An apparatus, system, and method for subjecting biomass to pyrolysis to extract energy products using a pyrolysis unit comprising generally concentric chambers including a combustion chamber and at least one pyrolysis chamber. Each chamber is in communication with an adjacent chamber such that a directed, generally-deoxygenated heated gas stream passes through the combustion chamber to each of the pyrolysis chambers in turn. Additionally, each pair of adjacent chambers shares a heat-conducting wall, further promoting heat transfer throughout the unit. A heat source, which can be a burn enclosure configured as part of the pyrolysis unit, produces the heated gas stream. Biomass introduced into the pyrolysis unit is pyrolysized by the gas stream, resulting in exhaust containing non-condensing gases, bio-oil vapor, and entrained char. The exhaust is directed from the pyrolysis unit to other parts of the system where the bio-oil and char can be separated from the exhaust and collected.