I have wondered if there is also a water purification effect with ground water but never saw anyone mention it before.
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I’ve read somewhere that there could be issues with polycyclic hydrocarbons in char, depending on how it is produced.
But otherwise I would figure it helps to improve water quality by direct filtration, and perhaps more importantly by increasing biological activity in the soil, helping to break down certain kinds of toxic chemicals.
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That would depend on the gasification process. If it was geared to high thoughput pyrolysis, the char remains mostly intact.
I agree that cereal straw shouldn’t be much of a disease issue, but growing the same crop years in a row is asking for soil pest issues. Depending on the crop there could be too much straw to work in anyways, or in the case of flax, it just doesn’t break down in a timely fashion, so has to be burnt or baled.
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I think I would agree that Tom is onto something with the importance of keeping some of the crop residues to be worked back into the soil. From what I have read about soil building and no-till methods of farming, at least a portion the residues should probably be allowed to stay. A book I read talked about 3 forms of soil organic matter - The living, the dead, and the very dead. Basically, soil organisms, food for soil organisms (crop residue), and the wastes from soil organisms (humus). It seems to me that by burning EVERYTHING down to char, you are going to wind up with a lot of the very dead (i.e. charcoal which cannot be further broken down, and is hence very stable). Probably there is a balance to be found, where you leave enough food for the microbes, but does that leave enough fuel to run all the other processes? I dont know, I sort of hope some researcher looks into it.
I feel like I remember hearing about forestry operations in the scandinavian countries that were literally vacuuming the forest floor and using all the biomass for district heating - but they found that it was depleting the forest soils. I dont remember where I heard it - maybe one of our northern members knows something about it?
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Carl, that’s true. Not only limbs and stuff were taken care of. Even stumps and roots were dug out of the ground and chewed down to chips.
That was back in the 60s-70s. Since then we learned roots and limbs contain the most “fertilizer” and let them stay put.
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I hear what you are saying, and it’s an interesting concept, the 3 categories of soil organic matter.
In practice I don’t think it would be possible to convert all the organic matter into char, the root mass is going to be left in the soil. Certain crops (like flax, or hemp), the straw has to be gotten rid of anyways.
Also, there is a practical limit to how much char can be added to soil before negative effects (but it’s a significant tonnage per acre). Even then char could be spread on forest land. We could actually reduce CO2 to pre-industrial levels this way.
To me it looks like the best solution for our energy needs. I still doubt we could replicate the energy use of the fossil fuels age, but with adjustments we could live within our means long term.
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Maybe this is wood compost?
Rindert
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No, they take away all the tops and twigs, drive it out to the road, put over paper so it should dry and drive it to heat plants.
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In the mean time, it make a good road bariar in case you slide off the road.
TomC
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I do not remember the detail of a text that I read a long time ago but it had to do with the importance of compost in the soil. He explained the farm field like an engine that needed to burn so many BTU’s per acre. So the soil needs X amount of plant material in it in order to produce Y amount of crops per year. The soil needs to burn compost. That was how the planet survived in the old days. That is not to down play charcoal added to the soil. Compost is needed and charcoal is quite helpful. Possibly it could reduce the amount of compost needed.
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If a carbon negative combine harvester were built I see the benefits as this. No diesel being consumed by harvester thus not putting that co2 into atmosphere and avoiding all the carbon intensive processes to produce that diesel fossil fuel. By utilizing ag waste as fuel that part of waste that is not allowed to decompose prevents decomposition gasses like methane and co2 from being put back into atmosphere. The biochar that would be produced would be a good soil amendment and would sequester carbon in soil making this harvester truly carbon negative. Lastly the increased carbon in soil could reduce the need for fertilizer which is also carbon intensive to produce and damages the environment and waterways.
I would be thrilled if someone smarter than me could quantify this somehow. Put numbers on these benefits to assess cost benefit sort of thing. Like average acre harvested in this manner could offset the carbon footprint of two households. Or the carbon offset by harvesting 100 acres in this manner would only offset the carbon footprint of two households.
