Newsgroup: it.discussioni.ingegneria
Titolo: Etanolo da cellulosa

[crosspost]
Facendo una ricerca mi sono imbattuto in questi articoli che ho trovato
molto intressanti
http://www.ornl.gov/sci/scale/pubs/Nuclear%20News%202007-3-3.pdf
http://mit.edu/ans/www/documents/seminar/F08/forsbergpaper.pdf
oppure
http://www-pub.iaea.org/MTCD/Meetings/PDFplus/2007/cn152/cn152p/IAEA07%20Japan%20Forsberg%20Rev.pdf
ed allora ho cercato di approfondire un p� il problema.
L' enfasi in quegli articoli � sull' uso dell' energia nucleare, tuttavia,
indipendentemente da quale fonte si usi, mi sembrano interessanti alcuni
fatti :
1) le attuali raffinerie di petrolio consumano da sole in Usa il 7% dell'
energia consumata nel Paese
2) il 70-80% dell' energia rispetto al potere energetico del combustibile
liquido finito nell' attuale produzione di etanolo (tipicamente da mais) �
di origine non rinnovabile; e pi� della met� del totale � calore a bassa
temperatura (180 �C, 10 atm) per fermentare/distillare il prodotto.
Occorrono circa 260 MW termici per produrre un miliardo di litri/anno di
etanolo
3) particolare interessante, a differenza del mais/barbabietola o canna da
zucchero, la materia prima � enorme ed estesamente diffusa e non richiede
necessariamente che terreni debbano essere coltivati; secondo la pagina di
wikipedia :
http://en.wikipedia.org/wiki/Cellulosic_ethanol
"Cellulose is present in every plant, in the form of straw, grass, and wood.
Most of these "bio-mass" products are currently discarded.[citation needed]
It is estimated that 323 million tons of cellulose containing raw materials
that could be used to create ethanol are thrown away each year in US alone.
This includes 36.8 million dry tons of urban wood wastes, 90.5 million dry
tons of primary mill residues, 45 million dry tons of forest residues, and
150.7 million dry tons of corn stover & wheat straw.[37] Transforming them
into ethanol using efficient and cost effective hemi(cellulase) enzymes or
other processes might provide as much as 30% of the current fuel consumption
in the United States - and probably similar figures in other oil-importing
regions like China or Europe.[citation needed]
Moreover, even land marginal for agriculture could be planted with
cellulose-producing crops like switchgrass, resulting in enough production
to substitute for all the current oil imports into the United States.[38]
Paper, cardboard, and packaging comprise a substantial part of the solid
waste sent to landfills in the United States each day, 41.26% of all organic
municipal solid waste (MSW) according to California Integrated Waste
Management Board's city profiles.[citation needed] These city profiles
account for accumulation of 612.3 tons daily per landfill where an average
population density of 2,413 per square mile persists. Organic waste consists
of 0.4% Manures, 1.6% Gypsum Board, 4.2% Glossy Paper, 4.2% Paper Ledger,
9.2% Wood, 10.5% Envelopes, 11.9% Newsprint, 12.3% Grass & Leaves, 30.0%
Food Scrap, 34.0% Office Paper, 35.2% Corrugated Cardboard, and 46.4%
Agricultural Composites, makes up 71.51% of land fill. All these except
Gypsum Board contain cellulose which is transformable into cellulosic
ethanol[37] because they are the leading cause of methane plumes. Methane, a
greenhouse gas, is 21 times more potent than carbon-dioxide.[39]
Reduction of the disposal of solid waste through cellulosic ethanol
conversion would reduce solid waste disposal costs by local and state
governments. It is estimated that each person in the US throws away 4.4 lb
(2.0 kg) of trash each day, of which 37% contains waste paper which is
largely cellulose. That computes to 244 thousand tons per day of discarded
waste paper that contains cellulose.[40] The raw material to produce
cellulosic ethanol is not only free, it has a negative cost - i.e., ethanol
producers can get paid to take it away "
Il costo di impianto � per� oggi ancora apprezzabilmente superiore :
"...This translates into $7/annual gallon production capacity in capital
investment costs for pilot plants (this would work out to $.35/gal over the
20-year life of a facility); future capital costs are expected to be lower.
Corn to ethanol plants cost roughly $1-3/annual gallon capacity, though the
cost of the corn itself is considerably greater than for switchgrass or
waste biomass "
Ora, � chiaro che buona parte del consumo di petrolio (e gas) pu� essere
evitato nel trasporto attraverso il ricorso a treni elettrificati, veicoli
elettrici ed ibridi o pompe di calore e il solare termico (o il
teleriscaldamento, preferibilmente da fonti non fossili) per il
riscaldamento/acqua calda; tuttavia, come spesso si mette in evidenza, ci
sono usi non facilmente elettrificabili (o per nulla elettrificabili) come
navi, aerei, treni diesel o parte del trasporto privato che necessitano
almeno un p� di combustibili liquidi e per i quali i bio-combustibili
possono essere una strategia vincente
Commenti ed opinioni sono ovviamente ben accetti

 usi, mi sembrano interessanti alcuni fatti :
http://www.forum-macchine.it/printthread.php?t=8183
http://it.geocities.com/cinemaprealpib/Risorse/prealpi41_apr2006.jpg
http://www.bper.it/gruppobper/incontri/pdf_71/79_82_Fittipaldi.pdf
http://it.wikipedia.org/wiki/Gassogeno

 Commenti ed opinioni sono ovviamente ben accetti
Oltre ai modelli a legna, ci sono anche quelli avanzati, a
carbone:
http://www.tronmodels.com/detail.asp?id=1266&idgrp=9