Carbon Capture and Storage: the “Fourth Generation” Biofuels

Developments in biofuel production are evolving so fast that there is recent talk about  “fourth generation biofuels”. The Biopact website (URL above) provides key features of the waves of the so called “nth-generation biofuels”. The four generations of biofuels can be distinguished from each other by: (1) the feedstock used, and (2) the processing technology adopted.

"First generation biofuels" use food-based feedstocks (like corn, sugar cane or soybean) as raw material, and utilize processing technologies like fermentation (for ethanol) and trans-esterification (for biodiesel). “Second generation biofuels” are produced from non-food feedstocks, like lignocellulosic plant biomass (switchgrass, poplar) and non-edible oilseeds (Jatropha) through the conventional method mentioned above and by themochemical routes (for the production of liquid “synthetic biofuels”). “Third generation biofuels” uses similar production methods on specifically designed or “tailored” bioenergy crops (often by molecular biology techniques) to improve biomass-to-biofuel conversions. An example is the development of “low-lignin” trees, which reduce pre-treatment costs and improve ethanol production, or corn with embedded cellulase enzymes.

 “Fourth generation biofuels”, are simply a step further from the third generation biofuels. The keywords are “carbon capture and storage (CCS)”, both at the level of the feedstock and/or the processing technology. The feedstock is tailored not only to improve the processing efficiency, but it is also designed to capture more carbon dioxide, as the crop grows in cultivation. The processing methods (mainly thermochemical) are also coupled to “carbon capture and storage” technologies which funnels off the carbon dioxide generated into geological formations (geological storage, for example, in exhausted oil fields) or through mineral storage (as carbonates). In this way, fourth generation biofuels are thought to contribute better to reducing GHG (greenhouse gas) emissions, by being more carbon neutral or even carbon negative compared to the other generation biofuels. Fourth generation biofuels epitomize the concept of “Bionergy with Carbon Storage (BECS)”

Related links on carbon capture and storage: http://pangea.stanford.edu/~mhesse/news/CARBON%20CAPTURE%20How%20to%20breathe%20easier.pdf
http://en.wikipedia.org/wiki/Carbon_capture