Biofuel Feedstocks

The Bioenergy Research Group at the University of Hawaii at Manoa is presently investigating 2nd generation lignocellulosic feedstocks; particularly tropical C4 grasses such as Napier grass, Napier grass-pearl millet crosses, and energy cane. In contrast to 1st generation starch and sugar crops, 2nd generation feedstocks do not compete directly with the food industry, and can be grown on marginal (i.e., non-prime) agricultural land. Examples of 1st and 2nd generation feedstocks are given below.


Fig. 1 Examples of 1st generation feedstocks


2nd generation feedstocks can be agricultural residues such as leftover fibers following sugarcane juicing and corn harvesting (i.e., bagasse and stover, respectively) or forest residues. In addition, 2nd generation feedstocks refer to dedicated energy crops which are typically grown on marginal agricultural land for the primary production of biofuel/bioenergy. These crops include but are not limited to switchgrass, sorghum, miscanthus, energycane, etc.




Fig. 2 Examples of 2nd generation feedstocks


Tropical C4 grasses are known to grow exceptionally well in Hawaii (and other (sub)tropical regions), and have been reported to attain impressive yields of 42 dry tons/acre*yr (Osgood et. al, 1996). The climate in the (sub)tropics allows for year-round feedstock production, and subsequently continuous biofuel and biobased product generation. Specifically, an approach known as green processing can be implemented as an upstream preprocessing strategy to fractionate crude crop samples into solid (dewatered) fibers and nutrient-rich juice for biofuel and bioproduct generation, respectively. Napier grass (also known as merker grass, elephant grass, and banagrass) has been of particular interest to the Bioenergy Research Lab based on its high moisture content and biomass yields per unit area. Moreover, the juice from Napier grass appears to have implications in the production of fungal protein co-products of high market value.




Fig. 3 Napier grass grown at the Waimanalo Experiment Station, HI