use Hereford's ample supplies of cow manure as fuel.

Driven by the high cost of natural gas, about 10 of 39 ethanol plants under construction are being designed to run on coal, according to Robert McIlvaine, who runs a market research firm in Northfield, Ill.

Mr. Conway of the Agriculture Department called the move to cheaper and more abundant coal to run ethanol plants "preferable."

But Nathanael Greene, senior policy analyst at the Natural Resources Defense Council, which has supported ethanol's use, disagreed, pointing out that burning coal normally produces twice as much greenhouse gas as natural gas.

"This is going to significantly increase the local air pollution," Mr. Greene said, "and diminish the benefits of using ethanol."

AFRIQUE DU SUD - Bioéthanol et PGM
Syngenta a déposé en mai une demande d’autorisation pour l’importation et la transformation du maïs 3272, génétiquement modifié pour produire une enzyme alpha-amylase [1]. Cette enzyme transforme l’amidon du maïs en sucre, lequel sera alors industriellement transformé en éthanol. A l’heure actuelle, l’enzyme est ajoutée manuellement après production par des micro-organismes. Il faut préciser que les “déchets” de ce maïs, une fois l’éthanol produit, pourront rejoindre les autres produits dérivés commercialisés. Dans l’UE, ce dossier (UK/2006 /34), déposé selon la procédure 1829/03, concerne la transformation, mais inclut l’alimentation humaine et animale, car elle n’exclut pas que des produits dérivés se retrouvent dans la chaîne alimentaire. Syngenta précise que la culture se fera hors de l’Europe [2]. Aux Etats-Unis, le dossier (n°05-280-01p) n’a pas encore été validé [3].

China plans to boost ethanol output


China last year produced about 920,000 tonnes of ethanol, which it plans to boost to nearly 4 million tonnes by 2010, according to a US Agriculture Department attache report.

As part its biofuel development policies, China aims to meet 15 per cent of its transportation energy needs this way by 2020, said the USDA attache report dated August 8 and made available.

"Presently biofuels are approximately 1 million tonnes. China's policy objectives are produce 12 million tonnes of biofuels - including ethanol and biodiesel - annually by 2020, pushing it up to 15 per cent of the nation's transportation fuel use," the report said.

China, the world's third largest ethanol producer after the US and Brazil, is trying to cut its dependence on imported oil.

Late this year, China will release implementation plans of the biofuels component of its 2006-2010 planning period, the report said.

Implementation questions include whether China sets a national target for ethanol in its national energy mix, it noted.

"Ethanol producers' dependence on government subsidies will determine industry growth. Ethanol subsidies have been declining and may be phased out entirely by the end of the ... period," the report said.

Attache reports are not official USDA data.

To see the full report, visit the USDA's Foreign Agricultural Service website at http://www.fas.usda.gov/scriptsw/attacherep/default.asp.

jlvx a écrit :cultivées dans des "serres", chauffées avec la combustion des résidus desdites plantes (donc pas de risque en réutilisation en aliments pour bétail)...