B.E.E.F: A Sustainable Process Concerning Negative CO2 Emission

Subscriber access provided by University of South Dakota

Article

B.E.E.F: a sustainable process concerning negative CO2 emission and profit increase of anaerobic digestion Qingyao He, Mingfei Shi, Feihong Liang, Long Ji, Xin Cheng, and Shuiping Yan ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b04963 • Publication Date (Web): 21 Dec 2018 Downloaded from http://pubs.acs.org on December 24, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 23 11 2 3 42 5 63 7 8 4 9 10 5 11 12 6 13 14 7 15 16 8 17 18 9 19 20 10 21 22 11 23 24 12 25 26 13 27 28 29 14 30 31 15 32 33 34 16 35 36 17 37 38 39 18 40 41 42 19 43 44 20 45 46 47 21 48 49 22 50 51 52 23 53 54 55 24 56 57 25 58 59 26 60

ACS Sustainable Chemistry & Engineering

B.E.E.F: a sustainable process concerning negative CO2 emission and profit increase of anaerobic digestion Qingyao He†,‡, Mingfei Shi†,‡, Feihong Liang†,‡, Long Ji§, Xin Cheng¶, Shuiping Yan*, †,‡ †

College of Engineering, Huazhong Agricultural University, No.1, Shizishan Street, Hongshan District,

Wuhan 430070, PR China ‡

Key Laboratory of Agricultural Equipment in Mid-lower Yangtze River, Ministry of Agriculture and Rural

Affairs, Wuhan 430070, PR China §

CSIRO Energy Flagship, Mayfield West, NSW 2300, Australia

¶

Department of Management Science and Engineering, School of Economics and Management, China

University of Geosciences, Wuhan, 430074, China * Email: [email protected]; Tel: +86-27-87288723; Fax: +86-27-87288723

ABSTRACT: In organic wastes utilization, negative CO2 emission and increase of profit can be achieved simultaneously based on anaerobic digestion (AD) through a novel Bio-Energy, Electricity, and NH4HCO3 Fertilizer (BEEF) system. In BEEF concept, organic wastes are anaerobically digested to produce biogas, and then renewable ammonia recovered from biogas slurry is used to upgrade biogas. Negative CO2 emission can be acquired by transferring the separated CO2 into greenhouse plants or other carbon sinks. Compared with the baseline scenario that all the biogas from AD plant is combusted in a CHP unit, this study found that the average negative CO2 emission with ~277 Nm3/h and net profit with ~RMB¥ 365/h were acquired simultaneously by adopting BEEF system where animal manures were digested in a 1000 Nm3-biogas/h AD plant. Meanwhile, BEEF system output the useful energy about 100% higher than the baseline scenario. Reducing the energy consumption of ammonia recovery could increase both the negative CO2 emission and net profit. Overall, this system provides a pathway to the sustainable nutrients and carbon management to deal with the climate and environmental problems. KEYWORDS: Anaerobic digestion, Biogas upgrading, Ammonia recovery, Negative emission, Carbon dioxide 1

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 8 20 21 9 22 23 24 10 25 26 27 11 28 29 12 30 31 32 13 33 34 14 35 36 37 15 38 39 40 16 41 42 17 43 44 45 18 46 47 19 48 49 50 20 51 52 53 21 54 55 22 56 57 58 23 59 60



Page 2 of 23

INTRODUCTION Greenhouse gases (GHG) like CO2, CH4 and N2O emissions from agriculture production are estimated to

account for 12% of global anthropogenic GHG,1 and the inadequate management of residues is responsible for the GHG emissions.2 Additionally, the inadequate management of residues also results in serious consequences such as water and soil contamination, air pollution and poses the threat to human health. Therefore, a good management of residues in agriculture is required for climate change and environmental issues. Anaerobic digestion (AD) is a mature technology widely used to convert the biodegradable biomass residues into a renewable clean energy, biogas (typically ~ 60% CH4, balanced by CO2), and organic fertilizer including biogas digestate without containing any pathogenic bacteria, which may be a good approach to disposing the agricultural residues for cutting down their environmental risks. AD can reduce GHG emissions in the life cycle.3 For instance, the anaerobic co-fermentation of organic fraction of municipal solid waste was reported to contribute to the reduction of CO2 emissions with 32 to 152 kg CO2/ton organic waste. 4 In addition, if CO2 can be captured from biogas and subsequently stored or utilized, not only CO2 emissions will be avoided, but also bio-methane can be generated to meet the natural gas demand.5-6 Various technologies have been adopted for biogas upgrading, such as water scrubbing, pressure swing adsorption, chemical absorption and membrane separation.7-11 Regardless of biogas upgrading processes, the consumption of exogenous electricity, heat or chemicals is inevitable resulting in CO2 emission, which implies the potential of cutting down GHG emission by using AD may be limited during biogas upgrading from a life cycle perspective.6 Clearly, the consumption of exogenous resources may lower the economic benefit of biogas upgrading. So, biogas plants have to rely on the financial aid from the government nowadays mainly due to its low energy efficacy or solo product output. As the primary byproduct, biogas digestate is always treated as organic fertilizer for crop cultivation because of its higher nutrients. However, direct application of biogas digestate also results in GHG emissions (0.4 kg-NH3-N/kg NH4+-N, 0.035 kg-N2O-N/kg -N).12 Therefore, 2


