Continuing the "brainstorm" that my tangential comment earlier exposed, "small scale" biochar exists on a continuum: from commercial kilns; down to either a. high-tech backyard burn-barrel retort designs (rusty barrels) or b. forest-slash burning fire-pits extinguished with wither water or covered with a plate-steel lid; further down to backyard recreational fire-pits (portable or laid-brick) doused with water; further down to fireplace-canister biochar micro-kilns; down to (really?) dutch-oven style kilns. Every person faces unique situtations and scenarios.
And, regarding the "purpose" for the output, ultimate soil-amending applications are relatively homogenous EXCEPT for timing: how soon will the charged and nutrified biochar be added to edible gardens. Some people recommend a few weeks of "charging", yet others suggest that on-site or in-situ charging will happen anyway, so don't worry.
But, my marine-toilet composting problem has always been "timing". I was faced with finding a suitable compost pile in which to dump my pre-composted human waste. Observers asking, "Watcha doin'?" were always triggered by the answer--which meant 'sneaking around"... But, by taking the peat-moss and compost mixed composting-toilet output as feed for micro-biochar production, I can answer probing questions by saying, "This is biochar from my yacht's woodstove." And then just dump it in forests or trash or landscaping without qualms.
However, "charging" or nutrifying the biochar with urine is still needing further investigation. I just read that using urine as the moisture and mineralizing step with plant-based compost for the biome can be a, uh, sweet package-deal. I'll let you know if it works. What I do is use grass and other vegetable compost piles to create non-manure compost. This I use to mix in the marine composting toilet with human waste. (This actually deoderizes almost instantly and yields "earthy" compost in days.) Then I'll pyrolyze that mixture in fireplace sized cannister kilns and mix it again with more plant-based compost. Then I'll use that in the urinal holding tank/bucket to absorb and break-down the urea to prevent ammonia production (hopefully). Then the automatically charged and nutrified compost/biochar mix can be distributed to gardens or forests without even being recognizable as composting-toilet output. And all this on a weekly basis (meaning total quantity is less than a 5 gallon bucket).
Now, the secret I haven't mentioned is that this is actually a model for disaster relief shelters that help villagers stay on their property, safe and healthy as they plant permaculture gardens to augment their bags of rice food supply.