martes, 29 de enero de 2013

Algae in Paris Revisited

JANUARY 25, 2013

On occasion we publish letters on Green Building Elements. In this case, Kstor, writing from France, is critical of the energy promises made by Ennesys and Origin Oil in a Jan. 11 post about growing algae on buildings using wastewater to then generate energy. In spite of real optimism to generate renewable energy using a sustainable infrastructure, the criticism here is articulate and should be carefully considered by those intrigued by the promise of algae.

Photo: Algae floating from Shutterstock
Kstor writes:

The idea of growing algae on buildings using wastewater is not new. As a matter of fact, it originates from the French architect studio X-TU back in 2008 (and they have a patent on it), which will soon deliver the first prototypes of their biofacade concept in cooperation with a world-class French public laboratory on microalgae controlled cultures (see recent press releases and articles in French about it).

The problem here is more what Ennesys tries to achieve, when they promise to cover 80% of the building’s energy needs thanks to microalgae productivities of 150T/ha (see many other articles and their press releases).

Those figures are just not correct, as any microalgae specialist will immediately notice. These kinds of productivity are theorical, and can only be achieved in lab conditions with a 12 h direct flow of photons and constant temperature, pH, nutriments, carbon inputs, etc… In outdoor conditions, the maximum productivity in Paris would be around 30 T/ha with the most advanced intensified PBRs – which they do not have – as a scientific article clearly demonstrate: “Theoretical Investigation of Biomass Productivities Achievable in Solar Rectangular Photobioreactors for the Cyanobacterium Arthrospira platensis”.

It would be wise for Ennesys, and especially for their partners and investors, to “land on earth” and announce more realistic figures- unless they want to nourrish a greentech bubble…

Thanks for the letter. We invite Origin Oil and Ennesys to respond.

Thanks to Jean-Louis Kindler at Ennesys for this answer:

There is abundant scientific – both private and public – literature confirming the figures demonstrated a few decades ago by NREL / DOE in the US showing average yields in the range of 30 dry g/m2/day in outdoor facilities, not even using advanced intensified PBR’s (just type “microalgae yield per acre” in any search engine).

Your assertions are based on theories and furthermore on assumptions on our system’s configuration. Our system’s performance is being measured with our real size, outdoor demonstrator.

ORIGINAL ARTICLE Source of discussion

Origin Oil & Ennesys Use Paris Building Wastewater to Grow Algae for Energy
JANUARY 11, 2013

This post provides an interesting glimpse at a recently opened Paris building that generates energy from wastewater. The companies involved in this venture: Ennesys and Origin Oil.

Photo: Ennesys
OriginOil and its energy systems partner Ennesys unveiled this pilot project at the high-rise La Défense area in Paris, which has 37.7 million sq ft of office space, where they are fusing two essential functions of the smart buildings of the future: energy generation and wastewater clean-up. They have developed a solution that converts wastewater from commercial buildings into energy.

Here’s a short video

Jerry Schranz, part of the public relations team, informed me this system takes wastewater from the building (that is derived from bathroom waste water, kitchen water, etc.). This water is then used to grow algae, which is nourished by wastewater. The Algae Appliance invented by OriginOil scientists, processes the water and algae to produce methane, which is then used to power the building. Importantly, the flat panel bioreactors (where the algae grows) can be used on vertical surfaces, so skyscrapers are a huge area of opportunity for this type of energy production.

Algae Appliance invented by OriginOil
Photo: Ennesys
While the French government has mandated that new commercial buildings must produce more clean energy than they consume and purify or recycle water, OriginOil views these conditions as laying favorable ground for its technologies to be broadly adopted.

Congratulations to Ennesys and Riggs Eckelberry, Origin Oil’s CEO, on this demonstration of sustainable energy.

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