A downdraft gasifier and method of gasification with high yield biochar that utilizes a plurality of high throughput, vertically positioned tubes to create a pyrolysis zone, an oxidation zone beneath the pyrolysis zone and a reduction zone beneath the oxidation zone. A rotating and vertically adjustable rotating grate is located beneath the reduction zone of the gasifier. In addition, a drying zone is located above the pyrolysis zone so the heat of the gasifier can be used to dry feedstock before it enters the gasifier. By optimizing the grate height and rpm, feedstock retention time in the drying zone, the drying zone temperature and feedstock moisture content, the result is gasification of biomass with a high yield and continuous biochar production.