Large-scale Industrial Cultivation of Marine Microalgae (ICMM) Proposed as a Way to Provide Food and Fuel in a Post Fossil Fuel World

Green Car Congress recently posted a story about an article in the magazine Oceanographydetailing a proposal to obtain liquid hydrocarbon fuels and protein for animal feed from large-scale industrial cultivation of marine microalgae (ICMM). Analysis indicates that coproduction of food and fuel is needed in order for algal bio-fuels to achieve production costs comparable to liquid fossil fuels. The authors argue that cultivation of marine micro algae is potentially an order of magnitude more productive (presumably per square meter of ocean cultivated) compared to biomass production on land. They further argue that the fact that salt water is used rather than fresh water can help to manage the demand on this important resource. They particularly emphasize the comparison of algal proteins to soy protein, maintaining that not only is the production more efficient but that the algal protein is potentially of higher quality. If ICMM is as efficient as projected then it may be possible to reforest marginally productive agricultural land thus leading to the removal some amount of CO2 from the atmosphere as well as helping to preserve land based bio-diversity.

Presumably intensive cultivation and harvesting of select species of marine microalgae over a large area will have negative effects on ocean bio-diversity, although this issue is not discussed in the Oceanography article. The authors do discuss the nutrient requirements of ICMM as as a sustainability issue. To achieve high productivity marine microalgae require a higher ratio of phosphorus to nitrogen compared to land based agricultural systems. The authors freely admit that the current use of rock phosphates in agricultural production is not sustainable in the long term and that nutrient recycling will have to be pursued. However, they argue that ICMM is very compatible with nutrient recycling since nearly 100% of the phosphorous in waste stream can be taken up and used by the microalgal population. This fact is in contradistinction to soil based agriculture in which nearly 80% of applied phosphorous is quickly transformed into stable forms which plants cannot utilize. Land which has undergone years of regular phosphorus applications has lots of phosphorus in it in stable forms that plants cannot digest. We may eventually be able to develop more complex system of agricultural production which utilize this phosphorus is place, but today’s highly productive (per acre and per labor hour) corn and soy bean rotations are not such a system.

My own view of the ICMM proposal is that it makes sense only if it is part of a long term plan to reduce the total human impact on the biosphere which includes other important effects in addition to green house gas emissions. We need to produce food for human beings, and if ocean farming can help us to do so with lower total impact on the biosphere then such a proposal is worth evaluating. However, if ICMM is being proposed in the context of a world of 10 billion human beings who expect constantly increasing standards of consumption (including such things as getting a large percentage of our protein from high on the food chain and frequent rapid travel over long distances) as a normal part of the operation of the economic system, then farming the ocean may just be one more step on the road to ecological disaster.

Columbia Researchers Develop Low Cost Water Electrolyzers Utilizing Angle Titanium Mesh Electrodes

Several month’s ago Green Car Congress published a story about the development of water electrolyzer designs which do not require an ion exchange membrane separating the two half cells of the device. Since ion exchange membranes are quite expensive such designs have the potential to reduce the costs of hydrogen producing water electrolyzers. Furthermore, the researchers who published the paper in question argue that the elimination of the ion exchange membrane can relax the design constraints of MEA (Membrane Electrode Assembly) based electrolyzers and can potentially lead to design configurations which have other cost reductions in addition to the membrane manufacturing cost.

As the diagram below indicates this form of electrolyzer does indeed appear to have a very simple design. It would appear that the most costly components would be the titanium mesh electrodes impregnated with the appropriate catalysts.

Membrane Free Electrolyzer with Titanium Mesh Electrodes

The researchers used platinum nano-particles attached to the titanium mesh as catalysts. They were able to operate prototype electrolyzers in both acidic and alkaline solutions but obtained the highest electrolysis efficiency (72.5% based on the HHV of H2 at a current density of 100mA/cm2) for with alkaline electrolyte. This efficiency is comparable to that of current commercial alkaline electrolyzers such as those produced by Nel (formerly a division of Norsk Hydro). Alkaline electrolysis is economically attractive because it does not require the use of platinum group metals as catalysts.

In spite of the interesting initial results, one should not get too excited yet about this electrolyzer design entering the market place in the near future. Although the overall electrolytic efficiency of 72.5% is comparable to commercial alkaline electrolyzers an additional hydrogen loss of 10% occurs during the gas collection phase of the separation process reducing the effective efficiency to 65.3%. This loss of efficiency may not be a deal breaker since it is cost/kg that matters. Furthermore the electrolzyer in question is a non-optimized preliminary prototype and substantial optimization may be possible. The electrode current density of 100mA/cm2 is a factor of three lower than the current density of commercial alkaline electrolyzers although again similar comments to that just made about efficiency apply.

Another problem is that some amount (probably more than 1%) oxygen crosses over to the hydrogen side to the electrolysis cell and contaminates the hydrogen gas at the collection point. PEM fuel cells require less than 5 ppm V of oxygen content. Although further optimization may reduce the amount of crossover, orders of magnitude improvement seem unlikely. Nel claims that their electrolyzer systems produce H2 with less than 2ppm of O2 after purification. Whether or not a fraction of a percent O2 contamination represents a significant economic barrier to the production high purity H2 is not clear from any information that I have located so far.