Mark, Greg, List
I like your idea and will start looking up the macroalgae citations found at
your site.
But I suggest (as did Greg Rau) that you investigate the biochar alternative to
your proposed conversion through biogas. I see three main benefits to biochar
over your CCS option as it impacts the Carbon Dioxide Removal portion of this
list. First is that liquifying and deep-sequestering the accompanying CO2 seems
unlikely to be ready soon - and will always be pretty expensive (especially at
small scale). More importantly, char obtained from pyrolyzing your macroalgae
will provide out-year benefits from up to millenia. Lastly, natural gas
transport to the mainland seems likely to involve considerable expense - more
so than moving a solid or liquid.
Your possible project in Fiji could have a valuable char side immediately,
while a BECCS approach seems likely to be many years away - so you will be
foregoing the promising sequestration potential of ocean biomass that Greg is
looking for.
A good place to see the current status of pyrolysis and biochar at what seems
to be the leading commercial biochar (and biofuel?) entity is only 20 miles
east of you. Look at (I have no connection):
www.coolplanetbiofuels.com
Ron
----- Original Message -----
From: markcap...@podenergy.org
To: r...@llnl.gov, "geoengineering" <geoengineering@googlegroups.com>
Sent: Tuesday, October 2, 2012 7:05:42 PM
Subject: Oceans? RE: [geo] Natural land air capture nutrient limited
Greg,
Another solution is rapid nutrient recycling, as happens in the Ocean
Afforestation ecosystem.
Deploying the Ocean Afforestation ecosystem over 4% of the world's ocean
surface would imply cycling about 16 times the global artificial nitrogen plant
fertilizer production. The recycle will happen over distances of a few
kilometers and time scales of a few months. The ecosystem would also be cycling
proportional masses of all the other nutrients needed to grow macroalgae.
Perhaps more important than nutrients, land plants are limited by fresh water
and the timing of fresh water (no good to rain in August if the corn kernel
silks lacked water to deploy July).
Mark E. Capron, PE
Oxnard, California
www.PODenergy.org
-------- Original Message --------
Subject: [geo] Natural land air capture nutrient limited
From: "Rau, Greg" < r...@llnl.gov >
Date: Tue, October 02, 2012 10:53 am
To: geoengineering < geoengineering@googlegroups.com >
Possible solutions:
fertilize
genetically select/modify
reduce CO2 recycling (CROPS, Biochar)
all of the above.
Greg
Nature | News
Earth’s carbon sink downsized
Abundance of soil nutrients a limiting factor in plants’ ability to soak up
carbon dioxide.
• Amanda Mascarelli
01 October 2012
Plants need enriched soil to make use of increasing carbon dioxide.
As carbon dioxide levels in the atmosphere continue to climb, most climate
models project that the world’s oceans and trees will keep soaking up more than
half of the extra CO 2 . But researchers report this week that the capacity for
land plants to absorb more CO 2 will be much lower than previously thought,
owing to limitations in soil nutrients 1 .
Because plants take up CO 2 during photosynthesis, it has long been assumed
that they will provide a large carbon ‘sink’ to help offset increases in
atmospheric CO 2 caused by the burning of fossil fuels. Some scientists have
argued that the increase might even be good for plants, which would presumably
grow faster and mop up even more CO 2 . Climate models estimate that the
world’s oceans have absorbed about 30% of the CO 2 that humans have released in
the past 150 years and that land plants have gulped another 30%.
But the latest study, by ecologists Peter Reich and Sarah Hobbie at the
University of Minnesota in St Paul, suggests that estimates of how much CO 2
land plants can use are far too optimistic. Plants also need soil nutrients,
such as nitrogen and phosphorus, to grow. But few studies have tested whether
soils contain enough of these nutrients to fuel growth in proportion to rising
CO 2 .
“This work addresses a question that’s been out there for decades,” says Bruce
Hungate, an ecosystem scientist at Northern Arizona University in Flagstaff.
"It's a hard question to answer, because it takes a long time to see how
ecosystem carbon and nitrogen cycles change." Long-term growth
In a 13-year field experiment on 296 open-air plots, the researchers grew
perennial grassland species under ambient and elevated concentrations of both
atmospheric CO 2 and soil nitrogen.
“Rather than building a time machine and comparing how ecosystems behave in
2070 — which is hard to do — we basically create the atmosphere of 2070 above
our plots,” says Reich.
Reich and Hobbie found that from 2001 to 2010, grasses growing under heightened
CO 2 levels grew only half as much in untreated as in enriched nitrogen soils.
Researchers do not have a firm grasp on the complexities of nitrogen and carbon
cycle interactions, so “the vast majority of models do not adequately reflect
nutrient limitation”, says Adrien Finzi, a biogeochemist at Boston University
in Massachusetts. “The real strength in this study is that now we have this
13-year record of a single ecosystem. It provides a really strong case for the
claim that soil resources and nitrogen limitation in particular can impose a
major constraint on carbon storage in terrestrial ecosystems.”
A study published in March modelled nutrient cycling across the globe to
predict how much carbon plants could sequester over the next 100 years when
nutrient limitations are taken into account 2 . Those simulations, which
included nitrogen limitations in northern hemisphere soils and phosphorus
limitations in the tropics, predicted that land plants will absorb 23% less
carbon than is projected by other models.
Researchers say that much more work is needed to understand how nutrient
dynamics will affect carbon uptake — particularly in forest ecosystems, which
are expected to be important carbon sinks. Often, says Hungate, these
ecosystems seem to offer a “partial, natural, easy solution” to the climate
problem. “But it turns out that in reality, ecosystems are complex and only
have limited flexibility.”
Nature
doi:10.1038/nature.2012.11503 References
1. Reich, P. B. & Hobbie, S. E. Nature Climate Change advance online
publication, http://dx.doi.org/10.1038/nclimate1694 ( 2012 ).
Show context
2. Goll, D. S. et al . Biogeosciences 9 , 3547 – 3569 ( 2012 ).
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