Conversation with Mario Tredici and Jan Wurm (February 2015)


In spring 2013, Arup drew attention of the world of green building technology through the realization of the BIQ House in Hamburg, a pilot project in which, for the first time, microalgal photobioreactors were used as architectural components with the goal to capture and transform the energy coming from the sun into some other kind of energy valuable for the building.

In February 2015, I had the chance to have a conversation withJan Wurm and Martin Pauli, the engineers at Arup that have led the consortium comprising SSC and COLT International for the design and the monitoring of the SolarLeaf Façade System of the BIQ House in Hamburg, and with Mario Tredici, microbiologist at the University of Florence with a strong background in microalgae characterisation and cultivation.

At that time, after two years of running, on the one hand Arup has collected scientific data as a basis to further develop the technology, on the other hand, other consortium worldwide had started to explore this dynamically growing field of research.

Today, after another three years, no other microalgae based architectures appeared in the panorama. A number of internationally funded research project demonstrated that producing energy out of microalgae is very difficult today because of the very low reachable EROI values. The application of this technology is quite difficult. Nevertheless, I still believe there is a lot of potential, specially thinking about algae to produce healthy food within the architectural environment. That’s why I think that today is a good moment to publish some excerpts of this three years old interview. No matter what one thinks, the BIQ is a milestone in the integration of biotech in architecture.

CG: Mario, your group at the Florence University Dipartimento di Scienze delle Produzioni Agroalimentari e dell’Ambiente is leader in the scientific study of microalgae. To make a long story short: micro algae can be cultivated in open systems (open ponds) or in closed systems (photobioreactors). In both systems, there is a water based medium in which the cells grow through photosynthesis. The algae solution needs to be agitated all the time to avoid deposits and oxygen accumulation. When the solution is saturated with grown algae, the algae needs to be harvested and new cultures can restart, while the harvested biomass can be treated to get to different markets. What is the state of the art of microalgal technology both in research and in industry?

MT: I started to grow algae in ponds in the 1980s in Calabria (southern Italy). But very soon I’ve been attracted by the idea of closed reactors. My first realization was an alveola panel, a multirib policarbonate double sheet, massively produced by the industry. We took a sheet of that material, we put it firstly horizontal, then vertical, with the algal solution mixed by a pump. Here’s a simple and efficient photobioreactor at a reduced cost. At that time I was working for the Consiglio Nazionale delle Ricerche (CNR). The CNR sent an alveola panel reactor to a fair in Moscow in 1990.The model was very new and didn’t have a great success. But Otto Pulz (for a long time head of microalgal biotech at IGV GmbH, one of the major algae research centers in Europe) saw the reactor and produced a series of them. He was more successful than us because he could make several pilots and start to produce them in a more industrial way compared to us. The lesson was clear, having good idea is not enough, you have to develop and bring them to the market.

Then I could verify that the idea of moving the culture with the pumps wasn’t that efficient and was stressing the algal cell, so we started to use bubbling (blow pressurized air into the solution) to agitate the culture. This is what we are doing today, we blow air in our reactors. What we are focusing on now is to further and further reduce the cost of the bioreactors. Our latest system, the Green Wall Panel, is made by polyethylene flexible film to create algae growing chambers sustained vertically by a metal structure. The cost is relatively low: from our economical analysis, the cost of producing biomass with that system in one hectare is close to 7 €/kg. this system has been provided to a number of companies including ENI, ENEL, and a big company in Saudi Arabia.

Talking about numbers: the production of microalgae biomass in the world is less than 20,000 tons / year. It’s a tiny volume compared to agricultural production where we talk of billions of tons. It’s a niche technology. 90-95% of this biomass is produced in open ponds. Probably less than 1,000 tons is produced in closed bioreactors. Bioreatcors are mainly of tubular kind. Why is the production of algae so small? Because it’s very expensive. The cheapest products are made in China and in India in open ponds and the cost of production is around 4-5 $/kg.

CG: Jan, the BIQ House in Hamburg is a pilot project in which for the first time in the history of architecture algal bio-tech is applied to the built environment. The photobioreactor panels filled with their green algal solution are at the same time a strong architectural feature and a smart facade innovative biotechnology. How does the system work?

