Solar Power isn't Feasible!

Solar Power isn't Feasible!
This cartoon was on the cover of the book "SolarGas" by David Hoye. It echoes the Sharp Solar slogan "Last time I checked nobody owned the sun!"

Tuesday, September 22, 2009

Culhane's "Melodic-Mnemonics": Science Education through Music Video

On October 1st, 2009 in Geneva Switzerland, Melody will host an

International Forum on Music as a Catalyst for Environmental Awareness

"Under the patronage of UNESCO and the United Nations Environment Programme (UNEP) and with the support of the Swiss National Commission for UNESCO, the Association Melody for Dialogue among Civilizations ( is organising a two-part programme with the theme "Music for a Green Planet".

One is an International Forum to be held at Geneva’s International Conference Centre (CICG). High-level participants will explore the relationship between music, the environment and sustainable development. It will focus on the potential of music and musical dialogue to heighten awareness of environmental issues – such as water, the oceans, forests, energy and climate change. This Forum will be followed by the second part of the programme, an innovative multi-cultural concert at Geneva’s prestigious Victoria Hall".

As we prepare to participate as speakers at this exciting "Melody Dialouge" Conference we are pausing to review how we got started in this business of using music to teach science:

The video above was the first Melodic-Mnemonic song I wrote during my first year as a science teacher at Crenshaw High School in South Central Los Angeles back in 1989.

The lyrics can be obtained here if you want to sing it with your own students, kids or medical school friends:

Why did I pick this topic? Because an understanding of "the lives of a cell" (to quote the title of one of my favorite books by Lewis Thomas which I read in high school -- or rather, in spite of high school!) seemed fundamental to all of our understandings of how our ecosystems and our environment works. As Lewis Thomas wrote,

"I have been trying to think of the earth as a kind of organism, but it is no go. I cannot think of it this way. It is too big, too complex, with too many working parts lacking visible connections. The other night, driving through a hilly, wooded part of southern New England, I wondered about this. If not like an organism, what is it like, what is it most like? Then, satisfactorily for that moment, it came to me: it is most like a single cell."

I didn't write the song to "teach" cell biology to my students, rather I wrote the song because I was in love with the book, in love with the topic, in love with biology, in love with life. I felt there was no better way to celebrate my love of science than to use the artistic side of my brain to express how I was learning to see the world.

I actually started this trend in 1985 when I was at Harvard and was inspired by Stephen J. Gould when he came into class and sang the geologic eras as a close-harmony acapella song accompanied by a tape of his singing group doing the doo-wop. And Tom Lehrer's song about "The Periodic Table" was played for us in Chemistry Class by Nobel Prize winner Dudley R. Herschbach who was also my house master at Harvard's Currier House.

My very first song for science was thus written for my Harvard Senior thesis in Biological Anthropology in 1985, called "A Talking Seal? Get Outta Here". It accompanied a music video that Steve Sessions and I made of Hoover, the Talking Seal -- the only known mammal to spontaneously reproduce human speech.

My second science music video was "The Classification Rap", which was aired on Beverly Hills Community Television from 1990 to 1995 and may have been seen by a few hundred people, but now, thanks to "youtube" has been seen in the past two years by more than 30,000 viewers and is used in schools all over the world. From the emails I get each month on my youtube account I've learned that kids are being inspired by this to make their own songs to help them and their friends learn science. It is certainly fun communicating and interacting with science students around the world this way, decades after I have formally left the class room.

But the Cytoplasm Blues, my very first attempt at this when I moved to "the 'hood" to start tackling the "inner city school problem" evolved during my first month teaching when I brought in a guitar and, in a Burl Ives fashion, tried to explain through a call and response song how to think of "the lives of a cell" and what went on within the cell membrane, using easily understandable metaphors. The call and response theme worked well in place of "rote memorization" -- by getting the students to use a time honored Cab Calloway type technique they seemed to enjoy the repetition that goes with memorization much more.

Of course back in 1989 we didn't have things like "video projectors" and "Power-Point" and other visual multi-media easily available, so I would write all the vocabulary on the blackboard and put up posters and diagrams of cells and organelles around the room. Then I would get out my guitar and get some of my students to literally stand on the tables with me (in a Robin Williams, 'carpe diem' Dead Poets Society kind of way!) , holding diagrams of cells they themselves had made and start the call and response song. Using "Drama in Education", acting out the story of the "lives of a cell", gave the students a kinesthetic, whole-body-whole-mind, multiple intelligence feel for the subject matter.

