TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The reactor recirculation pump is a peripheral vane pump. The backpressure to the reactor recirculation pump is less than 50 pounds per square inch. The reactor includes a reactor sidewall, and the reactor nozzle is directed away from the reactor sidewall. The pretreatment tank further comprises a pretreatment tank sidewall, and the nozzle is directed away from the pretreatment tank sidewall. The reactor includes a reactor bottom outlet, a reactor top inlet, a reactor headspace, and a reactor sidewall and the biodiesel reactor system further comprises: a reactor recirculation line extending from the reactor bottom outlet through the reactor top inlet; a reactor recirculation pump positioned in the reactor recirculation line a reactor nozzle connected to the reactor recirculation line discharge, and the reactor nozzle is positioned in the reactor headspace and directed away from the reactor sidewall. The reactor recirculation line includes a low pressure side and a high pressure side on opposite sides of the reactor recirculation pump, and the catalyst and alcohol are charged on the low pressure side of the reactor recirculation line. The biodiesel reactor further comprises: a reactor headspace, a catch basin positioned in the reactor headspace, an alcohol drain line positioned at least partially exterior to the reactor, and a heat exchanger connected to the alcohol drain line and the catch basin includes a catch basin drain connected to the alcohol drain line so liquid collected in the catch basin drains by gravity into the alcohol drain line; a reactor headspace, and the reactor nozzle is positioned in the reactor headspace; and a pretreatment tank including a pretreatment bottom outlet, a pretreatment top inlet, a pretreatment headspace and a pretreatment sidewall, a line connecting the reactor to the pretreatment tank, a pretreatment recirculation line extending from the pretreatment bottom outlet to the pretreatment top inlet, a pretreatment recirculation pump in the pretreatment recirculation line, and a pretreatment nozzle connected to the pretreatment recirculation line discharge and the pretreatment nozzle is positioned in the pretreatment headspace and directed away from the pretreatment sidewall. Preferred Method: The method further comprises: (f) spraying the oil feedstock onto a reactor liquid surface through a nozzle during step (b); (g) recirculating the biodiesel layer after step (e); (h) heating the biodiesel layer while recirculating; (i) catching alcohol in a catch basin positioned in a reactor headspace within the reactor; (j) charging an oil feedstock to a pretreatment tank; (k) charging the glycerol from step (e) to the pretreatment tank; (l) recycling the oil feedstock and glycerol in the pretreatment tank through a pretreatment recirculation line and a pretreatment recirculation pump such that the recirculation pump cavitates; (m) allowing the oil feedstock to split from the glycerol after step (l); and (n) splitting the oil feedstock from the glycerol after step (m); and charging the oil feedstock from step (n) into the reactor in step (a).