NOVELTY - Process (P1) for modifying the content of a pyrolysis oil product, involves: (A) treating a pyrolysis oil vapor comprising a carbonyl-containing component with an atomized alcohol or amine under conditions allowing a condensation reaction between the carbonyl-containing component and the alcohol or amine, to generate a reaction product; and (B) condensing the pyrolysis oil vapor and the reaction product to form a pyrolysis oil product having an increased ester or amide content when compared to a condensed pyrolysis oil product not treated with the atomized alcohol or amine.    USE - For modifying the content of pyrolysis oil product (claimed).    ADVANTAGE - The method provides in-line reactive condensation processes via vapor phase esterification of pyrolysis oil (bio-oil) to decease reactive species concentration and water content in oily phase of two-phase oil i.e. by removing undesired acidic compounds, and increases quality of bio-oil. The pyrolysis oil product obtained after treatment with atomized alcohol or amine has decreased carboxylic acid content, and increased stability and heat value by forming pyrolysis oil (bio-oil) product, when compared to a condensed pyrolysis oil product not treated with atomized alcohol or amine. The method provides for condensation reactions between heated pyrolysis oil vapor and atomized alcohol or amine, so that carboxylic acid products of pyrolysis procedure are converted to corresponding esters or amides. The introduction of atomized alcohol or amine into stream of uncondensed bio-oil vapor quickly cools and condenses vapors while simultaneously esterifying resultant bio-oil. Thus, by delivering alcohol to pyrolysis oil vapor, non-catalyzed one-step combined condensation esterification reactions are possible between some or all of carbonyl component species of pyrolysis oil vapor, and provides simple procedure to improve storage stability and heat-yield properties of bio-oil. The addition of alcohol during condensation of pyrolysis oil vapors increases stabilization of bio-oil by quickly quenching bio-oil vapor to prevent secondary reactions and by simple dilution of reactive species before reactions can occur. In addition, carbonyl compounds including carboxylic acids e.g. acetic acid and which occur in high concentrations in pyrolysis oil vapor undergo Fischer esterification upon mixing with ethyl alcohol at elevated temperature to produce esters and water. Due to lower polarity of esters compared to carboxylic acids, solubility of water in oily phase of bio-oil will be reduced. Thus, water produced during esterification will be concentrated in aqueous phase of bio-oil and reduces water content of oily phase. Rapid condensation, esterification and acetylation will stabilize bio-oil more effectively than simple condensation, and increases thermal and oxidative stability. The ability to produce esters from carbonyl components and in particular from carboxylic acids in bio-oil is thus a step in development of fuel-quality pyrolysis oils. When left in bio-oil, esters increase heating value compared to carboxylic acids they replace. Esterification of bio-oil may also reduce viscosity and acidity, while increasing stability of oil, by removal of acids that would otherwise catalyze condensation reactions leading to polymerization of bio-oil components. Further, resulting esters not only improve quality when they remain in pyrolysis oil, but can also be removed easily by distillation due to their higher volatility compared to acids from which they are derived; and can be used further such as for fabrication of valuable class of polymers i.e. polyesters. The esterification also reduces corrosive ability of bio-oils, by replacing acidic hydrogen in carboxyl group for more inert alkyl-oxygen bond; which also improves safety to handle bio-oils. An additional advantage of method is that any alcohol may be used to condense and esterify bio-oil vapor depending on what esters are desired as the end product. The relative size of esters determines flash point and boiling point of bio-oil produced. A bio-oil produced by condensation with methanol has lowest flash and boiling points. A disadvantage of longer chain alcohols is significant reduction in reaction rate. However, if acidic catalyst is employed, the reaction rate can be increased.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a pyrolysis oil product having an increased ester content and increased stability when compared to a pyrolysis oil product not treated with an atomized alcohol or amine, obtained by the process (P1); and    (2) a system for generating a pyrolysis product, comprising: a pyrolysis unit configured to receive and pyrolyze a biomass, to generate a heated pyrolysis oil vapor having carbonyl-containing component; a reactive condensation unit operably communicating with the pyrolysis unit, and configured to receive the pyrolysis oil vapor and atomized alcohol or amine, to form a reaction mix within the reactive condensation unit, and further configured to deliver a condensate to receiving vessel; and a receiving vessel operably disposed to receive the condensate comprising pyrolysis oil product from the reactive condensing unit.