Culhane and his students at Crenshaw High School, South Central L.A. in 1989 act out the "lives of a cell" in "The Cytoplasm Blues"

The experience led us to become one of the NASA/McGraw Hill/Business Week "Challenger 7" Teaching Fellows. McGraw Hill Published Culhane's lesson plan for teachers around the country to replicate (click on scanned pages to enlarge. You can also download the entire document as a pdf at

Each Challenger 7 fellow (Barbara Durrett, Tom Greene, Bonnie Price, Thomas H. Culhane, Terry Thode, Helen Martin and Marc Sacerdote, shown above with McGraw Hills Charlotte Frank and Richard Morgan) were invited to visit the halls of congress and received a 3,000 dollar award for educational excellence from first lady Barbara Bush.

At the time we called our Melodic-Mnemonics Science Education through Music and Video Program "Bio-Rhythms" because we were teaching biology through Rhythm And Poetry (RAP) and music. Later we expanded to cover all areas of the environmental curriculum.

The method we use now in workshops around the world is very similar 20 years later except that the technology has caught up with the vision. Students can record music and video on their laptops and download the images -- which we used to painstakingly scan from their textbooks -- from the internet and then share their "self-made educational materials" with the world on youtube.

The simplest way to do a melodic-mnemonic is what we show in the Cytoplasm Blues video:

1) Record the song onto your laptop and put it in the audio track of your video editing program, or as an audio file in Powerpoint.
2) Type the lyrics into PowerPoint (or's Impress (freeware!) or any equivalent presentation software.)
3) Browse the web for the appropriate images to illustrate the lyrics and concepts (or, better yet, shoot pictures or video of your own diagrams, drawings, models or live action illustrations!) and put them onto the appropriate slides.
4) Export the slides as a series of .jpg or .png images.
5) Arrange the slides according to the beat in the video program so that they flow with the music.
6) Export your video for youtube.

This is the first step toward creating a melodic-mnemonic music video. Once you have done this what you have, in effect, is a "storyboard" of what you can then turn into a real music video.
The next step is to go out into the field and shoot your band and your singers performing the song, and shoot all your "B-roll" footage of the subjects being discussed in the song and then edit them in to replace the slides and make your own MTV style video!

In this way, the science textbook can truly be "brought to life!"

At the time, back in 1989, when this was much harder to do, and we still had to get training and work in our community access television studios to be able to do this stuff, we teachers realized that the technology was on the thresh-hold of becoming something everybody could use and afford.

I made a speech to the school that our class turned into a really cheesy over-the-top (but still sincere) poor-quality video while learning to edit and composite music.

The script, the philosophy of which we stand by even more vehemently 20 years later, was as follows:

"Once upon a time, school was boring. But that was before "Bio-Rhythms". Bio Science Education Through Music Video. Feel the Beat."

"Now who says school shouldn't be a three-ring circus, huh?

"You see anybody buying tickets to get into biology these days?

"But all that is going to change and let me tell you why:

"Over the past 40 years, ever since the advent of the electric guitar, the technologies of music and television production have changed the way we learn. There was simply no way that high school could compete.

"Now let's face facts folks, you would have rather been home watching television and listening to the radio, right?

"But today, the means of production have fallen into the hands of the masses. And that means that the same technology that the entertainment industry was using to woo kids away from their studies, is now affordable by even the most poorly paid professionals in our country -- I'm referring to the American Teacher.

"Today, with a little bit of creativity and enthusiasm the classroom can be turned into a production workshop, a place where students and teachers from every discipline can put their subject knowledge to use, creating not "busy work", but a product that they can be proud of.

"Now I teach science in the inner city, but our approach can be applied to all areas and all curricula, turning our children from idle consumers into active producers, having fun and learning at the same time, that's what "Bio-Rhythms" is all about.

"All of our children are capable of creative genius. The education problem isn't with them; the challenge is for us to teach them in the ways they learn best...

"Bio-Rhythms: Isn't it time all of our children got turned on to science?"

We would like to think that when we and our colleagues were "touching the future" twenty years ago, we were inspiring a new generation of young people who themselves may now be teachers or parents or both, to use a holistic approach to science education that puts music and video and art firmly into the science curriculum, merging left and right brain together to make science and learning about how to face the challenges of our environment as fun and empowering as it is important.

More examples of our music videos can be found at

Monday, September 21, 2009

Biogas Water Heating Trial 1

The first video clip shows the heating of 2 liters of water with biogas for 18 minutes. We see the full unthrottled six brick flame and the throttled flame.

The second video clip shows the spreadsheet calculations for determining how much of a smaller quantity of hot water must be added to a larger quantity of cold water to get bath temperature water.

Graph shows the temperature curve for heating 2 liters of water with tonights biogas using 6 bricks for pressure, but restricting the pressure using the stove valve . X-axis is time in minutes, Y-axis is temperature in degrees C. We will replicate this with the valve wide open, giving a higher flame but a shorter burn,  to see if this makes much of a difference.

One of the questions I often get is, "cooking with biogas is all fine and good, but what about using it to heat bathing water? Does it produce enough?"

Tonight I started experimenting with this.

We had two sunny days in Germany this weekend with average daytime temperatures between 18 and 20 degrees and tonight were able to use the biogas for 18 minutes.

