Figure 4. SEM images of the materials obtained by calcining (a) duck, and (b) chicken eggshell waste at 900C

From

Application of Eggshell Wastes as a Heterogeneous Catalyst for Biodiesel Production

Achanai Buasri, Nattawut Chaiyut, Vorrada Loryuenyong, Chaiwat Wongweang, Saranpong Khamsrisuk

Sustainable Energy. 2013, 1(2), 7-13 doi:10.12691/rse-1-2-1