Study Suggests Climate Change-Induced Drought Caused the Mayan Collapse

The amount of vegetable matter that you need to produce the massive amounts of oil that humans use, would take up all the worlds arable land,leaving us nowhere to produce food for the every expanding population.

For comparison, world oil consumption is 80 million barrels per day, which, shared between six billion people, is 23 kWh/d/p. So even if all of Africa were covered with jatropha plantations, the power produced would be only one third of world oil consumption.

The only thing that seems potentially viable is algae grown in water enriched with co2 captured from industrial plants. But obviously that requires some advanced carbon capture technology. It would also require land, though not as much as other biofuel ideas.

What about algae?

Algae are just plants, so everything I?ve said so far applies to algae. Slimy underwater plants are no more efficient at photosynthesis than their ter- restrial cousins. But there is one trick that I haven?t discussed, which is standard practice in the algae-to-biodiesel community: they grow their algae in water heavily enriched with carbon dioxide, which might be col- lected from power stations or other industrial facilities. It takes much less effort for plants to photosynthesize if the carbon dioxide has already been concentrated for them.

In a sunny spot in America, in ponds fed with concentrated CO2 (concentrated to 10%), Ron Putt of Auburn University says that algae can grow at 30 g per square metre per day, producing 0.01 litres of biodiesel per square metre per day. This corresponds to a power per unit pond area of 4 W/m2 ? similar to the Bavaria photovoltaic farm.

If you wanted to drive a typical car (doing 12 km per litre) a distance of 50 km per day, then you?d need 420 square metres of algae-ponds just to power your car; for comparison, the area of the UK per person is 4000 square metres, of which 69 m2 is water (figure 6.8).

Please don?t forget that it?s essential to feed these ponds with concentrated carbon dioxide. So this technology would be limited both by land area ? how much of the UK we could turn into algal ponds ? and by the availability of concentrated CO2, the capture of which would have an energy cost (a topic discussed in Chap- ters 23 and 31). Let?s check the limit imposed by the concentrated CO2. To grow 30 g of algae per m2 per day would require at least 60 g of CO2 per m2 per day (because the CO2 molecule has more mass per carbon atom than the molecules in algae).

If all the CO2 from all UK power stations were captured (roughly 212 tons per year per person), it could service 230 square metres per person of the algal ponds described above ? roughly 6% of the country. This area would deliver biodiesel with a power of 24 kWh per day per person, assuming that the numbers for sunny America apply here.

A plausible vision? Perhaps on one tenth of that scale? I?ll leave it to you to decide.

Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/z26aZQNp_2Q/study-suggests-climate-change-induced-drought-caused-the-mayan-collapse

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