by David Schwartz
s an environmental engineering professor at California Polytechnic State University, in San Luis Obispo, CA, Dr. Tryg Lundquist researches how wastewater can make algae biofuel and how algae biofuel can be the impetus for better, low-cost, wastewater treatment. In addition to his research projects, Tryg teaches water chemistry, wastewater treatment, and animal waste treatment. “A glamour job?” I ask him.
“Yes, for environmental engineers recycling waste is a glamorous job, especially these days,” he says. “We design the facilities ‘at the end of the pipe’ that bring resources back into use—water, nutrients, energy, materials—as much as practical.”
Tryg got his Ph.D. from UC Berkeley in environmental engineering and worked for the renowned algae wastewater expert, Professor William Oswald. It was Oswald who built the world’s first large scale high-rate (as in raceway) ponds for wastewater treatment and pioneered algae biofuel research. This was at the Richmond Field Station, near Berkeley, starting in the 1950s. “In his New York Times obituary, they called Oswald the ‘Michael Jordan of Algae’,” Dr. Lundquist points out. “He was more of a basefall fan, but that will do.”
Tryg worked with Oswald for many years in research and engineering on the use of algae to treat municipal wastewater as well as to remove selenium and nitrate from the toxic agricultural drainage waters that had made Kesterson Reservoir infamous. After Oswald passed away in 2005, by which time Berkeley had closed the Algae Lab at Richmond, Tryg took up the offer to move to Cal Poly in San Luis Obispo to continue the work on algae biofuels and wastewater treatment. There he has built a program, the Algae Technologies Group, with seven faculty members, from environmental engineering, microbiology, marine biology, chemistry, food and animal feed, all cooperating in the area of algae biofuel and wastewater treatment.
Dr. Lundquist has recently also served on several committees advising the U.S. Department of Energy on algae biofuels, including for the development of the “Technology Roadmap” (published in final form last year) and most recently as lead reviewer of the Office of Biomass algae program (presentations now available on the web).
“The biggest project at the moment is the NAABB consortium (National Alliance for Advanced Biofuels and Bio-products), which is receiving almost $50 million from DOE over three years, with large cost-share from the 30 organizations involved,” he says. “They are just finishing up their first year, and they are working to develop technologies and the methods along the whole production chain to meet the economic goals of algae biofuels production while achieving a positive energy balance. An approximately equal amount of DOE funding is going to other R&D consortia and projects.”
We spoke with Dr. Lundquist recently about the interface between wastewater treatment and algae.
What is involved in treating wastewater with algae?
Algae have treated wastewaters since time immemorial. Wastewater flows into ponds, lagoons, or streams, where algae grow and produce oxygen, which supports the bacteria that break down the organics in the wastewater. Over the last century, better controlled systems for treatment of wastewaters were developed, some using engineered ponds, also called oxidation ponds. These are at least five feet deep and mixed weakly by wind, which makes them inefficient. Large land areas are needed and only modest amounts of algal biomass are produced. Still they are the method of choice for thousands of communities around the U.S., and many more worldwide.
Raceway or “high rate” ponds are an alternative technology that is shallower and mechanically mixed. Raceway ponds are basically solar collectors that accelerate algae production and wastewater treatment. Early versions were developed by Bill Oswald back in the fifties. In the 1970s, paddle wheel mixing was introduced at the Richmond Field Station, and this is the design that is now used around the world to produce algae for nutritional products and also being considered for algae biofuels production. Thus this field of algae biofuel really came out of wastewater treatment with algae.
Now we are moving beyond the original objective of just treating organic wastes. We want to recover nutrients like nitrogen and phosphorus from the wastewaters. Conventional mechanical wastewater treatment processes, such as activated sludge, also can remove nutrients. For nitrogen, it’s done through the process of nitrification followed by denitrification. But this destroys most of the fixed nitrogen while consuming more electricity, and at high cost. Algae wastewater treatment will be more sustainable than conventional treatment because it uses less electricity, can produce biofuels as a co-product, and recovers nutrients.
