Critique #1[edit source]
I believe that this page should either be heavily modified, or removed. Here's why:
David House, author of The Complete Biogas Handbook (www.completebiogas.com) said about Jean Pain on a forum at Journey To Forever, that:
On an on-line video of Jean Pain’s car, his rooftop tank looks like a standard K, which is 9.25 x 60 (inches), the volume of which at 1 atm is 1.76 cu ft. (That's all US tanks and units, of course, but it serves for a starting point.) At 1,000 psi, such a tank would hold 128 cu ft. It would require a very expensive pump to get to the 2400 psi required to liquefy the methane.
His biogas tank is batch filled, clearly. The video says he fills it with partially digested compost, and that it is producing biogas after a few days, the implication being that it is producing biogas in usable quantities. That would be unusual, but set that aside. At peak production, he may be getting two digester volumes per day in biogas, which of course would be about half CO2. But set that aside, and assume that he is getting two volumes of methane per day. His digester appears to be about 4 feet in diameter and 6 feet high, which would mean that it has a volume of just above 40 cu ft. So when we give it every benefit of the doubt, this digester is calculated at generating around 80 cu ft of methane a day. Every dry cu ft of pure methane has 912 BTU. Gasoline has energy content of 114,000 BTU/gal, so it takes 125 cu ft to directly equal the energy in one gal of gas. Generally speaking, however, methane is not the direct equivalent of gasoline when using both fuels in a given engine. Methane will usually not burn as efficiently, so that less of the energy in the methane comes out as mechanical force. (But set that aside...)
If, given all the fudge factors in his favor, he is only able to produce the energy equivalent of a gallon of gasoline every day and a half or so-- and assuming that he is not burning any in his stove to make tea, etc.-- then, yes, perhaps he could run his car off a long hose for a while, but he will not be going to town using a K-sized tank at 250 psi. And note, as well, that these calculations do not take into account the fuel used to cut and gather the wood, run the tractor for shredding, etc. etc.
I have a hard time understanding how biogas conversion, which at best only converts 60-70% of the volatile solids (VS)-- not the total solids (TS)-- into biogas, can possibly produce more energy than combustion. This is the case because the method used to determine volatile solids is usually combustion. In other words, wherever less than 100% of the VS are converted, that process has clearly produced less energy. Best case: biogas produces 60-70% of the energy that combustion does.
Whether there would be less work involved in feeding wood into a stove to produce hot water and for cooking, vs. creating that enormous compost pile after all the energy which has been put into shredding and stomping, etc., I don't know, for certain, but it does seem as though Thoreau, using 19th century technology, would have gotten rather more energy out of Jean Pain's wood than Jean Pain did, using 20th century technology. [End of David's comments]
Replies to critique # 1[edit source]
- Thank you for this critique! It is the first I have come across, and maybe explains why no one (that I know of) has succeeded in drawing useful quantities of methane out of a Jean Pain compost system.
- In saying that though, I have recently created a small version for hot water only, and depending how long it lasts, it could be that this system is VERY cost effective. I'm in Canberra, Australia. Woodchip is (at present) a waste product of local arborists, and they are only too happy delivering 15 tonnes of chip at my door free of charge. The pipe and fittings has cost me AU$200, but I can't be sure what the embodied energy cost is of that mostly high density polyethylene pipe and fittings... lets say twice as much, totaling $400. I reckon the cost of chipping is worth the humus I have at the end of the system's life, given how poor the soils are we have here. So, let's say the system costs AU$400 and lasts at least 5 years with free woodchips being delivered.
- I have turned off my electric hot water and am using only the heated water exchanged from the compost. I expect to get 3 months from this small (3-4 cub metre) pile I have made. I could be heating my house with it as well - the rate and volume of water being heated to 60 deg C in my system is impressive (120L in 10 minutes). So, that is a saving of about $40 per month in electricity bills. It would take 10 months for this system to pay for itself. At the size of my pile now, that would be just over 3 reinstalls of woodchip. Jean Pain's size lasts 18 months. (I expect at least 5 years out of the pipe under these conditions, but likely many more years than this). The system pays for itself quickly (in my context). If Australia goes carbon economy, electricity costs will rise 60-70% over 3 years, so the system will pay for itself in under half a year - but who knows what the cost of the pipe would become!