Page 3 of 23 11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 8 20 21 9 22 23 24 10 25 26 27 11 28 29 12 30 31 32 13 33 34 14 35 36 37 15 38 39 40 16 41 42 17 43 44 45 18 46 47 19 48 49 50 20 51 52 53 21 54 55 22 56 57 58 23 59 60


appropriate nutrients management, especially for NH4+-N, is required from the point of environmental protection and the climate change control.13 Due to the unique advantages of lower heat consumption of ammonia and its CO2 absorption rate analogous to monethanolamine (MEA) in CO2 capture, many ammonia-based CO2 capture pilot plants have been erected in the past decades.14 In our previous study, we have put forward a novel approach to recovering ammonia from biogas slurry and using it as the renewable CO2 absorbent.15 Ideally, it is possible to upgrade biogas through ammonia-based CO2 capture process, in which ammonia recovered from ammonium nitrogen-rich biogas digestate is consumed without the requirements of any exogenous chemical commodities. Although the ammonia recovery from biogas digestate, biogas upgrading by ammonia, and biogas utilization in combined heat and power (CHP) were extensively reported, there have been few integrated studies of the nexus of these units in a system to achieve a higher overall energy efficiency, a higher net profit, and less GHG emissions simultaneously. In addition, the mass distributions and energy flows in an integrated system are still unknown. Bio-Energy, Electricity and Fertilizer production (BEEF) system is put forward in this study (Fig. 1). Ammonia recovered from biogas slurry is used in an ammonia-based biogas upgrading process to reduce the exogenous chemical absorbents and energy consumptions. The utilization of the biogas slurry after ammonia removal can also reduce the direct application of nitrogen to the soil so as to decrease the GHG (NH3 and N2O) emissions. Besides, the energy required by the processes of ammonia recovery and biogas upgrading can be fully supplied by biogas without consuming any exogenous energy, therefore, a sustainable energy and environment process can be obtained. Comparing to the conventional ammonia removal methods and biogas applications, the BEEF system is supposed to achieve better financial benefits and an analogous energy efficiency. Especially, this novel system is aimed to provide a pathway to the sustainable nutrients and carbon management to deal with the climate and environmental problems. 3



CO2 utilization

CO2 output Bio-methane output

Biogas

Biogas storage

Biogas upgrading

NH4HCO3 output

Biogas CHP

0

Biogas 100%

Livestock and poultry wastes input

NH3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 1 30 2 31 3 32 33 4 34 35 36 5 37 38 6 39 40 41 7 42 43 8 44 45 46 9 47 48 49 10 50 51 11 52 53 54 12 55 56 13 57 58 59 14 60

Page 4 of 23

Electricity output

Biogas digestate Anaerobic digestion

Ammonia recovery

Biogas residual

Fig.1. Schematic diagram of bio-energy, electricity and fertilizer production (B.E.E.F) based on anaerobic digestion of organic waste. 

