NOVELTY - System (100) comprises: (a) first and second condensers (104) and a compressor (106) coupled between them; (b) a reactor configured to receive the feedstock mixture from the second condenser and to output a fatty acid methyl ester (FAME) precursor containing excess reactant; (c) a flash column (122) operating at vacuum pressure and configured to separate excess reactant from FAME precursor to produce FAME product; and (d) a set of heat recovery regimes configured to recycle heat from FAME product to feedstock mixture and FAME precursor.    USE - The system is useful for producing biofuel including biodiesel.    ADVANTAGE - The system: has increased energy efficiency than traditional biofuel production systems; reduce and/or eliminate the release of green house gases and/or toxic molecules; reduces or eliminates the use of chiller to condense methanol, thus lowering capital and operating cost and complexity; and recovers heat from the finished product, thus eliminating use of boilers and increasing safety while handling the finished product.    DETAILED DESCRIPTION - System (100) comprises either: (a) first and second condensers (104) and a compressor (106) coupled between them so that the first condenser operates at a vacuum pressure and the second compressor operates at a positive pressure, where the compressor draws excess reactant into the first condenser to contra-flow in direct contact with a feedstock and pushes compressed remaining excess reactant into direct contra-flowing relation in the second condenser with a feedstock mixture obtained from the first condenser such that the remaining excess reactant is condensed into the feedstock mixture, (b) a reactor configured to receive the feedstock mixture from the second condenser and to output a fatty acid methyl ester (FAME) precursor containing the excess reactant, (c) a flash column (122) operating at the vacuum pressure and configured to separate the excess reactant from the FAME precursor to produce FAME product, and (d) a set of heat recovery regimes configured to recycle heat from the FAME product to the feedstock mixture and the FAME precursor in an order determined by a flash temperature of the excess reactant and a reaction temperature of the feedstock mixture; or (a1) a set of condensers arranged serially in fluid flowing relation and configured to combine liquid reactant methanol with a vegetable oil feedstock and recycled vapor methanol, where each individual condenser operates at a higher pressure than a preceding individual condenser, (b1) a reactor configured to receive an output from the set of condensers and to produce a biofuel, (c1) a flash column configured to separate excess vapor phase methanol from the biofuel and to direct the separated excess vapor phase methanol as the recycled vapor methanol to the set of condensers, and (d1) a set of heat recovery regimes configured to recover heat from the biofuel in an order determined by a reaction temperature of the reactor and a flash temperature of the flash column. INDEPENDENT CLAIMS are also included for:    (1) a system (B) comprising a reactant assembly configured to introduce a reactant to a renewable feedstock, a product separation assembly configured to separate a resultant biofuel from the reactant, and a recycle assembly configured to recycle the separated reactant to the reactant assembly;    (2) producing biofuel, comprising (a2) introducing a reactant to a renewable feedstock, (b2) producing a biofuel from the renewable feedstock, (c2) separating the reactant from the biofuel, (d2) recycling the reactant to react with additional renewable feedstock, and (e2) transferring heat from the recycled reactant to the additional renewable feedstock;    (3) producing additional biofuel precursor, comprising (a3) producing a biofuel precursor from a renewable feedstock, (b3) recovering waste heat from the biofuel precursor at least in part by utilizing mechanical vapor re-compression, and (c3) recycling the recovered waste heat to additional renewable feedstock to produce additional biofuel precursor; and    (4) a system (C) configured to accomplish the method of producing additional biofuel precursor.    DESCRIPTION OF DRAWING(S) - The figure shows biofuel processing system.    System (100)    Condenser (104)    Compressor (106)    Heat exchanger (110)    Flash column (122)