The Arbourist has a post about a small company that has a proposal to create liquid fuels out of water and carbon dioxide from the air. While the proposal looks promising, since, as far as I can tell, it takes more energy to create the liquid fuel than is released by burning that fuel, and that any carbon extracted from the atmosphere while creating the fuel will ultimately be re–emitted when that fuel is used, I have difficulty seeing how much of a difference this particular technology would make. (See also my comments at the Arbourist’s post). However, if new evidence or technology emerges that allows this technology to make more of a difference, I will certainly change my mind about it.
And The Arbourist’s post got me thinking. Since there has been much resistance to making more than a token effort to reduce greenhouse gas emissions, perhaps it is time to put geoengineering on the table. That might potentially be the best hope for avoiding disaster. While I am not actively suggesting we start geoengineering, I am suggesting we put it on the table. This is important considering our collective failure to make much effort towards mitigation of global warming and climate change.
Geoengineering is not science fiction. Several of the proposals have analogues that happen naturally. And it is not decades away. As far as I can tell, the following proposals are pretty much shovel ready, and we could start tomorrow if there was a serious effort, and with no significant research yet to be done or technology to be developed:
- Atmospheric sulphur aerosols
- Grassland restoration
- Cool roofs
- Enhanced weathering
These proposals each have a number of advantages and disadvantages (discussed after the jump):
Atmospheric sulphur aerosols is putting various sulphur gases (like sulphur dioxide [SO2] or hydrogen sulphide [H2S]) into the stratosphere. There, they form droplets and increase albedo, decreasing the amount of sunlight received and therefore lowering temperatures immediately. This has a direct analogue in what happens after powerful volcanic eruptions.
In the 1960s, Project STORMFURY was an unsuccessful attempt to weaken hurricanes by cloud seeding them. One of the more advanced techniques they used was a gun–like device that shot silver iodide (the substance used in cloud seeding to create condensation nuclei) into clouds. This device should be readily–adaptable to shoot sulphur aerosols. Combined with high–flying airplanes, this should result in a crude way of creating stratospheric sulphur aerosols. Other methods of getting sulphur aerosols into the stratosphere, such as balloons and artillery, are still in the research phase. Sulphur aerosols don’t last long, so this would have to be an ongoing project.
Atmospheric sulphur aerosols don’t actually remove carbon dioxide, so it is only a method to deal with global warming. It does not solve other problems associated with increased carbon dioxide concentrations, like ocean acidification. In addition, sulphur aerosols also damage the ozone layer. Therefore, atmospheric sulphur aerosols may well cool the climate. but at the expense of increased skin cancer and cataracts.
Grassland restoration is using various agricultural techniques, such as no–till farming, to increase the storage of carbon in soil.
No–till techniques can sequester carbon by not allowing contained carbon to be released by soil microbes. In conjunction with winter cover crops, this can restore agricultural soil into a net carbon sink. This method also requires less use of mechanized equipment than conventional farming, therefore directly reducing emissions. Furthermore, no–till farmland reflects more light, therefore having a secondary cooling effect. In addition, no–till farming can, if done correctly, increase income and yields. You see that? There’s good money in saving the planet.
The methods of no–till farming can also be directly applied to a home garden, so even non–farmers can participate. This is known as no–dig gardening.
However, many no–till methods increase pesticide use. In addition, this method cannot sequester carbon indefinitely, as soil will eventually become saturated and absorb no more. Also, there is the possibility that soil can, in certain conditions, become a carbon source, especially if no–till methods are abandoned, which raises questions about the permanence of this form of carbon sequestration. In addition, incorrect use of cover crops can deplete the soil of nutrients, especially nitrogen. No–till methods (including no–dig gardening) are also more difficult to do than conventional methods.
Cool roofs are using light–coloured roofs, therefore increasing reflectivity and cooling urban areas. This especially applies in cities, offsetting the urban heat island effect.
Cool roofs are perhaps the simplest geoengineering technique. Anyone who can install (or build) a roof can engage in cool roofs. And by reflecting sunlight from a house or building, it can reduce the costs of cooling and air conditioning, thereby saving energy and money. It is quite possible that a cool roof will pay for itself in cost savings.
However, merely increasing reflectivity does nothing for ocean acidification and other effects of increased carbon dioxide concentrations. Furthermore, if the roof is used to reflect sunlight, it cannot be used to install solar generators, requiring a consideration of opportunity costs associated with each option.
Enhanced weathering is grinding up olivine (Mg, Fe)2SiO4 into sub–millimeter (0.2–0.6mm) particles and allowing a chemical reaction to take place that uses water to lock away carbon dioxide into carbonates. This happens naturally (but slowly) and it requires no energy since the reaction is exothermic. What we are merely doing is increasing the surface area so the reaction proceeds faster.
Olivine is one of the most common minerals on the planet, and it is found almost everywhere. If these sub–millimeter olivine particles are scattered in a thin (sub–centimeter) layer on tropical beaches in humid areas, the action of waves and tides will erode the particles smaller, allowing them to weather even faster. The products of this reaction are alkaline, and can therefore deal with ocean acidification. All of these olivine particles will weather in a few years, allowing the process to be repeated. This can also be done in cooler or drier areas, although it proceeds slower. This can also be done by using the olivine particles as a soil amendment, but again the reaction is slower. And since olivine is abundant and even a by–product of mining, there is no shortage of raw materials; the primary difficulty is producing the particles and transporting them to beaches. Once converted to carbonates, the process is more or less irreversible save for a volcano or a furnace, therefore permanently sequestering CO2 and removing it from the atmosphere. Lastly, since this reaction is exothermic, if carefully handled, the heat produced by it is theoretically available for other uses, such as a power plant.
However, the few years to weather is under optimal conditions (humid tropical beaches) and doing this elsewhere is accordingly slower. In addition, grinding up olivine and transporting it takes energy. Lastly, enhanced weathering is, as of writing, not available as a carbon offset. Hence, there is little economic incentive under current conditions to actually engage in enhanced weathering.
Geoengineering is most emphatically not a substitute for mitigation of global warming. Put succinctly, the best way to remove carbon dioxide from the atmosphere, is not to put it there in the first place. Additionally, geoengineering could well already be politicized, and its use might reduce incentives to not emit carbon. Furthermore, there is no absolute guarantee that geoengineering will work as effectively as has been suggested. For those reasons, it is still better to reduce carbon emissions as well. I suggest an increasing carbon tax, offset with cuts to payroll and income taxes and a rebate. This system will therefore always provide an economic incentive to reduce carbon emissions and conserve energy.
We should also reduce barriers to the use of, and red tape blocking the implementation of, renewable energy. Perhaps we can use some government (or private) research funds as technology inducement contests a la the X Prize or Virgin Earth Challenge. Lastly, most scientists believe that the dangers of nuclear power are far overblown, especially when compared to the threat from global warming. Despite Fukushima, I still think nuclear power looks real good as a means for future energy production.