METHODOLOGY

System Description, Scope Definition, and Calculation Method. BEEF system consists of four main units, namely, anaerobic digestion, ammonia recovery, CHP, and biogas upgrading unit in Fig. 1. BEEF is designed 1 Organic wastes such as animal wastes, food wastes are digested in an to undergo the following processes: ○

AD plant to generate biogas and biogas digestate. H2S is assumed to be removed during the biogas storage or 2 removed by the alkaline biogas slurry after ammonia removal with little energy consumption.15-17 ○

Renewable aqueous ammonia (RAA) is recovered in the process of vacuum membrane distillation (VMD) from biogas slurry after the solid-liquid separation using decanter centrifuge or discontinuous centrifuge.13 3 Partial biogas is combusted in CHP unit to supply the heat and electricity required in the ammonia recovery ○

and biogas upgrading units. As the heat consumption in BEEF system is much higher than the electricity 4 The residual biogas consumption, the surplus electricity generated form CHP can be used in power grid. ○

4


Page 5 of 23 11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 8 20 21 9 22 23 24 10 25 26 27 11 28 29 12 30 31 32 13 33 34 14 35 36 37 15 38 39 40 16 41 42 17 43 44 45 18 46 47 19 48 49 50 20 51 52 53 21 54 55 22 56 57 58 23 59 60


is upgraded in biogas upgrading unit using RAA to generate bio-methane, nearly pure CO2, and NH4HCO3. Systemic inventory analysis was performed in Excel®. Reference systems and parameters (biogas production, biogas upgrading, CHP) for each route were well selected (Table S1 in Supporting Information). VMD experiments were carried out to measure the heat consumption and the details are shown in Supporting Information. The primary mass input into BEEF system is the feedstock for anaerobic digestion (Fig. 1). CO2 emission into the atmosphere could be avoided ideally by fixing the separated CO2 in greenhouse plant or through other possible utilization pathways. The generation of heat and power from the CHP unit, the pretreatment of biogas digestate, and solid liquid separation can be considered as CO2 neutral process.15 Renewable energy generated from this system includes bio-methane and electricity. Biogas utilization via CHP is the most popular process in biogas plant, which is also regarded as a carbon neutral process. Therefore, the amount of CO2 emission avoided (negative CO2 emission in Nm3/h, QCO2 ,A ) in BEEF system compared with the scenario of biogas utilization via CHP can be calculated by the following equation:

QCO2 ,A =(Qbiogas -Qbiogas,comb )

(1)

where Qbiogas and Qbiogas,comb indicate the total biogas production (1000 Nm3/h) and the biogas combustion amount in the CHP unit (Nm3/h), respectively;

 represents the volumetric fraction of CO2 in biogas (%).

As partial electricity is consumed in the ammonia recovery and biogas upgrading process, thus the total electricity output (TEO) can be estimated as follows:

TEO   Qbiogas,comb  EC,A  EC,U

(2)

where α represents the electricity generation efficiency of CHP (%); EC,A and EC,U (MJ/h) represent the electricity consumptions in the ammonia recovery and biogas upgrading units, respectively. In biogas upgrading unit, CO2 is captured by ammonia. Heat (~150 °C) required for the possible CO2-rich solvent regeneration can be supplied by the bio-methane combustion. The total bio-methane output (TBO) can 5



Page 6 of 23

be calculated by the following equation:

TBO = (Qbiogas -Qbiogas,comb )-QCH 4 ,U

(3)

where  represents the volumetric fraction of CH4 in biogas (%); QCH 4 ,U indicates the bio-methane consumption (Nm3/h) during the biogas upgrading. The total operating and maintenance (O&M) cost input (TCI) can be expressed by the sum of each unit:

TCI  CAD  CCHP  CAR  CBU

(4)

where CAD, CCHP, CAR, and CBU (RMB ¥) indicate the cost of anaerobic digestion for biogas production, CHP, ammonia recovery and biogas upgrading, respectively. Similarly, the total revenue of BEEF system can be expressed by the sum of the revenues from each product, and the total net profit can be obtained by subtracting total cost from total revenues. The overall energy efficiency in BEEF system (η, %) can be calculated as follows:1

=

Energyoutput Energyinput

100

(5)

where Energyinput means the overall energy input into BEEF system, including the chemical energy, heat, and electricity, while the Energyoutput indicates the overall energy output from the BEEF system excluding the waste heat and unusable chemical energy. Swine manure (SM), cattle manure (CAM), chicken manure (CHM) and food waste (FW) are used as the model feedstocks in an AD plant in BEEF system, which is called SM-, CAM-, CHM- and FW-based BEEF system, respectively. The basic parameters such as total solids content (TS), volatile solid content based on dry matter (VS), total Kjeldahl nitrogen content (TKN), and biogas yield, are available elsewhere,19-22 which can be found in Table S2. 

