From the Wikipedia page 
Konacha (粉茶?) or Bud Tea is a type of Japanese green tea, composed of the dust, tea buds and small leaves that are left behind after processing Gyokuro or Sencha. Konacha is cheaper than Sencha and is often served at sushi restaurants. It is also marketed as Gyokurokocha (玉露粉茶?).
Konacha has a strong flavor and is therefore good for use in cooking.
There are a number of companies marketing the tea.