Of course, being a solar energy system, it will be limited to warm sunny regions, at least for nutrient removal. For organic matter removal only, ponds are used even in northern Canada. But due to the long winter, algae biofuel production in Canada is not the best bet.
What are the increasing priorities for the people who operate wastewater facilities?
Over the past few years, keynote speakers at the Water Environment Federation annual conference have emphasized that in the future we will need to not just remove nutrients from wastewater, but actually recover them. Decreasing electricity consumption at wastewater plants is another theme, to cut down on the greenhouse gas footprint. On the nutrients side, the specter of “peak phosphorus” has been brought up and also the waste of using fossil energy (natural gas) to produce ammonia fertilizer which then requires more fossil energy (electricity) to convert back to nitrogen gas. What we need to do is to recycle as much of that as possible. Algae are one way to do this.
What technologies are you working on in these areas at Cal Poly?
At Cal Poly, we are studying raceway wastewater ponds both with and without CO2 addition. With CO2 addition, algae cultures are able to remove both nitrogen and phosphorus simultaneously to less than typical discharge limits. Thus, we hope to achieve the highest levels of biological treatment using no net electricity while producing biofuel feedstocks and recovering nutrients.
The technologies that we are developing are ways to grow algae that can assimilate nitrogen and phosphorus in as small a footprint as possible and then recover that biomass so it can be reused for crop production. That’s been the objective in this field for decades, since work in the 1970s at UC Richmond Field Station, and with quite a few others working on it since. Biofuels provide another opportunity to use that biomass, recover oil from it, and still recover and reuse the nitrogen and phosphorus.
What are some of the opportunities for algae cultivators at wastewater treatment facilities in the U.S.?
In terms of the biofuel industry, a lot of companies and academics are starting to take on wastewater treatment as a goal, because the wastewater treatment infrastructure is degrading in the U.S. Many treatment plants were built using federal funds during the seventies and eighties, but those funds are not available anymore. Also discharge standards are higher now, so overall, a lot of new treatment infrastructure needs to be constructed.
So, I would say to an algae entrepreneur: if you can find a location that has a suitable climate and flat land and a wastewater facility, there might be a good synergy there. But, we still have some work to do, in particular in managing the algae in our ponds. We know we can make certain algae dominate in high rate wastewater ponds, and that these can be made to produce the right kind of oils for biodiesel. But we need to work out the details to consistently produce high-oil algae. For now, we produce renewable fuel in the form of biogas by digesting the algae.
What algal strains seem to work well in wastewater treatment environments?
Mainly the green algae such as Micractinium, Chlorella, Pediastrum, Actinastrum and several others. In terms of lipid production, that’s pretty variable. We’re getting up to 30 percent lipid content, though we are not trying yet to maximize lipid production. Right now we project that we would be able to achieve between 1,200 and 1,500 gallons per acre per year of biodiesel, perhaps more in the longer-term. However, lipid productivity has not been our main emphasis at this point. Our immediate goal is to make wastewater treatment affordable and effective. But we are also keenly interested in improving oil productivity, and that is of increasing importance in our research. For example, I would like to do some more research on strain selection.
How do you harvest the algae from the wastewater?
Traditional wastewater pond systems often have too much algae discharged with the effluent—often due to overloading as cities have grown. Removing the algae with chemical coagulants is quite expensive. Even modern dissolved air flotation, centrifugation, and the like use a lot of power. This is the same challenge we have in biofuel algae. Low-cost, low-energy intensity harvesting is still work in progress, both in our laboratory and most of the biofuels research groups.
The cheapest, most energy efficient thing you could imagine for harvesting algae would be to have them spontaneously settle to the bottom of a harvesting tank, and then scoop them up. Our goal is to make the algae coming out of a high rate pond settle in a clarifier, because we know it’s the only method that’s likely going to be both low energy input and affordable.
