Biochar from wood chips

I've decided to try something new.  At least, new to me.  I generally use waste lumber from a truss company and waste from construction sites to make biochar.  It uses a waste product, so I like that.  I still have to cut the wood into smaller pieces generally to fit into my retort.  I've decided to try using wood chips to make me biochar.  The advantages I see are:

1) More wood fits into the retort if I use wood chips, because air spaces are minimized
2) I won't have to break up the charcoal when it's done.  The wood chips are an ideal size already.  My chipper makes chips about 1/4" in size.  
3) I can chip the same lumber waste I already use, or use dead trees from my land without nearly as much work with a saw.
4) Chipped wood dries much more quickly than bigger pieces, so if I use trees, they can be dry and ready much sooner than split wood or the like would be.
5) Chipped wood turns to charcoal more readily than bigger pieces, so I use less wood in the large barrel to carbonize the chips than I would for larger pieces of wood, so less wood is wasted.
6) The smaller pieces of charcoal takes up less storage room if I don't need them or have the chance to inoculate them right away.

Anyone have any thoughts?  I'm pretty sure someone will say to use a pit or trench or some other method, but the retort has a number of advantages for me in my situation, so I will be using it for the time being.

I would use a pit Trace.....hahaha, couldn't help myself (sorry).  I completely understand how pits are not ok in certain locations.

Just curious, how do you dry your woodchips?   That and time/energy to chip would be my only other considerations.

I just spread them out in the sun on a tarp.  They dry surprisingly quickly.  If you spread them pretty thinly and turn them a time or two, they will dry in a day, assuming you started with fairly dry wood.

A pit would actually work fine for me except that I haven't gotten very good at using one yet, so I get a much better product using a retort, and with my retort, I can pretty much start it and walk away and when I come back the next day, I have charcoal.  No muss, no fuss, no tending after the initial 20-30 minutes of loading it and getting it burning good.

It seems like a lot of time, effort and gas to make chips for char. Perhaps chainsawing logs into short chunks would be a workaround?

Now if you could take someone else's already chipped "waste" wood to make char, that would be a different story.

Douglas Alpenstock wrote:It seems like a lot of time, effort and gas to make chips for char. Perhaps chainsawing logs into short chunks would be a workaround?

Now if you could take someone else's already chipped "waste" wood to make char, that would be a different story.

My PTO chipper easily chips 8" logs if I ever wanted to chip anything that big.  It will chip the 2x4 and 4x4 scraps I normally get in far less time than I can cut logs into short lengths and split them.  For that matter, I can chip an 8" log far, far faster than I can cut it into stove length and split it.  I've never compared the amount of diesel I use in the tractor for an hour of PTO time VS an hour of chainsaw use.  If I compare time and effort to make enough chips to fill the retort, to the time and effort of cutting pieces with my chainsaw and splitting, would be a huge win for the chipper, and I'm pretty sure it would win in the fuel department too.  The exception to that is the times when I get lumber cut offs that are small enough to go directly into the retort.  Those take some time and effort to drive to, pick up and load, but I would say they are the most cost and time effective by far.  Most often the stuff I get from the lumber company is broken 2x4s and 2x2s of various lengths from 2' to 8'.  The 8' long ones are boards that have split.  All of those have to be cut down to length of course.  If I ever get good at it,  the trench method would be the most efficient use of those.

Ah, I see, a big chipper. It's worth a try; and wood chips always have a use somewhere.

Pardon me, but I can't recall what kind of retort you're using. It sounds like a TLUD. Will it get enough draft with the chip sizes you can make?

Douglas Alpenstock wrote:Ah, I see, a big chipper. It's worth a try; and wood chips always have a use somewhere.

Pardon me, but I can't recall what kind of retort you're using. It sounds like a TLUD. Will it get enough draft with the chip sizes you can make?

Yeah, I'll never have a problem of too many chips  I use all the fresh trees that I coppice or pollard for chips for the gardens, but the chips from dead trees I use on paths, or in compost more often.

I don't really know what you call the retort-style I use.  It's a barrel of about 35 gals inside a 55 gal barrel.  I fill the inside barrel with the soon-to-be-charcoal material and burn the wood in the outer barrel.  I've used planer shavings and the like packed into the inner barrel really tightly and the results were good, but that material is so small the wind can carry it off easily, so it really only works well if I mix it into compost immediately.

I could never keep my TLUD (nested barrel, top load, updraft) retort lit.  Not sure what I was doing wrong, but I gave up after maybe a dozen tries.  My next attempt will be a tilted burn barrel (see: https://www.youtube.com/watch?v=bNOiVCpRWXw ).  I will see if that works.  Hopefully I still have an unmodified barrel around...

As you may have seen, Trace Oswald has been very successful with this model.
John S
PDX OR