Although we had a very good meeting, there are no simple answers. Again, it comes down to where you live, the low and high temps, and the sources of carbon and hydrogen. I will pass along my take on the discussion.
First of all, the correct algae must be selected to minimize the energy demand; with heat being a primary concern where I live. In principle one could select indigenous strains since they will clearly do well in the climate, but these may not be high producers of oil. Also, the cost of collection, drying, and processing, can vary from strain to strain. Likewise, if the ambient temps are too low for high producing strains, either the cost of heating can kill the energy and dollar profits, or growth can be reduced to unacceptable levels.
So it is not just a question of the growth rate and yield for a given strain, one must consider these as a function of light and heat. Also, just to complicate matters, there are issues of disease resistance and resistance to invasive species. Presently there is someone here in Oregon who has a grant to study all of this, but the research is in progress and the professor was not at liberty to pass out names. There are strains that have been used in programs like the Aquatic Species Program, and if the ambient conditions for an application are naturally compatible to those in Roswell, New Mexico, for example, then one can probably get the information needed and start with those strains. In some cases it may be necessary to license the strain for commercial [or private] use.
Next, there is the issue of carbon. In industrial applications the carbon is provided as a waste product. For farming, it is likely that a carbon source is needed. Production rates will probably be too low if the ambient CO2 is the only source of carbon. It may be possible to run a biodiesel powered generator or heating system, and then bubble the exhaust through into the algae stream as both a source of heat and carbon, but this only makes sense in principle; calculations are needed to be sure for any particular application. Ideally, one would supplement the ambient CO2 levels to precisely the levels needed for maximum growth rates. But the net hydrocarbon gain would still be limited to the ambient CO2 absorbed. The increased growth rate due to temperature may make it worth the effort since it is most generally a threshold problem for growth, and not a conservation of energy problem, however, if we start getting into maximum growth rates, then I would imagine that conservation of energy may play a more significant role.
A key concept in the bio-fuels world is that of local energy sources. There are three things that I have in abundance on the property: Wood, leaves, and grasses. I have acres of it! It might make sense to use an aerobic composting system to provide, carbon, hydrogen, and heat. It could be an elegant solution and he wanted me to contact anther group to investigate this concept, but again, this is only in the abstract. Much homework is needed to determine if this is practical.
There was enthusiasm for the yields cited. Apparently 10,000 to 15,000 gallons per acre-year is a reasonable expectation given the proper selection of algae
Mutation is a concern. A strain might mutate and produce less oil if stressed too little. The idea of yogurt-like eternal production from one start may not hold true.
Disease and invasive species are a real concern as is containment of non-indigenous strains. I suspect that the latter may become an issue if we start seeing algae farms popping up everywhere with each testing various strains.
Although not considered a common problem, it is possible that molds toxic to humans could inadvertently be grown.
There was little enthusiasm for greenhouse technologies as it seems unlikely that the operating costs will be low enough. Some stuff out there seems more like a scam than a genuine effort. Covered ponds are thought to be a better choice.
Cold press extraction is probably good enough. I have read that both hot press and chemical extraction are used, but it may depend on the strain of choice. As mentioned, some strains are easier to process than others.
The line between private use and commercial production is drawn at about a million gallons a year. The reason for this is the cost of ASTM testing, which can be several thousand dollars per batch. As it stands now, at least here in Oregon, one can bypass ASTM testing if all users are part of a Co-op.
When looking at the economics of this, it is important to realize that there are three products: Biodiesel, high quality glycerin [I don’t really know what high quality means here. I assume that it refers to purity], and mash. The glycerin can be sold, and in many [or all?] cases the mash can be used as a high quality, prion-free feed for most livestock. Also, it is possible to further extract ethanol and hydrogen from the mash. Questions of yield and processing costs drive the option of continued extraction, and I haven’t heard of this actually being done yet.
Bio-plastics should be another huge market for the plant oil producers. .
I’ll probably think of a few more things and post again later.
