Economical Recovery of Ammonia from Anaerobic Digestate

www.makingenergy.com

Ammonia Nitrogen Recovery
and
Biomethane Production
through
Anaerobic Digestion


ANAEROBIC DIGESTION

=
AMMONIA EMISSIONS


AMMONIA IS IMPORTANT
Toxic to anaerobic bacteria
A toxic regulated gas
Health impacts from PM2.5 Production
Health impacts from NOx & Ozone
N2O Greenhouse Gas at 310 x CO2
N2O Stratospheric Ozone Depletion
Terrestrial Ecosystem Alteration
Surface Water Eutrophication
Groundwater Nitrate Concentrations

www.makingenergy.com ANAEROBIC DIGESTION
AMMONIA AND SULFIDE INHIBITION


AMMONIA IS A
REGULATED TOXIC GAS

OSHA
Clean Air Act
Emergency Planning &
Community Right to Know Act
(45 kg NH3 / d)


AMMONIA PATHWAY TO ENVIRONMENT


AMMONIA ENVIRONMENTAL IMPACTS


CONTROL OF AMMONIA EMISSIONS
REQUIRED IN THE EU

REQUIRED IN CHESAPEAKE BAY WATERSHED

May Be Required in
Puget Sound
San Francisco Bay

ALL ANIMAL WASTE & FOOD WASTE DIGESTERS

ANAEROBIC DIGESTION ATTRIBUTES

RENEWABLE ENERGY PRODUCTION
CH4 GHG EMISSION CONTROL
SOLIDS & ODOR REDUCTION

on the other hand

NOT PROFITABLE - EXPENSIVE
SOURCE OF AMMONIA EMISSIONS
LOW VALUE ENERGY PRODUCT (BIOGAS)


GOALS OF
ABC (AMMONIUM BICARBONATE) PROCESS
• IMPROVE ECONOMICS OF AD

• RECLAIM AMMONIA NITROGEN AS A PRODUCT

• ECONOMICALLY PRODUCE A HIGHER VALUE ENERGY

PRODUCT

• REMOVE TOXIC NITROGEN FROM THE DIGESTER &

ENVIRONMENT


Existing
Approaches to Ammonia
Treatment

RECLAMATION DESTRUCTION
• Strip to make Ammonium Sulfate • Nitrification / Denitrification
• Strip to make Aqua Ammonia • AS via Nitrite
• Ion Exchange to Ammonium Sulfate • Sharon - Anammox
• MAP (struvite) (<20%) • Wetlands
• Duckweed
• Algae

PROVEN PROCESSES
TO RECLAIM NITROGEN

Lime + Gas Memb + Ion Exch + Algae +
Process Acid Acid Acid Dilution
ABC

Concentrated
Product (NH4)2SO4 (NH4)2SO4 Organic N (NH4)HCO3
Acid Liquid

CaO +
Chem Used H2SO4 Salt + H2SO4 Polymer None
H2SO4

Sludge Yes Yes None

Biofuel
No No No No Yes
Production

Cost $ / lb N $5.00+ $??.?? $3.50+ $1.50± <$1.00±


BIOMETHANE PRODUCTION TECHNOLOGIES
Water Scrubbing
Pressure Swing Adsorption (PSA)
Chemical Scrubbing with Amines
CO2 “Rain”
Chemical Scrubbing with Glycols (such as Selexol™)
Membrane Separation
Cryogenic Separation

COST OF CLEANUP = $3.00 TO $5.00 / 1000 CF
VALUE OF NATURAL GAS WITHOUT CREDITS = $4.00 / 1000 CF

ABC NITROGEN RECOVERY

US PATENT 7,806,957

1.SOLID LIQUID GAS SEPARATION
2.NATURAL PROCESS TO INCREASE PH (NH4+ ⇒ NH3)
3.AMMONIA STRIPPING (NH3 L ⇒ NH3 G)
4.PRECIPITATION OF AMMONIUM CARBONATE & BIOMETHANE
PRODUCTION ( NH3 + H2O + CO2 →
NH4HCO3 )

