Irradiation is an option for biomass size reduction. Following a gross procedure to reduce field supplies into at least chip size, one can employ high-energy radiation such as gamma radiation and/or microwave radiation to accomplish fine particle reduction (Wasikiewicz et al., 2005). Not only does a high-energy radiation treatment produce fine particles, but it can also favorably alter the physical and chemical properties of the biomass, depending on dosage (Bouchard et al.,

2006) . Irradiation has been shown to decrease the DP (Bouchard et al., 2006) and make microstructural changes to the irradiated cellulose pulp (Dubey et al.,

2004) . These changes include an increase in the carbonyl contents and an overall improvement in the vulnera­bility of the cellulose crystalline regions to reagents (Stepanik et al., 1998). This in turn leads to a higher rate of enzymatic hydrolysis. Furthermore, irradiation leads to a significant increase in sugar yield (Yang et al., 2008).

An electron beam cuts biopolymers such as cellulose, hemicellulose and lignin into smaller chains. Analysis by powder X-ray diffractometer and Fourier transform infrared spectroscopy confirm the electron beam treat­ments reduce the degree of crystallinity and improve the sugar yields from enzymatic hydrolysis from treated samples (Karthika et al., 2012).

Electron beam irradiation is preferred over irradia­tion using a radioisotope. First of all, electron beam is safer. Turn off the power and the electron beam stops. A radioisotope is continuous and thus requires signifi­cant safety precautions to handle and dispose of. Furthermore, dosages delivered by high-energy electron beam can be controlled and they can provide more po­wer per dose. This is a feature that would be useful in the continuous treatment of LB (Auslender et al., 2002).

Compared with microwave and gamma ray treat­ments, treatment by electron beam is more energy effective. The larger particle sizes, that it can treat, signif­icantly offset the negative effect of higher dosage. That said, there still remains the challenge of the limitation of electron beam source and the potential limitation on the scale of operations. Even though all these irradiation options reduce the particle size and reduce the DP, they are too expensive to use in full-scale operations. Currently, the prospects of engaging an irradiation treat­ment, even if in conjunction with other environmentally friendly treatment options, does not look promising due to the excessive energy requirements. Table 27.3 shows a comparison of these irradiation treatment methods on a variety of wood species.