Methane - Bio Gas

[ETC]

This is a decent read

www.homepower.com/files/methane.pdf

The below is condensed from many sources (compiled mid 2006)...

Biogas-Methane-Properties-Production-Use

+ Methane Properties

-> Methane (CH4)

-> is very light at .55:1 to air, odorless, colorless, tasteless

-> The flash point of methane is -369 Fahrenheit or -223 Celsius

-> The boiling point of methane is -260 Fahrenheit or -162 Celsius

-> The auto-ignition temperature of methane is 999 Fahrenheit or 537 Celsius

-> Paper scorches and turns brown at about 450 Fahrenheit.

-> Methane has a flammability range of 5% to 15% in air

-> That means that over 15% methane in air will not ignite.

-> Compressed and stored in the tank

segregation of methane, nitrogen and oxygen occurs

-> As methane is drawn off, and nearing tank depletion,

methane percentage to air can approach 5% to 15%, and explosion can occur

-> Methane gas cools on expansion through a nozzle.

-> It will not ignite when it expands out a nozzle, it will require an ignition source.

-> Any spark or energy source will ignite the methane.

-> Liquefaction of methane is high tech. To liquidfy "pure" methane (LNG) requires

-> psi >1110

-> Temp below -160 F (above this temp it will never liquidfy)

-> note, trace gases modify these parameters

-> Natural Gas (commercial)

-> BTU = about 1,000 per cu-ft

-> 80% methane, 10-55% carbon dioxide,

some hydrogen, nitrogen and other trace gases.

-> no trace hydrogen sulfides

-> BioGas (Pig or Cow Dung)

-> BTU = about 600-700 per cu-ft

-> 55-70% methane, 30-35% carbon dioxide,

some hydrogen, nitrogen and other trace gases.

-> trace hydrogen sulfide (mixed with water = Corrosive Sulfuric Acid)

+ Production, Method type and flow

-> Methane Digester, constant flow, dual stage (2 tank horizontal layout)

(the better system is to have 2 Digester production units)

-> Production Feedstock = pig \ cow excrement

-> how much is required depends on the system and tank size...

-> Daily (or weekly) in a "constant flow" type system or

-> Every 3~4 months in a "static" type system.

+ Production Issues

-> odor, smell during production = controllable

-> maintain temp of digester unit within range of 85` ~ 105` F (95` F is perfect)

-> use waste heat from engines, passive solar (with maybe thermal cistern)

-> must scrub and dry gas at source, before compression pump

-> remove trace hydrogen sulfides (mixed with water = Corrosive Sulfuric Acid)

-> I've seen where

engine temp =+ 195` negates the acid problem (this removes the water)

-> Over-Production of Methane Gas can be a significant issue

-> see the section on storage

-> what to do with over-production?

-> burn it off (far better than releasing into the atmosphere)

-> give it away, (probably can't sell it due to gov regulations)

+ Production By-Products and Issues

-> The Cow/Pig Dung slurry is a nitrogen rich organic fertilizer

-> It has an odor

-> Disposal of the Cow/Pig Dung slurry

-> Sell or give it away in bulk

-> Provide a service to spray it on crops, fields, pastures

(note equipment needed)

-> unknown how long after application does the odor linger

-> May be health issues of using it on gardens, and

-> Will be gov regulations requiring compliance

+ Methane Storage and Issues

-> Commercial Quantity Distribution, Storage and Transport

-> as LNG (not LPG),

compressed to >2,500 psi and cooled to > -165` F with Liquid Nitrogen

-> shipped in racks of cylinders,

made from large heavy gauge steel or composite epoxy-carbon

-> as CNG, Commercial Automobile Fuel

-> as Gas, compressed to >2,500 psi, not cooled

-> stored in cylinders,

made from heavy gauge steel (scuba type) or composite epoxy-carbon

(these are very different than cylinders used for LPG fueled cars

-> Do-It-Yourself Storage, Transport

-> for all uses, engine fuel, cooking, lighting, heating

-> as Gas, compressed to around <300 psi with shop AC compressor(s)

-> stored in common standard propane or LPG cylinders

-> requires many cylinders

(note the implied gas over-production and logistical issues)

-> note, not very practical for cars @ 300 psi

= small qty of methane = limited distance (see below)

+ Methane as Engine Fuel and Issues

+ Biogas Methane Percentages and BTU

-> Internal Combustion Engines require

18 cubic feet of methane per horse-power per hour

-> About 225 cubic feet of methane gas

equals one gallon of gasoline (@ sea level).