- I have not attempted to extract methane yet, but am planning to. If all I get is a quantity enough to cook a meal each day for 3 months, then that is an added bonus, as the system has already paid for itself in water heating alone. Your skepticism about Pain's methane quantities seems fair to me. How disappointing.
- Would it all be more efficient if we just burned the wood? Perhaps, if you used a rocket stove mass heater, it would... but you wouldn't have the humus at the end of the system, and you would need more expensive materials such as an insulated storing tank, and dry storage space for the fuel. The real beauty of Pain's system is its ease of set up - provided you have ready access to woodchips as waste.
- Like vege oil for diesel, this system is not one that scales. But it is one that some people can use and save quite a bit of money with, generating good soils while they go.
- The question I have though, is about toxins in the HDPE pipe. Do any gases leach from the pipe when heated to around 60 deg C, and when 500kpa of cold water pressure is being heated to that temperature? I am noticing a faint smell in our system, and am currently trying to find out what is happening to the pipe. I am thinking to find someone to analyse the water and vapor coming from the system. Any tips on how I might go about this?
- Leighblackall 10:20, 18 April 2010 (UTC)
Critique # 2[edit source]
Readers Digest ran an article, November 1981, giving more numbers on Pain's method. They sound reasonable to me, but I haven't tried to make or compress methane.
http://www.journeytoforever.org/biofuel_library/methane_pain.html
To sum up, the methane digester is not a closed batch system but taps off to many tyres and a compressor. He may have had an expensive compressor, he was a serious hobbyist. His car was equipped to only run 100km, meaning at 25mpg/10kpl, he was packing about 2.6 gal / 10 litres petrol-equivalent in two tanks. (That Citroen truck of theirs actually probably got closer to 50mpg/20kpl.)
Highlights:
"Buried inside the 50-ton compost, he says, is a steel tank with a capacity of four cubic metres. It is three-fourths full of the same compost, which has first been steeped in water for two months. The tank is hermetically sealed, but is connected by tubing to 24-truck-tyre inner tubes, banked nearby in piles. The tubes serve as a reservoir for the methane gas produced as the compost ferments.
"Once the gas is distilled, washed through small stones in water -- and compressed," Pain explains, "we use it to cook our food, produce our electricity and fuel our truck." He says that it takes about 90 days to produce 500 cubic metres of gas -- enough to keep Ida's two ovens and a three-burner stove going for a year. Leading to a room behind the house, he shows me the methane-fuelled internal combustion engine that turns a generator, producing 100 watts every hour. This charges an accumulator battery, which stores the current, providing all the Pains need to light their five-room house.
As Ida drives off in their truck, I see on the roof two gas bottles shaped like long cannon shells. These have a capacity of five cubic metres of compressed gas, allowing her to drive 100 kilometres. Jean says that ten kilos of brush-wood supply the gas equivalent of a litre of high-test petrol. All that is needed to use it as motor fuel is a slight carburettor adjustment."
Ajmot 03:33, 23 October 2010 (UTC)
I believe that the page needs to be rewritten for clarity, and expanded slightly.
It should be made more clear that it's two systems, one physically located inside of the other.
The outer system is simply a compost pile, which turns ground wood into compost, heat, and CO2. It doesn't require much extra work to ensure that composting occurs -- all that's needed is a sufficient supply of fresh air, and that the temperature remains inside a (fairly wide) range.
The inner system is a digester, which requires elevated temperatures (provided by the surrounding pile of compost), and turns soggy ground wood into biogas (methane + CO2) and mulch. It requires more careful temperature control to ensure maximum methane production. Under certain circumstances, it needs heat to be added; under others, heat must be removed. The temperature tolerances are slightly smaller... if care isn't taken, the digester will basically cook itself to death, and the heat will kill the bacteria.
The heat produced by the compost pile suffices to not only heat the digester as needed, but also produces extra heat which can be used for domestic hot water and space heating.
The excess heat produced by the digester of course can also be used for hot water and space heating.
