Algae liquefaction: what is is, and why it might be the key to affordable, drop-in algae biofuels

February 22, 2015 |

algae-PNNLOf all the pathways to drop-in algae biofuels, few have remained as promising as hydrothermal algae liquefaction.

It may not roll off the tongue, but it might be the most important technology to come along in years. Here’s why.

This past week, news has arrived from Colorado that Merrick & Company was engaged by Genifuel Corporation to provide the design and commissioning of a hydrothermal processing pilot system for Reliance Industries.

The technology originated at the Pacific Northwest National Laboratory — and the Federal Laboratory Consortium just awarded PNNL the 2015 Excellence in Technology Transfer for its work on the project. Unlike traditional extraction methods, which separate lipids out of algae to make biodiesel, PNNL’s process converts whole algae into biocrude, fuel gas, and usable byproducts. This doubles the yield of biofuel from algae and cuts the cost of production by 86 percent, according to the NAABB algae consortium which wrapped up its work recently.

Merrick was responsible for the design of the facility, which uses heat, pressure, and catalysts to chemically and physically convert wet feedstocks into natural gas or oil that can then be further refined into aviation fuel, gasoline, and diesel. The system is skid mounted with electrical, instrumentation, and controls components that are compatible with the standards of India, where it will be expanded to a larger scale after testing is finalized on the current system.

A big part of cutting algae drop-in biofuels’ cost from $24 to $7.50 per gallon

NAABB in its close-out report referenced identifying systems to reduce the cost of algae biofuels from $24.00 per gallon to $7.50 — and this PNNL/Genifuel project was right at the heart of it.

NAABB reported “the development and demonstration of a combined HTL-CHG process that uses algae concentrated from the pond.”

That’s “hydrothermal liquefaction” and “catalytic hydrothermal gasification”, to those who prefer their acronyms decoded.

NAABB explains: “Wet algal biomass (15 -20% solids) is fed directly to the HTL system, which produces bio-oil and an effluent water stream that phase separates without the need of solvent extraction. Th e bio-oil stream is readily upgraded via hydrotreating to hydrocarbon fuel. Th e hydrotreated oil can then be fractionated into jet, diesel, and naphtha fractions. The effl  water stream is then processed with CHG to recover additional fuel in the form of a methane gas/carbon dioxide mixture, and the water stream.”

The result? A biocrude ready for upgrade to hydrocarbon fuels. The consortium reported that this process resulted in the most oil, the best economics and the best lifecycle assessment on greenhouse gas emissions.

As NAABB noted: “advantages of the HTL-CHG processing pathway include: (1) capture of 85% of the carbon in algae as fuel-grade components (bio-oil that can be upgraded to diesel, jet, gasoline, and syngas); (2) production of a bio-oil that can be readily converted to meet diesel and Jet A fuel standards; (3) effective wastewater treatment to reduce the organic content and provide methane for process energy; (4) recycle of water and nutrients (nitrogen, phosphorous, and other trace minerals for algal cultivation; and (5) significant decrease in capital and operating costs compared to processes requiring high lipid-yielding algal biomass and extraction of the lipid from the biomass.

What’s next in the drive towards $3.00 per gallon algae drop-in biofuels?

There are two paths still at this stage thought to be in the running in the nearer-term.

There’s Algenol’s system, for which the company is continuing to reference a target cost of $1.27 per gallon for its ethanol product. Upgrading to diesel and jet fuel would presumably more than double that cost. Reliance is very much behind that system as well.

But then there’s this Genifuel pathway. But far more work is needed, because the NAABB reported that the consortium reached the $7.50 mark, even including the astonishing gains associated with this technological pathway.

There are two phases — the drive towards $5.00 per gallon fuel — which the DOE is targeting for 2019, and then the second phase to get to $3.00 per gallon.

Phase 1, from $7.50 to $3.00 per gallon

The DOE is targeting two R&D efforts in the first phase, that relate to whole algae liquefaction — in this case, making algae production more CO2 efficient and protecting the crop from predators.

Crop protection. DOE writes: “Novel, safe, and effective strategies need to be developed to control culture contamination events that result in diminished target feedstock yield(s). Additionally, integrated pest management systems need to be developed to control pathogens and herbivores. Examples of research that would contribute to crop protection include but are not limited to: Rapid detection systems to enable preventative treatments to ponds; Biological systems and/or engineering to increase resilience of culture; Novel chemical treatment protocols that are scalable, environmentally acceptable, and economically feasible.”

CO2 utilization. DOE writes: “Algae utilize a diversity of carbon concentrating mechanisms to maintain adequate carbon stores for photosynthesis. Target improvements may be measured through enhanced photosynthetic efficiency, increased carbon efficiency, and improved rates of transfer, either into carbon reservoir, or uptake by algae from the reservoir. Improvements must result in improved productivity that could lead to higher feedstock yields.

Phase 2, from $5 to $3 per gallon

There are four activities.

CO2 cost

In their 2012 NREL survey, Ryan Davis and Andy Aden projected CO2 costs at between $36 and $70 per ton — that includes the merchant costs plus any conditioning. Free CO2 – well, it isn’t exactly free, because in the free or “cheap” scenario, CO2 conditioning will have to be done by the project owner. Using Davis and Aden’s sensitivity projection, it could represent up to $0.66 per gallon of triglyceride oil, in terms of cost savings for the project.

Liner cost for ponds.

Overall, liners are expected to add as much as $2 per gallon of triglyceride oils, according to Sun, Davis et al. As Michael Bowowitzka and Navid Moheimani observed in their book “Algae for Biofuels and Energy”: The installed price for pond liners is expected to make overall economics considerably more challenging. To ultimately achieve economic viability, proper site location and system design will be important to optimize such that a need for plastic pond liners is greatly reduced or eliminated, thus mitigating this cost bottleneck. 

Ash content

As NAABB principal investigator José Olivares remarked to the Digest: “Often our highest ash content was associated with blown in and settled dust/sand, residual salt from the saline waters, etc. It is a real world issue. Even Sapphire provided a similar observation and challenge.” It’s an epic challenge — as NAABB noted, organic matter in their R&D ranged between 40-76 percent, post harvest. That’s a huge upside opportunity — as clearly, it costs to harvest and process all that dust-affected or dust-adjacent algae.

What may emerge are technologies that, if effect, aggregate dust in a manner not entirely dissimilar to aggregating algae. Dust flocculates — after all, that’s what comets, planets and stars are starting out with: cosmic dust. It may not be a case of keeping it out of the pond, but rather rendering it harmless to the pond by getting dust to the bottom of the water as quickly as possible.  Bottom line: Get the dust to the bottom of the pond, and out of the light.

Water cost and usage

Though water doesn’t cost much per gallon, it adds up. Recycling is your friend, evaporation your enemy, Yet, Davis and Aden report that it is not so much the water but what’s in the water that counts. We mentioned suspended dust — but even more powerful is the value of suspended nutrients in the water or in the algae biomass. Think NPK as any farmer does — nitrogen, phosphorus and potassium.  In their 2012 review, Davis and Aden found that 100% nutrient recycle could impact the cost of algae triglyceride oils by more than $2 per gallon, compared to 0% recycle.

The Bottom line

It’s big news that the Genifuel project is moving from pilot, and making the first steps of the transition towards commercial scale. Lots of other challenges need to be addressed, however, if we are to see algae biofuels reach their potential and not simply have this technology make nutraceuticals a whole lot more affordable.

Not that anyone would mind a 50% price-cut in omega-3 nutritional supplements. But the world needs more than a better source of fish oils.

More on the PNNL / Genifuel system, here.

 

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