carbon farming = sun harvesting?

Am I correct to think that the best carbon farming practice would be essentially a farm that is the most efficient at harvesting sunlight (and water...) The larger the canopy, the more carbon is being sequestered. 1 acre of annual crops would have a 1 acre flat canopy, but 1 acre filled with trees and shrubs and annuals (with a very 3 dimensional canopy) would have a canopy that, if flattened out, would be much larger than the 1 acre it is in, hence capturing more sunlight per acre, sequestering more carbon?

I think that's the basic idea - plants use photosynthesis to take carbon dioxide from the air and turn it into biomass.

https://eo.ucar.edu/kids/green/cycles6.htm

I love the idea of being as serious about capturing sunlight as capturing water. Any light that hits the ground is wasted energy, and if it hits bare ground, it irradiates your soil biology and kills the life therein. Even sunlight beating on organic mulch dries things out.

When I walk around my food forest, I'm constantly looking for places to tuck a plant in, anticipating what will come out, and what will be able to fill the vacuum. Annuals are great for this, particularly when trees loose their leaves. In Southern California, I can plant greens and other cool weather crops all over under my fruit trees in the late fall, knowing that they'll get 4 months of sunlight. Right now, I'm slowly taking those crops out (as well as my winter cover crop) and filling the gaps with summer veggies.

In my region, most things grow better with some shade, so I think I can stack a lot of layers in, to capture the maximum sunlight.

One other thought: carbon farming is also about getting as many living roots growing across your land, and pumping as much carbon down into the soil throughout the year. 60% of a plant's energy is directed below the surface, so carbon farming is all about transferring that sunlight energy (via photosynthesis) down into the soil (via root exudates). The next time you walk out into the sunlight, imagine the pipeline of sugars running down from the leaves, through the stems of your plants, straight into the soil where a mob of hungry microorganisms are waiting to be fed.

Like an IV for bacteria and fungi.

I also love the idea of keeping the carbon as long as possible. So instead of letting you carbon plant trunk get eaten every year you keep it locked up in big perennial tree trunk.
Also prefer if the carbon get eaten by slow moving, long lived, deep dwelling fungi vs quick cycling surface dwelling microbes. And if we could store some of the carbon as biochar, locked up onsite even if it doesn't help the food forest produce any better, actually even if it hurts it a bit it is still better to store it on site.

S Bengi wrote:I also love the idea of keeping the carbon as long as possible. So instead of letting you carbon plant trunk get eaten every year you keep it locked up in big perennial tree trunk.
Also prefer if the carbon get eaten by slow moving, long lived, deep dwelling fungi vs quick cycling surface dwelling microbes. And if we could store some of the carbon as biochar, locked up onsite even if it doesn't help the food forest produce any better, actually even if it hurts it a bit it is still better to store it on site.

what makes you think biochar wouldnt help a food forest?

Miguel Laroche wrote:Am I correct to think that the best carbon farming practice would be essentially a farm that is the most efficient at harvesting sunlight (and water...) The larger the canopy, the more carbon is being sequestered. 1 acre of annual crops would have a 1 acre flat canopy, but 1 acre filled with trees and shrubs and annuals (with a very 3 dimensional canopy) would have a canopy that, if flattened out, would be much larger than the 1 acre it is in, hence capturing more sunlight per acre, sequestering more carbon?

Yes you are correct , harvesting sunlight is the most important part, but it is not quite so simple as your conclusion afterwards. Capturing carbon is the first step, but capturing carbon is not the same as sequestering carbon. It depends on how long you hold it. Different biomes hold onto that carbon for differing lengths of time and at different %'s. It's a very complex subject that generally takes years of study to even partly understand.

As a general rule of thumb, while shrubs and annuals do also capture sunlight, they seldom sequester the carbon they capture for long. You would be looking for systems that capture and sequester the carbon at least medium to long term. That would be in woody material and deep in the soil mostly. The best at sequestering in woody material is trees, and the best for sequestering deep in the soil, perennial grasses. So any permaculture system of carbon farming that concentrates on those two guilds would be a bit better at carbon farming than one that relied more heavily on shrubs and annuals.

