Thursday, January 22, 2009

Growing Algae on Marginal Land.

There is an inevitable compromise to be met between growing crops to make biofuel from and crops for food. The Earth has around 15 million km^2 of arable land available, which if used in its entirety for the purpose, could provide around 1.5 billion tonnes of rape-seed oil which is equivalent to 11 billion barrels of crude oil, still far shy of the 30 billion barrels of conventional oil currently consumed annually, and we still need to feed a rising global population, predicted by the WHO to transcend 9 billion by 2050.

The problem is that crop production is highly limited in its ability to harvest sunlight through photosynthesis, and as an alternative we might consider growing algae as a source of oil. Many strains of algae are more photosynthetically efficient than many land-based plants, and studies have demonstrated that up to 100 times the quantity of oil can be produced per hectare from algae, e.g. chlorella, than from say rape-seed, i.e. closer to 100 tonnes (700 barrels) as compared with around one tonne (7 barrels).

Algae offer the further advantage that they do not require quality arable land and they can be grown on saline water (e.g. in deserts) on on wastewaters. Thus there is the potential to use them to clean wastewaters in the process as an additional benefit. Algae can be cultivated in open-pond systems or in tubular bioreactors, the latter for example may be similar to the Agri-Drip tubing used for irrigation, and so can be laid out across any land, including land-fill sites or any kind of marginal land, such as is often classified as brown field.

It is the yields of algae that are their most attractive feature and it is estimated that 3,200 km^2 of land area could provide enough algal-oil to fuel the United Kingdom, replacing the equivalent of some 40 million tonnes of crude oil. For comparison, the area of Cornwall is 3,500 km^2, or just 1.4% of the U.K. mainland area. In the latter calculation, it is assumed that transport is converted to more efficient diesel engines which derive 50% more in terms of tank to wheels energy than petrol engines do. It has also been proposed that algae production might be used as part of a carbon-capture strategy, since algae grow more efficiently in an atmosphere containing around 15% CO2, and this is readily provided from the effluent of coal and gas fired power stations.

Thus algae may also contribute to meeting our carbon emissions targets. The non-lipid (oil) component of algae, i.e. carbohydrate and protein, may find additional use as high-value products for food production, or the carbohydrate can be digested and fermented as a source of bioethanol and other fuels. Thermal cracking of the algae per se can form a source of biochar, for carbon sequestration and soil-improvement, and syn-gas which may be burned directly as a fuel or converted via Fischer-Tropsch catalysis to synthetic low-emission diesel fuels.


Anonymous said...

Hullo Chris!

Quoting from

"...The fungus is reported to hold several properties that far exceed current biofuel sources. Current biofuel sources have to refined before being converted into biofuel, a painstaking and not always environmentally friendly process. The fungus has a clear advantage over these biofuels because it produces “myco-diesel”� directly from cellulose. The shortened production process means a reduction in costs and carbon dioxide released into the atmosphere.

Because current biofuels are derived mostly from food crops that are required to be grown and harvested on farmland, they have a substantial impact on food supply and prices. The fungus, however, can be grown in factories, eliminating any such impacts..."

Sustain_ably yours,

Professor Chris Rhodes said...

Hi George,

right, I'll look into this in more detail and try and do some sums to get a feel for the scale that might be met.

On first glance, it looks good though!



Unknown said...

Algae is indeed the best solution for a number of reasons; wastes remediation; cleaner air and water; rapid growth rates (doubling in as little as 2 hours); produces either fuel, feed or food; geographically diverse - depending on growth strategy; not sun limited – mixotrophic strategy.

Imagine a scenario where thousands of acres of algae are being grown for fuel and a natural disaster impacts the food and feed crops – well algae can come to the rescue because food and feed algae species can replace the fuel producers and start to kick out 600 to 800 pounds of food per day per acre. This would be dry weight and suitable for a population because of the high quality proteins, fats, and carbohydrates. Algae can seriously be considered an either/or food, feed, or fuel and that is the kind of flexibility civilization needs to develop.

A successful algae strategy does not require algae to be grown in high light (desert environments) to be successful. Simply utilize mixotrophic species of algae to reduce light dependence and algae can be grown anywhere successfully. The Canadians and Irish will be happy to tell you they have no problem growing algae. Take a look at NASA’s SeaWIFS project (see this link - and you soon discover the right conditions outside of the desert exist naturally and are very dependable.

Salt water is a great approach near oceans, however if saline is your choice inland then you need an endless supply of saline water so you can flush through your system continuously otherwise need lots of fresh water to keep you saline concentrations from going to high. An alternative strategy is to utilize grey and brown waters that need additional treatment (algae love these nutrients) prior to release (polishing, tertiary treatment) and do this in areas were there are lots of these wastes. Ideally your customers for the algae products and bi-products will be close as well so you’re not shipping half a country away.

We suggest areas that are rich in industry, livestock production, and human footprints because of the synergies associated with adopting a waste to energy while cleaning the environment. Ross Youngs,

Professor Chris Rhodes said...


I am thinking that algae does offer much, both micro and macro (i.e. seaweed), in terms of providing biomass for food and fuel.

I accept your reasoning and I have been looking to work with a local university on how to grow the stuff!



Professor Chris Rhodes said...

Hi George,

right, that fungus feeds on sugar very well but more slowly and with lower yield on cellulose. So, part of the limitation is the availability of cellulose and the competition of it with enzymatic conversion to sugars/fermentation to ethanol.

I think it does look (I can't seem to find much in the way of quoted hydrocarbon yields from cellulose) promising but again, it is at the very early limits of research, so it can't help us get over the "gap" in oil supply...



Anonymous said...

People have been trying, fantacising, calculating, scheming and dreaming of the possibilities of producing fuel from algae for decades. Unfortunately, the economics have never really worked. Even when oil was over $100/bbl it didn't work. Why? A few reasons. One of the main ones being, it is very expensive to process the algae, more specifically it is costly to separate the water, which the algae grow in, from the algae itself. Even such cheap methods as spreading the algae in the sun for evaporation of the water (this is being done by companies in California) is not viable, because you somehow have to scoop the algae out of the water or make it settle out of the water before drying. An interesting alternative that I have seen is biofuel producers feed the algae to small crustaceans, which are then easily separated from the water and they are processed, however the usable oil fraction is less than 10%. These two methods are probably the cheapest, but not commercially viable. Until they can overcome the issue of separating algae from habitat, algae will continue to be a fantasy.

Professor Chris Rhodes said...

Would you take a look at the later posting (Thursday, January 29, 2009
"Fuel Algae Growing a Success.").

Apparently the University of Nevada are growing a particular (but unspecified) strain of algae year-round in open-ponds. This does sound promising but as I allude the energy and financial costs of turning it into biofuel by transesterification must be met on top of this.

As you say, the algae would need to be dried to a large xtent in the first place.

Growing algae does gowever offer the potential of a source of biomass grown on non-arable (i.e. marginal ) land and thus produced it might be processed by other means, e.g. thermal gasification in processes that use water as a chemical reactant to effectively "steam reform" the material.

I note Ross's comments about fast growth etc. There is the issue of providing nutrients which might be done in part from wastewaters, runoff waters etc. and so provide a means for cleaning them.

I think as part of a long-term integrated system, algae may have much to offer but probably not in time or on a large enough scale to get us through the oil/gap/peak era that is imminent, but it's probably a better or quicker bet than hydrogen, say.

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