RESULTS AND DISCUSSION Mass Balance and Energy Consumption in Ammonia Recovery Process. Ammonia recovery from

biogas slurry using VMD was investigated (Fig. S1). An orthogonal experiment (L9(34)) optimizing the 6


Page 7 of 23 11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 8 20 21 9 22 23 24 10 25 26 27 11 28 29 12 30 31 32 13 33 34 14 35 36 37 15 38 39 40 16 41 42 17 43 44 45 18 46 47 19 48 49 50 20 51 52 53 21 54 55 22 56 57 58 23 59 60


operating parameters was performed to get a better ammonia separation performance and minimize the energy consumption (Table S3). When the initial TAN concentration is 1.5 g-N/L, the TAN concentration on permeate side is 33.2 g-N/L with ammonia removal rate of 56% (Table S4 and Fig. S2). Under the same conditions, the TAN concentration on the permeate side could be estimated to change from 11 to 99.6 g-N/L with the variation of the TAN concentration in feed solution from 0.5 to 4.5 g-N/L. Clearly, the TAN concentration in RAA is mainly dependent on the TAN concentration in the raw biogas slurry. The average heat consumption in VMD when using biogas slurry with 1.5 g-N/L is about 3.5 MJ/kg-permeate (Fig. S3A), which is slightly higher than that from aqueous ammonia solution and water (~3 MJ/kg-permeate). This result is in accordance with Criscuoli’s result using cross-flow membrane module for VMD tests (3.9 MJ/kg-permeate).23 When the typical biogas slurry with 1.5 g-N/L is adopted as the feed solution, the average heat consumption of ammonia recovery is about 106.6 MJ/kg-N, while the value can decrease gigantically to 35.5MJ/kg-N when the initial TAN concentration is 4.5 g-N/L (Fig. S3B). Apparently, there is a significant negative correlation between the heat consumption of ammonia recovery and the initial TAN concentration in the biogas slurry directly determined by the type of feedstock and organic loading rate in the AD plant. When SM, CHM and CAM are used as feedstocks, the TAN concentration in the biogas slurry can be changed in the range of 2.0 – 3.6 g-N/L,15, 24 3.5-5.0 g-N/L, and 0.5-1.5 g-N/L, respectively.20, 25 It should be noted that using multi-stage VMD and/or recovering the waste heat and minimizing the heat loss can reduce the heat consumption of ammonia recovery effectively by up to 90%.26,

27

So in this study, the heat

consumption of ammonia recovery from SM- and FW-based biogas slurry is reasonably estimated to be about 45 MJ/kg-N based on their possible initial TAN concentrations in biogas slurry when adopting the multi-stage VMD technology. Similarly, the heat consumption of ammonia recovery from CHM- and CAM-based biogas slurry is about 25 MJ/kg-N and 135 MJ/kg-N, respectively. Additionally, the cost of ammonia recovery using VMD is set at about RMB ¥7.7 /m3-permeate based on the data from reference (Table S5).26 7



Page 8 of 23

Mass and Energy Flows. The calculation details of mass and energy flows of each unit are listed in Table S6, and the mass balance of the solid-liquid separation is shown in Table. S7. In SM-based BEEF system, only 8.0% of the total fresh matter (FM) is transferred into biogas and 92% of FM is left in the biogas digestate (Fig. 2A). Because of the heat requirement in ammonia recovery unit, 23.5% of the total biogas is split into CHP, and then 76.5% of biogas is used for bio-methane production. Additionally, 3.7% of FM can be recovered from biogas slurry to form RAA in ammonia recovery unit, and then this mass can be transferred into NH4HCO3 by the reaction between CO2 in biogas and RAA in the biogas upgrading unit. So if the mass balance is concerned in BEEF system, we can obtain bio-methane (2.2% FM), NH4HCO3 (4.8%), nearly pure CO2 (2.7% FM) and biogas residual (88.4% FM). Carbon and nitrogen balance is also tracked in Fig. 2A. 25.46% of the total carbon (TC) from SM is transferred to biogas after AD. Then about 5.98% of TC is transferred into CHP unit, and 19.47% of TC is transferred into biogas upgrading unit to become bio-methane (11.66% TC), NH4HCO3 (0.78% TC), nearly pure CO2 (6.9% TC). Notably, the split fraction of biogas into CHP unit is determined by the total heat requirement in ammonia recovery unit (Table S6). For a given AD plant using the given feedstock, the fraction of biogas split into CHP unit is nearly constant. Similarly, about 24.64% of TN can be recovered from biogas slurry using VMD to form 5 w.t.% RAA (Fig. 2A), and this TN can be totally transferred into NH4HCO3. Certainly, the recoverable TN mass in BEEF system is affected by the feedstock type in the AD plant. For instance, 47-55% of TN in CM can be recovered into RAA and consequently into NH4HCO3. AD only converts 60% of total chemical energy (TCE) from the feedstock into biogas, meaning that about 20% of TCE is remained in the biogas residual and other is wasted energy (Fig. 2B).28 Due to the energy consumptions of ammonia recovery and biogas upgrading, about 14.1% of TCE is transported into CHP unit through biogas splitting to generate heat and electricity. In CHP unit, almost all the heat and some electricity (about 6.7% of TCE) are transported into ammonia recovery unit to keep the ammonia recovery running, while 8