Step 1

Remove Residual Solids and Strip
Gases

Increase pH to 8.3 ±
PILOT SCALE

15 MINUTE HRT

Step 2

Further Increase pH to 10.5

ADDITION OF CAUSTIC CYANOBACTERIAL
RMOVAL OF CARBONATE


AMMONIUM (NH4+) TO NH3 GAS


CAUSTIC COST
BELT FILTER PRESS FLOW = 600,000 GPD
AMMONIA CONCENTRATION = 800 MG/L
TOTAL FILTRATE AMMONIA = 4,000 PPD

CAUSTIC (50%) REQUIRED (PH 8.3 - 10.5) = 2130
GPD
CAUSTIC COST @ $1.50 / GALLON = $3,200 /D
CAUSTIC COST = $0.8 / POUND NH3


CYANOBACTERIA CONSUME BICARBONATE
CARBONATE SYSTEM CONTROLS PH
CO2 + H2O ↔ H2CO3 ↔ H+ HCO3-
CO2 TO pH 8.3
HCO3 TO pH 11

CYANOBACTERIA LIMITATIONS
AMMONIA TOXICITY

GROWTH RATE INHIBITION

WATER TURBIDITY & LIGHT PENETRATION


CYANOBACTERIA PHOTO-BIOREACTOR
FIXED FILM REACTOR

LARGE BIOMASS FOR GROWTH & CARBONATE CONSUMPTION

LARGE SURFACE TO VOLUME RATIO

MINIMIZE TURBIDITY EFFECTS FOR LIGHT PENETRATION

Reactor must be scalable


ROTATING PHOTO-BIOREACTOR

SEVERAL GROUPS OF ORGANISMS


Step 3

Strip Ammonia
a) Ammonia Gas (NH3) Formation f (pH & T)
b) Stripping f (T & G/L)


Step 4

Precipitate Ammonium Bicarbonate
&
Produce Biomethane


ABC FAVORABLE REACTION

Ammonium Bicarbonate Formation

(NH3 + H2O + CO2 -> NH4HCO3 )

∆r G° ( KJ / Mole) = -18.5

Δ r H° (KJ / Mole = -126.5

Ammonium Bicarbonate Nitrogen

“InOrganic”, Pathogen Free, Unadulterated, Low Carbon Footprint,
Solid Crystaline Nitrogen Recovered from Organic Waste

FERTILIZER
ENVIRONMENTAL ATTRIBUTES

NITROGEN USE EFFICIENCY (NUE) BROADCAST

M< ABC ≈ U < AS < CABC

NITROGEN USE EFFICIENCY (NUE) IN GROUND

M< ABC ≈ U ≈ AS < CABC

CARBON FOOTPRINT

CABC < ABC < U < M < AS
M = MANURE
ABC = AMMONIUM BICARBONATE
U = UREA
AS = AMMONIUM SULFATE
COATED AMMONIUM BICARBONATE
NUE = N IN PLANT / N APPLIED

ABC PILOT PLANT AT
MUNICIPAL SEWAGE DIGESTER


Results of Pilot Operation

55% Ammonia Removal at
G/L = 248.35, 55°C, pH 9.25

Equals Model Results

Removal Inhibited by Low Temperature

Biogas Results

Averaged over 97.2 % Methane

Stripped Ammonia as a
Function of CO2 Added


RPB pH as a Function
of
Number of Lights in RPB
December 2 to December 13
RPB pH

Number of Lights


RPB Light & pH Response Time (Control)
pH of RPB

Number of Lights


Average pH Over Pilot Period


Average pH Tacoma Samples


Average TAN Over Pilot Period


Average TAN Tacoma Samples


Average Alkalinity Tacoma Samples


Average Dissolved Oxygen Tacoma Samples


Average COD Tacoma Samples


Low Temperatures Terminated
Pilot Operation


Initially
Process Produced No Solid Precipitate
Reaction Kinetics Much Slower Than Thought
(High Stripping Gas Stream Velocities)


Six Minutes Precipitate Formed


15 Minutes Reaction Complete

Ammonium Bicarbonate Solids


Lessons Learned
 Sodium Hydroxide may be used to raise pH at a cost
approximately equal to the value of ammonia.

 Use of cyanobacteria to raise pH feasible at low cost.

 Power requirements for lighting are low.

 Use RPB for pH, Temperature Control and Stripping

 Ammonia removal and recovery can be profitable.

Economical Recovery of Ammonia from Anaerobic Digestate

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