(above if for commercial CNG)

-> Natural Gas (commercial)

-> BTU = about 1,000 per cu-ft

-> 80% methane, 10-55% carbon dioxide,

some hydrogen, nitrogen and other trace gases.

-> no trace hydrogen sulfides

-> BioGas (Pig or Cow Dung)

-> BTU = about 600-700 per cu-ft

-> 55-70% methane, 30-35% carbon dioxide,

some hydrogen, nitrogen and other trace gases.

-> trace hydrogen sulfide (mixed with water = Corrosive Sulfuric Acid)

-> odor, smell during combustion = none

+ Methane as Engine Fuel Issues

-> EFI engines will likely have issues with the computer adjustments (re-chip)

-> No catalytic converter issues from resulting compounds of combustion

-> No exhaust oxygen sensor issues from resulting compounds of combustion

-> Increased engine emissions output = increased o2 and NitOx

-> Corrosion Issue =

trace hydrogen sulfide mixed with water = Corrosive Sulfuric Acid

-> Scrub and dry gas (at source before compression and storage)

-> Using a gas membrane separator or

-> Bubble methane gas through column of

CaCO3 (calcium carbonate, or limestone) slurry

-> i've seen where engine coolant temps @ +195' F avoids the water formation

but is likely still present in the exhaust system

-> Range of engine compression ratio for methane use is 8:1 to 20:1

-> Perfect compression ratio = 15:1

-> For gasoline engines...

-> Compression can be raise slightly with a turbo or blower

-> For diesel engines - usually no problem for idi or di

-> Injecting Methane Gas

-> For gasoline engines, Carbed or TBI

-> below the butterfly valve is preferred

-> drill the base of the carb base or use drilled spacer plate

-> For gasoline engines with Direct Injection

-> after the throttle butterfly valve is preferred

-> For diesel engines, idi or di

-> after the throttle butterfly valve is preferred

-> note this is an amendment to the incoming air or

the diesel needs a spark ignition (a major engine modification)

+ Methane as Cooking Fuel Issues

-> all Thailand cooking burners are set up to use LPG.

They will have a small pill size (orifice).

They will require modification to use biogas...

both in orifice size and the fuel/air mixture ratio.

One cannot switch back 'n forth between the fuels without issues.

To use LPG is a stove setup for biogas is very, very dangerous.

I don't know but suspect that

1 tank of LPG = 15~20 tanks of biogas (pig manure)

"One cannot switch back 'n forth between the fuels without issues."

Methane generation and usuage projects that I have been envolved with use a Johnson Burner. The main source of fuel was the low-pressure methane gas and when the pressure dropped below a certain level, the fuel oil source would kick in. It worked rather well actually.

ETC (Jim)

One of the conclusions derived from our project, was that the focus must be on either gas or electricity, to reap the greatiest benefit overall.

My personal recommendation, from past experience, is to generate methane to power a water cooled generator, and the water is not only circulated through the generator's radiator, but through tubing that allows the water to heat the digester, to keep the digester temperature at the optimum 35-degree celcius. That will eliminate the need for a heat exchanger and still keep the process at maximum output, if loading specs have been followed. I might mention, that maintaining optimum operation temperature methods, may vary depending on yearly local ambient temperatures.

[glomp]

Have you checked the cost of the engine generator set? To make serious money it's going to have to be a big set.

The initial outlay will be millions of baths for a useful amount of power, just for the engine and generator. Unless you just love renovating and babysitting home converted engines.

I doubt the utility will hook you up for free even under the small producer programs unless you are close to some big lines. 3phase syncronisation to the grid has to be handled by some sort of device too.

This is under the asumption you will try to make your primary income from selling power. Subsidising local farm power usage seems as pie in comparison.