JW: The 200 m² of installed bioreactors generate biomass and solar thermal heat, while they absorb CO2 emissions. The BIQ looks at the integration of bioreactor technology on a building level, and the important first step to show its technical feasibility. The next step should be to optimize the system and build- up an infrastructure to demonstrate the feasibility on a commercial level. We have completed the installation and started the operation of the system in March 2013, so almost two years ago, and are well in the optimization stage.

The original concept that was developed with the architects SPLITTERWERK was more demanding, more inspiring in terms of the architectural solution. There should have been a complete external active skin integrating photobioreactors and photovoltaic panels and fully enclosing the internal building volume. During the negotiations with the investor and developer the scheme was altered to account for the risk of exposing such a novel technology. As a result the bioreactor panels were fitted as a secondary louver system – similar to an external shading device. Although this had strong architectural implications, from a strategic point of view it was the only way forward to safeguard the pilot project and to investigate the technical feasibility of the system.

The solar thermal heat that is harvested from the reactors is employed to provide hot water and heat for the apartments. In terms of biomass we harvest up to 6kg of microalgae per day, just about a bucket full, that we use for research purposes. This amount is not enough commercial purposes. This could change if we can establish an infrastructure to process the harvest, but for this we would need higher quantities. In principle the commercial use of certain strings of microalgae is very promising, as they are rich of vitamins, amino aids and lipids that are valuable both for the food and the pharmaceutical industry. Microalgae could play an essential role in the urban food chain, as it potentially could also be processed to fish food to feed aquaponic cultures. There is still a big gap between the harvest of the BIQ and an industrial scale. But we want to use the BIQ project to explore different aspects of the value chain by experimenting with different strains and cooperate with potential processors.

CG: Mario, micro-algal biomass can be used to process energy: algal biofuel or ethanol can be easily produced out of harvested algae. The problem is the production cost. As any other alternative energy sources, also algal biofuel will have a chance when the price will be comparable to fossil based fuel. The feeling is that without public funding, algal biofuel production is not economically viable today. How far are we from commercial microalgal biofuels?

MT: Concerning biofuels, the main problem is that cultivating algae is very expensive. It’s impossible to compete with fossil fuel, but even with sugar or palm oil. 90% of what you find in the web concerning algae oil doesn’t have technical/scientific support and hasn’t been proved. Craig Venter, the famous entrepreneur and science man in the U.S. known for having cloned the human genome, was given by Exxon a few hundreds million dollars to make oil from algae. After two years of work he concluded that it’s not possible. With the algae that are around in nature, we cannot have cheap algae oil to compete with fossil fuel. Personally, I completely agree with him. It doesn’t mean that one day someone won’t be able to get biomass at very low cost. But going below 0.5 $/kg means reducing the cost to 10% of the actual present cost. Today it’s not possible, in 20 years maybe.

Let’s now talk of growing algae for other products. Feed for example. That’s possible because algae are very rich in proteins (50-60%). You can have very nice feed, food or specialty chemicals like pigments, antioxidants, carbohydrates, cosmetics, etc. There is a market in these cases. Other good examples are aquaculture and cosmetics. In these sectors, biomass coming from some Diatoms or Nannochloropsiscan reach a value of 150-200 €/kg. The production plant of Microalghe-Camporosso (Imperia), half hectare of surface, uses our Green Wall Panels photobioreactors to produce inocula and open ponds for producing 5 different species of algae that reach interesting prices for cosmetic industries mainly in Germany and France.

CG: Jan, Mario, I understand that the algal biomass is valuable for a number of markets. But, another interesting thing is that during the growing process, through their photosynthetic activity, algae transform water and carbon dioxide into sugar and oxygen. Algae also need nutrients like nitrates that can be easily found in gray-waters. In other words, algae, while growing, create a positive secondary effect of natural filtering air and water. When applied to the built environment, this secondary effect appears to offer a very promising potential to reduce ambient pollution. We could imagine living architectures that breathe and clean air and water. Is it a real potential?

JW: Talking about water purification, as you mentioned briefly, on a building it would make sense to use the gray-water as a source of nutrition for the algae. Doing so would be a way to clean the water and reduce the effort of central infrastructures for waste water plants. To add the functionality of water purification on top of the generation of heat and biomass is interesting to us. If we have an anaerobic digester, we could also use the organic waste of the toilet together with the biomass to produce bio-gas. In the BIQ a similar concept will be investigated by our partner SSC through a separate research project.

