In the beginning, Dr. Rudolf Diesel set out to make an engine that would run on powdered coal. He moved on to oils and proceeded to make one of the best engines ever invented.
Rudolf Diesel worked on various designs for his engines for over a decade, and he was granted a patent in 1892 for an engine designed to burn the cheapestfuel then available–powdered coal. By 1897, Diesel abandoned powdered coal,substituting kerosene as the fuel.
He went on to demonstrate an engine running on peanut oil at the Paris world fair.
Mr. Rudolf Diesel’s cars at the Paris Worlds Exposition (Fair) in 1900 ran on peanut oil.
Most peanut oil/ diesel combinations run off diesel for the first five to ten minutes. This allows the vehicle to warm the peanut oil up to the temperature needed to for it to burn in the engine. This one hundred sixty degree temperature is what is necessary before the peanut oil fuel should be allowed to run through the injector.
Vegetable oil is more viscous, the heating is just to make the oil flow at the same viscosity as cold #2 Diesel. (For some reason folks run off to flammability as the ‘issue’ when it is viscosity.) But that ‘omnivorous’ nature of Diesels has always attracted me to them. There is a long history of running Diesels on bio-fuels and coal.
But the desire to run on coal and similar solids has persisted to this day. Coal has a major issue from silicate materials in the ash. This tends to “polish” and erode the metal surfaces. I’d always figured that, since coal was dead compressed trees, this same ash problem would show in in using trees / charcoal. In a small way it does, but it is much less and manageable.
There is an organization dedicated to running coal in Diesel engines. Perhaps they can be interested in Charcoal too (hey, my briquettes have coal in them ;-)
Sidebar on Algae
I’ve also seen descriptions of using dried algae dust in the air intake of Diesels.
You can use hard to light high Octane (low Cetane) fuels as a ‘co-fuel’ directly in the air intake of a low compression Diesel. I’ve run propane into an International Harvester Scout and drove it a couple of miles that way. Back in the ’70s I was in a Mercedes Diesel that drove through a ‘propane cloud’ from a venting tank at a Hot Air Balloon Meet and we “surged” until out of the gas stream (about 5 feet). That was what gave me the idea to try it in my Scout in the ’80s. Up to about 3/4 of ‘stoichiometric mix’ it seems to work well, with the Diesel injection acting as a kind of ‘spark plug’ to light it off.
Later, Caterpillar came out with a ‘kit’ for their stationary engines with complete computer control to use natural gas. I like to imagine that they started that investigation due to my postings about it. (There were some Cat guys active in the news group then). But I was levering off of a Masters Thesis that tested stationary Diesels with Natural Gas fumigated in the air intake from the Berkeley Engineering Library ( I did my homework prior to risking my Scout ;-) so they deserve ‘first credit’. So There is a long tradition of this.
I’ve seen a proposal to use Diesel exhaust heat to dry pond algae, and feed that dry dust into the air intake as fuel, recycling the CO2 back to the algae grow pond. It ought to work, and fairly well. Given the paper below, it looks like an ‘Algae Water Slurry” should also work. Don’t know if it is a ‘patentable idea’ to skip the drying step, but it’s “My Idea” ;-) Some algae can be up to 50% by weight oils, especially if grown in a nitrogen deficient environment. (They store energy for when nitrogen does show up, so they can divide fast then…) So a simple dewatering to about 70% algae ought to work fine. Algae can yield 10 to 100 times more tons / acre than land plants. So everything in the paper about tree / charcoal availability is “several times over” for algae.
The Charcoal Paper
This is a fascinating paper out of Mississippi State University. Folks from the North and East / West coasts tend not to think of Mississippi as a forest state, but it is. Lots of paper goods come from “down south” where large areas are farmed on a relatively fast crop basis. A sapling grows much faster than a full grown tree, so if you harvest a load of saplings every 5 to 10 years, you get more wood / acre than if grown to full sized trees. That’s where your “T.P.” and paper towels come from. Not from old growth redwoods or giant Georgia Pines… So these folks are well experienced at high tons / acre fast cropped wood for pulp production.
Coal vs. Charcoal-fueled Diesel Engines: A Review
R. PATTON,1 P. STEELE,2 and F. YU3
1 Mechanical Engineering Dept., Mississippi State University, Mississippi, USA
2 Forest Products Laboratory, Mississippi State University, Mississippi, USA
3 Department of Agricultural and Biological Engineering, Mississippi State, Mississippi, USA
Real Science and honest research from Real Scientists. A refreshing change from the Global Warming fantasy computer toy world. These guys are playing with hot iron, flames, and things that grow. Gotta love it.
