If this is a major breakthrough in biofuels, it only highlights the tremendous challenges of replacing existing fossil fuel consumption, even the modest fraction (5-7%) represented by commercial aviation, from current primary productivity (plant growth).

From my comments on reddit's /r/RenewableEnergy, given that the article is horribly rambling and deficient on clear statements of facts and details: http://www.reddit.com/r/RenewableEnergy/comments/1whett/boei...

Synopsis:

⚫ The plant in question is Salicornia bigelovii, commonly known as "pickleweed". This grows in coastal saltwater and brackish wetlands, and is common on the west coast of the US. It grows in warm / temperate climates, doesn't appreciate freezing temperatures.

⚫ It's apparently being harvested for its relatively oil-rich seeds (30% oil fraction), with possible carbon sequestration.

⚫ The study looks at combining biofuel production with aquaculture of shrimp and/or talapia, effluent of which provides fertilizer for biofuel growth.

⚫ While it tolerates salt up to 60 ppt, maximum growth is at 20 ppt, falling to ~30% at 50 ppt.

⚫ Several conversion pathways are listed in the slide deck: fermentation, biochemical, and hybrid. All of these require significant additional energy inputs and/or conversion losses, meaning lower EROEI. Nothing I've seen gives a net EROEI for the process(es).

⚫ If I'm interpreting the unlabeled red arrow on page 19 of the slide deck[3] properly, oil yield in gallons/acre-yr is between 48 and 102 gallons (between soybean and sunflower productivity).

⚫ At 75 gal/acre-yr (mean of range) and 21.5 billion gallons of aviation fuel consumption in the US (2000 FAA estimate), 28.7 million acres would have to be under cultivation. That's about 450,000 mile2, or a region 670 miles on a side.

If you're having trouble visualizing that: start off in Shreveport, Louisiana. Drive west until you reach Almagordo, New Mexico. Turn north. Continue to Fort Colins, Colorado. Head east, until you find yourself in the charming burg of Osceola, Iowa (it's south of Des Moines, you may have heard of that). You're on the home stretch now: back to Shreveport. That's roughly what a 670 mile square looks like on the map. Oh, and you've just circled (or squared) the entire state of Kansas without ever entering it. And Oklahoma. That's driving through seven (large) states and surrounding two more.
And that's just for getting aviation fuel from biomass. Nothing for your car, or trucks, or heating oil, or electrical generation.

Here it is on Google Maps: http://goo.gl/maps/AuKxO

Another perspective is gained if you look at the opportunity cost of biofuel energy production.

Consider the competing use for that land. It's not agriculture (I'm buying into the assumption that this is non-arable desert land). But it is solar productivity (plus other environmental service, which I'll omit), and these are rivalrous uses: a solar photon intercepted by pickleweed isn't available to a solar PV cell, and vice versa. Which gives us an opportunity-cost calculation basis.

Let's accept your assumption that halophyte production gives us 100 gallons of oil per acre. That's 2.38 barrels of oil, or 4,047 kWh electric equivalent (not counting for conversion or utilization losses).

Commercially available solar PV nets about 15% efficiency. We'll assume 6 hours of productivity per day, and I'll even throw in a 15% utility area (that is, solar cells cover 85% of the available acreage. GNU units conversion tells us that in a year, that acre will provide 1130 MWh. Halophytes deliver, at best, 0.36% of this -- our opportunity cost is 99.64% over solar electric generation, in terms of net energy delivered. AT BEST.

Which isn't to say you'd never want to produce liquid fuels (they're really useful). But they're going to be tremendously expensive in terms of alternative energy production sacrificed.

One of the more influential pieces I've read on the prospects for biofuels is Jeffrey Dukes 2003 article "Burning Buried Sunshine". It lays out the basic facts: a representative years' fossil fuel consumption (1997) represents the primary productivity of 400 years of paleolithic plant matter. Because of conversion inefficiencies, those 400 years of growth actually occurred over some 5 million years or so. In present terms, it would represent 21% of all present net primary productivity (plant growth), of which humans already consume 14%. Conclusion: biofuels will only ever represent a very small fraction of present-day fossil fuel consumption.

http://globalecology.stanford.edu/DGE/Dukes/Dukes_ClimChange...