Small Scale Methane

In my work in the remote villages of Eastern Kenya, I searched for a way to provide cooking fuel and lights that did not degrade the local forest cover and require hours of extreme labor chopping and carrying fire wood. I met a crusty, retired, Prussian cavalry officer from the Eindhoven stove group who was promoting methane fuel from biomass—mostly manure and grass. Already the inhabitants of the huge dumps of Nairobi had discovered that rotting garbage produced a gas that they could cook with—the fire of God they called it. I began to experiment with easy ways to enclose biomass in anaerobic (air-excluded) vessels or bags and extract the gas the evolved. The 3-drum digester you see was a design that was quite successful and produced enough gas each day to cook the villager's biggest meal and provide reading lights at night for school children. There is no loss of water or nutrients in the liquid effluent which went straight to the tree nurseries.

Basically methane is generated from the microbial digestion of properly mixed biomass that has the desired water-nitrogen-carbon and heat ratios that support rapid bacterial growth and consumption of this material. An acid substrate forms quickly and then the methanogens devour this. A byproduct of their digestion is flatulence which is, like in humans, a flammable gas. Think of the problem when we eat too many beans or veggies, and you get the idea. The gas produced is combined with sulfur and carbon dioxide and is very wet. To get pipeline quality natural gas/methane from this gas called bio-gas, you must scrub the sulfur by passing it through an iron filings filter. You remove the carbon dioxide by bubbling it through lime water, and the excess moisture will condense on the pipes and must be led away to U-tubes where it can evaporate.

To understand the entire process, just think of the digester as a huge cow stomach. Chopped nutrients go in and are “ruminated” into a brew that is bacterially digested in the gut. Gas and a slurry are pushed out as new material is fed into it. This is called a plug-flow system—grass in, sludge out in equal volumes. If a floating lid is placed over the digester tank, the bubbles of gas and carbon dioxide will be captured and lift the cover. With a little pressure, this gas can be forced along a pipe to an inverted tank in a water bath/seal, which will float up with the gas under pressure. To push the gas to a point of use, a bucket weighted with water can be used to achieve the desired inches of water column pressure needed to make any device work.

At our farm, as you see in the photo, we have a digester that holds 1,500 gallons of water and slurry. The gas-collector/top of the concrete digester (buried in the ground for insulation) is a floating steel tank 4’ wide x 9’ long x 2’ deep. The single small gas collector tank has now been replaced with 2 fiberglass tanks for added gas collection. We use it for cooking and demonstrations mostly, but it is now at capacity, and when connected to the genset which runs on propane and or natural gas, it will run the 16 kW generator for 1 hour for each 3 cubic meters of gas we make. Our sole substrate for making methane of very high quality is grass clippings which have a perfect C:N ratio and produce such good gas that we do not need to filter it.

The photo of the gas burning reveals a high quality flame of dark blue with no orange tips or smoke. Here is the closest thing to a free lunch I have ever known! The amount of gas we could produce is virtually unlimited and the effluent is perfect for fertilizing trees—a little too low in pH for veggies or grass. There isn’t room to discuss all the safety issues, but I can say that it is much safer to use in the house than propane.

Our system has been running for the last 4 years with very little maintenance. As a demonstration unit, it has surely proven to be worth every dollar invested. If you are interested in a spreadsheet with calculations of each component and productivity, then you can contact me through my profile.

Update

Well, I say this all the time, but I am constantly amazed at how quickly time flies now. If only I had known this at 20--when a whole summer took years to pass. Now, the year passes so quickly, it turns my head as it moves past. :)

But as time passes, so projects progress. Our barn is nearing completion and the garden was productive this year. We just finished our first batch of very tasty spaghetti sauce and we are making salsa today. Yumm! We have had delicious watermelons and cantaloupes, but the squash, peppers, and beans did not fare as well. The plants produced enough for some fresh produce, if not to put up. We are looking forward to a fall crop of potatoes and peas. It is still too hot to plant much in August, so we usually plan for September and October--adding fall crops as well as green mulch like clover, rye, and vetch.

We should have some updates on solar and wind power in the next month or two.

Persimmons - Yum?

Along our main drive, we have planted persimmon trees. Some are native species and do not produce much fruit, but others produce large orange fruit in the winter, starting in November. Now, persimmons are a tricky fruit. They are terribly bitter and astringent if they are not eaten at exactly the right time, but when you get a good one, they taste better than a ripe mango. :)

This is one of the smallest trees on the property, but it has a nice symmetry. The fruit can be used to feed people and livestock, but ours mostly feed birds and bees.


As they ripen, they turn a lovely deep red. If not picked, they fall to the ground and then insects and birds love the sweet syrup and flesh.

Many Things to Be Grateful For

I found this shot of two of the three generations on our campus sharing a snack at a very messy table, but then I started looking at the picture and it is quite symbolic of our family. There on the wall is a lovely very large painting done by the youngest girl in our family. Below that is a portrait brought home from Africa--one of many momentos of a different life. The mess on the table is pretty common, along with the book reading. We don't have cable TV, so our time is spent reading, working, painting, thinking, and sometimes watching DVDs. It also struck me that we are very lucky to share this time together with a granddaughter, parents, and children all living near and with each other, sharing a commitment to a life filled with peace, fellowship, and fun (and good food! :D).

And of course, there is always the beauty of the outdoors to be grateful for (yes, I found some more lovely photos of flowers from the summer LOL).

Barn and Garden Update

The garden is pretty much done for the fall. We planted some peas, broccoli, lettuce, and cabbage for the winter, but the chickens have eaten most of the lettuce and the others have not produced much. :(

The one thing we did harvest the winter was GOURDS!! Lots and lots of gourds. Here is a sampling. The one on top was painted as a swan (gorgeous, huh? :D)

I took this picture of the gourd flowers this summer and they are quite lovely...along with the shadows on this green gourd. It is such a little treat to find old pictures that brighten your day.

The barn is also moving along. Mostly weatherproofed now and siding and trim are slowly going up. There has been a break over the past few weeks what with thanksgiving and family coming up. We had a lovely thanksgiving, enjoying time with the 3 kiddos and Auntie S.

Remembered Beauty

Here are few of the lovely flowers around the property, taken this summer in the hot Texas sun, which is nice to remember right now in the dreary cold of winter. :)

Barn Raising - sort of

Well, the barn is under construction! It is a 2-story building with living quarters above. The bottom floor will have a milking parlor and kitchen for processing of food and milk. It also has storage and an office space. This has been built primarily by two guys....pretty impressive huh? :D It has taken about 6 weeks to get here.
The floor is concrete and the walls are typical wood construction except for the fact that it is braced way above code.