What interested me most was that they look at where ash comes from, and how to get rid of it. For trees, the silicates are largely from dirt and blowing dust. Take the bark off, much less issue. This is likely also why coal is so full of silicate ash; the dust and dirt blow in and are incorporated into the coal deposits. Just using charcoal instead of coal is a major reduction in ash content. But they don’t stop there.
They looked at extracting the ash from wood and from charcoal. As most of it is not silicate, but based on soluble minerals, they tried washing with water, hydrochloric acid, and acetic acid. The answer was that water washing worked best. (I got the impression they were a bit surprised by that, but too reserved to say so…) What was more surprising, was that they got the ash content of their Charcoal Water Slurry (ChWS) down to below that for the Diesel used in ships and such. Higher than #2, but lower than Bunker oil.
This level (650 ppm) is between the specification for #2 diesel fuel (100 ppm) and #4D diesel fuel (1,000 ppm). These early results are promising. Wood appears to be relatively easily leached with mild solvents and low temperatures.
“Promising”? Talk about your understatement…
I didn’t see a date on the paper, but it has citations from 2007, so likely about 2008. Reasonably recent. That means their cost data are ‘reasonable’ with only a small uplift in in the costs of oil products since then. So while they find the economics are beneficial, they will be better now.
They also report on some “issues” with Coal Water Slurry (CWS) and ways to fix them. Such as an ‘additive package’. It is not clear if such a package would be needed with charcoal.
2. Development of an additive package. An additive package was developed that allowed the CWS to be stored up to one year, transported over long distances, and pumped or injected like diesel fuel. The CWS used an additive package consisting of a gum (xanthin gum) to reduce settling and a dispersant (naphthalene ammonium sulphate) to reduce viscosity. At high solids loadings, the dispersant was needed to keep the viscosity below 200 cp. Under some cases, a biocide (formaldehyde) was also needed. An oil-antiagglomerant (Triton X) was added near the point of use. It was only needed when the CWS in the fuel lines contacted diesel fuel. Standard diesel fuel is sometimes used as a coal agglomerant in coal cleaning operations; the antiagglomerant prevented this from happening in the engine (Arthur D. Little, Inc., 1995, 44).
Were I doing the design of the fuel, I wold look more at a ‘Coal Organic Slurry’ (COS ?) using a heavy alcohol or gasoline like solvent. That would likely help with the ‘biocide’ aspects along with some of the ‘dispersant’ needs and would allow lower solids loading, so less need for dispersants. But it might increase the need for an ‘oil-antiagglomerant’ if gasoline like materials were used. (Hmmm… need some coal dust, gasoline, alcohols, water, and a jar… quick test to see what works better.) It is unclear if charcoal behaves like coal in this context. The use of an organic ‘carrier’ could potentially also avoid the need for a ‘pilot injection’:
The engine used a pilot injection of #2 diesel fuel (DF2) to assure ignition. Ignition delay using twin pilot injection at 4–5% of the total energy provided ignition delay roughly equivalent to that in a standard diesel engine (Arthur D. Little, Inc., 1995, 69). The engine performance was comparable to that in a standard diesel engine. On an energy basis, brake specific fuel consumption (BSFC) was comparable, whereas NOx and CO emissions were reduced by 50% and 85%, respectively (Arthur D. Little, Inc., 1995, 62).
Bolding added by me.
At any rate, the use of “slurry” has been studied and potential solutions to potential problems identified. Not a large set of ‘unknowns’ here. Just some minor ones with good clues.
The economics are also very interesting.
Economics of Charcoal-fueled Diesel Engines
The average price of #2 diesel fuel, at the refinery without taxes, is $2.18/gal (August, 2007) (Energy Information Agency, 2007). To penetrate this market, slurried charcoal must be sold for substantially less than that. Projected fuel costs are shown in Table 5.
Cost basis: Wood from short rotation woody crops has been reported at $50/ton dry
Gallon Barrel Equivalent diesel price $1.26 $53.20 Diesel price (August, 2007) $2.18 $91.56 Savings/barrel of #2 diesel fuel $38.44
So about 1/2 the recent wholesale price of Diesel. For a truck with a 100 gallon tank, that’s about $100 per fill up. I think that matters…
They go on to estimate the contribution of increased engine cost and maintenance costs on a per gallon basis. It adds about 15 cents / gallon, so it is a strong net win even if there are more engine costs.
All up costs, about $1.41 / gallon of Diesel equivalent for fuel and engine costs. I’d like to be running fuel at $1.41 instead of $4.30 / gallon… ( I know… there’s about 1/2 buck of taxes and another 1/2 buck of distribution and some profit and…)
But how much is there available?