We decided to put 2 liters of water in a cooking pot (about what you would use to cook spaghetti) and see how hot it would get (water heating is a very energy intensive process). In 18 minutes it reached 84 degrees. It might have gotten hotter if we had remembered to cover the pot earlier -- we only put the cover on after 11 minutes, so we lost a lot of heat to the room!

Originally I wanted to see how long it would take to boil 2 liters of water for a pot of spaghetti using my biogas, but when I ran out of gas after 18 minutes having reached a temperature of 84 degrees -- not hot enough to finish the spaghetti -- rather than throw the water out I changed my plan and decided to see how much bath temperature water (between 32 and 40 degrees) this 2 liters of 84 degree water might give me.

I have created a table in Excel (note: you can use "Calc",'s Open Source Spreadsheet if you don't want to spend the money on Excel!) called “how to get water to bath temperature” for the families I have been working with in Cairo. It uses the common physics formula for mass and temperature showing that the final or “total” Temperature of a body of water (Tt) is equal to an initial mass of water multiplied by its temperature plus the mass of a second body of water that is added to it multiplied by its temperature, divided by the sum of the two masses.

Tf = ((m1*T1)+(m2*T2))/(m1+m2)
Variables Values Calculations Formulas Description

I had previously calculated what it would take to heat 40 liters of water for a bath (the amount I usually use, which is twice what most under-capitalized Egyptians use in the "poor communities.") The formula showed that if you boiled 10 liters of water and added 30 liters of cold tap water you could take a 40 liter hot bath (at 38.5 C, hotter than your body temperature, so it would feel hot).

m1 30 30.0 (m2*(Tt-T2))/(T1-Tt) mass of water one, the bathtub
m2 10.5 10.5 (m1*(T1-Tt))/(Tt-T2) mass of water two, the water you are going to add
T1 17 17.0 ((Tt*(m1+m2)-m2*T2)/m1) temperature of water one, the bathtub
T2 100 99.9 (Tt*(m1+m2)-m1*T1)/m2 temperature of water two, the water you are boiling
Tt 38.5 38.5 ((m1*T1)+(m2*T2))/(m1+m2) Final total temperature desired

I algebraically manipulated the equation on the spreadsheet so that one could plug in any of the variables to get any of the other unknowns and demonstrated it to the families. We noticed that the average rule of thumb was that you can take a bucket of water at pipe temperature (average 17 degrees celsisus) and add roughly 1/3 of a bucket of boiling water and get it up to the required 38.5 degrees for a bath or clothes washing. This mathematical explanation satisfied the families, who claimed they already knew the principle of this, boiling about a third of the quantity of water on the stove to prepare a bath. This home grown appreciation of an alternative way to get hot washing water is not captured in most attribute tables. As has been reported for India, many residents in Cairo may be exercising a preference for effectively boiling water using biomass or low cost waste materials, defying the modernist assumption of a linear “energy ladder” (see Gupta, forthcoming, Amacher 1993, Barnes 2002, Arnold 2006, Pohekar 2006) Thus, the status quo, if properly explored, may be very revealing!

In our recent experiment shown in the video we heated 2 liters of water with biogas for 18 minutes and got it to 84 degrees.
By the time we went to add it to 5 liters of tap water (at 17 degrees) it had dropped to 82. The theoretical temperature we should have gotten according to the formula was 35.57 degrees:

Spreadsheet formula:
A2 =((B2*C2)+(D2*E2))/(B2+D2)
where A2 is the cell with the final temperature, B2 contains the biogas heated mass, C2 the temperature reached, D2 the larger tap water mass, E2 the temperature of the cold tap water.

T final Mass 1 Temp 1 Mass 2 Temp 2
35.57 2 82 5 17

We recorded a fluctuating 33 to 32 degrees, still very comfortable for a bath, and attribute the difference to losses from pouring and mixing (losses to the air and to the walls of the bucket) and possible inaccuracies of the measuring device. The bottom line is that it was still plenty warm for a bath.

Given that we can get an hour to two hours of biogas from the 1000 liter digestors we build in Cairo, it should be no problem each day to heat enough bathing water for one or two or more people. The average Cairene in my sample used a 20 liter bastila for bathing and heating about 5 liters on the stove to about 90 degrees, mixing it with 15 liters of cold tap water at about 17 degrees, achieving roughly the same temperature as in our experiment. The formula shows it equaling 35.25 degrees C.

T final Mass 1 Temp 1 Mass 2 Temp 2
35.25 5 90 15 17

In 20 minutes of biogas heating we could have gotten the 2 liters up to 90 degrees. This implies that 50 minutes of heating would raise 5 liters to that temperature. On good biogas production days, even with 90 to 100 minutes of gas one should be able to double that amount and provide 2 20 liter baths.