As for selling gas for stove use i read that the burners has to be enlarged for methane use. Increasing the amount of gas in the mixing. What happens if natural gas is used in a converted stove? Nothing stops renters, visitors, the inlaws or such from unknowingly connecting natural gas bottles.

The users of your gas losing eyebrows might cause problems.

Any ideas on this?

[ETC]

"Have you checked the cost of the engine generator set? To make serious money it's going to have to be a big set."

Maybe you missed my intention here, and it is not to make serious money; It is to add an element to thai farmers lives that will allow them to save money in the long-run and maybe allow them to afford running pumps for irrigation, or for fish ponds, just to mention a couple.

"The initial outlay will be millions of baths for a useful amount of power, just for the engine and generator. Unless you just love renovating and babysitting home converted engines."

Using your "serious money" hypothesis, I would agree with you, but that is not the objective here.

"I doubt the utility will hook you up for free even under the small producer programs unless you are close to some big lines. 3phase syncronisation to the grid has to be handled by some sort of device too."

The program I would suggest would be for onsite usage and not grid hookup, and we haven't even mentioned the high nitrogen fertilizer that is produced with a much more readily usable form of nitrogen nutrient.

"This is under the asumption you will try to make your primary income from selling power. Subsidising local farm power usage seems as pie in comparison."

Nope! Wrong assumption. Losing money needlessly is not my goal, but leaving a positive foot print on earth is.

"As for selling gas for stove use i read that the burners has to be enlarged for methane use. Increasing the amount of gas in the mixing. What happens if natural gas is used in a converted stove? Nothing stops renters, visitors, the inlaws or such from unknowingly connecting natural gas bottles."

I would not cut the Thai farmers short, as they have done a lot with very little for a very long time. Folks that own diesel cars could just as easily fill the tank with regular gasoline, but that does not stop the automakers from making diesel cars. With new technology comes education, and we are all subject to that in one way or another.:jap:

Any ideas on this?

Edited August 31, 2010 by ETC

[ETC]

When considering domestic digesters, to produce the methane to generate electricity, special consideration should be given to Microturbines as a possible viable option.

Microturbine Cost

Capital Cost

$700-$1100/kW

Advantages to microturbines include a very compact size (about the same size as a refrigerator), a small number of moving parts, light-weight, low-cost, and increased efficiency. Using new waste heat recovery techniques, microturbines can achieve energy efficiencies of up to 80 percent.

[ETC]

To quote glomp "The initial outlay will be millions of bahts for a useful amount of power, just for the engine and generator. Unless you just love renovating and babysitting home converted engines."

I suggest, that if Microturbines become a viable option, and I believe they will, then just two million baht should generate around 56Kw. (based on the high $1100/Kw cost figure and omitting original setup costs). Now I know that is cost prohibitive for the average Thai farmer, but the technology speaks for itself. I believe there is a middle ground that shows promise. Time will tell. :jap:

Edited August 31, 2010 by ETC

[WatersEdge]

Hi Gentlemen,

I've watched this thread with interest,

because I have a hog barn with methane bubbling up

from the manure distribution trenches into open air.

It does annoy me to watch money drift off into the blue.

My residential electricity costs B3.77 / kWh with all taxes included.

At $1,100 / kW

THB30 / USD

that comes to 8,753 hours operation at full capacity

to break even.

That comes to almost exactly 1 year of 24 hour operation

I intentionally neglect the fuel cost.

56kW is a convenient size for many applications.

If the Generator is 0.90 efficient,

then it's a nice 50 kW Genset.

It may seem like a high cost,

but looking at all the factors, I like what I hear.

With 80% Turbine Thermal Efficiency,

I'm taking your word on that...

compared against a standard Diesel engine at 30-40%

The Turbine is especially attractive.

More than Twice the power output on the same fuel.

The initial cost of a diesel engine is much much lower

In Thailand $80 per kW for a 14 hp Kubota Diesel operating at 30% Thermal Efficiency

This means that you need a 24/7 application to maximize the return.

It would take longer to break even in Thailand were fuel is readily available and reasonably priced.

The attractive side of a turbine would appear in a country where electricity is unreliable,

fuel is expensive, and waste animal and field material was abundant.

