Sustainability Hacks: Auto-feeding Wood-fired Generator

Here’s a project that’s hard to categorize. It generates electricity by burning wood. The diamond-plate wrapped column to the right is a magazine that stores the wood, which is gravity fed as pieces below are consumed. The heat is used to drive a power turbine which is responsible for generating the electricity.

This begs the question, is this a sustainability hack? From one perspective it’s burning renewable biomass. Right now that’s wood, but it could be compressed blocks of grasses or wood manufacturing byproducts. So in this sense it is sustainable. Unfortunately it still doesn’t solve the problem of carbon emissions.

The build log for the project is both image and video heavy. You can see the initial prototypes which are not self-feeding, but burn so hot that there’s a nice pink glow to the entire assembly. But by the time they get to the final prototype it’s running much more efficiently, and can put out a peak of over 100 amps!

[Thanks DerAxman]

48 thoughts on “Sustainability Hacks: Auto-feeding Wood-fired Generator

  1. You forget that wood and other biomass is CAPTURE CO2. So, if you re-release it, you are still more or less carbon neutral. The alternative is rotting wood releasing CO2 and possibly methane (worse) without the electricity.

    1. Craig Christ is right. Biomass is part of the carbon cycle. CO2 only becomes an issue when fossil fuels are dug up and burned, putting CO2 in the air that had been locked away for tens or hundreds of millions of years.

      It’s that CO2, NEWLY INTRODUCED TO THE ECOSYSTEM, that might be contributing to global warming.

    2. Rotting wood wouldn’t necessarily release the stored carbon.

      Carbon neutral would imply that it doesn’t release carbon back into the atmosphere at all. Wood burning releases carbon that may be part of the carbon cycle, but releases carbon none-the-less.

      1. Carbon neutral means that carbon emissions are offset by carbon absorptions elsewhere. A tree took in carbon, then released it while burning. That’s carbon neutral (but not “zero carbon emissions”).

        Digging up fossil fuels and burning them is not carbon neutral. (OK, technically, over a span of hundreds of millions of years, it is neutral, since fossil fuels started out as biomass. But global warming is concerned with the last few thousand years only.)

      2. @Bob

        A tree took in carbon, and would have kept it locked away for 100-200 years if you didn’t burn it.

        Then after it’s dead, some of that carbon would get buried, and spend the next 200 million years out of the atmosphere, if you didn’t burn it.

        If you truly wanted to be carbon neutral, that is, not increase or decrease the atmospheric carbon over the natural state, you would only gasify the tree partially and bury the resulting charcoal.

      3. Rotting wood absolutely releases CO2. There are areas in forests where the CO2 from decaying trees is so bad that you can suffocate. Decay comes from direct oxidation from exposure to the atmosphere; bacteria eating the cellulose and other materials; and insects eating the dead tree. Direct oxidation, fairly obviously, releases CO2. Bacteria also release CO2, and often their byproducts are more easily oxidized by atmospheric oxygen, which also produces CO2. Insects are just like mammals when it comes to breathing, and to top it off can release significant amounts of methane, which is an even nastier greenhouse gas.

        Want to avoid having any impact on the environment? I’d suggest dying, except decaying bodies release significant amounts of both CO2 and methane. Oh well.

    3. Cutting the carbon cycle short by burning biomass means that you’re still increasing the CO2 in the atmosphere because you’re stopping natural carbon sequesterization.

      How do you think the coal, oil and gas deposits were formed?

      1. “How do you think the coal, oil and gas deposits were formed?”

        By the remains of dead carbon containing life forms being subjected to TREMENDOUS pressure over VERY long period of time. Burning biomass IS a carbon cycle. Burning biomass is a carbon cycle humans can actually observe, unlike a carbon cycle that took multiple geological time periods to create the coal, methane, and petroleum humans now consume. Burning either biomass or “fossil” fuel produces CO2. Only the biomass cycle has sustainability built into it, any other cycle is irrelevant for man, because the world as we know it will be destroyed to create another layer of fossil fuels.

    4. It is not entirely true. It depends on the wood. If you talk about rapid growth trees like eucalyptus that recapture CO2 quickly, its ok. But slow growing trees it can take decades to recapture carbon. Besides most of the tree is cellulose it degrades on CO2, methane (that is worst than CO2 for greenhouse effect) is only produced in anaerobic conditions, normally, only the roots degrade producing some methane. And not to forget, if you burn you procuce carbon in minutes, if tree is biodegraded it takes much more time realeasing C02 about the same velocity a growing tree would capture it back.

    1. Spot on! The carbon in fossil fuels has been sequestered over a very long period of time and the environment we are adapted to live in today exists in part because it is trapped underground.

      It’s absolutely fine to burn wood to release energy so long as the wood gets replaced with new plants which soak up the CO2 again. I read somewhere that new growth gobbles up carbon out of the air at a much higher rate then mature trees do too. So then it’s merely a question of maintaining enough acreage of timber to keep this thing fired up.