Is it worth it? The India experience is that the biogas is better utilized for cooking, and most families who have biogas digesters still use propane bottles for heating water for bathing. Nonetheless people don't always eat at home, and it is useful to see if it is worth trying to heat bathing water with gas that, after all, came from kitchen scraps. My feeling is that it definitely is.

Further experiments have to be done to determine whether or not it is best to use the biogas to heat the whole 20 liters to bath temperature or heat a smaller quantity to near boiling and add it to 15 liters of cold tap water. There are pros and cons to both, and they are experienced daily by the enterprising Egyptians who heat their bath water on the stove using bottled gas (60 % of Manshiyet Nasser's Zabaleen and 25% of Darb Al Ahmar are in this category).

Placing 20 liters of water on a stove can break the stove and many elderly people and young people can not lift the 20 liters, particularly without spilling. On the other hand, the larger quantity of water never gets hot enough to be dangerous. 5 liters heated to near boiling is lighter in weight, so it can be heated much easier on the stove, but it is very dangerous to carry; spilling causes scalds that puts many people in the hospital every year. Heating 2 small batches of 2.5 liters (a spaghetti pot worth of water) would be safer, but while waiting for the second 2.5 liters to heat one would lose much of the heat in the first batch. If one has a two burner stove one could heat two batches of 2.5 liters simultaneously but many families have only one burner.

What will weigh in here is the efficiency of heating large versus small quantities of water, given that biogas is in limited supply each day. Certainly families using biogas can supplement with bottled gas when needed, but we would like to have the data for the times when fossil derived natural gas is either too expensive or is simply unavailable.

Saturday, September 19, 2009

مخمرات البيوجاز

تتكون آساسا من حيز مناسب يسمح بتوفير ظروف الهضم الاهوایي وتحقيق الظروف المناسبة لنشاط الكائنات الدقيقة وبحخم يكفى كمية المخلفات المتوفرة بعد خلطها بامائ بالنسبة المطل،بة مع إمكانية تجميع وتخزين الغاز المنتج لسحبة عند الحاخة للاستجدام مع توفير وسيلة مناسبة لإدخال المادة العصوية بالقدر و الشكل المطلوب وكذا وسيلة لإخراخها بعد التخمير آو الهظم لضمان استمرار العملية بكفاءة والمخموات تتفاوت في آحجامها حسب كمية المخلفات المتاحة او كمية الغاز المطلوبة كما آنها تختلف من ناحية التصميم فمنها البسيط (منخفض الانتاجية) ومنها المصمم بطريقة توفر آفضل ظروف التخمير لزيادة الانتاجية (شكل ١ - آ ب ج) مخمر بيوغاز هند ي الطراز  و مخمر بيوغاز صيني الطراز   شكل رقم ١ - ٣ بعض مخمرات البيوجاز المنزلية البسسيطة< 


Friday, September 18, 2009

Still experimenting with small engines on biogas

 After a week of cold days (averaging 15 degrees) with clouds and rain we finally got a couple of sunny days to fill our 200 liter biogas tank. We wanted to see how many minutes we could run the generator on this amount. Unfortunately a little over half of the gas was lost experimenting with the in-line oilers (which didn't work) so by the time we got the engine going we had less than 100 liters to work with.  We ended up getting 3 minutes of run time from this (and we had to oil the crankshaft through the spark plug hole.)

All in all it may have been a godsend, because when we pulled the spark plug to see if it was still oily we found it dry. Had the engine run dry it might have been ruined.

We still feel the need to find a way to use two-stroke engines with biogas because 2-strokes are cheaper, more robust, smaller and more often found in "developing countries" and among the "poor" than 4-stroke engines. Obviously 4-stroke engines are much better suited for biogas because they are "self-oiling".  But it would be nice to figure out how to get the right amounts of oil into a two-stroke running on our biogas.

As you can see in the video, we had put too much oil in through the spark plug port, leading the engine to smoke like crazy. Note that this smoke has nothing to do with the biogas. Biogas burns absolutely cleanly with no smoke or smell.  This shows also that the major problems with two stroke engines (and why motorcycles, lawn mowers and rickshaws produce so much pollution) is almost completely due to the oil associated with the fuel.

This will be our last test of two stroke engines for now, until we can solve the oiling problem (maybe using motorkote will help? Since biogas is not a solvent like gasoline, if a better lubricant were in the motor maybe it would last longer.)

In Cairo at Hanna's next month  we will convert a 4 stroke engine to run on "tri-fuel" (principally biogas, but with the option to revert to other fuels if necessary -- 4 stroke engine conversion kits give you hybrid tri-fuel possibilities!) and figure out how long we can run it on a 1000 liters of gas.

