David House

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since Feb 19, 2010
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Recent posts by David House

So friends,

It's time again for another (much improved!) biogas workshop, offered by me, David House, author of the Complete Biogas Handbook, hosted by the University of the District of Columbia, in DC, on April 18-19th. You can learn more about the workshops by visiting http://completebiogas.com/workshops.html, but meanwhile, let me give you an idea of what I've been doing, and what will be presented in the workshop.

When preparing for the workshop in Brooklyn, NY last year, where we were going to present low-cost, tropical-climate biogas digesters, I began to think about biogas in the US, where digesters really require insulation and heating. I realized that it is possible to build such a digester, and when I got back to Oregon on my farm, I started experimenting with the ideas that I had developed. Materials testing proved that it would be possible to make digesters out of rigid polystyrene foam, so that, for the most part, the insulation is the container.

Thus the standard "poly-panel" digester, which requires about $350 in materials, is a 2.6 cu m slurry vol; (90 cu ft, 680 gal) digester that can utilize food waste, and which might provide as much as 7.5 cu m of biogas daily. (Just for comparison, a family of four would need a single cu m of biogas for daily cooking...)

So the workshop in DC will offer complete information about biogas, and will show you how to build as many of these digesters as you wish. I hope to see you there...

David William House
8 years ago
Jacques Gauthier,

I think Jean Pain was... not entirely accurate in his reports. The video is misleading at best. See http://www.appropedia.org/Talk:Jean_Pain_system.
8 years ago

I've built several digesters, and wrote The Complete Biogas Handbook (www.completebiogas.com). Obviously then I have some thoughts about various digesters and substrates.

Horse manure will not generate as much biogas per dry pound as cow manure, and cow manure will not generate as much biogas per dry pound as pig manure. And no manure will generate nearly as much biogas as food waste (2x to 3x as much per dry pound). Further, building what I would call a practical digester from a 55-gal drum is either difficult or impossible, because in order to have what I would call " practical biogas" you will need to be generating enough gas to fuel some need: light, heat, cooking, electricity. Each use has its own hourly requirement. For light, it's about 100 liters per hour (3.5 cu ft); for heat it depends on ambient temp, size of place to heat, insulation and how hot one wants it to be (all pertinent details fully explained the book); for cooking figure about a cubic meter a day (35 cu ft); and for an engine or generator, it's pretty high at 425 liters per hour per HP (15 cu ft).

A digester kept warm and fed the right stuff will generate about its own volume in biogas per day, and a 55-gal drum is about 7 cu ft (200 l). That means that a warm 55-gal digester will not provide enough biogas to cook with, although it can offer some light if you have the right kind of lantern. (Like a Coleman lantern, but modded for biogas. These lamps are hard to keep working because the mantles are so brittle...)

The IBCs (Intermediate Bulk Containers) are 1 cubic meter (35 cubic feet), and so if you have the right slurry and keep it warm, a digester made from one of these will generate enough biogas for daily cooking, but it will be hard to make one work well for a long time as a continuous fed device. Most of the IBC digesters that I have seen work at very low solids (i.e. those that use toilet waste), and as such they will not generate their own volume daily.

More? I suggest visiting the complete biogas site and reading all the pages about building your own digester. Then ask any other questions you have. If I have time, I will answer. Meanwhile also in late April, I will be teaching a workshop that will give you all the info you need to pursue "practical biogas". Details at www.completebiogas.com/workshops.html
8 years ago

Well... I'm back for a while. (Last here in 2010, was it?)

Learn about and use biogas

Biogas is “the original natural gas”. Put together materials similar to those used in making a compost pile, keep the stuff warm, wet, and away from the air, and bingo: a burnable gas is produced. Use it anywhere you might use fossil natural gas, but without the fracking. You can cook, heat, provide light, and with enough biogas, even run engines or vehicles.

On the weekend of April 26th-27th, in Brooklyn NY, David House, the author of The Complete Biogas Handbook (referred to by some as “the bible of biogas”), will be offering a biogas workshop. The first day of the workshop offers complete information about how to understand, successfully make and properly use biogas. David will show you examples of and provide plans you can use to make any of the four most common types of small scale biogas digesters (the sealed containers used to make biogas).

You can bet that most of us live near a grocery store or a restaurant that is throwing away food every day. What if you knew how to build a digester and generate biogas from that food waste? David will show you the example of a small restaurant where, from food they are presently throwing away (less than a pick-up load a week), they-- or someone else-- could generate better than 20,000 cubic feet of biogas every month!