Page 9 of 23 11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 8 47 48 49 50 51 52 53 54 55 56 57 58 59 60


only 0.02% of TCE is consumed in the biogas upgrading unit. As a result, 90.6% of electricity is output into the power grid. Since CO2 regeneration heat consumption is about 42.42 MJ/h (Table S6), partial bio-methane (about 0.1% of TCE) is consumed to generate this heat, resulting in only 45.8% of TCE is output in the form of bio-methane. In BEEF system, about 50.3% of TCE could be output to form the valuable products including bio-methane (45.8% of TCE) and electricity (4.5% of TCE), which is about 100% higher than the useful energy output of direct on-site combustion of biogas in CHP.29 Clearly, BEEF is a more effective energy output system. 593.6 kg-CO2/h, 2.7% of FM

A. Mass flow CO2 utilization

339.7 kg- CH4/h, 2.2% of FM

933.3 kg-biogas/h, 6.1% of FM Biogas storage

CO2 output C: 6.9%

733.7 kg-NH4HCO3/h, 4.8% of FM

Biogas upgrading CHP

0

286.7 kg-biogas/h, 1.9% of FM

Biogas digestate

Anaerobic digestion

27.3 wt.% NH4HCO3 C: 0.78% N: 24.64%

561 kg-NH3 H2O/h, NH3 N:24.64% 3.7% of FM

C: 100% N: 100%

Livestock and poultry wastes input，15280 kg-FM/h，100%

Bio-methane

Biogas, C: 19.47% Biogas, C: 5.98%

1220 kg-biogas/h, 8.0% of FM

C: 11.66%

14061 kg/h，92% of FM C: 74.54%, N: 100%

Ammonia recovery Biogas residual

13500 kg FM in effluent，88.4% of FM

9


C: 74.54% N: 75.36%


B. Energy flow

45.8% 45.9%

Biogas storage

Bio-methane 0.02% 14.1% CHP

60% Chemical energy in biogas

Waste heat recycle

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 1 23 2 24 25 3 26 27 4 28 29 5 30 31 32 6 33 34 7 35 36 37 8 38 39 40 9 41 42 10 43 44 45 11 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 23

0.1% Biogas upgrading

0

4.5%

Electricity

6.7% 2.8% Conversion loss Biogas digestate

100% Chemical energy

Anaerobic digestion

Waste heat recycle

Ammonia recovery

20% Chemical energy potential in biogas redisual

26.9% Waste heat & conversion loss

Fig. 2. Mass flow (A) and energy flow (B) in Bio-Energy, Electricity and Fertilizer production (BEEF) system based on an AD plant with 1000 Nm3/h biogas yield using swine manure (SM) as the feedstock.

Economic Evaluation and Energy Efficiency Analysis. Apart from the biogas digestate, the primary product outputs in the BEEF system include electricity, NH4HCO3, bio-methane, and nearly pure CO2 (Fig. 3). Highest electricity, lowest bio-methane and CO2 are achieved in CAM2-based BEEF system. This is because much biogas is utilized in CHP unit to generate heat for meeting the high heat requirements of ammonia recovery ascribed to the low TAN concentration in the CAM-based biogas slurry. The highest NH4HCO3 output is observed from Fig. 3C in CHM2-based BEEF system, mainly because CHM2 has a high TKN content and then has the high TAN concentration in the biogas slurry after AD.