Our conservative estimate from this experiment, where we got about 3 minutes from about 100 liters is that we will get about 30 minutes -- a half hour -- from our Cairo systems.  If the generator is a 1 KW generator and we can run it for 30 minutes we can "bank" about 500 Wh in a battery system. Then that 500 W can be used to power 5 twenty-watt light bulbs (100 watts worth) for about 5 hours (or maybe 4, considering losses). That would be a good result if each day or two a family could produce and store enough electricity from their garbage to run their lights for the evening.

Today's experiment is therefore encouraging.

Other encouraging things:

We had had concerns that this open tank design led to losses and that we would need to create totally airtight containers but now that we have covered the digester with plastic and seen it does not fill with gas  we feel more confident that it does not lose a lot from the sides and we can save money and time continuing to use open telescoping digester designs.

In practice we haven't seen any filling of the plastic bag with gases evolving from the open gaps on the outside of the tank. This suggests that methane losses are negligible.  Perhaps the anaerobic bacteria avoid these areas because of the possible air exposure and build their biofilms inside the total anerobic chamber inside. 

One very useful comment we got on youtube was to try replacing the bricks with a 30 liter water tank (given that we need 23 to 25 kg to run the engine) which would allow us to vary the weight by adding or removing water and would distribute the weight more evenly. While the current design of the "cage" surrounding the gas collection vessel precludes this option for the moment, we will incorporate this suggestion into future designs.

Note we've had to abandon the air compressor oilers completely and placed the regulator where it should be, below the engine.  Something that is not shown in the video is just how many times we tried to start the engine and were unable.  Either there was too much oil in the line, or not enough gas, or the air-fuel mixture was wrong. Finally, by removing the in-line oilers, draining some of the oil that was stuck in the feed tube and priming, then starting (as usual for biogas with the choke wide open) we got it to start. But by the time we were able to get the gas flowing properly we had wasted more than half our gas, so we were running on a bit less than 100 liters which lasted the 3 minutes shown.

The very conservative estimate now, considering that we get about 12 to 15 minutes cooking on the same amount of gas, is that running the engine consumes about 4 to 5 times as much gas.  In the 1000 liter systems where we get about 2 hours of cooking gas we thus estimate half an hour of electricity generation. But these are very conservative estimates based on a single flawed sample.  The literature says that 1 cubic meter (1000 liters) of biogas should give about 2 KW of power.  This might be for more pure gas however (our mixture of home made biogas is said to be about 60 percent CO2).  We will be optimistic and hope for an hour of electricity with a 1 KW motor, but would still be happy with 500 Watts worth. That would be just enough to make this worthwhile at the home level.

We'll report back when we know more.

Suggestions and comments are welcome.

Wednesday, September 16, 2009

California Unplugged: Solar CITIES at the Los Angeles Eco-Village in 2001

Digging through our archives we found this 8 year old Christian Science Monitor article talking about our activities at the Los Angeles Eco-Village at the turn of the century (!) which also features our colleagues, friends and inspirations, Julia Russell, (founder of the Los Angeles Eco-Home ), Lois Arkin (founder of the Los Angeles Eco-Village) and Lara Morrison (one of the guiding lights and board directors at the LAEV).

You can download a high-resolution PDF of the article here: Science Monitor.pdf

Now that we are working on eco-home/eco-village concepts in Cairo, Egypt, Essen, Germany and Santa Rosa, California it is great to go back and see how we started. Thought you might enjoy sharing the history too!

A special treat is seeing this picture (below) of Alvaro Silva from Solar South Central when we were working on an electric car conversion using Mike Brown's book "Convert It".
The actual electric motor shown in the picture made its way from the L.A. Eco-Village to Solar South Central, then all the way to Cairo for workshops there and is now here in Germany awaiting its chance to be part of an electric car conversion here.
Meanwhile Alvaro was recently working with us on the green-retrofit of the 460 Lucas home in Santa Rosa and will be coming to Cairo to work with us in October. What goes around the world, comes around the world!

Friday, September 11, 2009

Animation of a simple telescoping biogas digester

For this simple animation describing just how simple it is to build your own biogas digester I downloaded Google Sketchup 7 and then used Google 3D Warehouse to download a model of a digester by roilbilad130 called "Biogas untuk limbah dapur" (which is Indonesian for "Biogas for Kitchen Garbage"). I changed the food inlet pipe and the fertilizer output pipe in the model to reflect the way they work in the ARTI India systems we have been building in Cairo and Germany and set different sequence animation key frames in Sketchup and did screen capture in Snap Z Pro. Building real digester is about as easy as building a digital one in sketchup -- it really is just two plastic barrels, one inverted inside the other, with three pipes -- one to get the food in, one to take the liquid fertilizer out and one at the top to deliver the gas to your cookstove or generator. 1000 liter tanks should get you about 2 hours of cooking gas a day if you live in a warm climate. As shown, we intend to use psychrophilic bacteria at the bottom to increase cold weather production.

The psychrophils can be obtained from lake mud in the arctic circle area. We will be obtaining our samples working with Dr. Katey Walter Anthony and Laurel McFadden at the University of Alaska, Fairbanks.

