Fuel for Legacy Vehicles in a “Carbon-free” Environment

Electric vehicles will not solve our emissions problem: there are over a billion petroleum driven vehicles, and they will not go away any time soon. Additionally, people have a current investment, and while billionaires might throw away their vehicles, most ordinary people will not change unless they can sell what they have, which in turn means someone else is using it. This suggests the combustion motor is not yet finished, and the CO2emissions will continue for a long time yet. That gives us a rather awkward problem, and as noted in the previous posts on global warming, there is no quick fix. One of the more obvious contributions could be biofuels. Yes, you still burn carbon, but the carbon came from the atmosphere. There will also be processing energy, but often that can come from the byproducts of the process. At this point I should add a caveat: I have spent quite a bit of my professional life researching this route so perhaps I have a degree of bias.

The first point is that it will be wrong to take grain and make alcohol for fuel, other than as a way of getting rid of spare or spoiled grain. The world will also have a food shortage, especially if the sea levels start rising, because much of the most productive land is low-lying. If we want to grow biomass, we need an area of land roughly equivalent to the area used for food production, and that land is not there. There are wastelands, but they tend to be non-productive. However, that does not mean we cannot grow biomass for fuel; it merely states there is nowhere nearly enough. Again, there is no single fix.

What you get depends critically on how you do it, and what your biomass is. Of the various processes, I prefer hydrothermal processing, which involves heating the biomass in water up to supercritical temperatures with some additional conditions. In effect, this greatly accelerates the processes that formed oil naturally. Corresponding pyrolysis will break down plastics, and in general high quality fuel is obtainable. The organic fraction of municipal refuse could also be used to make fuel, and in my ebook “Biofuel” I calculated that refuse could produce roughly seven litres per week per person. Not huge, but still a contribution, and it helps solve the landfill problem. However, the best options that I can think of include macroalgae and microalgae. Macroalgae would have to be cultivated, but in the 1970s the US navy carried out an exercise that grew macroalgae on “submerged rafts” in the open Pacific, with nutrients from the sea floor brought up from wind and wave action. Currently there is work being carried out growing microalgae in tanks, etc, in various parts of the world. In principle, microalgae could be grown in the open ocean, if we knew how to harvest it.

I was involved in one project that used microalgae grown in sewage treatment plants. Here there should have been a double benefit – sewage has to be treated so the ponds are already there, and the process cleans up the nitrogen and phosphate that would otherwise be dumped into the sea, thus polluting it. The process could also use sewage sludge, and the phosphate, in principle, was recoverable. A downside was that the system would need more area than the average treatment plant because the residence time is somewhat longer than the current time, which seems designed to remove the worst of the oxygen demand then chuck everything out to sea, or wherever. This process went nowhere; the venture needed to refinance and unfortunately they left it too late, namely shortly after the Lehman collapse.

From the technical point of view, this hydrothermal technology is rather immature. What you get can critically depend on exactly how you do it. You end up with a thick brown fluid, from which you can obtain a number of products. Your petrol fraction is generally light aromatics, with a research octane number (RON) of about 140, and the diesel fraction can have a cetane number approaching 100 (because the main components are straight chain C15 or C17 saturated hydrocarbons. Cetane is the C16 equivalent.) These are superb fuels, however while current motors would run very well on them, they are not optimal.

We can consider ethanol as an example. It has an RON somewhere in the vicinity of 120 – 130. People say ethanol is not much of a fuel because its energy content is significantly lower than hydrocarbons, and that is correct, but energy is not the whole story because efficiency also counts. The average petrol motor is rather inefficient and most of the energy comes out as heat. The work you can get out depends on the change of pressure times volume, so the efficiency can be significantly improved by increasing the compression ratio. However, if the compression is too great, you get pre-ignition. The modern motor is designed to run well with an octane number of about 91, with some a bit higher. That is because they are designed to use the most of the distillate from crude oil. Another advantage of ethanol is you can blend in some water with it, which absorbs heat and dramatically increases the pressure. So ethanol and oxygenates can be used.

So the story with biofuels is very similar to the problems with electric vehicles; the best options badly need more research and development. At present, it looks as if they will not get it in time. Once you have your process, it usually takes at least ten years to get a demonstration plant operating. Not a good thought, is it?

New Zealand economic development, 1970s

The previous post outlines the background to my first job. The New Zealand government decided it had to do something about developing the economy, and I was hired by the national chemistry laboratory to find a use for lignin, since New Zealand had a lot of timber approaching harvest. Needless to say, I failed. There is now a saying, you can make anything you like from lignin, except money! I am not alone in that failure. In fact I did not stay with it very long because all the country’s troubles were exacerbated in the early 1970s with the first oil crisis. This hit new Zealand very hard because there was even some doubt as to whether we could get any oil, even if we paid enough for it. The government requested their science department to give options of what to do, and I was given the task of finding as much as I could about bioethanol ASAP. (Others were given similar tasks on different energy sources.) I presented my summary in about a week, plus typing and editing time. (No computers then!)  How had I done that so fast? My reasoning was, someone must have had this problem during the war, so I went back into the departmental files, and found all the details of farming practices, costs, processing costs, etc. All I had to do was to update the costs.

The net result of that was that the government knew enough to make ethanol if it wanted to, and it knew what the costs would be, subject to a small uncertainty due to different inflationary effects in different sectors. To the best of my knowledge, very little, if any, bioethanol was made.

This government knee-jerk reaction got nowhere in one sense. The problem was, the government had set up similar quests elsewhere, and the experienced bureaucrats beat the scientists all the time. They set up panels, committees, got large amounts of funding, and then commissioned all sorts of reports. What is interesting about this is that when the energy crisis died down, there must have been hundreds of cubic meters of reports somewhere, and when the next energy crisis came along about 30 years later, these reports were forgotten. Sound familiar?

However, in the 1970s, quite a bit was done on alternative fuels. There were cars running on compressed natural gas (the cylinders taking up most of the boot space on small cars), liquefied natural gas, and methanol/petrol blends. Service stations became interesting puzzles: where did you go in an unfamiliar service station to get what you wanted? The lasting lesson, however, was that once the oil crisis died down, the supply of these alternatives began to die. When that happened, you had to reverse the significant changes to your car. The better strategy, and one I followed, was to stick to petrol and pay the increased price. Also, in some cases, such as with methanol blends, the necessary information remained dispersed across so many reports. Nobody correlated everything, so the chances are, much of what was learned has been forgotten.