10


Page 11 of 23

(B) 6000

500

5000 Electricity output (MJ/h)

(A) 600

Bio-methane (Nm3/h)

400 300 200 100

4000 3000 2000 1000

0

1

SM

SM

2

3

SM

0

2 1 2 1 2 1 3 M M M FW FW M M CH CH CH CA CA Feedstock

1

SM

(D)

(C)

2

SM

3 2 1 2 1 2 1 3 SM CHM CHM CHM CAM CAM FW FW Feedstock

350

800

300 600

CO2 output (Nm3/h)

NH4HCO3 output (kg/h)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 2 33 34 3 35 4 36 37 5 38 39 40 6 41 42 7 43 44 45 8 46 47 9 48 49 50 10 51 52 53 11 54 55 12 56 57 58 59 60


400

200

250 200 150 100 50

0

1

SM

SM

2

0


1

SM

3 2 2 1 2 1 2 1 3 SM SM CHM CHM CHM CAM CAM FW FW Feedstock

Fig. 3. Outputs of primary products in BEEF system when using different feedstocks in the AD plant: (A), bio-methane; (B), electricity; (C), NH4HCO3 (dry matter); (D), nearly pure CO2. The lowest (~RMB¥ 674.6/h) and highest (~RMB¥1284.7/h) O&M costs are observed in FW2- and CHM2-based BEEF systems, respectively (Fig. 4A). Additionally, the overall O&M cost of BEEF system can be lowered by decreasing the cost of biogas production (Fig. 4A). The lowest biogas production O&M cost by using food wastes as feedstock in AD lead to its overall O&M costs lower than that by using animal manure as the feedstock. The revenues of BEEF system affected by the type of feedstock are shown in Fig. 4B. Biomethane, electricity, and NH4HCO3 are reasonably priced at RMB¥ 2.5/Nm3, RMB¥ 0.5/kWh, and RMB¥0.5/kg-NH4HCO3 (dry matter), respectively. Highest revenue (~1717.68 RMB¥/h) can be achieved in CHM2-based BEEF system.

11



(A)

Biogas production FW2

(B)

Biogas upgrading CHP Ammonia recovery

Bio-methane

FW1

FW1

CAM2

CAM2

CAM1

CAM1

CHM3 CHM2 CHM1

CHM2 CHM1 SM3

SM2

SM2

SM1

SM1

200

400 600 800 1000 O&M cost (RMB￥/h)

1200

NH4HCO3

CHM3

SM3

0

Electricity

FW2

Feedstock

Feedstock

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 17 2 18 3 19 20 4 21 22 23 5 24 25 6 26 27 28 7 29 30 8 31 32 33 9 34 35 36 10 37 38 11 39 40 41 12 42 43 13 44 45 46 14 47 48 49 15 50 51 16 52 53 54 17 55 56 18 57 58 59 19 60

Page 12 of 23

1400

0

200

400

600

800

1000 1200 1400 1600

Revenues (RMB￥/h)

Fig. 4. Operation and maintenance (O&M) costs (A) and revenues (B) of BEEF system using different feedstocks. The O&M costs for each unit are listed in Table 1, Table 5, and Table 8. Four biogas utilization systems are discussed in this study including BEEF, upgrading all the biogas (System Ⅰ), consuming all the biogas in CHP (System Ⅱ) and combusting all the biogas in the boiler for heat supply (System Ⅲ). In System Ⅰ, heat and electricity required in biogas upgrading is assumed to come from natural gas combustion with the electricity generation efficiency being 35% and heat generation efficiency being 82.5%.18 In System Ⅱ, the electricity generation efficiency is about 35%.29 In System Ⅲ, the heat generation efficiency of biogas boiler is about 82.5%.18 Clearly, System Ⅰ has the highest overall energy efficiency with about 55.9%, while System Ⅱ has the lowest overall energy efficiency with only 21% (Fig. 5A). As for BEEF system, the overall energy efficiency is up to about 55.9% when FW2 is used in AD plant, which is equalized to that of System Ⅰ. The overall energy efficiencies of BEEF system using different feedstocks are generally higher than that of System Ⅱ. On average, the overall energy efficiency of BEEF system in this study is about 48.4%, which is slightly lower than that of System Ⅲ. This indicates that BEEF is still a high energy efficiency system in spite of the consumption of partial biogas for ammonia recovery and biogas upgrading. Whatever feedstocks are adopted, BEEF system obtains a positive net profit due to its output of diverse valuable products including bio-methane, electricity and NH4HCO3, which has an advantage over System Ⅰ and System Ⅱ with little or even negative net profits because of the output of single product (Fig. 5B). The FW-based BEEF system can obtain the highest net profit due to its lowest O&M cost as shown in Fig. 4A. 12


