The world emits about 35 billion tons of C02 every year. Of this, close to 10 billion tons (about 30%) of all CO2 emissions come from just power plants.
This is both bad news and good news.
Bad news because the world’s power consumption is only going to increase with time, which implies even more CO2 emissions from these power plants.
Good news because 30% of CO2 emissions come from fairly concentrated sources. There are only 5000 utility power plants and about 50,000 smaller, captive power plants – and a majority of CO2 emissions from power plants come from the utility scale ones. This means we have to deal with only about 5000 sources to confront about 25% of the total emissions!
So, this is the lay of the road. Which is why there has been a lot of talk recently about how the CO2 from power plants could be captured and sequestered.
A number of solutions have been explored both for capture and for storage/sequestration. However, none of the methods being explored are both sustainable and technically feasible. Some, like underground storage of CO2, appear technically feasible, but there are concerns about its sustainability/effects on geology. Others, such as storing it as a mineral carbonate appear sustainable, but technical feasibility is still a question mark.
This is where an interesting solution in the form of algae-based CO2 sequestration makes its appearance. I have personally done a good amount of research in this area, and have had the fortune to do some work for Reliance in India and Lafarge in France. This is an exciting area indeed, though there are significant challenges in this avenue too. The story goes like this: You grow algae right next to a large power plant (you could grow it even in wastewater); the algae, during its growth captures a whole lot of CO2. Use the algae thus grown for making biofuels, biofertilizers whatever. True, if used as a biofuel, all the CO2 is not exactly sequestered in an absolute sense, but it can be considered sequestered in a relative sense.
The sustainability of algae based CO2 capture is fairly well established – it indeed is perhaps the most sustainable of all the avenues we know right now. The technical feasibility is not equally clear, but there have been some significant efforts worldwide in this regard.
For those who are interested to know further might want to consider reading a report by the biofuels section of EAI – Oilgae Comprehensive Guide for Algae-based CO2 Capture.