[freeztar]

Originally Posted by CraigD

[*]Hydrogen requires all of the energy it contains, and then some, to produce, as bad as some alcohol producing processes, is about the hardest fuel in the universe to store and handle, but produces no carbon when burned.

What about H2 and CH4 produced during pyrolysis, Craig?
It's easy to produce, but I'm not sure about collection and storage.
In any case, it seems to be ideal.

[CraigD]

Originally Posted by freeztar

What about H2 and CH4 produced during pyrolysis, Craig?
It's easy to produce, but I'm not sure about collection and storage.
In any case, it seems to be ideal.

AFAIK, hydrogen, CH4 (methane), and other “reformed” fuel gases are made from more massive hydrocarbon molecule fuels, and have no more energy than these source fuels. I’m only familiar with CH4 -> H hydrogen reformers - a few years ago, a friend of mine was interested in a GE’s home fuel cell, a heavily subsidized program involving a refrigerator-sized, hydrogen fuel cell producing about 2000 W when supplied with residential natural gas (mostly CH4). I understand that such reformers can be about 80% efficient (though they produce CO waste gas, an especially dangerous gas to get near a PEM fuel cell).

Other hydrogen reformer that was big news a few years ago were ones that allowed medium size consumer electronics – PCs, mostly – to be powered by small PEM or anode/cathode fuel cells with hydrogen supplies by methanol, or other hydrogen-carrying liquids, like sodium borohydride. This Inforworld article describes such a system, producing about 20 W for 3 to 4 hours from a pen-sized replaceable fuel cartridge costing about US $1.50.

Though reformed hydrogen systems have a lot of useful applications, I don’t think they’re very promising for “heavy” power system needs, such as vehicles, residential and industrial heating and cooling, and electric power generation. From a practical engineering perspective, if you have a hydrogen-carrying liquid such as alcohol where you need power, it’s easiest and most efficient to just burn it, rather than reforming it into hydrogen and burning the hydrogen or using it in a fuel cell.

[freeztar]

Originally Posted by CraigD

AFAIK, hydrogen, CH4 (methane), and other “reformed” fuel gases are made from more massive hydrocarbon molecule fuels, and have no more energy than these source fuels.

What do you mean by this? H2 and CH4 are produced naturally through the pyrolysis. I guess the "reformed" part is throwing me off.

Another example is the conversion of sawdust or waste wood into bio-oil for the production of electricity or syngas, using a fixed fluidized bed pyrolyzer from Dynamotive.

In many industrial applications the process is done under pressure and at operating temperatures above 430°C (806°F). Anhydrous pyrolysis can also be used to produce liquid fuel similar to diesel from solid biomass or plastics [1]. The most common technique uses very low residence times (<2 seconds) and high heating rates using a temperature between 350-500 °C and is called either fast or flash pyrolysis.

Pyrolysis - Wikipedia, the free encyclopedia

BioOil’s potential use as a fossil fuel replacement is already well established. Customers for BioOil can include local, regional and national electrical utilities and power producers operating with partial or complete fuel substitution depending on scale and application. The opportunities for industrial applications are too numerous to list but some immediate applications in primary industry are kilns and boilers in pulp and paper, process heat in boilers in sawmills, metallurgy, oil and gas industries, as well as in secondary industries such as greenhouses, district heating and stationary engines.

Pyrolysis fuels have a very complex chemical composition, containing a multitude of different compounds. The specialty applications of these compounds in industrial processes and manufacturing are just beginning to be explored. They represent a potentially very large market for value-added products derived from BioOil.

Dynamotive Energy Systems | The Evolution of Energy

[CraigD]

Originally Posted by freeztar

What do you mean by this? H2 and CH4 are produced naturally through the pyrolysis. I guess the "reformed" part is throwing me off.

Hydrogen reforming refers specifically to the process of extracting hydrogen (and, as a by-product, CO) from methane (CH4) by adding water and heat – it’s thus commonly termed “steam reforming”, and is how most hydrogen gas is currently produced. I was generalizing the term a bit – perhaps inappropriately – to refer to any process that creates one fuel from another.

In this more general sense, pyrolysis – the simplest form of which I’m aware consists of simply capping a large mass of organic waste and using the resulting methane at the pressure the system produces – is a reforming process. Like many practical fuel reforming schemes, the added energy – heat - needed for the reaction is supplied by the source fuel itself. A famous, small-scale system of this kind was one promoted by the PRC government for rural use, in which the waste manure from a single household produced cooking and lighting gas for the house.

Burning the methane produced by this, or any pyrolysis system, produces less energy than burning the feed fuel (manure, etc.), but is much cleaner burning, and easier to deliver to burners, lamp mantles, fuel cells, etc.

Fuel from biomass seems a very good solution for situations where large biomasses are available and there’s a need for gas fuel, but gas fuels aren’t ideal for all applications. In particular, they’re not ideal for vehicles. And, as with other renewable fuel schemes, I’m unsure if sufficient biomass exists, and whether facilities to gasify it can feasibly be made, to 100% replace the power needs currently satisfied by fossil fuels.

[freeztar]

Thank you, Craig, for elucidating.

I also have strong doubts that biofuel technology can replace current consumption. Nonetheless, it has the potential to create a major deficit in atmospheric carbon.
I know little to nothing of the tech behind fuel cells, but I have read that they can be built to be as safe as traditional fuel tanks. (from the book Natural Capitalism)

If I find the book I'll post an excerpt.

[CraigD]

Originally Posted by freeztar

I know little to nothing of the tech behind fuel cells, but I have read that they can be built to be as safe as traditional fuel tanks.

