Friday, December 24, 2010

Real Challenges in Algae-based CO2 Capture


Real Challenges in Algae-based CO2 Capture

I thought it would be good to revisit the topic of CO2 capture (and partial sequestration) by algae, where the idea is to use the CO2 from concentrated CO2 emitting sources, especially power plants, to grow algae and use the biomass to produce biofuels. The concept is enticing in that it solves two problems in one go – reduces the net amount of CO2 released into the atmosphere while providing us with a renewable source of biofuel.

But, as will not be surprising, there are significant challenges this concept faces, and it can be safely said that it will take at least five years before anyone can convincingly come up with a biological/engineering model that can accomplish this sustainably. All the same, it is a domain that has exceptional potential. With this in mind, the Oilgae team does a continuous review of this field; I thought I’d share some of our latest thoughts about algae-based CO2 capture with you.

You will appreciate this is a relatively vast topic to be covered in a single newsletter; so I will limit myself to revisiting the real challenges that we see in algae-based CO2 capture.

I would request who would like more details on any of the challenges listed below to send me a note so I could answer specific questions (to the extent possible, that is).


It is difficult, if not impossible, to capture 100% of CO2 that is pumped into the ponds
This could be an important challenge, given that the total cost of CO2 capture, cooling, transportation and ultimate transfer to the ponds is one of the largest cost contributors for algae biofuel production. A literature review suggests that it might be difficult to achieve capture %s that are higher than 75%.


Energy costs for constructing sumps
The % of absorption of CO2 increases significantly if sumps are constructed in a customized manner within the ponds. However, construction of these pumps could add a few % points to the total cost.


Storage of CO2 during night
Algae consume CO2 during the daytime and they do not consume any CO2 during night when they in fact respire and let out CO2. Thus, any system needs to ensure that there is a storage of CO2 piped from the power plant. This could add to costs.


Overall economic viability
Ultimately, the challenge for algae-based CO2 might not be technical or biological in nature, it is more likely to be economic. The costs of algae-based CO2 capture are still quite unclear.


Industrial incentives and perception
Where the power plants have no penalties for not sequestering the CO2 that they generate, there is little incentive for these plants to invest in uncertain technologies such as algae-based CCS. And at a time when implementing even a pilot-scale algae-based CCS effort could cost in millions, a lack of clear incentive or penalties will be a severe inhibitor to research efforts.

While Copenhagen was a disaster, I am not sure how much better Cancun has performed in the context of getting national mandates on CO2 capture / sequestration.


Water source near the power plants
It requires about a million liters of water to make 1 T of dry algae biomass. In order for a large power plant to have algae cultivation that sequesters millions of T of CO2 per year, it is imperative to have access to large quantities of water., which the power plants might not have access to.

Narasimhan Santhanam

1 comment:

iVision4U said...

OK, I might respond with another comment as I have not got past your first point. You refer to the capture of CO2 as an actual capture and transport to Algae ponds. From what I understand, the absorption, scrubbing, cooling and compressing of CO2 is an extremely expensive process. For an algae farmer it appears to be cheaper (although not environmentally sound) to use a propane CO2 emitter as a source for CO2 feedstock. If the goal is to sequester CO2 using algae, the only economical solution is to grow the algae on-sight which is a massive challenge to incorporate it into an existing industrial infrastructure. Please respond if you are aware of a cost effective capture and transport method.