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I read resently that 15% if the waste biomass is still gathered for fuel. Rest is left to decompose. (In avarage). I guess some soils could take more, some less.
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Those would be good numbers to have. The main barrier that I can see is equipment manufacturers will want no part of the added complexity, at least until it became an absolute necessity due to fuel shortage.
So that leaves it to an enthusiastic farmer, or some NGO or university.
But the actual works of a straw gasifier for stationary applications is just what the skill set of this group could be applied to.
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It has a lot of problems. I worked on this some. Very fragile charcoal bed and we all know what that spells. Maybe pelletized. For me it made more sense to use switch grass, or what ever, to fuel the soil and use wood to fuel my crankshaft. Nature speaks in a soft voice - sometime!
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That would take more hard work than smarts, I think.
Rindert
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Somewhere in my files I have a patent or other documentation of a straw gasification system. It is do-able, just takes a different mindset and approach.
The first article makes an interesting reference to production of char. It seems moving grate systems will work. I have an idea for straight heat production metering in chopped straw into a swirl burner, the carbonized embers flying out for collection in a low oxygen environment, or an auger fed downdraft system, no restriction, just straight flow through, the idea being to not reach slag forming temps and collect the char.
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There are several problems which come from the heavy dependence on chemical fertilizers to boost fertility which is probably what you are getting at.
Soil is a living mass even though we don’t think of it that way. I want to say something like 80% or more of all living biomass is in soil microbial life. This depends on the organic matter in the soil. It also is necessary for water retention. Chemical fertilizers tend to be too concentrated and toxic to the soil microbial environment. But what is often over looked or not understood is how plants depend on microbes in the soil to collect nutrients for them and transmit the to the roots.
The concern I would have with gasification and harvesting would be around fire risk. Field work tends to involve dead plant material in high volume and dusty areas. I wonder how much or that cloud of dust around a combine would be willing to become a fireball given a spark. A farmer near me managed to burn up an old diesel tractor this summer. Fortunately the operator was able to get out. But diesel fuel really isn’t that flammable so I was surprised but it did being back the risk of fire in field work to me.
I am still in the lack of funding planing stage by my goal is an electric tractor with solar and wood gas power generator as a backup. To me using wood for heating and running a motor in a safe environment make since but I wonder about safety in a field for the most part farming involves dangerous equipment which is already complex and had enough to keep running. The trouble with harvesting equipment is that unless it is factory farming you have a narrow window of the year where it has to work or you loss the crop. In agro business they tend to contract out harvesting to companies which just burn through equipment as a cost of doing business.
All of that said managing organic matter in soil can be complex. Typically you want to compose outside the field because the microbes which can break down the plant waste tend to be damaging to the same crop next year. That is one benefit of raising livestock the waste is good fertilizer which doesn’t harm the crops. It is also one reason why carbonizing thicker stocks could be good for field management.
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Agreed regarding attention to soil health. The fire risk I feel is a bit overstated, there’s always a risk of sparks / ignition around machinery, bearings can get hot, friction can set stuff off. And a straw unit shouldn’t be of a design stoked in a field, it would have to be contained and picking up part of the straw waste stream for pyrolysis.
But I do agree it’s a level of complexity no manufacturer will R&D willingly. Stationary could have some use, particularly for heating, straw is quite cheap and local in many places.
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I built a vortex combustion chamber for chopped switch grass. A blower was used to introduce the straw into the burner. The nice thing about it was that you could produce straw charcoal plus flame heat with this system. The glowing char that settled to the bottom helped to keep the flame lite. The blower was feed by hand. There is a simple feeding mechanism with an inclined slowly rotating disk that was panned for the feeding scheme. An individual referred to the the vortex burner as a “thesis generator” because it attracted a number of college students to wright them however, because of the challenges, the concept soon dies off.
I also made some methane from composted wood chips. For me woodgas blows it away because of the obvious reasons.
There is a modern term called “appropriate technologies” or something like that. Only when a person has lived some of these schemes can one understand that term!
All of our biomass’ are important and have a best place of use. In other words; would you use a sledge hammer or your head to knock a hole in a cement block wall? That is the question that faces us today…
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