  We study entire solutions of the biharmonic heat equation on complete
Riemannian manifolds without boundary. We provide exponential decay estimates
for the biharmonic heat kernel under assumptions on the lower bound of Ricci
curvature and noncollapsing of unit balls. And we prove a uniqueness criteria
for the Cauchy problem. As corollaries we prove the conservation law for the
biharmonic heat kernel and a uniform L-infinite estimate for entire solutions
starting with bounded initial data.