Page 13 of 23

The lowest net profit is found for CAM2-based BEEF system, which may be attributed to the low NH4HCO3 output. Averagely, the net profit of animal manures-based BEEF system is about RMB¥365/1000 Nm3-biogas. BEEF system SystemⅠ: ony biogas upgrading SystemⅡ: only biogas used for CHP SystemⅢ: only biogas used for heat supply

70 60 50 40 30 20 10

(B) 1000 Net profit (RMB￥/1000 Nm3 biogas)

(A) 80 Overall energy efficiency (%)

11 2 3 42 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 3 22 4 23 24 5 25 26 27 6 28 29 7 30 31 32 8 33 34 9 35 36 37 10 38 39 40 11 41 42 12 43 44 45 13 46 47 14 48 49 50 15 51 52 53 16 54 55 17 56 57 58 18 59 60


BEEF system SystemⅠ: ony biogas upgrading SystemⅡ: only biogas used for CHP

800 600 400 200 0

0

1

SM

2

SM

1

3 2 1 2 2 1 1 3 SM CHM CHM CHM CAM CAM FW FW

SM

2

SM

Feedstock


Fig. 5. Energy efficiency (A) and profit (B) of BEEF system. Costs of biogas upgrading are listed in Table S8.

Negative CO2 Emission. For assessing the avoidable GHG emissions, the scenario that all the biogas from AD plant is combusted in a CHP unit, and all biogas digestate is taken into land application is selected as the baseline. In the baseline scenario, the global warming potential resulted from CO2 emission is assumed to be negligible, while CH4 leakages, NH3 and N2O emissions are inevitable.12, 30 CH4 emission is estimated at 1.79% and 0.2% during CHP and biogas upgrading process, respectively. NH3 emission is estimated at 0.3 kg NH3N/kg TANapplied, and that 1% of the deposited NH3-N is re-emitted as N2O-N.12 So, emissions of other GHG including CH4 and N2O should be considered in the baseline scenario. Fig. 6A shows negative CO2 emissions of different feedstock-based BEEF systems, where CO2 negative emissions refer to these CO2 separated from biogas in the form of nearly pure CO2 gas and NH4HCO3 based on the assumptions that these CO2-rich products can be transferred into the plant or soil in agriculture.31 The highest negative CO2 emission is acquired in the CAM1-based BEEF system, which might be explained by the fact that this BEEF system consumes the less biogas for ammonia recovery, thus more CO2 could be separated from biogas to avoid CO2 emission into atmosphere. An average of negative CO2 emission with 13



~277 Nm3/1000 Nm3-biogas is achieved in animal manure-based BEEF system, suggesting that about 69.3% of CO2 emission generated from AD plant can be avoided. The result also indicates that reducing the energy consumptions of ammonia recovery from biogas slurry is of importance for achieving the high net profit and negative CO2 emission simultaneously. Due to biogas upgrading and ammonia recovery from biogas slurry, BEEF system can obtain lower CH 4 and N2O emissions compared to baseline scenario (Fig. 6B). An average of ~40.57 Nm3-CO2 equivalent/1000 Nm3-biogas is avoided to emit in BEEF system due to lower CH4 slip in biogas upgrading unit than that in CHP unit. Highest CH4 and N2O emissions avoided (~144.6 Nm3-CO2 eq./1000 Nm3-biogas) can be acquired in the CHM2-based BEEF system mainly because of more ammonia recovery from biogas slurry leading to less NH3 emission. It should be noted that these GHG emissions derived from CH4 and N2O (Fig. 6B) can be avoided permanently only on the premise that the ammonium bicarbonate and bio-methane is used well and

(A)

140 120

400 350

(Nm3/1000 Nm3 biogas)

(B) Other GHG emissions avoided (Nm3- CO2 eq/1000 Nm3 biogas)

no more emissions occurred. Therefore, in this study, only CO2 captured from biogas is taken into account.

Negative emissions of CO2

11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 8 20 21 9 22 23 24 10 25 26 27 11 28 29 12 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 13 48 14 49 15 50 51 16 52 53 54 17 55 56 18 57 58 59 19 60

Page 14 of 23

300 250 200 150 100 50

Avoided N2O

100 80 60 40 20 0

0 3 2 1 2 1 2 2 1 1 3 SM SM SM CHM CHM CHM CAM CAM FW FW

Avoided CH4

2 1 3 2 1 2 1 3 2 1 SM SM SM CHM CHM CHM CAM CAM FW FW Feedstock

Feedstock

Fig. 6. CO2 negative emission (A) and other GHG emissions avoided triggered by N2O and CH4 emission control (B) in BEEF system.