This “bioflocculation” harvesting was also first investigated about 30 years ago at the Richmond Field Station, headed up by John Benemann and Bill Oswald. But it was never made reliable enough to implement at large-scale. Over the past four years of pretty intensive work at Cal Poly, I believe we have bioflocculation worked out pretty well. We are entering an optimization phase with almost 20 small raceway ponds under a California Energy Commission grant. The algae engineering consulting firm, MicroBio Engineering, Inc. that I started with John Benemann is a partner with Cal Poly on this project. We hope to be demonstrating low cost harvesting at large-scale fairly soon.
OK, but what do we get when you have settled algae? Maybe three or four percent solids, a hundred times better than the pond water. Of course, it’s still a very soupy biomass that needs to be dewatered. But that’s an age-old activity of the wastewater industry, so there are lots of ways to dewater biomass or sludge at this concentration. One low energy method is solar drying, but that has its own set of problems in terms of requiring more land and degradation of the biomass. So dewatering, and/or oil extraction from wet biomass, is still an area that needs work.
At this point have you extracted oil?
Only for the analytical process. We haven’t done any large-scale extractions. We’re evaluating those oils in terms of carbon chain lengths, and they’re predominantly C-16 and C-18, so that’s about right for biodiesel.
What other applications do you see for algae cultivated in wastewater?
Many groups are moving into high value co-products to help support the fuel production in the near-term. Wastewater treatment is a high value service. But with biomass grown on municipal wastewater, we cannot produce an animal feed co-product. When we are talking about animal wastewaters, that is a different story. Of course, there are worries about pathogens, which could be addressed with pasteurization. Oswald found long ago that he could pelletize algae with things like barley and, in the process of pelletizing, that heated up the biomass enough that pasteurization could be achieved without additional steps. They also found that the algae were equivalent to soy meal in terms of digestability for a variety of animals.
We have animal wastes and a feed mill here at Cal Poly, so that’s something else that we would like to move into—doing some production and feeding trials with this kind of unusual production capability we have.
What are the nutrients present in wastewater and what nutrients are still needed for algae growth?
Wastewater is a great fertilizer, and algae need the same fertilizers as other plants, just more of it. Municipal wastewaters have more than enough nutrients, N, P, K, etc., to grow several crops of algae. The missing factor is CO2. Basically the source of all these nutrients is us, eating and excreting food nutrients, so all the essential elements and growth factors are present in the waste, but carbon is limited, because we exhale much of it. So for algae treatment, we add CO2 to our cultures. With CO2 we’re able to produce, during summer, up to about 30 grams of algae biomass per square meter per day.
What are the steps a municipal wastewater treatment facility might best take to incorporate algal treatment?
We get a lot of calls from wastewater treatment plants that are interested in this, and they’ve got a lot of very good motivations. Often the city council wants to make the city more green and sustainable. The wastewater plants are already doing a good job of that, but they want to do more in terms of cutting down on their energy use by using algae and solar energy to treat the wastewater and then also producing biofuel.
For a lot of those folks we have to say, “Sorry. We can’t help you,” because they don’t have enough flat land in their neighborhood, or they’re in a cold climate. As a rule of thumb, you’d want to be at a latitude south of San Francisco in order to consider nutrient removal with algae treatment. That corresponds with the areas for biofuel production as well. The further south you get, the less area you are going to need, due to the higher annual sunshine and warmer temperatures. It would probably not be worth building the infrastructure in a climate with only six or seven months a year of growing season. In some cases, hybrid mechanical systems may be practical for places with mild winters.
Any further advice for an algae cultivator who wants to approach a wastewater treatment operation for co-location and mutual benefit?
Something that can be a problem is enthusiastic algae developers promising more than they can deliver. The wastewater utility folks are knowledgeable and very practical, and used to dealing with technology vendors. They’ll figure it out pretty quickly if you are not up front with them about the capabilities of your technology.