Dr. Anand Karve, inventor of the household biodigester process in Pune India reminded me to "think like a sacred cow": cows eat food, not manure, he told me, and the bacteria in the cows stomach and intestines also eat that food, mixed with saliva and water. The goal is to replicate the inside of a cow's digestive tract to help the bacteria get the most energy from the food. We only use the dung/manure to"innoculate" the system on the first day because it is the easiest non-invasive way of getting the "bacterial biogas experts" out of the animals' guts and into the tank.

In many respects making biogas is similar to making yoghurt. If you have a friend who has an active culture of methanogens from their own biogas digester (or from a septic tank, or from their baby's diaper (:)) ) just put them in. If you don't use manure, however, I'm not sure what or how much to feed them in the beginning. We will let you know as soon as we do since to culture the psychrophils from the arctic mud we will need something to encourage their growth.

The process working with mesophils from animal dung, however, is started very simply by taking about 40 or 50 kg (maybe 4 to 6 10 or 15 liter buckets) of manure (we used horse manure in Germany, cow manure in Egypt, but any manure will do) and mix it into the bottom container with water (this is per 200 liters of water but we just go ahead and fill the whole thing even up to a 1000 liters of water; it may make the wait time for first flammable gas a bit longer as it takes the bacteria time to reproduce and fill that volume, but it worked fine for us as we didn't want to haul in more manure.). Then put the top barrel on and open the top valve so all the air escapes and the top barrel sinks down into the bottom barrel all the way.

You then close the valve at the top so no air can get in and just let it sit there for anywhere from 2 weeks to a month (depending on climate). During this boring period the bacteria will multiply. At first they will just produce CO2. After a few weeks open the valve and flame test with a candle (we didn't use a flashback arrestor! Doh! :) ) . The first couple of times the escaping gas will blow out the candle. Eventually, after a few days, the methane content will exceed 50%.

Once the gas starts to burn you can start feeding your digester ground up food waste (mixed in a blender with water, about 1 to 2 Kg a day, but start slowly so as not to overwhelm the bacteria; start with 200 grams then 400 the next day etc.). Soon the CH4 content at the top of the tank will exceed 60% (since CO2 is water soluble it can get up to 70%) and can be directly used in cook stoves and engines. Hope that helps explain it. It works well and is fairly simple you'll find. Give it a try !

Remember you only have to put the manure in THE VERY FIRST DAY. After this no more manure is needed (though our neighbor at Imbrahm Recycling who has a 1 million Euro commercial operation says adding some fresh manure every couple of months keeps the bacterial colony in top form. Logically the bacteria are symbionts in animal guts and, having co-evolved there, reproduce there best. In the artificial environment of a plastic tank there is no guarantee that succeeding generations of bacteria will be selected for the right traits.). To start another digester, however, you don't need manure, just the effluent from another active digester! Started with this active culture the waiting time is much shorter.

The following description of the process by inventor Dr. Anand Karve of ARTI India in his paper "Taking Action to Rid the World of Indoor Air Pollution" is very useful and can be found in its entirety at proceedings of the CleanAirSIGe-conference: 16 -27 July 2007:

"The current process of biomethanation, which uses feedstocks like cattle dung, human feces, distillery effluents etc. is highly inefficient, because the nutritionally available calories and nutritive value of those substances is quite low. Common sense tells us that the energy output of a system must be matched by the input. Methane has a calorific value of 11000 kcal/kg. If one wants a high output of methane from this system, it must also receive input having a correspondingly high calorific value. Nowadays, municipal solid waste (MSW) is also being used as a source of methane. Food rests in the MSW have a relatively high calorific value. But in the process currently being used MSW is subjected first to aerobic fermentation, in order to reduce its bulk. The predigested material, having very few calories left in it, is then fed into the anaerobic digester for producing methane. This is called a biphasic fermentation system. As a rule of thumb, one can state that biogas production systems operating on human or animal faeces, distillery effluent, or two phase digestion of municipal solid waste, all produce about 100 kg methane per ton of feedstock. The traditional biogas generating systems require about 40 days to complete the process. The time can be shortened by using thermophilic bacteria and digestion under higher temeperature, but the input to output ratio remains unchanged.

'Use of cattle dung as the feedstock is the main factor limiting widespread use of methane as household fuel in rural India. The present domestic biogas plant requires daily about 40 kg cattle dung (from 6 to 8 heads of cattle). Because the dung must ferment for about 40 days, the size of the biogas plant is also large. Restrictions of space, money and absence of sufficient animals prevent many aspirants for having a biogas plant based on this technology. The servicing of this plant requires mixing the dung with water to make the feedstock, filling it into the biogas plant and the disposal of about 80 to 100 liters of effluent slurry. These chores must be done daily and they are considered to be a bother by the users.

