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New Life Cycle Analysis Finds that Current Technology for Producing Algal Biodiesel Can Jeopardize the Overall Energetic Balance; Oil Extraction Technique Is Key

Lardon2
Total energetic debt of 1 MJ of biodiesel and its distribution within the production chain. According to the study, only the wet extraction on low-N grown algae has a positive balance. Credit: ACS. Click to enlarge.

Biodiesel production from microalgae, while looked upon as an environmentally advantageous source of fuel, suffers from several drawbacks at the current level of technology that can jeopardize the overall energetic balance, according to a life cycle analysis (LCA) by a team of researchers in France. An open-access paper on their work was published online 27 July in the ACS journal Environmental Science and Technology.

Despite strong interest and investment in development, there is as yet no industrial-scale production of biodiesel from microalgae, the researchers noted, and hence no thorough LCA of the production chain from culture to fuel is currently available. The key objective of the study was not to offer a LCA of current microalgal biodiesel technology, the authors wrote, but to identify the obstacles and limitations which should receive specific research efforts to make this process environmentally sustainable.

For the study, the team extrapolated laboratory observations combined with known processes developed for first generation biofuel to design what they termed a realistic virtual industrial facility. They analyzed two different culture conditions (nominal fertilizing or nitrogen starvation) as well as two different extraction options (dry or wet extraction). For the algae strain, they used Chlorella vulgaris. The best scenario was compared to first generation biodiesel and oil diesel.

The team performed a cumulative energy analysis to analyze the total energetic debt of 1 MJ of biodiesel and its distribution within the production chain (see chart above). Cumulative Energy Demand (CED) includes energy used at the facility but also energy required for the production of the required inputs (fertilizers) and construction of infrastructure buildings.

When taking into account all the energetic debt of the process chain, it appears that only the wet extraction on low-N grown algae has a positive balance. Other scenarios lead to negative energetic balance despite a 100% energy extraction from the oilcake. It can also be noticed that the application of a nitrogen stress improves the CED by 60% whereas CED is only increased by 25% with the wet extraction. Obviously low-N culture has lower fertilizer requirements but also implies a lower drying and extraction effort while the wet extraction needs a larger initial production due to its lower extraction yield.

...Energetic balance of biodiesel production from microalgae shows that it can be rapidly jeopardized ending up with a counter-productive production chain. Whereas production of fuel differs slightly from the simple production of energy (production of a storable product useable in automotive engine requires specific properties), it is mandatory to have at least positive energetic balance.

—Lardon et al.

Their analysis showed that any improvement of oil extraction technique would have a direct impact on the sustainability production— 90% of the process energy consumption is dedicated to lipid extraction (70% when considering the wet extraction). They concluded that specific research must investigate new processes in lipid recovering with limited drying of the biomass. They also found that in comparison to conventional energetic crops, high photosynthetic yields of microalgae significantly reduce land and pesticide use—but not fertilizer needs.

They suggested several improvements which could contribute to reduce most of the impacts. of large-scale production:

  • The choice of microalgal species maintaining high lipid and low protein contents with sustained growth rates (e.g., low-N culture, strain selection, or modification);
  • The setup of an energetically efficient extraction method; and
  • The recovery of energy and nutrients contained in the oilcake.

More generally, LCA appears as a relevant tool to evaluate new technologies for energy production. Even when dealing with young and immature technologies, this tool identifies the technological bottlenecks and therefore supports the ecodesign of an efficient and sustainable production chain.

—Lardon et al.

Resources

  • Laurent Lardon, Arnaud Hlias, Bruno Sialve, Jean-Philippe Steyer and Olivier Bernard (2009) Life-Cycle Assessment of Biodiesel Production from Microalgae. Environ. Sci. Technol., Article ASAP doi: 10.1021/es900705j

Comments

Henry Gibson

There is an English, at least, story about an man named Rumplestiltskin who could spin straw into gold. This is a good analogy to the modern version of the alchemists attemps to turn lead into gold namely bio-fuels. This is actually turning gold into lead.

There were people who about 1900 developed a method to turn grains into gold and developed very high priced breakfast cerials where a few penneys' worth of grain was turned into a box of material that sold for several dollars.

Algal oil is probably suitable for human or animal food.

The food versus fuel debate should continue well after the time that nuclear energy is used to create massive amounts of hydrogen which is combined with CO2 to make glycerin which is one of the simplest foods digestible to humans, but Quorn organisms might be discovered to use it to make proteins. Brewers yeasts make vitamins out of simple foods and some protein as well. Organisms can combine hydrogen with CO2 to make ethanol to be consumed diluted so that people can relax. ..HG..

HarveyD

The search for alternative liquid fuel sources will go on as long as we have hundreds of millions of ICE machines to feed at the rate of 100 milion/barrels per day and more soon.

Edible grain (such as corn) ethanol and most other agro-based fuels are not sustainable and constitute and interim solution at best.

Sooner or latter (the soonest the better) most transportation vehicles, all HVACs, industrial and commercial energy consumming processes etc will be electrified and liquid fuel consumption will be reduced to a fraction of what we use today.

In the longer term, cleaner essential liquid fuel will be produced with sun energy and other natural elements.

Producing and distributiing all the clean electric energy required is a manageable challenge in the short, medium and long terms. Effective technologies already exist and new, more efficient one will be developed.

