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Biofuel

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BIPVguy

BIPVguy

Mechanical
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Jul 23, 2007
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Hello,

I would kindly ask for some information regarding biofuels.

1) How much land under crops is needed for 1ton of biofuel (biodiesel, ethanol)?
2) Is there any thermal power plant built in the world that utilizes biofuels in boilers instead of oil, coil etc.
3) What is the energy efficiency of a biofuel burned in the boiler not car engine?

I have googled only information regards biofuel utilization in car engines but not in thermal plants for heat / power generation.

Thanks
 
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It would be insane to burn crop-derived ethanol in a stationary power plant. (So I'm sure there's a tax break somewhere to do just that).

Bagasse from sugar cane is burned directly in many boilers at sugar refineries.

 
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Visit the "Where Engineering is going in the next 5 years" forum and visit the threads:
"Back to Cellulose Ethanol" and "Bio-fuels.... good or bad?" where these questions are already well developed.
You can also visit the number watch website and view the thread Carbon the lifeblood of our planet where engineer David Taylor has done some rough calculations on the benefits.


JMW
 
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Benefits of what?
 
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They use plain old hay in northern europe, send it to a low pressure gasifier, and the fuel gas is co-fired in coal fired boilers with coal.

On a per acre basis, perhaps sawgrass or hemp might have the highest yield . May also increase the value of the houses downwind.
 
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There is a newly built 50 MWE plant in Benson minnesota USA that burns 100% poultry litter. There are about 5 more in the UK, roughly same size.

See the web page for IEA bioenergy for european efforts to co-fire straw, wood, animal waste in boilers.
 
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I found teh national geographic article to be very "matter of fact" only not supporting where the authors facts come from. One cannot so plainly state such facts as the warming of the earth in quantitative terms without looking at teh overall bigger picture. The fact is that our planet's issues need to be addressed but articles like this which dont support thier numers do perhaps at best to gain peoples interest, but usually just fuel the fire of inaccuracy.

I think the biggest paybacks will ultimatly come from advances in battery technology and more efficient power generation.
 
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BIPV,

Question #1 - answered above

Question #2 - Why on earth would you take a product specifically formulated for combustion in IC engines and burn it in a boiler ? Why noy simply grow a crop and burn the biomass in a boiler ? This is probably not economic in many countries, but has been done in the past.

Question #3 - Makes no sense, an industrial boiler is designed for a specific fuel (including specific coals). Throwing something else into it (including peat, wood, bagasse, and old piping designers) it only makes the unit operate off the design point.

Do yourself a favor,... Get a copy of the superb book "STEAM" by B&W and spend a quiet productive weekend reading it..

-MJC

 
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as an update:
- "torrefied wood" is one option of a biofuel that can be burned in a coal fired boiler with minimal impact on the boiler and mills and its air pollution equipment

-"e-grasss" or elephant grass is probably the most energy efficient biofuel for firing in boilers and provides the greatest harvest in terms of BTU/acre- the latest estimate is that there is an 8:1 ratio of energy released in the boiler vs energy consumed by planting , harvesting ,transporting , drying and pulverizing provided (a) it is burned in a fluid bed bed boiler 50% coal and 50% e-grass and (b) the crop is allowed to dry in the field over the winter season. High levels of K, Na, Cl etc cause issues with other boiler types.
 
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The question that interests me is how much area is required to power say a 10MW power plant? What type a care is required to grow the biofuel? How much water?

There is a large area for growing biofuels, but with little water. Or the prime areas are now used for food growth.

Interesting enough, the untillable areas in creeks, and bar ditches seem to grow weeds and trees very well, but currently are under harvested.

And why do trees grow so well under power lines?

 
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<
as per the above link, 20,000 acres of e-grass would be required in Florida to generate 130 MWe net electricity. But that scenario is not the most efficient process. See the IEA-bioenergy webpages for alternate schemes which may be more efficient.

The above link assuems multiple harvests per year, which implies more energy losses due to the need to dry the grass. It also converts the e-grass to a liquid biofuel prior to firing in a boiler, which implies more energy losses in the conversion to liquids in the prompt gasifier.
 
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for energy yields per acre, and ratio of usable energy vs energy input see: (e-grass= miscanthus)

<
To maximize the ratio of usable/ input, must minmize energy for drying, transport, and grinding==> this implies drying over the winter season in the field, and combusting in a fluid bed boiler ( no pulverization)

for a good summary of the impact of co-firing biofuels in boilers, see:

<
 
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We co-fire off-gas from our anaerobic waste treatment plant with a separate burner spud along with our primary fuel, #6 oil. The HV is ~600 btu/cf.

We also collect our VOCs and burn them in another heater instead of flaring. There is a lot of entrained nitrogen but the HV is still ~400 btu/cf.
 
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Many processes burn bio-mass as a side product of the manufacture of the end product. Mentioned already is bagasse fuel burned in sugar mills. The problem (in the USA at least) is that the cane sugar mills are antiquated and because the price of sugar is, or to now has been tariff protected, there has been no incentive to make the mills more efficient so all the bagasse that they generate goes to meeting the mill's needs for power, both electrical and mechanical. Beet sugar on the other hand which does not produce its own by product fuel and has to burn fossil fuels, principally coal to meet their energy needs are much more efficient. Others can speak to the efficiency of sugar mills in other parts of the world, but those that I have seen aren't much more advanced.

In the USA the problem also is that the time of the year that the sugar cane grind is occurring, the grid doesn't need power (fall to early winter) so the avoided cost of power is low and selling excess power isn't a profitable business. So they work hard to balance the process so that they burn what they make so that they don't have to landfill the excess bagasse.

Wood byproducts are burned by sawmills, plywood plants, OSB plants and paper mills. Sawmills and plywood plants burn bark and sawdust and planer shavings and mill waste. Some have enough excess to generate power for the grid but as a general rule, the mill consumes all the power generated.

Paper mills burn bark and the lignin chemicals "cooked" out of the wood to break down the fiber so that it can be made into paper. Again, the paper making process is so energy intensive that not only are they generating several dozen MW inside the mill with biomass and fossil fuels, they are usually purchasing up to an equal amount from the grid.

Rice hulls on the other hand are burned and all the output is sold to the grid.

But, point is they are generating power with bio mass. The question for those bio mass sources is whether there is a higher use for the bio mass. Wood in my part of the world is much more profitable made into lumber and paper than electricity.

rmw
 
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another promising method is "torrefication" of wood chips and e-grass. The dried brittle product can be directly dumped onto the coal pile and fed to coal pulverizers and burned in pulverized coal plants.

But , in long term steady state estimates of "sustainable" biofuel use, wood is not likely the answer- e-grass ( elephant grass , miscanthus) seems to have a much higher yield per acre per annum than wood.
 
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