For The "Imagining 2020 Series" - Contribution #4
Green Crude by Pete Fowler
I was very pessimistic until last year about our prospects of weaning off fossil fuels before reaching an irreversible
tipping point. Some positive feedback loop would kick in, like higher temperatures releasing trapped methane from arctic
permafrost and seafloor sediments. Increased atmospheric methane, about 30 times as potent a greenhouse gas as CO2,
would further raise temperatures. End result? Within a few decades Earth would be as hot as Venus. The whole of humanity
would go the way of the civilisations described by Jared Diamond in Collapse, who could see they were on a track to self
destruction but were unable to alter course.
In 2008 I read one of the most positive books ever written; The Singularity Is Near, by Ray Kurzweil. He points out that
whichever way you measure the rate of technological change, it accelerates exponentially. Moore’s law for instance
predicted in 1965 that artificial intelligence would double in complexity and halve in cost every two years. It’s held
for the last 44 years, and if it continues to hold until 2020, we’ll then have machines approaching human intelligence.
Kurzweil maintains that right now, nanotechnology, genetic engineering and robotics are the main drivers of
technological advance. The production of crude oil from atmospheric CO2 and water will be mostly a triumph of genetic
engineering.
Nature took hundreds of millions of years to produce the crude oil which, in about 200 years, we’ll have exhausted. If
we can speed up this process, and produce all our liquid fuels and chemical industry feedstocks, and some stock feed and
human food from atmospheric CO2 and waste, by a process many times as efficient as farming, without diverting farmland
or native bush, on the same timescale as the rate at which we deplete fossil fuel, we’ll have solved the problems of
peak oil and global warming, and a few lesser problems.
Conventional biofuel production isn’t particularly efficient. It requires fuel inputs for farm vehicles, and it either
diverts farmland away from food production or destroys native bush. Only an average 300 watts per square metre world
wide of sunlight is available for photosynthesis, and natural photosynthesis isn’t a very efficient way to convert
sunlight to chemical energy. The most efficient fuel crop is sugar cane, fermented to ethanol. It yields up to three
harvests a year. But it’s labour and land intensive, requires fuel for farm machinery and transport, it increases the
cost of food and only grows in the tropics. Because all conventional crops need further processing in different places
before they reach the petrol pump or dinner table, their total number of carbon kilometres is typically several times
the distance round the world.
What’s needed is a continuous process, not a batch process like conventional harvesting. The world is running out of
land suitable for conversion to farming. An algae reactor can be set up on land which is unsuitable for farming or
anything else, and can still produce more than 15 times as much fuel per hectare as canola or palms. Unlike natural
crude, it can yield a product free of contaminants like nitrogen, sulphur or benzene. The first generation will use
sunlight for their energy source, but later, as energy sources like pebble bed fission reactors and ultimately nuclear
fusion become available, these will drastically increase yield.
Some natural cyanobacteria can double their mass every hour. With genetic engineering, high temperature varieties, and
varieties which fix their own nitrogen from the atmosphere are possible. The obvious raw materials to use are untreated
sewage and atmospheric CO2, helping to solve two environmental problems. Eventually, when energy sources other than
sunlight are available, the demand for sewage will outstrip supply, and other sources of micronutrients will be needed.
But as with conventional agriculture, micronutrients are in principle recyclable. All you need is a way to reclaim
elements like phosphorus, sulphur, iron, molybdenum and the rest. This is feasible with a bioreactor producing algae,
but not on a conventional farm, where they drain away, and not only are they wasted, but they cause problems like
nitrate in drinking water and eutrophication in waterways.
The only high tech part of producing green crude is the final step; converting algae into oil. There’s no reason why
bioreactors can’t be operated in the world’s poorest countries, as well as everywhere else where a demand for the
products exists. Being a factory, rather than an outdoor farm operation, it can be conducted close to population
centres, or anywhere else. CO2 is available everywhere, and low-grade water supplies unfit for human consumption, almost
everywhere.
An obvious location for a bioreactor is right next to a thermal power station, where there’s waste CO2, waste heat and
transmission loss free electricity, but in principle one can operate anywhere.
The algae is harvested continuously, 24/7. Currently four technologies exist to extract the oil. 1. Dry the algae and
press the oil out. This is the simplest method.
2. Dissolve the oil in a supercritical fluid like CO2 at high pressure. When pressure is reduced the oil separates out
and the CO2 is reused. This is the most promising method.
3. Hexane solvent. Hexane, a hydrocarbon similar to petrol, dissolves the oil. The hexane is then separated from the oil
and reused.
4. Ultrasound breaks open the algae cells, and the oil is pressed out.
The remaining dry matter is a high protein stock feed.
A bioreactor producing algae which are processed into liquid fuels, foods and petrochemicals, is a machine for
converting waste, including CO2, into essential commodities which are getting scarcer every year. The only input needed
is energy. It’s a closed loop. There is no waste and no collateral damage to the environment.
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