      Coppicing is a relatively low effort way of harvesting a good tonnage of wood without all the complexities of growing from seed.

      1. “It’s absolutely fine to burn wood to release energy so long as the wood gets replaced with new plants which soak up the CO2 again”

        Problem is, the new plants are often species selected for their rapid growth and wood qualities at the expense of their need in water and impact on their biotope, among other stuff.

        Concerning the machine now, though very cewl I have trouble seeing how it’s different from the existing gasifiers (from a sustainability standpoint)…

    2. And with an output peaking at 100 Amps, it’ll work well with a zombie killing railgun. “Man the harpoons!!!” lol

      Adding a MHD generator to this could increase it’s overall output and some what offset the carbon emissions. More power for the same amount of carbon output.

  2. A power turbine? Typically you would name a turbine based on what pushes it. (wind turbine, steam turbine, exhaust gas turbine, etc). My car has a gasoline engine, not a power engine :) What motivates this particular turbine?

  3. I’m having trouble understanding how this machine works. Even after visiting the site and seeing the videos, it’s unclear to me how they are converting heat into pressure to run a turbine. Writeup fail.

    1. It looks like they are cooking the wood to release combustible gasses – carbon monoxide and hydrogen maybe – which get compressed and burnt like in a regular jet engine before the turbine. I guess the waste heat is used to cook the next bit of wood, closed cycle.

    2. It looks like a downdraft gasifier.

      You fill the hopper with wood, light it at the bottom, then pull air down through the column. You limit the incoming air so there isn’t enough oxygen to completly burn all the wood, and by the time the incoming air reaches the hottest part of the combustion zone, you only have enough O2 left to create carbon monoxide.

      Carbon monoxide burns pretty well in its own right, but you can also react it with steam.. CO + H2O => CO2 + H2. With the right catalysts, you can also get conversion to methane, methanol, ethanol, etc.

      In this case, it looks like they’re feeding the carbon monoxide straight into a turbine for final combustion, and using the turbine to run a generator.

      The new/interesting part seems to be the machine’s self-regulating control system, because woodgas generation has been around for at least a century. Google ‘syngas’, ‘producer gas’, or ‘gasifier’ for more info.

      1. It looks to me like the whole hopper is a combustion chamber, I say this because It Looks like the bottom, outlet of the hopper is connected directly to the turbine, the compressor outlets to to positions on the hopper! that is mental

  4. Stupid question here.

    Would it be possible to push the exaust through a green house to absorb the final exaust products? Maybe pack it with plant matter that has a high CO2 intake O2 output ratio. In turn dead plant matter is burned when possible.

    1. It’s actually pretty simple: Exactly as much plant matter that you draw through it.

      Think of it this way: A tree has so much carbon in it. That carbon is transformed by this machine into CO2. So a new tree will absorb that CO2 fully when it has the same carbon mass as the original tree.

      The only carbon input into this machine is the biomass input.

  5. Polymath

    Don’t know the math but it would probably take a preety big greenhouse. There has been some work done on bubbling exhaust CO2 through water to feed algae. The algae then make oil which can be pressed out and converted to biodiesel and burned in diesel engines but the carbon still ends up in the atmosphere. Or the algae could be dried and buried to sequester the carbon.

    1. I wonder if someone submitted a post about a rube goldburgian style apparatus that pulped up old newspapers and turned them into super dry logs ready to be burned in one of these generators that they might post it?

    1. I wondered that too….looked around on the site and found an earlier version got 80A at 12VDC…that’s a far cry from 100A `120VAC. Also, what did they use to load it down to determine the amperage?

  6. Honest question about co2 I’ve been trying to ask for years but haven’t been able to get a good answer: Since there is more of it in the atmosphere, why aren’t plants just growing faster to balance it out? In commercial greenhouses people raise the co2 levels to make e.g. tomatoes grow faster… why isn’t vegetation simply growing faster to balance out the addition of co2 into the atmosphere from fossil fuels?

    1. Plant quality also can (not always will) suffer if you pump up one factor without the others. Huge retail tomatoes are actually pretty flavorless because the amount of nutrients they can put in any individual fruit is limited in comparison to the carbon mass being packed away.

  7. Wood is carbon neutral as long as you’re planting trees to replace the ones you burn. Coal is not carbon neutral because no new coal is being formed; coal is a relic of an era before microorganisms learned to digest cellulose.

  8. Nothing is “carbon neutral” except nuclear.

    Luckily global warming/AGW is a scam, so there’s no need to worry.

    This generator would be nice in a remote wooded location, like a sawmill/lumber camp where there’s plenty of sawdust/bark/branches around to burn. Nice build.

  9. Maybe a silly question, but who actually wants to encourage people to burn a lot more wood? In my neck of the woods, there are actually wood burning restrictions, to limit the amount of smog in the air.

  10. Burning wood from a dry forest is about %75 carbon nutreal. From a swampy forest it may be less carbon neutral because mud covered wood is more likey to not rot and be sequestered.
    Mark B

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