Ivan Seeking said:
http://green.yahoo.com/blog/ecogeek/1023/venice-to-use-algae-for-50-of-its-electricity.html
On the subject of biofuels used specifically for electricity generation, Science just published a paper showing that, given the two options of electric vehicles and internal combustion vehicles, the bioelectricity option produces 81% more average transportation kilometers than does cellulosic ethanol burned in the internal combustion engine.
http://www.sciencemag.org/cgi/content/abstract/sci;324/5930/1055?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=biofuels&searchid=1&FIRSTINDEX=0&sortspec=date&resourcetype=HWCIT", JE Cambell, DB Lobell, CB Field. Vol 324, no 5930, pp 1055-1057.
Abstract said:
The quantity of land available to grow biofuel crops without affecting food prices or greenhouse gas (GHG) emissions from land conversion is limited. Therefore, bioenergy should maximize land-use efficiency when addressing transportation and climate change goals. Biomass could power either internal combustion or electric vehicles, but the relative land-use efficiency of these two energy pathways is not well quantified. Here, we show that bioelectricity outperforms ethanol across a range of feedstocks, conversion technologies, and vehicle classes. Bioelectricity produces an average of 81% more transportation kilometers and 108% more emissions offsets per unit area of cropland than does cellulosic ethanol. These results suggest that alternative bioenergy pathways have large differences in how efficiently they use the available land to achieve transportation and climate goals.
http://www.sciencemag.org/cgi/reprint/sci;324/5930/1019.pdf"
Campbell et al consider corn an switchgrass feedstocks, but they did not address algae. If the algae processing into ethanol is unchanged for bioelectricity, then we can look up the known numbers. My question: Are there any particular improvements to be gained in the fuel cycle efficiency for algae if the fuel is boiler grade only? Certainly there would be savings in ethanol distribution, but that also goes for corn and grass.
Here are the basic steps Campbell et al use for Corn/Switchgrass, Table S1 supporting material:
<br />
\begin{array}{l|rrrr}<br />
\mbox{} & \mbox{Corn}& \mbox{Switchgrass}\\<br />
\hline<br />
\mbox{--Harvest}\\<br />
\mbox{Harvest Mass (kg } ha^{-1}{ y^{-1})}& 8,746& 13,450\\<br />
\mbox{Harvest Energy Content (MJ } ha^{-1}{ y^{-1})} &157,427 &242,101 \\<br />
\hline<br />
\mbox{--Ethanol}\\<br />
\mbox{Gross Ethanol Production (MJ } ha^{-1}{ y^{-1})}& 73,424 &108,855\\<br />
\mbox{Gross Gasoline Equivalent (l } ha^{-1}{ y^{-1})} &2,335 &3,462\\<br />
\hline<br />
\mbox{--Electricity}\\<br />
\mbox{Gross Electricity Production (MJ } ha^{-1}{ y^{-1})} &52,140 &80,184\\<br />
\mbox{Gross Electricity Production (kWh } ha^{-1}{ y^{-1})} &14,483 &22,273\\<br />
\end{array}<br />
Edit: By comparison, generally I find the best case claim for algae ethanol production is ~5000 gallons ethanol per acre-year, or 46000 liters ethanol per ha-yr, or 30,000 liters gasoline equivalent per ha-yr. Does the energy output stand to improve if the end product is electricity? Does the cost improve?