Monday, November 03, 2008

Algal biomass as alternative energy source

This is a guest post by modest, Sydney-based journalist Sir Henry Casingbroke. Sir Henry previously contributed this related post.

I am surprised how little discussion there has been about one of the most obvious and painless ways of doing something practical about emissions of CO2 into atmosphere.

The main problem lies with electricity generated by burning coal followed by internal combustion engines using petroleum products.

Three vague “solutions” have been offered, none of which is likely to eventuate in Australia: (1) electricity generation from nuclear energy (2) carbon sequestration by piping carbon dioxide underground (3) “clean-coal” technology.

First, nuclear energy has the twin political problems of siting the disposal of spent fuel. As a uranium producer we wouldn’t be in a position to export the spent fuel overseas for storage, both morally and practically – we’d have to store here. It can safely be buried deep underground but it is at a huge cost and complexity as is currently done in Sweden. Then there is siting the facility itself - because nuclear power stations use water for cooling, in Australia they would have to be located on the coast to utilise seawater. But that’s where the vast bulk of our population is. The attendant complication is that electricity generation needs to be closeish to where it is needed because of the substantial energy losses in the high-power transmission lines – thus creating an impasse – nuclear generation needs to be on the coast and near people, but people don’t want nuclear power stations anywhere near them. This is obviously in a too-hard basket politically and so we can assume that nuclear power stations aren’t going to be built here any time soon. And even if one or two were to be built, that wouldn’t make much difference to our base-load needs, coal would still have to used for the bulk of our electricity so the problem would remain.

We do have an abundance of good quality coal and it is sited just where we need it – close to industry and major population centres, and furthermore, we have developed our industry and infrastructure around it. Abandoning coal as an energy source is just not going to happen, no matter what politicians and do-gooders say.

One of the “solutions” flogged around last year was carbon sequestration, which involves rerouting the CO2 that would go out the chimney by piping it underground instead. But geology would have to play an important part in this – carbon dioxide could leak to the surface through fissures somewhere else unless there is a uniform and solid rock formation enclosing the gas securely. The consequences of such leakage would be dire as CO2 in high concentrations and under pressure it would be lethal to people and animals. The problem here is that even if this technology was to work (doubtful), the geology under the land on which the coal stations are currently situated is not congruent with that type of solid, non-porous rock that is required to seal in the pressurized gas. That is because our power stations are embedded in a geology that contains coal and shale, both notoriously porous. The best thing that can be done is reduction in soot and particles in the air through mechanical and chemical scrubbing but CO2 will keep building up in the atmosphere in an increasing rate as the economy and the population grows.

Back to first principles. The holy grail in energy is to more efficiently and cleanly transform solar energy into power. Coal is a solar battery, i.e. solar energy stored in carbon (and which returns to the atmosphere as CO2).

While you can’t eliminate the carbon dioxide as you extract energy from coal, it is possible to recycle the CO2 in a useful way to produce more energy so that you minimise the amount of CO2 emitted per kilowatt of power.

The solution in the quickest timeframe is to grow algae biomass in ponds in proximity to power stations. Fast growing algae require lots of CO2. Some species of algae produce easily harvested oil that can be turned into diesel.

It was suggested as early as the 1950s that large-scale ponds growing algae could be used to transform solar energy into usable energy.

Coal power stations near population centres are ideal places to site such ponds because they emit plenty of CO2. Algal ponds can use wastewater and wastewater nutrients plus all that CO2 to grow the algal biomass. The CO2 and solar energy combine in photosynthesis. Photosynthetic organisms such as algae and photosynthetic bacteria in waste combine to make solar energy available in useable forms such as methanol from its algal biomass and diesel fuel from its oil for internal combustion engines.

(To make biodiesel you need methanol as a reagent because the oil straight from the plant is far too viscous to be used in an internal combustion chamber. Algal bloom biomass can provide both the methanol and the oil, although methanol can be also sourced from coal and natural gas.)

By siting auxillary diesel powered power generators alongside the coal steam turbine power generators it would be possible to thus use the algal biomass fuel in situ without having to truck it anywhere else. You would also have a source of methanol from either coal or the biomass. Again, the carbon dioxide emitted by the diesel power generator plants could again be recycled.