MT: There are several issues here. One is that you have to match the amount of polluted water that you are producing in the building with the capacity of the algae. And the second and most important is that the biomass will be low value. It’s not only because it’s growing on waste. But it’s because this water might have heavy metals or other pollutants. You won’t be able to use it for food, feed, pharmaceutical, cosmetics, etc. It can be only about energy, and it’s wet biomass. Getting energy is not easy unless, as you said, you go to anaerobic digester. It’s a possibility. Now I think it’s more important to concentrate on high quality biomass to sell at relatively high price. I think we need other advantages for the people that leave in the building. One important thing could be air cleaning, taking advantage from the photosynthetic production of O2, and fixation of CO2 and other gaseous contaminants. It would be nice to find ways to clean the air inside the building.

CG: Jan, Martin, the BIQ House is the first architecture that grows living algal cells. As any living organism, algae need maintenance, such as monitoring the solution and harvesting regularly the biomass. I would add the necessity to process the harvested biomass to turn it into products that can be marketed. In other terms, it’s a system that requires input (water, CO2, light, nutrients, energy and labor), and produces output (biomass, oxygen, heat). What is the balance both in economics and energy terms between the input and the output?

JW: The monitoring is ongoing and we can already say that its efficiency is depending on many interwoven parameters and the control algorithms will need to be fine tuned. We believe that it is possible to offset the energy used to run the system by the heat that is generated by the bioreactors and used to heat the interior space and the hot water similar to more conventional solar thermal collectors. The heat management system that goes along with it is complex and there is still room for optimization., which still needs to be heat exchangers, heat pumps, heat storage, etc. The important message is that existing components known from heat management of energy efficient and passive house buildings can be used and adapted.

There is something important about the economy of scale to make this technology work commercially. On the scale of the BIQ building, with 15 apartments and 200 m2 of facade, there is no commercial or economic sense to it. Scaling up would help for reducing the costs, not only the construction costs, but also the costs related to the maintenance of the system. While I believe that we can turn the integrated system in a complex but smooth running mechanism, I also see the risk of technical faults that will remain and thus it needs to be designed for redundancy which drives the cost up. Highly technical building systems can fail. In the long run I believe the integration and utilization of bio-chemical processes in our built environment will have to lead to simple and robust solutions / something we would like to look into with a follow-up project.

MP: From the monitoring point of view the system is working generally well. Since two years we are conducting a scientific monitoring. The aim is to identify correlations between the user acceptance and the technical and energy performance. In case some components, for instance the pumps are operating too frequently, we are using too much energy and the system is potentially running inefficiently. We also have photovoltaic cells on the rooftop which contribute to the creation of renewable energy. It’s been two years now that the system is operating. It’s impressive how it’s working and it’s natural that there are things that we need to adjust. There have been problems, there very likely will be challenges, but we can solve them.

CG: Let’s now think at the billions of square meters of built facades within the cities. It’s a lot of surface that is useless for agriculture right now. Thinking at the potentials of the biomass and the other benefits (like carbon fixation, oxygen production, water cleaning, thermal gain, etc.) having algae bioreactors integrated within the facades would be a great opportunity for having more environment friendly cities.

MT: Land will be the main problem in the next lets say 3-4 decades. We are almost running out of good soil. The food production must double in some decades. And there is no soil. It’s a big problem! So what you say really makes sense to me. But why instead of growing algae, don’t we grow vegetables? We could grow salad. But actually there are some reasons that make algae an interesting crop. For example: protein productivity from algae, that would be 10 times higher than from traditional cultures. Not just biomass, but proteins. We can imagine to produce with algae 10 tons of proteins/hectare of vertical surface. Soya, which is one of the most efficient crops for proteins is producing under the best conditions 1 ton/hectare. The idea could take the form of a bio-refinery concept. We can get proteins, and we can get from the algae also carbohydrates, oil, pigments, etc.


Mario Tredici is full professor of Microbiology at the Faculty of Agriculture of the University of Florence (Italy) and founder of the spin-off Fotosintetica e Microbiologica Srl.

Jan Wurm and Martin Pauli, from ARUP Berlin, are responsible for system design ams maintenance of the BIQ House in Berlin.

Cesare Griffa is an architect that, through his WaterLilly series, explores possible applications of microalgal bio technology in architecture.

The BIQ House was designed by SPLITTERWERK architects, the bioreactive façade-system “SolarLeaf” was designed and developed by Arup Germany together with Colt International and SSC and funded by ZukunftBau.

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