Page 10 - Biofuels for a More Sustainable Future

Biofuels technologies: An overview of feedstocks, processes, and technologies 3

the biofuels market with a growing number of potential feedstocks to be
used for biofuels production.
First generation biofuels are produced from food crops: (a) biodiesel
extracted from oil plants/plant materials (in the chemical process of transes-
terification and esterification), and (b) ethanol extracted from sugar-
containing plants/plant materials and converted to fuel in the process of
fermentation. Second generation biofuels are produced from nonfood crops
(e.g., crop waste, green waste, wood, and energy crops planted specifically
for biofuels production). Third generation biofuels are based on improvements
in biomass production, with algae being the main feedstock representing this
group as of today. Fourth generation biofuels aim at providing more sustainable
production options by combining biofuels production with capturing and
storing CO 2 with the process of oxy-fuel combustion or by application
of genetic engineering or nanotechnology.
Due to the wide range of feedstock application and process development
the evaluation of different biofuels in terms of their sustainability will clearly
depend on the combination of those factors. Thus in the face of the multi-
tude of discussions in this field, a closer look at each of the biofuel types is
needed for a holistic and science-based evaluation.
Although this chapter does not aim at investigating sustainability of the
respective biofuels technologies, processes, and feedstocks per se, it will pro-
vide an overview for a better understanding of those issues to be addressed in
the following chapters in this book.

2 Biofuels technologies and feedstocks

Globally, the total biofuels production has increased over time, with an esti-
mated ethanol production at 160 billion liters (42.3 billion gallons) in 2019
and biodiesel production at 41 billion liters (11 billion gallons) (OECD,
2010)(Figs. 1.2 and 1.3). The feedstock composition in the global biofuels
production has varied and changed considerably over time as well. Accord-
ing to OECD (2010) projections, on the ethanol market, coarse grains
(including corn) have reached the peak in 2016, while ethanol production
from sugar cane will increase throughout 2019. An increasing trend was also
projected for biomass-based ethanol with 11 billion liters (2.9 billion gallons)
on the market in 2019. On the biodiesel market, vegetable oils constitute the
main feedstock that is expected to increase up to 30.7 billion liters (8.1 bil-
lion gallons) by 2019 (OECD, 2010). Also jatropha and other nonagricul-
tural feedstocks (animal fats) make a smaller share in the biodiesel