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Can Solar Fuels Prevent an Imminent Petroluem Fuels Crisis?

In a nutshell, the answer to the question posed in the title of this article is, “No”. The full article can be found at It will also be published in the next issue of the journal Science Progress. I am merely putting the concluding section here, which refers to localisation and Transition Towns.

Overall summary and outlook.

In conclusion, we are faced with an overall serious energy problem, and most pressingly the challenge of how to fill the enlarging hole created by a declining production of conventional crude oil. It appears almost certain that there will be profound efforts made in obtaining “unconventional oil” from shale and in liberating gas from various geological formations by “fracking”; the production of “synthetic crude” from tar-sands will doubtless increase too. Noting that world light crude oil production peaked in 2005, it is increasingly the heavy oils, e.g. from the Orinoco Belt in Venezuela, that will need to be recovered and processed, requiring the building of a new swathe of oil refineries that can handle this kind of material. Thus, not only are supplies of conventional crude oil going to fall, but what is recovered will be increasingly difficult to process. How difficult it is to produce an energy resource is usually expressed by the Energy Returned on Energy Invested (EROEI). Thus in the halcyon days of the Texan “giant gushers”, 100 barrels of crude oil could be recovered using the energy equivalent to that contained in one barrel of crude oil, which gives an EROEI = 100. The figure has fallen since then, and presently EROEIs in the range 11 -18 are obtained for North Sea (Brent Crude) oil, and as low as 3 – 5 for heavy oil and tar sands “oil”.

Although shale-oil production and use is hardly environmentally “clean”, taking account of its carbon emissions (both in the retorting of shale and in burning the final fuel) and large water demand (3 – 10 barrels of water to produce each barrel of oil), it is trumpeted in some quarters that the US will become self-sufficient in “oil” by 2020. Current US production of shale-oil is around 0.5 mbd, and is predicted to rise to 3 mbd by 2020, but this must be gauged against a loss of conventional oil by 29 mbd across the world. Can solar fuels fill the gap? As we have seen, much of the solar fuel technology is very much at the research stage. Most of what is ongoing aims to produce H2, but even if half the “new” platinum recovered annually were used to fabricate fuel cells, only something like 1% of the billion road vehicles currently in existence could be so substituted by “hydrogen cars” over the next 10 years. Hence, a global transportation network based on hydrogen/fuel cells, let alone a full-scale solar hydrogen economy, is a pipe-dream. If hydrogen can be made renewably on the grand scale, as an energy carrier (it is not really a fuel, since it must be created from primary energy sources), it will probably need to be used by combustion.

The fabrication of electric cars runs into similar resource difficulties, especially in terms of rare earth metals, and so a strategy based on liquid fuels would seem most sensible. Liquid fuels are furthermore entirely compatible with the prevailing transportation infrastructure, in regard to the distribution of fuels and their deployment in internal combustion engines. The Fischer-Tropsch (FT) process is a well-established technology for converting syngas to liquid hydrocarbons, but the means to obtain H2 + CO on a large scale without using fossil fuels is not. Even when (or if) those clean technologies based on artificial photosynthesis are developed, a whole new generation and scale of FT plants will need to be installed, which at the level envisaged would take decades. Any such timescale must be judged against that for the depletion of conventional crude oil. Of those approaches considered here for the production of liquid fuels, the use of genetically engineered cyanobacteria looks the most promising, but even so, meeting the global demand for them seems to be a bridge too far. Producing millions of electric cars is just not a practical proposition, and the only realistic means to move people around in number using electrical power is with light railway and tram systems. The notion of personalised transport will be relegated to history by massive fuel prices, and an absence of any cheaper “car ownership” option. Our global civilization is underpinned almost entirely by crude oil – as refined into liquid fuels for transporting people and consumer goods around nations; for growing and distributing food; for mining coal, shale and all kinds of minerals, including metallic ores and rock phosphate for agriculture; and as a raw feedstock for the chemical industry, to make pharmaceuticals and to support healthcare. If our stalwart “black gold” is set to abandon us over the next few decades, and it is not possible on that same timescale to produce alternative liquid fuels – “the supply side” – we can only address the problem from the demand side.

This means a substantial curbing of transportation and a relocalisation of society, to become more locally sufficient, e.g. in food production, at the community level.
Such are the aims of the “Transition Town” movement. It is likely that energy production will become increasingly decentralized, and done at the smaller scale, to power such communities. Fuel too, e.g. for local agriculture, might be produced from algae at least on a regional scale, as integrated with water treatment schemes to conserve the resource of phosphate, and to avert algal blooms. Methods of regenerative agriculture, including permaculture, provide means to food production that demand far less in their input of fuels, fertilizers and pesticides, and actually rebuild the carbon content of soil. It is thought that 40% of anthropogenic CO2 emissions might be sequestered in soil using no-till practices. Solar energy may also be harvested usefully and directly in the form of heat (rather than converting it to a fuel), at greater efficiency than through PV, using concentrating solar thermal power plants, roof-based water heating systems, solar cookers, solar stills and water sterilization units, and homes especially designed to absorb and retain thermal energy. Though the foreseeable transition to a lower energy and more localised way of life is unequivocally daunting, there is hope.

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