In Yet More Slime I complained that the idea of biochar had merit but that it had been coopted and repurposed by various rent seekers as a way to advance their only tenuously connected agendas, and that opposition to biochar had increased because of it. More specifically:

When land is converted to organic farming the soil carbon increases for at least twenty years. If charcoal is incorporated the amount of carbon in the soil increases even more. Industrial farming on the other hand reduces the land’s ability to retain carbon. . .

Globally, there are 800GtC (gigatonnes of carbon) in the atmosphere. Every year plants capture 58GtC and transfer most of it to the soil. In due course 58GtC is released back to the atmosphere. This is the carbon cycle: every 14 years the entire weight of atmospheric carbon passes through the soil. The longer this carbon remains in the soil the less of it will be present as carbon dioxide in the atmosphere at any given time.

Plants, even their leaves, can be charred before they release their carbon. If this charcoal is incorporated into the soil it will lock carbon away almost permanently in the way that forest fires have locked charcoal into the soil. . .

There are two sources of greenhouse gas emissions. Those from fossil fuels - coal, gas and oil - should be controlled at source where the fuels are dug out of the ground. Land-based emissions need a separate regulation. The best one I have found is called the Carbon Maintenance Fee.

Under the Carbon Maintenance Fee proposals, countries would be paid an annual fee for the carbon contained within their borders. . .

Other proposals are based on regulations that would be difficult to enforce, e.g. 'you must reduce emissions by x percent!' The fee approach, however, would work by incentive. If a country’s carbon pool increases, its fee would also increase but, in addition, it would receive a substantial bonus. The reverse would apply to countries whose carbon pool reduces. Countries would therefore have an incentive to encourage organic farming, to bury charcoal and to retain their forests. The fee would need to be substantial so could be drawn from the proposed Tobin tax on currency trading.

This is a tired old redistributive scheme that exploits and misuses agronomic concepts.

Increase in soil organic matter has nothing to do with organic farming. Organic farming is merely a marketing claim based on a production method and does not increase the amount of organic matter in soils. It redistributes organic matter, impoverishing one place to enrich another. It's an accounting trick, cooking the books in order to show a profit in one spot by disregarding losses in another. It's even easier for large scale "industrial farms" to do this than for small scale hobby farms since it involves handling massive amounts of materials, and no one is better able to do this than the very largest heavy metal industrial growers. And so, to get a market premium for their produce some large scale industrial growers have done just that and now supply major retailers with "organic" foods.

To truly increase organic matter in soils it is necessary to produce it on site, not haul it in from somewhere else. The Keeling concept of fairly rapid recycling of atmospheric carbon does indicate an intervention opportunity to shift the balance of carbon from the atmosphere to the soil, but only if done by increasing growth on site and retaining a larger portion of the result.

The idea of a Carbon Maintenance Fee is the same sort of shell game. It merely shifts carbon around rather than increasing total sequestration, but that's the real objective since carbon is now seen as currency. The one and only objective is to redistribute wealth and any excuse will be used to justify the larceny. It's a shame that biochar has been harnessed to haul around this tired old idea since it is a loser. It depends on crooked accounting to show a benefit but if full "green" accounting is done the losses are shown. The fact that it is a loser guarantees that it will eventually be exposed since you eventually run out of other people's money to redistribute no matter how crooked and extensive the bureaucracy. It's a bureaucratic bubble that will eventually burst, leaving the earth further impoverished and the atmosphere further "enriched".

To increase soil organic matter in already exhausted soils, which includes most soils that have been in agronomic production for a while, you need to face reality. It's a slow process that requires a "bootstrap". To get it started you need manufactured fertilizer and a system to retain the increased production it brings. Slowly, over time, soil organic matter will build up. Using some of that production to make biochar retards that process at first since it repurposes some of the organic matter, depriving soil microorganisms of groceries. They can't eat charcoal, that's the whole idea. Over time the charcoal can have beneficial effects that make a better environment for microorganisms so they will make up for earlier losses so long as they have a continuing and increased supply of new organic matter to eat.

The reason to do this isn't that some bureaucrat with only the most cursory knowledge of agronomic systems bribes you to do it, it is to increase the value of your primary asset - your land - and increase your production of food and fiber. The reason to do it is that it is a superior agronomic system with increasing returns over time. The more growers that do this the more productive the whole system. The secondary effect that the atmosphere is being mined of its carbon is largely irrelevant so long as there is plenty. If done assiduously for long enough the atmosphere would be depleted of carbon and some bureaucratic wanker would want to start charging growers for the atmospheric carbon that they take for free, but not soon.