The second day will be mostly hands-on, but first you will learn the astonishing benefits of biogas, worldwide. Then those who have purchased a $30 kit will build their very own (it’s-yours-so-take-it-home) core for a very low-cost biogas digester. (If these digester cores are kept warm and well fed, they can produce enough gas for a family of 2 or 3 to cook all their meals, but the kits do not include insulation, a gas storage unit, stoves or other appliances.) Everyone who attends will get a copy of the Complete Biogas Handbook, and a CD containing the world’s best free information on biogas. Zero to biogas in two days!

Finally, at this workshop, a new, inexpensive, well insulated, 2 cubic meter digester design will be shown, and every participant will be given plans showing how to build it from widely available low-cost materials: a $175 value! (Kits for these digesters, different from the workshop digesters, will also be made available.)

For further details or to sign up, please visit the complete biogas web site, at the Biogas Workshops page . (Or if you wish, you can sign up by using the links just below.)

Register here. Get a core kit (workshops registrants only) here.

9 years ago
Dear Skip,

No piss, no vinegar. But I do try to be loyal to facts, where I know any. The stumbling block you will face (as far as the facts I know tend to make one assume) is storage. For mobile uses, it's not just calories, it's energy density, and methane ain't got it. Then there's the issue of where the energy for whatever compression is done comes from. Considering those factors may well impact your plans and it certainly should change your math...

That is not to say that biomethane is a poor source of energy for automobiles. Studies with which I am familiar do, in fact, support the idea of biomethane running automobiles. See http://www.renewableenergyworld.com/rea/news/article/2010/03/why-is-biogas-renewable-energys-cinderella .

As the article briefly demonstrates, biogas has been demonstrated to be superior to biodiesel or ethanol in providing energy from a given unit of land. (And yes, one can put the glycerol fractions from transesterification or the mash from alcohol into a digester and extract yet more energy from it.) But here's the kicker: the most efficient means of making this second-most productive source of bioenergy (pyrolysis delivers more, but with much greater GHG) is through generating electricity and then using that to fuel the transport.

Even so, that's just not where my passion is, and I will be leaving shortly for a workshop in Hawaii, so do forgive me, but I don't plan to further discuss biogas and automobiles. It would be great, however, if you kept looking around, and told the rest of us what you find.

Meanwhile, to answer your appended question, no, I have not scheduled a workshop for Chicago, but I expect there will be one this next year.

Be well....

12 years ago
In response to my mention of 15 cu ft per HP per hour, you said:

Also I believe your math may be a bit off as to the amount of fuel a given engine will consume per hour.

From FAO (http://www.fao.org/docrep/t0541e/T0541E0b.htm):

The normal thermal efficiency of [biogas] engines is 25-30%, and they use approximately 0.45 m  [i.e. 15 cu ft] of biogas per horsepower-hour.

With further regard to mobile uses,

I would be more than comfortable with enough gas to travel say 100 miles per day which... translates to what? about a 3000 or say 4000 gallon digester That's probably doable.

The problem with biogas for mobile uses is that methane is largely incompressible. Thus storage would require towing a large pressure vessel behind the car, i.e. storing the fuel as a gas, rather than the much more efficient storage that one gets with, for example, propane or butane, both of which liquefy nicely.

Be well.

12 years ago

Dear Skip,

Actually, whether or not it's heresy, my aim is not to convert the US. If that happens, wonderful, but two things tend to remove it from being anywhere near the top of my list.

The first is that in the US we use energy at industrial scales. To provide fuel for an internal combustion engine requires in the neighborhood of 15 cu ft of biogas per HP per hour. Thus a vehicle with 200 HP under the hood would require ~3000 cu ft of biogas per hour to run. Given that, as a rule of thumb, a digester will produce about one vol of biogas for each vol of digester per day, then to produce one hour's worth of fuel for the vehicle would require a digester of that same size (3000 cu ft). But of course, having only an hour's worth of fuel each day is not practical. We should have at least, say, 4 hours worth, so we need a digester of 12,000 cu ft, which is about 90,000 gallons-- four and a half swimming pools worth?

If we have a 30 day HRT (hydraulic residence time) on that digester, then we need to have enough organic matter on hand that we can dump in 3,000 gallons (~400 cu ft) a day.

Then we get to run one muscle car for four hours.

The second reason that I'm not avid to convert the US is that any practical approach to making a significant difference in this country would require enormous amounts of time, millions of dollars, and a fountainhead of sustaining legislation. Sounds like a lot of time in an office cubicle, to me.

My aim is a good deal lower. The WHO says that some 2 million people a year die of smoke inhalation and related causes. Most of these are women and the babies and children on their backs, and the smoke comes from wood fires. Biogas burns with a clean, clear, blue flame, and has no smoke.

Many studies, likewise, show that on average it takes 3-4 hours a day, every day of the week, to gather enough firewood for that dangerous cooking fire. Biogas provides an instant flame.

