I have a lot of twigs and branches and can get even more from the neighbours, it is a HUGE pile. I thought of producing biochar instead of cutting it up for the compost pile, because it is exhausting with secateurs.
I saw two designs on the net one is this Jolly Roger oven and the other one is either and earth pit or o metal cone.
Does the production of biochar produce smoke? (We have a terrible neighbour close by which tried to bring another neighbour in trouble).
Which of the designs is better suited to produce quality biochar?
Which of the designs is better suited to go through bigger piles?
Is it OK to use more or less green wood? Everything bigger will be cut up in firewood, I will use only thin sticks and twigs sometimes with leaves on them.

The lowest tech way to do it would be to make sure the material was all good and dry. You might consider restacking the pile. You'll want the pile to be as tall and peaked as possible and at least 5-6' tall but bigger is better within reason.

You'll light the pile on fire and let it burn down to just charcoal and then quench the char with water and a rake. Light the fire at the very top of the pile and let it burn down towards the ground.

The heat will radiate downwards gasifying and igniting the wood below, but the smoke created has to pass through the flames fully combusting the gases and making an almost smoke free burn.

Avoid wood much larger than 4-5", or be ready to pull out the unburned stuff and add to your next pile.

You'll know to quench the burn when the flame turns from yellow to blue and you start to get a layer of white ash forming on the char.

The Kon Tiki cone kiln is also great tech, just do a google search.

Matt Banchero wrote:
You'll light the pile on fire and let it burn down to just charcoal and then quench the char with water and a rake. Light the fire at the very top of the pile and let it burn down towards the ground.

The heat will radiate downwards gasifying and igniting the wood below, but the smoke created has to pass through the flames fully combusting the gases and making an almost smoke free burn.

I'll second/emphasize this bit. If everyone did it the issues with smokey bonfire would be basically gone. Light at the top and all the smoke gets burned up, as the combustion gases rise through the hottest bit of the fire and burn. Light at the bottom and the gases rise up and away from the heat without igniting.

I either do a kon - tiki or oa jolly roger - what is better?
I don't just pile it up or i'll get in trouble with the local fire service it needs to be somehow contained.
The jolly roger I could do that out of barrels myself but the con tiki I would have to ask someone and it would be expensive and I would have to wait for ages.

The earthpit technique is basically a Kon Tiki in the ground. Do not confuse an earth pit biochar burn with old world covered and smouldering techniques to produce cooking fuel. It's a whole other technique. Observe your burn days...don't put beans in your ears ect.

So which one is better of the two?
The jolly roger do you need to cut your stuff smaller? For the fire service it is more acceptable perhaps. Which are your experiences with these ovens?

I am the guy who (accidentally) developed the Jolly Roger TLUD biochar oven. During that era I had huge piles of wood chips on my two acres that had been dumped by busy contractors. I would spread the chips evenly to dry in the Florida sun and then burn them in those 55 gallon contraptions. The Jolly Roger oven prefers wood chips or any small chunk feedstock that is approximately uniform in density when loaded. This "balanced loading" is critical because the primary air is drawn through that column of fuel before combusting. You don't want to unevenly burn a fast ditch through part of it while the rest is left to smolder (due to a diverted chimney effect). This is its main weakness.

Brush, branches and windfall fuel is better suited to the simpler (and more elegant) cone kilns-- the Kontiki being a higher tech version. Your feedstock seems to be in this latter category, which requires less effort at every stage. Watch a few online videos so you can practice with a small pit, cone, wok or Kontiki model before committing larger piles of branches to your top lit fire. Kelpie Wilson's Greenyourhead blog is a friendly base camp.

For gardening purposes, the biochar from a Top Lit Up Draft device (stack of steel barrels) verses a Top Lit Open Draft device (cone, or pit geometry) is indistinguishable. Notice that "Top Lit" is the key common element. And that is what burns the smoke so efficiently.