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Best Sunlight to Biomass Plant

 
S Bengi
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Location: Massachusetts, Zone:6/7, AHS:4, Rainfall:48in even distribution
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Given that all leaves have a net sunlight to energy efficiency conversion ratio of just 5.4%.

100% sunlight → non-bioavailable photons waste is 47%, leaving
53% (in the 400–700 nm range) → 30% of photons are lost due to incomplete absorption, leaving
37% (absorbed photon energy) → 24% is lost due to wavelength-mismatch degradation to 700 nm energy, leaving
28.2% (sunlight energy collected by chlorophyl) → 32% efficient conversion of ATP and NADPH to d-glucose, leaving
9% (collected as sugar) → 35–40% of sugar is recycled/consumed by the leaf in dark and photo-respiration, leaving
5.4% net leaf efficiency.


Which plants store that energy in the best package for carbon farming?
 
David Livingston
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Elephant grass ? I know this is grown as a fuel in the UK . http://recrops.com/miscanthus
You could grow your own fuel annually
Imagine if you could use it in your rocket heater
Carbon neutral free heating even if you have no trees plus it perrrenial you just chop it down and it grows from the roots next year

David
 
Steve Farmer
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You have ample rainfall so I think hybrid poplars would be hard to beat. Even when you harvest them above ground you are leaving tons of biomass below ground, and you can coppice them annually or more than annually if you want to control their size. Cheap, easy to propagate and require almost zero care to keep them alive.
 
Neil Layton
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That 5.4% is an average.

There have been some good suggestions already, but I'd like to add one to the mix.

Find plants using the C4 photosynthetic pathway. Under drought and high temperature conditions, these plants fix carbon much more efficiently than plants using the C3 pathway.

Plants using the C4 pathway account for 3% of species, 5% of total biomass (because they tend to be annuals, not perennials) and account for 30% of annual terrestrial carbon fixation (only partly because they are concentrated in the tropics and subtropics, where there is more light).

The C4 pathway seems to have evolved relatively recently, but independently. Around 46% of grasses use the C4 pathway, including maize, sugarcane, millet and sorghum.

Some members of the amaranth and cabbage families do as well, and plant breeding from non-crop varieties of these might be considered a priority.

The main problem with this suggestion is that they account for, as I say, only 3% of species. You could stack your plant list towards them, but at the expense of overall diversity.
 
Eric Toensmeier
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The general rule is: anything perennial. Bonus points for woody perennial. Extra bonus points for dense, diverse plantings of long – lived woody perennials.
 
David Livingston
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I note Neil you state that the 5.4% is an average there fore some plants will do better and some not so good .
So I wonder which gets the highest %
Or is this more condition dependent ?
Should this not be better put which plant has the highest potential

David
 
Burra Maluca
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OK guys, I've asked once. Please keep stuff on topic. This forum is about carbon farming. If you want to make it about climate change, it has to go into the cider press.
 
Tyler Ludens
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Eastern gamagrass was suggested in another thread. I have a couple clumps of it in my kitchen garden, which isn't ideal for it as it would like more space, but it's a pretty cool plant:

http://agresearchmag.ars.usda.gov/2005/sep/carbon

http://www.actahort.org/books/638/638_40.htm

http://images.library.wisc.edu/EcoNatRes/EFacs/NAPC/NAPC07/reference/econatres.napc07.mbender2.pdf
 
Neil Layton
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David Livingston wrote:I note Neil you state that the 5.4% is an average there fore some plants will do better and some not so good .
So I wonder which gets the highest %
Or is this more condition dependent ?
Should this not be better put which plant has the highest potential

David


Actually, that's an easy one.

Sugarcane (Saccharum spp, mainly officinarum), with peak efficiencies around 8%. Efficiencies of sweet sorghum (Sorghum bicolor), and maize (Zea mays) approach this. The theoretical maximum is around 10%.

It's worth bearing in mind that monoculture sugarcane has its own problems, and there are issues to consider besides gross efficiency, so I would stand by Eric's more general advice above.
 
Thekla McDaniels
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Although there may be ONE species that has the best ratio of sunlight to biomass conversion, we know, and Tyler has already said that monocropping sugar cane brings its own problems. So, even where sugar cane can grow, it needs its friends and protectors.

It is good to know which are the super producers, so that we can build communities "guilds" of plants around the high performers, and not get too drawn into the idea of the one most efficient plant. We repeat that to each other often, that a single stand of plants is highly vulnerable to disease, predatory insects, nematodes etc. IMO a pure stand of a single species is a time limited thing. Diversity is key.

I grow C4 grasses and weeds in the summer, and their rate of growth is astonishing. Kochia scoparia and amaranth, both members of the chenopodiaceae have rates of growth so fast it is truly hard to believe, but our very hot season only lasts a couple of months. Here in the high desert, we have a cool season before and after summer, and the cool season grasses grow in both those seasons, with not much going on with the kochia and amaranth. And the cool seasons combined are more than twice as long as the very hot season when the C4s can do their thing.

So, in my climate, on a year round basis I wonder which plants would capture more CO2 per square cm or square inch of leaf surface, the hot season super star C4s, or the cool season plants such as orchard grass.

My conclusion is that to maximize photosynthesis on my property and in my climate, I need a mix, so that not only is something growing year round, but at higher and lower levels of surface, sub canopy and canopy, and all the intermediate levels. IMO the best "biomass plant" is a community of synergists making sure no photon of sunlight goes un-captured.
 
Douglas Campbell
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8-10% is a theoretical high end for conversion of incident solar energy to biomass.
Actual conversion efficiencies under most circumstances are closer to 1% (maybe 4% for sugarcane).

The very highest efficiencies are only reached under moderate light; even C4 plants can be come light saturated at noon on a clear day, so those photons are wasted (maybe that is the first line in the original poster's quote?).

the answer depends in part upon the goal:
-carbon sequestration into soil carbon or standing biomass?
-or total harvestable carbon
-or total usable harvestable carbon?

So, in a tropical harvest situation sugarcane is the current winner, because some strains have nitrogen fixation, and the gabasse left from sugar production can be used as fuel.
In a temperate carbon sequestration situation a tree species or perennial grass might win because it might sequester more carbon into soil.
Miscanthus is studied for temperate situations because the leaves and stalks can be harvested after yellowing, and they contain little besides carbohydrate; the nutrients are pumped down to the roots for another round of production.

I agree that theoretical peak productivity is not always the best criteria for a permaculture situation; diversity, disease resistance, pollenator support, habitat.... are all factors
 
Steve Farmer
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Plants are 3 dimensional. Photosynthesis can use reflected sunlight and to a lesser degree sunlight that has passed thru another leaf. Photosynthesis happens in the shade. A photon might have a 5.4% chance of being used by the first leaf it hits, but if that photon isn't used by the first leaf it doesn't just cease to exist. So the actual amount of sunlight that goes to photosynthesis can be higher than the experimental figures quoted suggest.
 
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