This system can be put into effect with current technology and without having to scrap our existing power generation infrastructure.

It has the added benefit of being comparatively simple way of reducing our reliance on non-renewable petroleum based fuels, it is intelligent and practical use of solar energy, and it uses wastewater around cities that otherwise pollutes the environment. Excess biofuel diesel generated at the ponds can of course be onsold for use in transport to power trucks, buses, trains and cars.

Finally, an article by Michael Briggs of the University of New Hampshire, physics department does some maths on how much land would be needed to produce algal diesel for all US transportation needs: the figure is 39,000 sq km.

By way of comparison, land made useless by dryland salinity in Australia is currently around 54,000 sq km and growing. (Algae would grow very well in salinity affected land.)

Of course, Australia’s annual diesel fuel usage is a lot less than that of the USA – our 8 billion litres vs 530 billion litres or 1.5%. Extrapolating this means we would consequently use a lot less land for all our transport diesel needs.

Currently, algal diesel would cost about twice that of petroleum based diesel. But factor in its CO2 ameliorating factors. Remove the removal of the fuel excise on biofuels, and we have a goer here. I imagine the cost would come down in time.


hc said...

The obvious economic question is to look at the cost of producing this type of energy were CO2 to be priced at $30 per tonne, $40 per tonne and so on. Then you need to know how much CO2 gets eaten by algae.

Steve said...

A couple of points:

1. I believe pebble bed reactors, which are being investigated in South Africa and China, would use gas turbines and not need to be next to the ocean. If so, siting them beside current coal plants would presumably be the thing to do. SA is still (slowly) gearing up to start building its prototype, but it seems to me a design well worth international support. (It has passive safety and is modular in design.)

2. An American company claiming some expertise in growing algae from CO2 exhaust says this:

"How large must an algae farm be to mitigate emissions from a typical power plant? **

Based on information in the US Energy Information Administration 2006 power plant database, for the approximately 500 power plants in the US that generate and sell electricity as their primary business and use coal as the primary power source, the average facility nameplate size is 655 megawatts. For this 'average' plant, when both the power plant and algae farm are in full operation, approximately 3400 hectares of algae growing area is required to consume 40% of CO2 emissions. To achieve a 5.2% reduction in CO2 emissions, which is comparable to the 2008-2012 Kyoto Protocol overall goal, 420 hectares of algae growing area would be required for the same 655 megawatt plant."

Here's the link:

3400 hectares is a big area, although it sounds less when you think of it as 34 km2, or a plot of land less than 6x6 km. (Hope my maths is right there.) I'm not sure how many existing power stations have that much spare land beside them. But I guess even if you have to set up the algae plant some distance away, you still would likely not be transporting it as far as geosequestration is going to require.

robert merkel said...

Algal biofuel is interesting, but it's a fair way from large-scale commercialization - particularly the more ambitious goal of growing enormous quantities of it in open pools of seawater.

See this post on Robert Rapier's blog.

Sir Henry casingbroke said...

I think it's a question of throwing some bucks at this. Merkel's links are very useful, one of which leads us to "biofixation of CO2 by microalgae" experiments. Such biofixation can be combined with production of biodiesel and thus defray some of the CO2 remedy costs, hence the costs of developing viable algal biodiesel technology should be seen in that context.

As regards development, compare US spending on the B29 bomber in WWII - $3 billion (x15 to get today's dollar value); atom bomb $2 bil. (x15) and B2 bomber, $30 billion; Iraq War $600 billion; Wall St bailout $700 billion.


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Tim Arthur said...

I have a keen interest in growing algae to be used as a fuel.
In a combustion process the algae will be burned to produce electricity. My point is that decomposition can be seen as a slower form of combustion. if one had to create these large 'algae bloom pools' one would catch the CO2 from the atmosphere yes you would. BUT this CO2 will just later be released decomposition or rather by me buying the dry biomass and burning it. At least I would get some energy from this. My company is going to be Ph, Phoenix Hydrogen. (from the ashes of the industrial civilization ises the hydrogen economy and the last/longest age of the human race in equilibrium with the earth). If we can just be smart about it the hydrogen transition is possible... I hope. If we start burning coal with these illusions of future CO2 capture... it will be the end of civilization as we know and love it.