I see Burma all over this equation.

The power to weight ratio of a Turbine is much higher than a Diesel.

I recall around 20 years ago,

a crop duster aircraft switched from rotary gasoline engine

to diesel turbine.

The Turbine offered twice the power at half the weight,

with fuel 1/3 the price and thermal efficiency 3X.

That means he paid 1/9 the previous fuel bill.

The high performance heavy load aircraft was suddenly able to carry far greater load,

at a fraction of daily fuel cost,

so the $100,000 Turbine cost was a bargain in every way.

As I recall, the expected Turbine overhaul time was over 10,000 hours.

Another comparison to the Gas Turbine

PhotoVoltaic Cells, Solar Electric Panels,

currently cost $4 per watt.

That's nearly 4 times the cost of this Turbine

PhotoVoltaic Cells operate only when the sun is shining,

so the return on investment is only coming in 1/4 of an average day.

That makes a Turbine 16 times more cost effective than a solar cell.

A one year return on investment is a good deal.

16 years doesn't make sense to anyone but government.

Can you specify what the $1,100 includes?

Is that Turbine only, or does it include the generator and gearbox?

A Turbine is high rpm, so it must be geared down to 3,000 or 1,500 rpm generator shaft output.

to produce 50 Hz electricity

For my use, I'm happy enough to use gas to boil Soybean before feeding to hogs

and supplement my diesel consumption in the pump engines.

A hog farm in this area produces all their electricity for the barns off the methane.

They don't bother to sell to the grid.

As I understand it, you need to decrease the compression ratio a bit,

as methane detonates at a lower heat than diesel.

They have a black poly tarp sealed over a below ground level lagoon,

so that the temperature requirement is maintained by the sunlight.

The tarp is ballooned up to a tightly stretched dome by the gas pressure inside.

[ETC]

Waters Edge,

This site will give you a good resourse on the Microturbines straight from one of the the manufacturer.

http://www.wbdg.org/resources/microturbines.php?r=secure_safe

Everything I stated in my previous post is covered there.

ETC

[ETC]

Another comparison to the Gas Turbine

PhotoVoltaic Cells, Solar Electric Panels,

currently cost $4 per watt.

That's nearly 4 times the cost of this Turbine

PhotoVoltaic Cells operate only when the sun is shining,

so the return on investment is only coming in 1/4 of an average day.

That makes a Turbine 16 times more cost effective than a solar cell.

Waters Edge

This portion of your post reminded me of a complex demo-biodigester model we made that incorporated the digester, photo-cells, and a corrigated heat gathering (sun) source. The batch-digester was a 100-gallon plastic barrel. The photo cells powered a salt water fish tank pump, that pumped the warm water, generated from the corrigated heat gathering source, through coils in the batch digester to keep the influent active. The gas was captured in a very large tractor tire tube, and the gas was used to heat bunsen burners and a gas cooking stove in our office and laboratory. It served as a show-and-tell for visitors and was a lot of fun to build and operate.

ETC

Edited September 1, 2010 by ETC

[ETC]

Might I add, that it was in the 1970's when I worked on all this and much has leaked from my old brain. I am however,

applying myself to get back up to speed again on the old and new technologies. It is a very interesting field.

ETC

[IsaanAussie]

I too am very keen on this technology and have the methane source in potential abundance. But I must say the devil is in the details, and issues such as storage and distribution, corrosion and contaminates are bad enough, but the danger aspects in this carefree society terrify me.

In my case everyone in the family and the village were very keen when I proposed to build a biodigester. But try and find a candidate to remove the scum blanket, or to mix the slurry prior to loading, not so keen. Most Thais treat pig manure the same way, with a hose, and from a distance.

So, geat idea but few people prepared to muck in.

[WatersEdge]

Yes,

Blending the old off the shelf stuff

with the latest and greatest

I see the capacity to come up with difficult low tech ugly fuels that barely burn

turning them into useful energy

Key is to convert it to a useful transportable form as near the source as possible.

I'm fascinated with downdraft gasification,

which converts a wide range of burnables

and their coarse sooty tar laden smoke

to mainly CO and H2 which burn nicely in an engine.

Alas, another topic for another thread on another day.