The major issue with various kinds of fuel cells (the term is a bit of a misnomer, as these devices are not containers for fuel, but generators of electricity that take fuel consisting of hydrogen and oxygen, and produce waste heat and water) is not safety – they and fuel containers they require have existed since the 19th century, been used without major incident in most manned spaceflight (with the exception of Apollo 13, which suffered a crippling explosion in one of its 2 oxygen tanks due to wiring that had been unknowingly damaged prior to launch, not anything related to its fuel cells) – but energy density. Compared to petroleum and alcohol-burning motors and their fuel systems, fuel cell-electric motor and their traditional fuel systems weigh 3 or more times as much. (the 4/2007 Scientific American article “Gassing Up with Hydrogen” (subscription or purchase requires for full article text) has a good discussion of these issue)

From an emissions perpective, hydrogen fuel cells are wonderful. The Apollo missions used their fuel cell exhausts for the crew’s water supply – it was nearly completely pure.

Another very major obstacle with fuel cells is cost. Currently, they cost about US $5/watt, about 3-6 times the cost of a diesel-powered electric generator. The sort of low-mass systems best suited for application such as vehicles cost about $10/watt for the fuel cell alone, ignoring the cost of the fuel storage and other systems. For comparison purposes, note that 1 horsepower equals 750 watts. A typical lawnmower engine (3.5 HP, or 2625 W), would thus currently cost about $26,250 for a fuel cell equivalent – though this comparison is likely somewhat exaggerated, as such systems would almost certainly use hybrid battery systems (like those used in current hybrid autos) to reduce the required power of the fuel cell.

[freeztar]

Thanks for the link on energy density. The table comparing different storage types was enlightening.

I think the problem with energy density could be worked around with some cleaver engineering (perhaps wrap-around fuel tanks that take advantage of unused space), but it seems that the current cost of fuel cells is the biggest prohibitive factor with hydrogen technology. Do you know if the fuel cells cost so much because of supply/demand economics or is it a technology/costly materials issue? Or both?

We've already been discussing the possible dangers to the environment (of which I'm not convinced of one bit), but what are the other hurdles for this technology?

[CraigD]

Originally Posted by freeztar

Do you know if the fuel cells cost so much because of supply/demand economics or is it a technology/costly materials issue? Or both?

The high cost of fuel cells is mostly, I think, one of material and fabrication cost.

The highest power/mass ratios are for fuel cells based on the PEM design. A preferred material for catalyzing the critical first and last reaction in this design process, splitting the H2 molecule into an H atom, and the O2 into O, is platinum, which is about the most costly metal on earth. Expensive catalysts are also needed to assure that the hydrogen supply is very pure. The membrane “backbone” material (eg: Nafion) also tends to be something costly and difficult to manufacture. And everything must be assembled with great precision – as we’ve previously noted, hydrogen is essentially the most difficult gas in the universe to contain.

Low power/mass ratio fuel cells can be made with less costly materials and fabricating (may designs look much like ordinary batteries), but such power/mass ratios make them poorly suited to vehicle applications. Many lower-cost designs also have difficult startup requirements, again unsuitable for power-on-demand applications.

For the last couple of decades, I’ve kept an eye out for advances in fuel cell technology. It’s worth noting that already, economies of scale and market interest (if not outright demand) has brought the cost of 1+ KW fuel cells down from tens of millions of dollars to thousands. From time to time, folk who can fairly be termed “scientific geniuses” attempt to use advanced physics (quantum dots, etc) to find breakthrough techniques to make fuel cell components as cheap as microelectronics, often with similar fabrication techniques (eg: photolithography, epitaxy). So far, despite a lot of brainpower and venture financing, these efforts haven’t much succeeded – though they have produced some valuable micro-fabrication spin-off technologies.

A concern I have with fuel cell technology is that I suspect it has been used disingenuously by people with financial interests in current fuel technologies – oil companies and auto manufacturers – to offer well-intentioned activists, enthusiasts, and policy a “competing alternative” to technologies that can be realized now, such as chemical battery-powered cars. This “alternative”, however, is one that no one can accurately predict when or if will be practical to bring to a large market.

I highly recommend the documentary “Who Killed the Electric Car” (discussion in this thread) for some background into the reasons for my concern. In particular, note that Alan Lloyd, who was instrumental in repealing the CA state regulations promoting zero-emission vehicles in that state, appears to be a good-faith proponent of vehicle fuel cell technology.

[Michaelangelica]

Miscanthus x giganteus
The economics are attractive enough now to draw investors who can afford to wait a few years to recover their stake. They're expected to improve markedly as demand and productivity grow: The glint in the wildcatter's eye is the gusher of a 300-acre energy farm costing about $6 million for land, interest and planting and turning at least $8 million in revenue over the life of the crop.

Caveny's new career as a cellulose prospector shows that the foundation of the bio-economy has begun to form without the aid of technologies needed to boost the output of plant photosynthesis and of the chemistry to convert plant fiber to fuel.

Caveny had been growing a small crop of his bushy Southeast Asian superweed, called Miscanthus x giganteus, on a test basis and now has all the knowledge he needs to make the jump to business. He's working with a commercial partner, Speedling Inc., to propagate the plant in the heat of Florida for sale as a transplant to farmers across the United States.

Modern wildcatters see gushers of green / Researchers have high hopes that a tropical grass known as a 'superweed' will one day replace crude oil

[Michaelangelica]

If you have lots of water, and can control their invasive habits, these three produce masses of biological material - especially the Water Hyacinth

Jerry Coleby-Williams alerts gardeners to waterweeds - water hyacinth, water lettuce and salvinia – which are considered a major problem for North Australian waterways.

Gardening Australia - Coming Up This Week 14/07/2007
(14/07 programme- notes not posted yet)