Biomethane Production from Pyrolytic Aqueous Phase: Biomass Acid Washing and Condensation Temperature Effect on the Bio-oil and Aqueous Phase Composition Shi-Shen Liaw 1,2 & Victor Haber Perez 3 & Roel J.M. Westerhof 4 & Geraldo Ferreira David 3 & Craig Frear 5 & Manuel Garcia-Perez 1 # Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract The aim of this work was to evaluate biomethane production by anaerobic digestion using aqueous phase from Fast Pyrolysis of Douglas Fir Wood as substrate. The effect of biomass acid treatment and condensation temperature on the bio-oil chemical composition and aqueous phase separation with a fractional condensation system coupled to Auger reactor during pyrolysis at 500 °C was reported. As the first condenser temperature was augmented from 40 and 80 °C, the bio-oil yield obtained decreased from 30 to 16 wt% and the aqueous phase yield in the second condenser (kept at 25 °C) increased from 27 till 37 wt%. When the untreated biomass was pyrolyzed, the aqueous phase collected in the second condenser (at the first condenser operated at 80 °C) was anaerobically digested at 100 ppm for 400 h results in 31.3 NmL of CH 4 /batch. However, the best result was attained after washed biomass with acetic acid (10%) previously to fast pyrolysis, obtaining 86.8 NmL of CH 4 /batch using just 10 ppm, perhaps due to halved of formed hydroxyacetaldehyde and estimated levoglucosan content increases by more than three times at this condition. Thus, the attained results confirmed the viability of the adopted strategy to improve the anaerobic digestion of the aqueous phase obtained by fractional condensation systems for biomethane production. Keywords Biomethane . Biomass . Fast pyrolysis . Bio-oil . Aqueous phase . Fractional condensation . Anaerobic digestion Introduction Pyrolysis is a promising technology to efficiently convert lig- nocellulosic materials into a crude bio-oil that could be further refined for the production of fuels and chemicals [1–5]. Although the energy density of bio-oil (around 26,800 MJ/ m 3 ) is about 6 to 7 times the energy of the feedstock [6, 7], it is still about 50% lower than that for petroleum-derived fuel due to its high oxygen content (35–40%) [8–10]. Pyrolysis oil has water content between 20 and 30 wt%. The water in the oil could come from the biomass moisture or could be a product of pyrolysis dehydration reactions [8, 11, 12]. The pH value of pyrolysis oil is typically between 2 and 4 mainly due to the considerable quantities of organic acids present in these oils [12, 13]. This makes these oils very corrosive to carbon steel and aluminum [14] and introduces stringent construction mate- rial requirements for their storage and transportation [12, 13]. The separation and utilization of the acids and water in the bio- oil is one of the main challenges facing bio-oil producers [15]. An aqueous phase rich in oxygenated organic compounds (C 1 -C 4 ) as well as the pyrolytic water can be separated from the heavy pyrolysis oil rich (C 5 >) by a fractional condensation system [16–18]. The heavy oil fraction recovered in the first condenser will be rich in fuel precursors and could be further processed for fuel and chemical production. The separated aqueous phase from the second condenser can be used, among Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12155-020-10100-3) contains supplementary material, which is available to authorized users. * Victor Haber Perez victorhaberperez@gmail.com 1 Biological Systems Engineering, Washington State University, Pullman, WA 99164, USA 2 College of Engineering-Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, CA 92507, USA 3 Processes Engineering Sector, State University of Northern Rio de Janeiro, Campos, Brazil 4 SuSTER BV, Mooienhof 203, Enschede 7512 EE, Netherlands 5 Regenis, Ferndale, WA 98248, USA BioEnergy Research https://doi.org/10.1007/s12155-020-10100-3