Off to secure a supply of corn cob.

Corn Harvest is in full swing, with the granaries starting to shell.

[ETC]

I too am very keen on this technology and have the methane source in potential abundance. But I must say the devil is in the details, and issues such as storage and distribution, corrosion and contaminates are bad enough, but the danger aspects in this carefree society terrify me.

In my case everyone in the family and the village were very keen when I proposed to build a biodigester. But try and find a candidate to remove the scum blanket, or to mix the slurry prior to loading, not so keen. Most Thais treat pig manure the same way, with a hose, and from a distance.

So, geat idea but few people prepared to muck in.

IA

Fortunatelly you have the base for any project you choose. As for finding locals to play an active role is a story in itself. I am of the opinion that you will have to sort through a lot of chaff to find the wheat. I was always tickled to see city folks, when they came to our farm, how they would tip-toe through the manure, or watch their faces when I shoved my arm in a cows/heifer's rectum during articical insemination. Being born to those things makes us immune and we have to be patient with the city-dwellers, as hard as that can be sometimes.

I know there are those that store the methane in propane bottles. (I am not familar with the process, but methane is natural gas). I think becoming familar with the process, on a farm level, would not be that difficult to ascertain. I believe the greatiest problem with corrosion is when methane is exposed to air and metal at the same time. Gas leaks are definitely your enemy.

I have an idea (not totally mine) of a very small digester that the locals might like, and they can get their experience on that, and then move up to larger digester. Once they can visualize the process, and the benefits, they may become more positve and want to participate.

Granted, there seem to be more unknowns then knowns, but if it was easy, where would we come in?

ETC

[IsaanAussie]

Granted, there seem to be more unknowns then knowns, but if it was easy, where would we come in?

ETC

ETC,

The answer is simple. Since we farang farmers all grow money trees, we should supply the fruits of our labour.

I'm no chemist but hydrogen sulphide and water would seem to be the corrosion source, both present in raw Biogas. Scrubbers, triple stage compression and all that stuff are beyond me.

The Thai government sponsered a program of building biodigesters in rural communities some time ago. From all reports most are now abandoned as technical support was not available nor was funding for general maintenance, or the labour available to do the "dirty" work.

I wish you luck but I would advise caution on any investment for community benefit if promises of assistance are given. Something for nothing will always be welcomed, as long as the cost remains the same and the effort is zero.

My pig septic system has a soakaway drainage system that locals have said will pollute the drinking water. That may be so, but the point is all those same people have sewage collection pits next to their houses and within 30 metres of their bore holes. Those pits have no base so the water can soak away. Strange how selective the thinking process can be.

Isaanaussie

[ETC]

Granted, there seem to be more unknowns then knowns, but if it was easy, where would we come in?

ETC

ETC,

The answer is simple. Since we farang farmers all grow money trees, we should supply the fruits of our labour.

I'm no chemist but hydrogen sulphide and water would seem to be the corrosion source, both present in raw Biogas. Scrubbers, triple stage compression and all that stuff are beyond me.

The Thai government sponsered a program of building biodigesters in rural communities some time ago. From all reports most are now abandoned as technical support was not available nor was funding for general maintenance, or the labour available to do the "dirty" work.

I wish you luck but I would advise caution on any investment for community benefit if promises of assistance are given. Something for nothing will always be welcomed, as long as the cost remains the same and the effort is zero.

My pig septic system has a soakaway drainage system that locals have said will pollute the drinking water. That may be so, but the point is all those same people have sewage collection pits next to their houses and within 30 metres of their bore holes. Those pits have no base so the water can soak away. Strange how selective the thinking process can be.

Isaanaussie

IssanAussie

Believe me when I tell you that I do understand your frustration.

ETC

Edited September 3, 2010 by ETC

[glomp]

I also thought about this, i doubt it would be easy to find some changs to shovel a few cubics of spent shit when emptying time is due.

Also it would take alot of paid time. Perhaps you could build it above ground and have a side that would be mortared in and then removed. Letting a small tractor or conveyor be brought inside the opened digester.

I belive pumps will only get you so far. Scum will be a problem sooner or later. Pumps also arent free.