Distillate diesel sold in 2005 had a heat content of 6.81 quads (Energy Information Agency, 2005). This is all use of distillate diesel for transportation—by trucks, barges, and railroads—as well as use by agriculture and off-road diesel. Heating distillate is not included in this demand. This is the target market for charcoal-water slurries (ChWS). At 70% efficiency, to replace 6.81 quads of diesel fuel, 9.73 quads of wood would need to be cut every year, corresponding to 573 million tons of wood, where wood contains 17 million BTU/ton of fuel value. The billion ton vision (Perlack et al., 2005) estimates that there are 141 million tons of logging residues available currently, and in the future there will be 226 million tons available. Moreover, currently energy plantations can grow 5 tons of wood per acre; in the future they will be able to grow 8 tons per acre. Finally they estimate that there are 60 million acres of land that can be used for growing energy crops. Table 8 summarizes these findings.
Thus, the potential wood supply is adequate to supply 76% of current diesel demand with today’s technology. In the future, potential supply will rise to 123% of current demand due to genetic improvements in tree growth and more intensive management.
It is a little unclear if they are talking about USA or Global in these estimates. I’m pretty sure it is “USA”. This graph shows a total of 27 Quads of energy used for Transportation from petroleum, so that 7 Quads of Diesel seems ‘reasonable’ as a USA number.
As some folks in Florida growing Eucalyptus have gotten 63 wet tons / acre (year 2 – two year average 38 tons / acre), and some fast growth Poplar species are near that as well, I think they are being understated in the potential yield, likely as they have mostly been focused on species suited to wood / paper pulp production. Dry tons of 10 / acre are also fairly well demonstrated. It is important to note, though, that using grass based biomass is not suited to this process. Grasses have enzymes that let them pick up and incorporate Silicates. The Silicate Ash content of grasses and bamboos is higher than woody species.
Frankly, given the much larger ‘tons / acre’ of poplars vs corn, and the energy losses in ‘corn to ethanol’, I think we could convert some small part of the ‘corn fuel land’ to ‘wood fuel land’ and be way way ahead on energy.
We have loads of energy sources. Rising petroleum prices (and the insanity of solar / wind electricity for cars and rising electric costs) are running headlong into the physics of other fuels and the low cost of growing trees. Already it is the case that charcoal bought in bags at Walmart are THE lowest cost / lb and almost the lowest cost / BTU of the “over the counter” fuels. (In California. Gasoline is a ‘rough match’ on $/BTU at $4 / gallon and the lowest cost is Natural Gas at about 1/3 that, delivered by pipeline to a fixed location).
The biggest competition to ChWS looks to be cheap natural gas. A comparative costing of the two fuels would be needed to figure out which is cheaper. As natural gas is very ‘engine friendly’, I’d expect most truckers and car owners would rather have a longer engine life. Then again, driving around with 100 Gallons Of Diesel equivalent of CNG or LNG (just waiting for a BLEVE – Boiling Liquid Expanding Vapor Explosion) might make some folks lean just a bit toward ChWS and the idea of a fuel that can’t be lit on fire with a torch. But the bottom line is just that those two are BOTH putting low cost options in place that makes ramping up transport costs and rising oil costs a bit hard to carry off long term.
The conclusion from the paper pretty much sums it up, so I’m not going to be trying to improve on it.
Charcoal-fueled diesel engines are feasible based on a review of the DOE NETL coal fueled diesel program. Charcoal is significantly cleaner and more environmentally friendly than coal. Cleaning the charcoal should have as its goal meeting current diesel ash and sulfur specs. Converting engines to dual-fuel capability should be much cheaper using charcoal rather than coal because the incremental emission costs should be much lower. Economically, ChWS is much cheaper than diesel fuel at current prices (August, 2007), and hence, provides an incentive to switch from petroleum-based fuels to ChWS. This also provides a way to reduce CO2 emissions and save money. Finally, the potential supply of wood (including plantation-grown wood) is adequate to supply over 3/4 of current diesel demand, and this supply will grow in the future.
From all of these standpoints, research investments in charcoal-fueled diesel engines are justified on economic security and economic and environmental grounds.
The “Doom And Gloomers” and the “Running Out Panic” folks are just flat out wrong.
There is no energy shortage, and there never will be. The “Peak Oilers” will, eventually, be right (in a few decades, maybe) and nobody will notice. Coal for a thousand years and charcoal (eventually algae) for thousands more. Uranium and Thorium for millions of years.
Charcoal, it’s not just for dinner any more!