Page 16 - Biofuels for a More Sustainable Future

Biofuels technologies: An overview of feedstocks, processes, and technologies 9

Table 1.1 Requirements for new standards under RFS2
Lifecycle
GHG
Type Volume by 2022 threshold Comment
Biodiesel 1 billion gal (3.79 50% For 2012 and beyond a
billion I)
Cellulosic 16 billion gal (60.57 60% Subject to annual
biofuel billion I) assessments
Advanced 21 billion gal (79.49 50% Anything but corn starch,
biofuel billion I) minimum of 4 billion gal
additional
Renewable 36 billion gal 20% b Minimum of 15 billion gal
biofuel (136.27 billion I) additional
a
Could be increased from 2013 onward.
b
Only applies to fuel from new facilities. ”Grandfathered” facilities are those (domestic and foreign) that
commenced construction before 31 December 2007 and ethanol facilities that commenced construction
prior to 31 December 2009 and usenatural gas and/or biomass for process heat.
Data from US Environmental Protection Agency (EPA), 2010. National Renewable Fuel Standard
Program—Overview. Office of Transportation and Air Quality, US EPA, Washington, DC, April 14;
Ziolkowska, J., Meyers, W.H., Meyer, S., Binfield, J., 2010. Targets and mandates: lessons learned from
EU and US biofuel policy mechanisms. AgBioForum 13(4), 398–412.

2.2.2 Algae biofuels (third generation biofuels)
The third generation of biofuels aims at improving the production of bio-
mass to make it a more viable (and sustainable) feedstock. Since the begin-
nings of this technology, the third generation biofuels have relied on algae as
the main feedstock (grown either naturally or artificially). Many studies con-
firmed that the algae feedstock can be competitive with other biomass
sources ( Jones and Mayfield, 2012; Ziolkowska and Simon, 2014; Laurens
et al., 2017; Adeniyi et al., 2018), thus making it, in many cases, more pro-
spective for company investments than cellulosic ethanol. The advantages of
algae as a feedstock relate to:
(a) Negative (carbon neutral) environmental footprint as by growing algae
2g of CO 2 are consumed for every g of generated biomass (Pienkos and
Darzins, 2009). At the same time, one ton of CO 2 can be converted into
60–70gal of algae-based ethanol (Hon-Nami, 2006; Hirayama
et al., 1998).
(b) Possibly no competition for fresh water as algae can grow in waste/
saline water environment.
(c) No competition for fertile land (i.e., no direct food-fuel trade-off ) as
algae is grown in closed photobioreactors or open ponds (water envi-
ronments) which can be located on any plot of land not suitable for