Foam-like robust starch/sodium montmorillonite (Na+-MMT) aerogels were fabricated through a freeze-drying process. Glutaraldehyde (GL) was used to crosslink the starch aerogels with the assistance of radiation supplied by a domestic microwave oven. The chemical reaction between GL and starch was analysed using Fourier transform infrared spectroscopy and water swelling tests. The microstructures and mechanical properties of the resultant crosslinked starch aerogels changed with GL concentration. By incorporating 5% (w/w) GL, the specific compressive modulus and absorbed energy increased by 2.4 and 3.3 times, respectively. In regard to starch/clay aerogel composites, Na+-MMT clay played the role of reinforcement. Moreover, clay addition created more porous structures and hence decreased the thermal conductivity of the aerogels. The biodegradability of the aerogels was studied using a homemade micro-respirometer. The starch aerogels exhibited higher biodegradability than poly(vinyl alcohol)-based ones and their corresponding films.