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Writing about the climate crisis My slow awakening to climate change Climate sceptics answered: | The October 2006 issue of your journal contains an exchange on the subject of global warming between a reader, Charles Perry, and editorial writer Tim Wright. There are in existence some ideas that bear positively on this matter, offering a way to control the phenomenon quickly and cheaply. Responding through your columns seems like an excellent opportunity to get them in front of your readers. First of all, Mr. Perry allows that carbon dioxide (CO2) is a greenhouse gas, but questions whether it produces the global warming being observed. By definition, CO2 is responsible for trapping some energy, rather a lot according to its concentration and measured properties. Since energy accumulates at or near the Earth’s surface, it is hard to imagine how it shows up other than as temperature or some temperature-driven effect, like wind velocity. Perhaps Mr. Perry knows of other ways to accommodate this energy. Other greenhouse agents exist, like water vapor Mr. Perry notes; this one has in place a natural controller (rainfall) which people have fooled with in the past (cloud seeding) and may do so again. For most other greenhouse agents, we must look to emission control. Mr. Perry wants to see proof that increased CO2 level results in higher temperature, beyond the observation that it happens. What would constitute poof to him, other than watching the rise of temperature as CO2 level goes up, which he won’t accept as proof? One might reduce the CO2 build-up rate or its level in the atmosphere and see if temperature behaves accordingly. This is the accepted way to show cause and effect; Mr. Perry would have to go along to get the proof he asks for. What is commonly prescribed to do this is CO2 emission restriction; we propose another way here. CO2 has two major sinks: Water and biomass. As the concentration of the gas in the air rises, the concentration in equilibrium with it in water rises. As the temperature of the water rises, its ability to hold gas (Bunsen coefficient) falls; for CO2, this amounts to about 3% less per °C rise. How this plays out in the future can be calculated. My estimate, based on constant 1990 emission rate, is for about 800 ppm in the air in 500 years, topping out at just over 900 ppm in 2000 years. The assumptions about emission rates are pretty arbitrary, not very realistic; a more rigorous calculation would probably give a more reliable answer, a bit different than mine. In any event, the oceans can hold a lot of CO2. Biomass as a sink has two parts; in the first, trees and other plants take CO2 out of the air to make biomass, and then return it when they die. If there is more CO2 in the air, the pool size increases, but it still rolls over at the end of each life cycle. Keeling has measured CO2 levels over a long period, and his famous sawtooth curve resulted.1 We see annual swings as deciduous trees go in and out of leaf, higher values with time, and wider swings (more foliage) with leaf mass increases, as Mr. Perry has noted. Another biomass sink is an important part of this equation; Wet soils, especially peat bogs. Plants that grow in swampy environments can fall into the bog, sink and digest anaerobically, forming peat instead of decomposing in the air and returning their CO2 to the atmosphere. This type of action has furnished the precursors of our fossil fuels in times past, and it continues today. Bogs typically grow about a foot in depth per millennium in temperate regions; over the Earth’s surface this ties up about half of what the oceans take up. Looking at this process in nature suggests that we might do something similar intentionally. Suppose we were to grow biomass to take dilute CO2 out of the air, then digest in anaerobically to make something close to peat plus a digester gas which we collect for further use [70% methane (CH4), 30% CO2]. We have then converted dilute CO2 from the air into two concentrated forms for segregation to keep carbon out of the active cycle; this way we can control CO2 levels in the air without restricting emissions. The process is called anthropogenic peat (AP) which refers to the digester residue. This can be segregated by simple land-filling, as it is digested enough to resist further decomposition in the soil. The pure CO2 resulting from sweetening digester gas can also be segregated, deep ocean disposal preferred. This may be easy to do because the biomass of choice at this time is sugarcane (high yield, CO2 conversion efficiency and digestibility), and many growing sites are close to fairly deep water. The yield of by-product CH4 is large and cheap. By “large” what is meant is if AP is installed to control the level of CO2 at today’s emission rate, enough CH4 is produced to satisfy about 1/3 of the world’s current total energy budget; “cheap” means a break-even cost, minus segregation cost of about $0.50/106 Btu. This is a significant amount of clean (compared to coal and oil) renewable energy at an attractive cost and it can solve the problem of CO2’s contribution to global warming without wrecking the global economy. Perry and Wright agree on one point at least: Emission reduction as now practiced is not working. It is axiomatic that it cannot work in the real world because to stabilize CO2 levels at the present value, present emission rate would have to be reduced about 70%. All the proposed cuts are of the order of a few percent, and they are not being achieved. Even if they were, the effect would be very small. None of this takes into account increasing population and the industrialization of countries like India and China which are exempted from emission reduction as “developing countries” but could take part in AP easily for profit. The 70% reduction figure was quoted twenty years ago: it looks like it is still the required level of emission reduction, which AP is able to get around. One applauds Mr. Wright for getting his family emission in line, but please, Sir, do not throw out your fountain pen or word processor; they will be sorely needed to get things back on track. And Mr. Perry, I hope you can accept at least a test of the AP concept, guaranteed not to wreck the economy. LITERATURE CITED 1Sagan, C., “Billions & Billions,” Random House, 1997 H. A. Hartung, Consultant | ||||
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Wingo is the project we started here on the archipelago outside Gothenburg to create a model of winning sustainable local development. You can visit wingo's website here. The website of our wind park has only just been registered. | |||||
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