here's an interesting pdf.
http://www.arb.ca.gov/research/seminars/rau/rau.pdfNear the end, there's a short segment on the use of iron and water to reduce CO2 and produce hydrogen (and FeCO3: siderite). About halfway through, accelerated weathering of limestone is addressed.
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Some fragments:
Biofuels are generally an inefficient way to harvest sunlight (which is where biofuel-"crops" generally get their energy from), and they typically require other inputs like (usable) water and something resembling soil (at least); and they typically must be planted, harvested, transported and processed (at least).
Also, topsoils must be maintained, even where fertilizers are used; if only because subsoils typically don't produce nearly as well as topsoils even with modern farming methods. Otherwise we'll end up "mining" (depleting, possibly exhausting) soils like we do oil.
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To better exploit wind and solar power (and intermittent production sources generally), we need to move away from a keeping-ahead-of-usage model for electric generation and closer to a use-what's available model. (Implicit in this model is the ability to boost baseload, since it won't be wasted.)
As part of this model, electrical/intermediate-product storage (typically "filled" when production exceeds usage) is necessary for times when usage exceeds production, but overproduction could also be used for other purposes (hydrogen for vehicles, water purification, industrial applications, etc). Industrial scale storage (like storing heat for thermal-voltaic applications) has some role in this, but end-user storage has significant benefits for the end-user, like being able to buy electricity when it's cheap and sell it back when it's expensive, saving on electric costs even when not a producer. (Such storage capability would also be a property improvement, and allow for uninterrupted power even when network-power fails.)
(I've also read of PVs that store electricity.)
Of course, this demands a smarter electrical network (network interfaces, and desirably, appliances), but this is a natural progression.
However, efficiency and thrift will remain the major tools available to the consumer, and even in an era of abundant energy (whatever resource), consumers should be conscientious in their usage.
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Limitless growth in resource use is impossible. The only question is when the various limits will be reached (which is often later than predicted, because those making the predictions don't allow enough for efficiency improvements, new technology, etc -- and because they don't look at the limits of the more ulterior/broader resources: eg, sunlight lies behind most food production).
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Even if the "developed" nations change their course significantly as regards CO2 production (and do so in ways that do more good than harm), the "developing" nations may more-than-offset any gains made in this manner.
(This applies to resource use, environmental degradation, more generally.)
Trade, investment, technology transfer, etc, should have been made contingent on adhering to certain environmental (etc) standards, since environmental degradation is a universal concern. Moreover, trying to "retrofit" these standards to existing agreements (and more importantly, existing systems/constructs/currents) presents a great hurdle; indeed, a seemingly insurmountable one, given the historical course, certain cultural perspectives and other circumstances.
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We've undone many balances in nature, and there's some risk that we will undo some balance or balances that are of such magnitude that the results will be catastrophic for mankind.
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Biogas/bio-electricity/biofuel:
* If energy production is done at (or near) the site of "fuel" (that which is directly used to make energy products) production, this minimizes transportation of such fuel;
* If the energy produced is in the form of electricity, this is typically usable on site and also easily, cheaply "transported" (transmitted) over the existing network;
* Byproducts should be those able to be used as feed/fertilizer, or for some other economic purpose; and
* If this byproduct can be well-utilized on site (nearby), then byproduct transportation is also minimal.
However, largescale biofuel production facilities (also largescale feed operations) typically require significant transportation (physical hauling) of the fuel and (as applicable) the products/byproducts -- or less-than-optimal byproduct use -- and greater organics loss to the original feed/fuel-production environments.
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Speaking of weird coincidences, I turned on the tv tonight, and there's Bill Murray playing a hit song from The Shadows of Knight, a group my buddy was in.