Normal resistance to change, oil and farming lobbies, politicians' vested interests etc are more of a problem to solve.

Lucas

100% of our land devoted to Corn would not meet our automotive energy needs and millions would starve.

4% of waste land devoted to the production of Algae based fuel production would meet ALL of our energy needs.

Why are we standing around debating?

sulleny

I'm with Lucas. Studies like this serve one purpose - tank the progress of the algae growers. It's clearly the best near-term liquid fuel and if the friggin balance is off to begin with - oh well. Either we solve the not so intimidating problems of algae - or stick with jet fuel for the next hundred years. The biology does most of the work - the engineering is mostly done. GMO work will tweak growth rates, output,quality etc.

Let's go. This planet is getting REALLY boring.

GreenPlease

^
Actually, EROEI is the single most important consideration when doing anything that has to do with energy. Right now, the EROEI varies between 20:1-100:1 depending on the field. Dropping down to an EROEI of less than 2 means that you are going to need a lot more land than said 4% if you are going to fuel it internally.

If EROEI turns out to be negative you'll only move us further down the path of total resource depletion.

I think Henry makes a good point: we should consider algae for its food benefits. The EROEI on using algae for food is much better than for fuel (high protein algae are easier to grow) and as long as it is greater than 1 it would be substantially better than our current system. The high per acre yields would also make siting locally very easy, further reducing energy necessary to transport the food.

Scott

I'm with Lucas and Sulleny with the idea of using this as a signal that more work is needed to turn this into something that is energy positive, and it will be done.

Algae will have food and fuel benefits combined. It is also naive to think that the enegy pool for future transport will be just electric. ICEs will dominate but will become increasingly greener as sustainable biofuels get off the ground, hybridisation. Electric fleets will be complementary, not competitive - this is how we should address this.

Arne

lucas:
4% of waste land devoted to the production of Algae based fuel production would meet ALL of our energy needs.

Says who? The promotional leaflets of algae companies?

This study shows that - as things now stand - to produce the fuel from algae you would need that 100% of farmland anyway.

sulleny:
Studies like this serve one purpose - tank the progress of the algae growers.

I think you and lucas should read better. The researchers' message was not: "forget about it, it's never going to work", but: "We're not there yet. More has to be done to make this work"

Good decisions are based on good information. It is important to report any finding, even if it's bad news. You two are killing the messengers.

HarveyD

Scott:

How many horse carriages and steam locomotives have you seen in operation in the last 12 months?

ICE vehicles will go the same way in the next 2 or 3 decades. Users fees + increased gas taxes could accellerate the transition.

Wireless or contactless quick recharges could be the solution for those who cannot push a power plug in the right place.

Getting recharged while moving will also come sooner or latter. That could expand e-range to infinity. The size of the vehicle would not matter that much. City e-buses (and city e-taxis) could use that technology within 3 or 4 years.

Electric airplanes is a greater challenge but on-board lightweight power generators + ultra efficient e-storage units could solve the problem for prop-type aircraft within 20 to 30 years.

Basically, every moving unit can be electrified and operate more efficiently for extended periods without repairs.

It is already done for most time keeping devices and so will it be for vehicles.

ai_vin

One idea for electric airplanes is to beam the energy up from a network of ground stations.
http://www.friendsofcrc.ca/Projects/SHARP/sharp.html

I personally would like to see the return of airships to our skies; with lightweight PV cell covering their tops they could be solar powered.
http://domesticfuel.com/2009/07/28/solar-powered-airship-to-fly-from-new-york-to-paris/

ai_vin

Another idea for airplanes might be biogas/biomethane.
"Russian aircraft manufacturer Tupolev is currently running a development program to produce LNG and hydrogen powered aircraft. The program has been running since the mid-1970s, and seeks to develop LNG and hydrogen variants of the Tu-204 and Tu-334 passenger aircraft, and also the Tu-330 cargo aircraft. It claims that at current market prices, an LNG-powered aircraft would cost 5,000 roubles (~ $218/ £112) less to operate per ton, roughly equivalent to 60%, with considerable reductions to carbon monoxide, hydrocarbon and nitrogen oxide emissions.

The advantages of liquid methane as a jet engine fuel are that it has more specific energy than the standard kerosene mixes and that its low temperature can help cool the air which the engine compresses for greater volumetric efficiency, in effect replacing an intercooler. Alternatively, it can be used to lower the temperature of the exhaust."

Rick

If I understand biomethane correctly, nobody squeezes the methane out of the bacteria -- the microbes excrete the gas and we gather it from the airspace above the biomass. Could some of the tweaking to some algae species include diverting the oil from storage within the cell, to excretion? Do any algae already have excretory organelles that could be joined up with the oil-producing mechanisms? If not, how radical a project would it be to insert such an organelle into algae anatomy?
If such a project worked... could oil oozing out inside a closed-pipe photobioreactor, or an open pond, be efficiently skimmed off or sucked out -- and would this do away with the most expensive and laborious parts of the product- harvesting process?

Would treating the individual alga cells more like long-term "dairy cows" instead of one-cycle "beef cows" introduce some opportunities for greater efficiency at the production stage as well? Would it change the research community's ideas about what would constitute a "well-formed alga"?

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