Sustainability: Humanity Perspective - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 782

establish. If the forest is to be managed for biomass production, determine the
optimum recycle time, biomass yield, and production rate for
(a) seedlings are very small, i.e. assuming X 0 z

0;
(b) seedlings amount to 2 kg-C/m 2 above ground standing biomass;
(c) seedlings amount to 4 kg-C/m 2 above ground standing biomass.
15.11. One way of managing a forest is to leave the shoots and small trees untouched, saving
time to clear the lot and planting for new seedlings. If this is achievable, the biomass
left over unharvested would be the same as the initial biomass standing. The lag time
can be shortened as well because of this practice. The growth curve is shown in
Fig. P15.10 . Assume that the lag time is 3 years of without growth after the immediate
last harvest, determine the optimum recycle time, biomass yield, and production rate
for
(a) X 0 ¼ 1 kg-C/m 2 ;

2 kg-C/m 2 ;

(b) X 0 ¼

4 kg-C/m 2 .
Also determine the average standing biomass by assuming exponential growth each
case. Comparing with direct graphical e numerical estimation, what is the error of
assuming an exponential growth at harvest?
15.12. Fig. P15.12 shows one of the best set of data from a cut-back study on short-rotation
willow crop grown in Canastota, NY (courtesy of Dr Timothy Volk, SUNY ESF). The
willow is cut to the ground and the growth rate on each harvest and then it regrows
from the stamp. There is no lag time during cut-backs. Determine the optimum recycle
time, biomass yield, and production rate. How does these numbers compare with
forest biomass?

(c) X 0 ¼