Much of that wood comes from forests that are not managed, by which I mean they are not replanted-- who has the money, in developing countries?-- and so those millions of wood fires turn out to be a significant contributor to the increase in CO2 in the atmosphere. Biogas uses ag wastes and manures the come from feeds, and it provides a wonderful fertilizer that can increase the fertility of the land.

There are other advantages as well, for the use of biogas in the developing world, but suffice it only to say further that the increased health and dramatically improved time available mostly to women and girls has been repeatedly shown to improve economic well being-- the women start or strengthen businesses, and the girls go to school.

So my aim is simply not domestic. I don't subscribe to any trickle down theories. To my way of thinking, if the poor of the world can improve their circumstances, using planet-friendly technologies like biogas, enough to have disposable income, then everyone will be far, far better off. We need not be worried about whether the rich will create businesses, and therefore should have more tax breaks. No. We need to improve the lot of the common man, who will then spend money. Businesses will flourish when they have customers, and investment will show up. It does not happen the other way 'round.

So if you want to learn how to build a small, modest, cheap digester, I'm your guy. If you want to learn about how to build a large, ostentatious, expensive digester to fuel a boulevard-centered lifestyle... Well, I'm busy elsewhere.

12 years ago
Dear friends,

As you may know if you've been visiting here for a while, I have in the past taught classes about biogas. Now, however, with the development of a new, low-cost design for a biogas digester, I am teaching "workshops". I call them that because there is a new "hands-on" section added to the previous class, so that anyone who attends-- you?-- will leave able to make their own digesters, in a variety of sizes and for relatively little money.

So, good to see you, so long, and until we meet again. Please visit www.completebiogas.com/workshops.html for complete details.

12 years ago

paul wheaton wrote:

That particular issue has been discussed many, many times.  The key difference is to consider the many types of heat and the value of a thermal mass.  Take a look at [url=https://permies.com/permaculture-forums/2831_0/alternative-energy/wofati-plus-a-rocket-mass-heater]this thread .

I appreciate the thread link. Thanks.

From reading in the referenced thread, however, it seems there is a confusion between having an airtight house and getting air from outside to burn. These are two separate subjects. Where one has an airtight house and a stove (or even worse, a fireplace) that burns inside air, the most dangerous situation is created, because the chimney of the stove/fireplace may become an air inlet if some other appliance or heater is exhausting air to the outside, creating a partial vacuum. When that happens during the time a fire in the stove/fireplace is dying, then while it is not creating a great deal of heat to force air up and out, it is (generally) creating a lot of carbon monoxide, which can be drawn into the house by the partial vacuum. Granted, such problems are worse for an open fireplace than for a well-designed stove, but they exist for either.

Regardless, then, it is never a good idea, as someone in the thread said (quoting you, I think) to live in a zip lock bag.

What makes more sense according to the physics is to have a house where the amount of incoming air can be controlled, and better, brought into the proper temperature range before it enters the house, as possible. One way to do this is to button up the house itself as well as it can be done, and to provide an air inlet via a pipe that brings outside air in from an earth-warmed heat exchanger, which will offer cooler air in the summer and warmer air in the winter. ( http://geoexchange.sustainablesources.com/ )

But to get back to the fireplace or stove, I would again say that it is rather better, for several reasons, to have it burn outside air. With regard to experts who support the idea, see http://oee.nrcan.gc.ca/publications/infosource/pub/Heat_and_Cool/Wood_Fireplaces_Section2.cfm or http://hearth.com/econtent/index.php/articles/upgrading_fireplace

Further, as mentioned, having a counter-current flow for incoming air provides the highest efficiency. I mention this again because while, as you pointed out, the issue of outside air-to-burn has been discussed, Google does not provide me with any evidence that counter-current flow has been discussed on permies.com. You, however, would know far better than I would.


13 years ago

If your goal is to generate electricity, you'd be far better off using the windmill directly for that. If you have batteries at the end of the process, why not leave out the stuff in the middle?

Farm-type windmills have very low efficiency, and any tower built high and strong enough to hold enough water to make, say, a pelton wheel practical, would be very expensive. Do forgive me, but it's a bit Rube Goldbergian to connect all those bits together.

More to the point it's crucial to understand how much energy is lost at each step, converting it from one form to another. I would not be surprised if you ended up with only 2-3% of the energy initially available in the sweep area of the windmill (and that amount depends primarily on wind speed). Whereas if you generate electricity from a properly designed wind turbine-- assuming that you have a situation that would make wind-electric power practical to begin with, i.e. where the wind blows at 10mph or better a sufficient percentage of the time-- you might reasonably get 10 times that output.

13 years ago