"ARTI developed in 2003 a new biogas technology which uses high calorie feedstock, consisting of starchy or sugary material. This material is capable of producing about 250 kg of methane per ton of feedstock (on a dry weight basis) and the reaction takes only 1 day to complete. In the case of a household biogas system, application of daily just 1 kg of feedstock is enough to provide a family with sufficient biogas to cook all the meals. The material that can be used as feedstock in the new biogas system consists of waste grain, seed of any plant species, oilcake of non-edible oilseeds as well as nonmarketable or nonedible fruits (wild species of ficus, overripe mango and banana). Even the flour mill can be used as feedstock.

"Because of the smaller quantity of feedstock and also because of the short reaction time, the digester size and also its price are drastically reduced. The gas holder of the domestic model of the new compact biogas plant has a capacity of just 750 to 1000 liters which is enough to cook two meals for a family of five. The user applies 1 kg feedstock in the morning and another kg in the evening. The total effluent slurry generated daily by this system is hardly 10 liters. Thus, this system does away with the daily drudgery of handling huge quantitities of cattle dung and the daily hassle of disposing of about 100 liters of spent slurry. The new biogas plant would be available at a cost ranging between Rp. 10,000 to 12,000. This technology brings cooking fuel in the form of methane within reach of every household.

"The apparatus itself consists of two plastic water tanks, which are generally available in shops selling sanitary ware and plumbing hardware. The top of each drum is cut open so that the smaller drum can nest in the larger one. The outer drum serves as the digester and the inner drum, which is placed upside down into the outer drum, serves as the gas holder. The inlet pipe for the input is a vertical pipe fitted inside the gas holder. It runs along the entire length of the gas holder. The gas outlet is also fitted on the inner drum.

"To begin with, the system is loaded with a slurry containing about 250 kg cattle dung and water. Then one waits about 2 weeks, til the gas emanation begins. The gas is tested by burning it. Once it starts producing combustible gas, one can start applying the high calorie input, as explained above.

"According to an estimate by the World Health Organisation, about 3 million people in the world die every year as a consequence of exposure to suspended particulate matter in the air, and that 85% of the deaths are due to indoor air pollution. The indoor air pollution is caused mainly by traditional cookstoves, using traditional biomass based fuels. Considering India's share in the world population, the estimated deaths due to indoor air pollution in India come to annually about 500,000. Although acute respiratory infection is the single largest category of deaths in children under 5 years of age, indoor air pollution remains a neglected topic in India, because the number of persons killed annually by polluted water is much higher than that killed by polluted air. It must, however, be emphasized, that while polluted water can be made potable by filtration, chlorination, boiling, reverse osmosis, distillation etc. there is no simple treatment to purify polluted air. It is therefore necessary to reduce the pollutant load in the air at the source itself. Methane as cooking fuel would prevent these deaths. It is nonpolluting, renewable, cheap and CO2 neutral.

"In addition to household fuel, it can also be used as fuel in internal combustion engines."

We at Solar CITIES urge you to build your own digester - even if you never used the fuel, you will find that it is much better than composting for dealing with kitchen garbage and making fertilizer!

T.H., Sybille and Kilian Culhane next to a telescoping digester they built with Hanna Fathy on his roof in Manshiyet Nasser's Zabaleen community, Cairo, Egypt.

Thursday, September 10, 2009

Running a small engine on household biogas (Biogas untuk limbah dapur) using "bricking' for gas pressure

A hearty thanks to British engineer Marcel Lenormand for prodding us to finish a project a long time overdue with a well timed blog comment: "Does 'bricking' the digester's floating dome produce insufficient pressure to feed the engine?".

We'd wondered the same thing but since we hadn't built a cage to hold the floating dome in place we couldn't test our intuition that the simple act of "bricking" would actually work because every time we put bricks on the gas filled dome it would tip over.

In India we had observed that some of the ARTI Urban Biogas systems families had built had various "cages" to keep the dome level as it fills but, swamped as we've been,  we hadn't put in the time, effort or money to complete our own digester. Like many of the urban poor we engage in what the literature calls "Incremental Housing" and "bricolage" (putting things together in a hodge podge fashion using whatever materials are available or lying around).

But the day after we had done our first engine conversion trial and met with success using a hand-drill water pump for pressure we got so excited to see if mere "brickage" with the "bricolage"  would do the trick we ran off to Bauhaus and bought the cheapest materials we could think of to make a cage to enable us to allow us to experiment with "bricking" -- a bunch of plastic plumbing pipes, elbows and fittings. Still it wasn't cheap -- 35 Euro for everything (this explains why so few people bother -- bricking isn't necessary for using the gas for cooking so the extra expense isn't needed if you aren't running a generator).