The CO2 was probably separated from the biogas by compressing the biogas, then bubbling it through water in a pressure vessel. Since CO2 is more soluble than methane, it is absorbed by the water, while the methane passes through. In a continuous system, the water could be cycled from the high pressure part of the system, to atmospheric pressure (where the CO2 separates and is discarded) and then pumped back to the pressure vessel. The book glosses over the details of how separation was done in Pain's system, but I suspect from the photographs that a batch process, instead of a continuous one, might have been used.
The use of a large compost pile to produce both heat and mulch is a well established technology. Appropedia should have a page (or at least a stub) devoted to this, which in turn would have links to websites describing how to produce hot water from a compost pile.
The use of a digester to produce gaseous fuel is also a well established technology. The page should have links within the text (probably from the phrase "anaerobic fermentation") to Appropedia's https://www.appropedia.org/Anaerobic_digestion page.
The upgrading of biogas to pure (or nearly pure) methane is also a well established technology. There should be a link from the Jean Page page to a page specifically about biogas upgrading... again, even a stub would be nice.
Leighblackall, you said, "
I have a hard time understanding how biogas conversion, [...], can possibly produce more energy than combustion.
"
The page, as written, doesn't claim that more energy is produced; producing energy isn't the main point. The main goal is producing large amounts of good quality compost, together with enough fuel production, while using inexpensive methods to produce that compost and fuel. By "enough," I mean enough to power all of the equipment used, and provide fuel to cook with and generate enough electricity to power a home, and perhaps have a little left over for driving for other chores.
If M. Pain wanted to turn 100% of that wood into energy, and didn't care to produce compost, he could have built a wood fired steam engine, or an internal combustion engine fueled by a gasifier. But the solid waste from either of those systems is ash, which does not improve topsoil to the same degree as compost.
--Ben Goldberg 00:42, 5 November 2010 (UTC)
I'm not siding here with either argument whether Jean Pain's work was useful, just calculating from published numbers in the following article on Jean Pain http://journeytoforever.org/biofuel_library/methane_pain.html :
Taking a tube as a torus with average diameter @ 30" and cross section diameter @ 12" I calculate the gas capacity of 24 truck inner tubes mentioned as approximately 4 cubic meters, total.
The article mentions gas production:
"Once the gas is distilled, washed through small stones in water -- and compressed," Pain explains, "we use it to cook our food, produce our electricity and fuel our truck." He says that it takes about 90 days to produce 500 cubic metres of gas -- enough to keep Ida's two ovens and a three-burner stove going for a year. Leading to a room behind the house, he shows me the methane-fueled internal combustion engine that turns a generator, producing 100 watts every hour. This charges an accumulator battery, which stores the current, providing all the Pains need to light their five-room house."
If true, this would mean using and refilling the full storage capacity 125 times in 90 days, or more than once a day. Yet the gas supply is mentioned to be sufficient for a year after 90 days of production. Unexplained is where the resulting 500 cubic meters would be stored. Not in the 4 cubic meter tire capacity, clearly.
Also, most cellulose based bulk batch digesters are doing quite well to produce 1 cubic meter of gas per day for each ten cubic meters of digester capacity. Or 0.1 daily gas/substrate volume ratio. The Pain digester is 4 cubic meters. Its output above calculates out to 5.5 cubic meter per day. That's a daily gas/substrate volume ratio of 1.375, or nearly fourteen times a typical tank digester output.
While it may be operating thermophillically at times and mesophillically at others, the rate quoted seems extreme. Also, a higher output rate in a single batch reactor simply means the gas capacity is used up more quickly, since new feedstock can not be added. A short high output rate would be a disadvantage in the case where there is a very low storage volume, as seems to be the case here.
Discussion[edit source]
Thank you all for this important discussion. I have put a Disagreement Template on the main page so that readers know that this is being currently debated.
Also, please sign your comments on this discussion page using the following code: --~~~~.
Thanks, --Lonny 15:36, 29 January 2012 (UTC)
Expansion[edit source]
Page might be better if it included some of the disagreement discussed here Joeturner 13:56, 7 February 2013 (UTC)