I am not trying to bad mouth shrubs and annuals. They often produce more food for people. But in the context of efficiency of farming carbon, trees and grasses are your powerhouses. So if you are in an area that supports a tallgrass prairie/savanna biome containing both long lived trees and deep rooted perennial grasses, and are focusing more on carbon farming rather than bulk food production, in my opinion I would try and plan your permaculture design optimizing these two guilds. Most permaculture is carbon farming though, no matter what you optimize it for. Even optimizing it for food will still sequester carbon in almost every case I can possibly think of.

I think that sun-harvesting/carbon-farming via living biomass is most productive at rebuilding soils, which has a double benefit: carbon draw-down (even if it's not long-term sequestration), but also fertility-building and water storage, which can lead to more living biomass, a virtuous cycle that increases carbon drawdown effects over a longer term.

The atmospheric carbon load, however, is not really the result of our depleting the soils or forest biomass, or even switching to shallow-rooted annuals.
We farmed for millenia with relatively consistent atmospheric carbon levels - volcanoes had more effect than early agriculture.

Modern changes in atmospheric carbon loads are the result of releasing fossil carbon, both fuels, and things like permafrost and methane hydrates.

To draw down those massive fossil carbon loads faster than they were burned may be beyond the scope that we can expect from any farming or forestry effort.
But let's not take the daunting scope of industrial excesses, or the likelihood that farm efforts will fall short of full compensation for that debt, as a "failure" of the carbon farmer's primary goals.

We can succeed in doing a whole lot of good by restoring what we can restore, drawing down what can be drawn down, and more importantly by maintaining the fertility, water storage, and diversity that will help the planet adapt to a changing climate.

The idea of buying carbon-farmed "indulgences" for climate-harming "sins" is a little bit naive. But if the primary goal, of reducing carbon load as much as possible, has already been seriously addressed, then supporting biomass- and soil-building stewardship farms, which can be done under the carbon credit system, is a worthy and meaningful way to apologize for the residual fuel consumption a person can't avoid. Until we built social infrastructure and culture to allow a carbon-neutral lifestyle, it's hard to wean ourselves from indulging in these travel, digital, or utility carbon debts.

However, I'd rather support small-scale farmers with multiple conservation benefits, which are measuring carbon-drawdown benefits, than farms with an exclusively-carbon-farming mandate. Just as I'd rather support multi-use farms that create wildlife corridors, than exclusive wildlife sanctuaries or exclusive food production farms. I don't think we have enough room on the planet to solve these problems one at a time, or to treat them as a zero-sum game. We need mutual-benefit, mutual-functional solutions if we are to actually gain ground on the imminent ecological collapse.

A "rational" engineer or mechanic breaks the problem down into little parts, solves one part, and believes he has made progress on the whole.
A holistic reasoner keeps the larger goal in mind throughout, and thus can recognize when breaking off individual parts, or even addressing them in the wrong order, is less efficient than keeping them connected.

Shrubs are often the nurse species for later-stage forest trees, which may not thrive in depleted landscapes without shelter. There's so much room for progress on all fronts, that choosing species for carbon-farming mass growth rates seems far less important than choosing species that will thrive, and build biomass, under the current and anticipated local conditions.

The dense, interplanted, multi-layered canopy the OP described would seem to include both the trees recommended by Scott, and the food crops which make most farms their primary income.

Grasses and diverse prairie species may be appropriate where forests are botanically unlikely; I don't have much experience in those climates, and grasses don't thrive on our shrub-steppe as well as the shrubs do.

Getting the moisture and soils built up seems critical. All this can be wiped out by one good wild-fire, with the stuff under the ground and the charcoal that is preserved by a cooler fire (in damper conditions) being the only carbon left to show for all that effort.

-Erica

Erica,
I really envy you! The Okanogan Highlands is really one of the most beautiful areas! So much potential for the permaculturist too! Shrub steppe, grasslands, and forests! Plenty of room for anything you want to do with the land!