The results shown in the video above prove that 4 3.5 Kg bricks (so 14 kg) is enough to keep the generator going when the pressure regulator primer is depressed (this indicates that without the regulator it would work just fine at that pressure), while the addition of two more 4.5 kg bricks, bringing our total to 23 kg (about the max weight of a full suitcase on an airline) provided enough pressure to keep the engine running and producing electricity with the regulator attached without keeping the primer depressed.

We could adjust the regulator to allow more gas in under the 14 kg pressure but for now we want to keep it set the way it came from so that if we need to use a standard CNG bottle we can.  The idea is to be able to use our biogas when we have it but also be able to run the household using the most climate friendly fuels available on the days when sunshine is not enough here in cloudy Germany.

(A note to our critics and to fossil fuel and nuclear industry shills and lobbyists: we concede that home-made biogas electricity generation and cooking fuel from garbage , do-it-yourself solar hot water, and self-wired PV systems may not be "economical". Thus we will try to build our own backyard nuclear power plant, rooftop oil refinery and basement coal gasifier next and see how they pencil out. We hear Ahmadinejad has some extra centrifuges; anybody got the other feedstocks?)

Tuesday, September 8, 2009

Generating electricity from biogas made from household kitchen garbage turns out to be "child's play"


On September 7 2009 we made family history by running a 650 Watt 2 stroke electric generator on kitchen-garbage-produced-methane on our porch in Germany. The procedure turned out to be pathetically simple, calling into question why many members of our species think we have to fight wars for foreign oil, and why we risk our children's futures with climate change and nuclear proliferation and the poisoning of our air, land and water when we can turn our "garbage" into clean burning fuel.

The engine was converted using a $189 type A carburetor kit from
in a couple of hours on a Saturday.

Converting an engine to run on biogas is child's play...

O.K., it isn't something a baby can do, but it certainly doesn't take any special training! We are not mechanics or engineers yet we found it extremely easy. The work consisted of removing the bowl float from the carburetor and then drilling out the carburetor with a hand drill. We then inserted a simple pipe connected to a gas fitting and stopped up all vents and holes (including the gasoline inlet) with black silicone. It was amazing that all the delicate engineering that goes into a carburetor for getting the right fuel-air ratios and getting the gasoline to vaporize correctly become superfluous. We found that converting a carburetor to allow an engine to run on biogas (or any source of methane) is actually a process of radically simplifying the carburetor.

The only unresolved issues are how to lubricate this two-stroke engine (our 4 stroke kit won't 't have those problems) and the best way to increase the pressure of the biogas. All are fairly trivial problems. The point is you CAN generate home power using your kitchen garbage and eliminate waste and filth and pollution and greenhouse gases.


The natural gas kit conversion for small engines is rather easy to apply. The kit cost $189, the engine/generator cost $110.

I used a two-stroke engine because it was cheaper, but we may run into problems with lubrication.

When we get to Cairo in October I will convert a larger 4-stroke engine. I bought another conversion kit for the same price for the 4-stroke engine/generator that will have no lubrication problems (and it allows hybrid tri-fuel use -- gasoline, propane and methane (biogas) can all be used, so when one is unavailable you simply switch to the other fuel).

I'm NOT a mechanic.

I'm NOT an engineer.

Far, far from it.

I was a musician, a writer, an actor and a high school teacher who later studied Urban Planning and Public Policy.

If I have any skillset is simply that I know how to read and I'm not afraid of manuals; this was my first attempt to do anything like this. A qualified week-end mechanic could use the same principles to convert their car to run on biogas.

Producing the biogas took 24 hours but the bacteria did all the work for us
-- from Saturday's kitchen garbage (food waste) we got Sunday's clean generator fuel (and fertilizerfor our rooftop garden).

Biogas is climate neutral and releases no toxic byproducts when burned.

Producing electricity from biogas using off-the shelf items is so pathetically easy
it is almost scary. It makes me wonder why people think we have to go to war for foreign oil, poison and pollute our land, air, fresh-water and oceans with oil spills, endure climate change, risk our children's lives with potential nuclear meltdowns, radiation and threats of terrorists
acquiring "dirty bombs" etc.

We know now that we can produce our own clean electricity using our own kitchen garbage, solving our energy and waste problems at the same time. Yes, quantity is an issue and it is doubtful that a family of four could produce enough waste to generate all their electricity (even saying "super size me!" all the time!) but the principle can be applied to community energy management; if all the wastes from kitchens, cafeterias and restaurants were used it would scale up nicely.

Improvements and scale-ups will come in time.

Help and suggestions are welcome.

We will continue this work in Egypt in October using a 4 stroke engine so we won't have to worry about oiling. When we get back to Germany we will purchase a 6.5 HP Hercules 4 stroke 2000 Watt generator and do the tri-fuel conversion on that.

But two-stroke engines are less expensive and more durable, and more common in developing countries

So, on behalf of the world's poor, we want to figure out how to use them.

What energy crisis?

Let's get out of this mess, shall we?