Reducing Greenhouse Gas Emissions

Leaving aside the obstinate few, the world is now coming to realize that our activities are irreversibly changing the climate through sending so-called greenhouse gases into the atmosphere. Finally a number of politicians (but not President Trump) have decided they have to do something about it. Economists argue the answer lies in taxes on emissions, but that will presumably only work if there are alternative sources of energy that do not cause an increase in emissions. The question is, what can be done?

The first thing to note is the climate is significantly out of equilibrium, that is to say, the effects have yet to catch up with the cause. The reason is, while there is a serious net power input to the oceans, much of that heat is being dissipated by melting polar ice. Once that melting process runs its course, there will be serious temperature rises, and before that, serious sea level rises. My point is, the net power input will continue long after we stop emitting greenhouse gases altogether, and as yet we are not seeing the real effects. So, what can we do about the gases already there? The simplest answer to that is to grow lots and lots of forests. There is a lot of land on the planet that has been deforested, and merely replacing that will pull CO2 out of the air. The problem then is, how do we encourage large-scale tree planting when economics seems to have led to forests being simply cut and burned? In principle, forest owners could get credits through an emissions trading scheme, but eventually we want to encourage this without letting emitters off the hook.

Now, suppose we want to reduce our current rate of emissions to effectively zero, what are the difficulties? There are five major sources that will be difficult to deal with. The first is heating. Up to a point, this can be supplied by electricity, including the use of heat pumps, but that would require a massive increase in electrical supply, and an early objective should be to close down coal-fired electricity generators. We can increase solar and wind generators, but note that there will be a large increase in emissions to make the construction materials, and there is a question as to how much they can really produce. Of course, every bit helps.

The second involves basic industrial materials, which includes metal smelting, cement manufacture, and some other processes where high temperatures and chemical reduction are required. In principle, charcoal could replace coal, if we grew enough forests, but this is difficult to really replace coal.

The third includes the gases in a number of appliances or from manufacturing processes. The freons in refrigerators, and some gases used in industrial processes are serious contributors. There may not be so much of them as there is of carbon dioxide, but some are over ten thousand times more powerful than carbon dioxide, and there is no easy way for the atmosphere to get rid of them. Worse, in some cases there are no simple alternatives.

The fourth is agriculture. Dairy farming is notorious for emitting methane, a gas about thirty-five times stronger than carbon dioxide, although fortunately its lifetime is not long, and nitrous oxide from the effluent. Being vegetarian does not help. Rice paddies are strong emitters, as is the use of nitrogen fertilizer, thus ammonium nitrate decomposes to nitrous oxide. Nitrous oxide is also more powerful and longer lived than carbon dioxide.

The fifth is, of course, transport. In some ways transport is the easiest to deal with, but there are severe difficulties. The obvious way is to use electric power, and this is obviously great for electrified railways but it is less satisfactory without direct contact with a mains power supply. Battery powered cars will work well for personal transport around cities, but the range is more questionable. Apparently rapid charge batteries are being developed, where a recharge will take a bit over a quarter hour, although there is a further issue relating to the number of charging points. If you look at many main highways and count the number of vehicles, how would you supply sufficient charging outlets? The recharge in fifteen minutes is no advantage if you have to wait a couple of hours to get at a power point. Other potential problems include battery lifetime. As a general rule, the faster you recharge, the fewer recharges the battery will take. (No such batteries last indefinitely; every recharge takes something from them, irreversibly.) But the biggest problem is power density. If you look at the heavy machinery used in major civil engineering projects, or even combine harvesters in agriculture, you will see that diesel has a great advantage. Similarly with aircraft. You may be able to fly around the world in a battery/solar-powered craft, but that is just a stunt, as the aircraft will never be much better than a glider.

One answer to the power density problem is biofuels. There are a number of issues relating to them, some of which I shall put in a future post. I have worked in this field for much of my career, and I have summarized my thoughts in an ebook “Biofuels”, which over the month of July will be available at $1 at Smashwords. The overall message relating to emissions, though, is there is no magic bullet. It really is a case of “every bit helps”.

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4 thoughts on “Reducing Greenhouse Gas Emissions

  1. There are plenty of rumors, and assertions, including from Mr. Goodenough, 94 years old, inventor of the modern Lithium Ion battery., that SOLID STATE GLASS BASED LITHIUM batteries have been developed in the lab. Some of this is peer reviewed, and published.

    The batteries charge very fast, and don’t burn up. They carry three times the energy density of contemporary Lithium Ion.
    The batteries presently used used flammable liquids. So they are armored. Solid state glass will not need this kind of heavy armor.
    Latest version of Tesla Model S goes 335 miles. By optimizing, it has gone nearly 1,000 kilometers…

    The obvious incentive is to put a worldwide carbon TAX. Actually not really a tax, but a compensatory payment for damage caused by carbon combustion… Anything else is a dubious joke…

    • I can’t comment on a battery that I know nothing about, obviously, but I would be surprised, Patrice, if what you say is correct. First, glass is not a good conductor, so it is not clear how the battery could get electricity to the wires. Secondly, the key to such electrochemistry is that one of the two ions goes between electrodes and gives up/takes on ionic character. That means no matter what, you need a solvent, although one possibility includes ionic liquids which are not very flammable. However, the most flammable component is always the lithium. Once started, nothing will put it out, so the heavy armour will almost certainly stay. Energy density is not the only aspect; power is also important. To get power, you need as large a surface area as possible to spread the components. Graphite has the merit of effectively forming LiC6, i.e. one lithium atom per graphitic benzene ring exposed to the surface. To pack that in, and allow access, the graphite is reduced to tiny spheres and coated (to stop the graphite from misbehaving). Again, graphite is important because it is conducting. Even if you get around the conduction problem, how does the lithium pack in? (I know – if we don’t know the chemistry, this is a rhetorical question.)

      It is true the graphite battery has its limitations. If you over discharge (which is possible as a motorist struggles to get to the next charging stop), you start making lithium oxide, which is irreversible. Overcharging at a higher voltage is also bad. You can get around that by ensuring the voltage never gets above a basic minimum, but this does limit fast charging. Of course these limitations may disappear if a different chemistry were used. However, the battery cannot work unless the lithium ions can move to the other electrode and deposit themselves stably, and I fail to see how that can happen with a glass electrode and no solvent 🙂

    • That a scientist can say that is totally depressing. I still think we can avert the worst of this, but we have to start now, and we have to reduce the CO2 levels, or reduce the solar input to the oceans. I remain lacking in confidence, and the likes off Trump and his advisors don’t help.

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