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#Anabolic reactionHCO3- + 2.1H2 + 0.2NH4+ + 0.8H+ = CH1.8O0.5N0.2 + 2.5H2O#Catabolic reaction: 0.25HCO3- + H2 + 0.25H+ = 0.25CH4 + 0.75H2O

#Full reaction1.25HCO3- + 3.1H2 + 1.05H+ +0.2NH4+ = CH1.8O0.5N0.2 + 0.25CH4 + 3.25H2O

RATESOrganic_decomposition20 rate = 1e-2/86400 # mol/sec30 moles = rate* TIME40 SAVE moles50 ENDENDSOLUTION 1EQUILIBRIUM_PHASESCalcite 0Dolomite 0CO2(g) -1.0SAVE solution 1ENDINCREMENTAL_REACTIONS trueKINETICSOrganic_decomposition-M 1 moles-formula H2 1-step 864000 in 100 stepsENDUSE solution 1USE kinetics 1USER_GRAPH 1 -headings time TDIC CH4(aq) P(CH4(g)) P(H2(g)) -axis_titles "Days" "Molality" "P(CH4(g)), atm" -axis_scale y_axis 1e-4 2 auto auto log -initial_solutions false -connect_simulations true -plot_concentration_vs x -start10 GRAPH_X TOTAL_TIME / 8640020 IF (TOT("C(4)") >= 1e-10) THEN tdic = TOT("C(4)") ELSE tdic = 1e-1030 GRAPH_Y tdic, TOT("C(-4)")40 GRAPH_SY SI("CH4(g)"), SI("H2(g)") -end -active true

SOLUTION 1 -pressure 200 -temp 90 -density 1 pH 7 charge units ppm K 1152 Na 47520 Mg 771 Ca 5840 Cl 86500 C 586.7 S(6) 61.5 -water 1Gas_Phase 1 -pressure 200 -temp 90 -fixed_volume H2(g) 160 CO2(g) 40 CH4(g) 0END

RATESOrganic_decomposition20 rate = 1e-1/86400 # mol/sec30 moles = rate* TIME40 SAVE moles50 ENDENDSOLUTION 1 -pressure 200 -temp 90 -density 1 pH 7 charge units ppm K 1152 Na 47520 Mg 771 Ca 5840 Cl 86500 C 586.7 S(6) 61.5 -water 1ENDGas_Phase 1 -pressure 200 -temp 90 -fixed_volume Hdg(g) 160 CO2(g) 40 CH4(g) 0ENDINCREMENTAL_REACTIONS trueKINETICSOrganic_decomposition-M 1 moles-formula H2 1 Hdg -1-step 864000 in 100 stepsENDUSE solution 1USE kinetics 1USE gas_phase 1USER_GRAPH 1 -headings time TDIC CH4(aq) Hdg(aq) CO2(g) Hdg(g) CH4(g) -axis_titles "Days" "Molality" "P(CH4(g)), atm" -axis_scale y_axis 1e-4 2 auto auto log -initial_solutions false -connect_simulations true -plot_concentration_vs x -start10 GRAPH_X TOTAL_TIME / 8640020 IF (TOT("C(4)") >= 1e-10) THEN tdic = TOT("C(4)") ELSE tdic = 1e-1030 GRAPH_Y tdic, TOT("C(-4)"), TOT("Hdg")40 GRAPH_SY GAS("CO2(g)"), GAS("Hdg(g)"), GAS("CH4(g)") -end -active true

SOLUTION_MASTER_SPECIES Acetate HAcetate 0 Acetate 59SOLUTION_SPECIESHAcetate = HAcetate -gamma 3.0000 log_k 0HAcetate = Acetate- + H+ -gamma 4.5 log_k -4.7572 -analytic -0.96597E+02 -0.34535E-01 0.19753E+04 0.38593E+02 0.30850E+02RATES Methane_formation-start20 rate = 1e-1/8640030 moles = rate* TIME40 SAVE moles50 END-end Acetate_formation-start20 rate = 1e-3/86400 30 moles = rate* TIME40 SAVE moles50 END-endENDSOLUTION 1 temp 90 pH 7 charge pe 4 redox pe units ppm density 1 C 586.7 Ca 5840 Cl 86500 K 1152 Mg 771 Na 47520 S(6) 61.5 -water 1 # kgENDGAS_PHASE 1 -fixed_volume -pressure 200 -volume 1 -temperature 90 CH4(g) 0 CO2(g) 40 Hdg(g) 160ENDINCREMENTAL_REACTIONS trueKINETICS 1Acetate_formation -formula CO2 -2 H2O 2 HAcetate 1 Hdg -4.5 -m 1 -m0 1 -tol 1e-08Methane_formation -formula H2 1 Hdg -1 -m 1 -m0 1 -tol 1e-08-steps 864000 in 100 steps # seconds-step_divide 1-runge_kutta 3-bad_step_max 500ENDUSE solution 1USE kinetics 1USE gas_phase 1USER_GRAPH 1 -headings time TDIC SO4-2 CH4(aq) Hdg(aq) Acetate CO2(g) Hdg(g) CH4(g) -axis_titles "Days" "Molality" "P(CH4(g)), atm" -axis_scale y_axis 1e-6 2 auto auto log -initial_solutions false -connect_simulations true -plot_concentration_vs x -start10 GRAPH_X TOTAL_TIME / 8640030 GRAPH_Y TOT("C(4)"), TOT("S(6)"), TOT("C(-4)"), TOT("Hdg"), TOT("Acetate")40 GRAPH_SY GAS("CO2(g)"), GAS("Hdg(g)"), GAS("CH4(g)") -end -active true