This is a guest post by Ben Peterson, author of the Wood Gasifier Builder's Bible.
A wood gasifier is a marvel of technology. Imagine being able to turn dead tree branches from your own property into motor fuel. Make power just about anywhere, at any time...for free. Sounds futuristic, right? Well, it's actually an age-old technology from the industrial revolution that is still used to this very day by homesteaders and folks in developing countries where power is expensive or non-existent.
Wood gasification is again growing in popularity as people return to the land in search of clean, sustainable living. Its utility is becoming recognized as more off-grid solar systems are installed and the reality of cloudy days and dark winter nights are experienced firsthand. "What can I use to fuel my backup generator that isn't petroleum based?"
My Experience Going Back to the Land
When my kids were old enough to swim in a pond and chase off coyotes, we bought an old homestead and moved onto 20 acres in the sticks. I wanted them to experience nature firsthand and not just read about it in a book. I get irked by concrete-dwelling city environmentalists, but I digress.
Our dilapidated old farm had two main problems: Weak power and mountains of wood waste. So I started looking for a solution to both problems and stumbled across wood gasification. It turns out people had used wood gasifiers to power 1 million cars, factories, boats and homes during WWII— a forgotten technology with real potential. Living in Western Washington, we have tons of wood. I like to joke that we are the Saudi Arabia of wood.
On July 4th weekend 2007, I was able to cobble some scrap metal together into one of these gasifier contraptions using a set of FEMA plans. A quick proof of concept. It only made a belch of gas, but it was magic! I felt like a wizard. Hillbilly witchcraft in action.
Then, I discovered the MOTHER EARTH NEWS wood gasifier plans from the 1970s used during the gas crisis. I grabbed my torch and a water heater and went to work! A major improvement, indeed. I was making steady gas now and my mind raced with the possibilities.
For a time, I built a new machine every week just to test new ideas and check the assumptions of others. There was a lot of good information online blended in with a lot of armchair theory. I'm not going to lie, it was frustrating at times.
But the frustration paid off during the catastrophic winter of 2008. The freeway flooded, then froze, water pipes too. Power was down for a long time. There was no gas in my town of 900 people. Luckily my kids had gone south with their mom. It was just me and my dog and our frozen farm as a laboratory to test wood gas in action. I needed power and all I had for fuel was wood. It was a perfect match.
I used a wood gasifier made from propane tanks to fuel an old Lincoln welder generator. This gave me both electricity and welding ability to keep working. The old welder generator was very forgiving and worked beautifully. I was able to get the lights back on and defrost pipes so I could flush the toilet and take a shower. It wasn't the fanciest setup, but it worked. It made me a believer.
Building a Wood Gasifier
Wood gasifiers can be built from mostly local parts like propane tanks and scrap steel. Expect to spend $1,500 and up for a low-budget DIY build. If you can afford stainless, then please use it in the high temperature areas to extend their life. A 180-amp mig welder or larger is desirable for the welding, but a stick welder can work if you use propane tanks.
Many people use oil drums, but I avoid them because they are very thin and prone to rust through or burn through. Why do the same job twice? I outline a complete step-by-step build in my book so you can see the entire process from start to finish.
1. Instead of having a weld shop build your gasifier, look for a blacksmith or metal artist. They have more passion and cost half as much.
2. If you use a fab shop, tell them you are an OEM (original equipment manufacturer) to get their best rates. Let them know this is a prototype.
You do need to modify the intake of your engine to accept wood gas and still run on its standard fuel, too. Here is a video I put together that explains the process better:
Challenges and Dangers
No fuel source is perfect and wood gas is no different. Here are the nitty gritty facts:
• Wood gas is best for spark-ignited engines; diesel engines need 20 percent diesel fuel to auto ignite.
• Wood gas has about half the power of gasoline, but this is overcome by using larger engines, which don't cost much more.
• It does take a little effort to gather and chunk wood. Small chips don't work well. Forget about using grass. Pellets can be problematic.
• There are hot surfaces on a wood gasifier. You wouldn't grab a wood stove would you?
• There is carbon monoxide in the gas, so use it in a well ventilated area. Don't use indoors. • Expect to run for several hours, but not 24/7.
• If you don't get your setup correct, you can make tar and stick an engine valve. (This usually only happens to newbies.)
• There is a small amount of soot in the gas even after filtering. Keep the gas above the dew point and it will flow into your combustion chamber nice and dry and get burned up with the rest. You may notice a darkening of your oil, but it's not a problem. Feel the oil between your fingers to validate it still has lubricity.
The Benefits of Wood Gasification
A wood gasifier is a marvel, because it puts refining capability on your own property and the cost of the fuel once you are set up is just the time it takes to pick up sticks and chunk them down. It has these benefits and more:
• Make your own fuel day or night.
• Keep your energy supply chain on your own property.
• Proven at scale during war time.
• High power capability compared to other renewables. 5-20 kilowatts stationary power is easily achieved.
• Portable, so you can take it with you in case of an emergency.
• Utilize cheap land with wood and avoid expensive power lines.
• Use the activated carbon (charcoal) for water filtration.
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