Introduction

I. What are the 2nd generation biofuels?

The 2nd generation biofuels use the waste from plants instead of potential food plants as feedstocks. As shown in Table 5, the feedstocks for the 2nd generation  biofuels are based on ligno-cellulosic materials.

Source: From 1st- to 2nd- Generation Biofuel Technologies, An Overview of  Current industry and RD& D activities, IEA Bioenergy

II. Sources and Processes

(1) Two sources:

i.  residues from crop or wood

  • agricultural feedstocks: Bagasse are concentrated at the processing plants, whereas cereal straws need to be collected separately form the fields, which is more costly.
  • forest  feedstocks: wood processing industries can provide forest feedstocks on site.

ii.  purposefully grown perennial grass or trees, possibly grown on marginal lands with lower yields, eg: the Biofuels Feedstock Development Program at Oak Ridge National Laboratory identified switch grass as a leading candidate for potential bioenergy crops.

Source: From 1st- to 2nd- Generation Biofuel Technologies, An Overview of  Current industry and RD& D activities, IEA Bioenergy

(2) Two ways to convert:

The 2nd generation biofuels are produced either biochemically or thermo-chemically, but there is no clear commercial or technical advantage between the two conversion pathways.

i. It is difficult to break down cellulose into its constituent sugars, especially when there are only a few natural bacteria systems to help break down cellulose. Processing ligno-cellulosic based 2nd generation biofuels is thus more expensive than processing the 1st generation biofuels.

Source: From 1st- to 2nd- Generation Biofuel Technologies, An Overview of  Current industry and RD& D activities, IEA Bioenergy

ii. Thermo-chemical conversion does not depend on bacterial or enzymatic processes, so the cellulosic nature of the feedstocks is less a concern.

III. Prospect

Compared to the 1st generation biofuels, the 2nd generation biofuels are still an infant  industry:

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