Sensitivity Analysis. To have a deep insight into the effects of primary variables on the negative CO2 emission and net profit of BEEF system, a systemic sensitivity analysis was conducted as shown in Fig. 7. The benchmarks of the sensitivity analysis are listed as follows: CH4 concentration in biogas is 60%; heat 14


Page 15 of 23 11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 8 20 21 9 22 23 24 10 25 26 27 11 28 29 12 30 31 32 13 33 34 14 35 36 37 15 38 39 40 16 41 42 17 43 44 45 18 46 47 19 48 49 50 20 51 52 53 21 54 55 22 56 57 58 23 59 60


generation efficiency of CHP is 45%; heat consumptions of ammonia recovery are set at 45 MJ/kg-N, 25 MJ/kg-N and 135 MJ/kg-N for SM- and FW-based BEEF system, CHM-based system and CAM-based system, respectively. The increase in heat generation efficiency of CHP can lead to the elevation of the negative CO2 emission but the reduction of net profit (Fig. 7). This may be explained by the fact that the increase in the heat generation efficiency results in the reduced biogas consumption in CHP with more biogas flowing into biogas upgrading unit, therefore, more CO2 can be captured. However, high heat generation efficiency also means low electricity generation efficiency. Thus, the electricity output decreases resulting in the reduction of electricity revenue. In real biogas plant, CH4 content in biogas might vary from 40 vol.% to 75 vol.%,29 and this variation has a greatest impact on the net profit and negative CO2 emission of BEEF system (Fig. 7). Negative CO2 emission increases with the decrease of CH4 content in biogas, however the net profit reduces. For example, although the negative CO2 emission with 400 Nm3/h can be acquired in the SM-, CHM- and FW-based BEEF systems, their net profits are negative when CH4 concentration in biogas decreases to 36 vol.% (ratio = 0.6 in Fig. 7). As CH4 concentration elevates to about 80 vol.%, the net profit of most BEEF systems increases to above RMB¥ 1000/1000 Nm3-biogas as shown in Figs. 7B, 7D and 7H. Interestingly, the negative CO2 emission inversely reduces when CH4 content reduces from 48 vol.% to 36 vol.% in the CAM-based BEEF system as shown in Fig. 7E. That is because more than 60% of biogas have to be utilized in CHP unit to satisfy the heat demand in ammonia recovery unit due to the lower heat value of biogas with 36 vol.% CH4 concentration. Unlike the other two factors, reducing the energy consumption of ammonia recovery can result in the increase of both negative CO2 emission and net profit of BEEF system. Therefore, as a promising and developing technology, ammonia recovery from biogas digestate is deserved to be explored to obtain low energy requirement. In addition, no more than 60% of total nitrogen in the feedstock is recovered in the form of ammonia, hence technologies remain to be further developed so as to recover more nitrogen during/after 15



AD. A, SM

B, SM

350 300 300

280

250

260 240

200

Energy consumption of ammonia recovery Heat generation efficiency of CHP

220 200 0.6

0.8

1.0

1.2

150 1.4

450

900

400

600

350

300

300

0


250

1.6

0.6

0.8

1.0

1.2

1.4

-300

1.6

D, CHM

320 350

300 280

300

260

250

240

200


220 200 0.6

0.8

1.0

1.2

150 1.4

1000 550 800 500

600

450

400 200

400 0


350 0.6

1.6

E, CAM

1200

CH4 concentration in biogas

600

0.8

1.0

1.2

1.4

-200 1.6

F, CAM 280

250

240

200

200

150

160 Energy consumption of ammonia recovery Heat generation efficiency of CHP

100 0.6

0.8

1.0

1.2

120 1.4

1000

450

Profit (RMB ￥/1000 Nm3 biogas)

300

Negative emission of CO2 (Nm3/h)


1.6


400


800

400 350

600

300

400

250

200

200

0

150

-200


100 50 0.6

16


0.8

1.0

1.2

1.4

-400 1.6




340


C, CHM Negative emission of CO2 (Nm3/h)

1200 CH4 concentration in biogas


320

500



400



340


11 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 2 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 3 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 4 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 23

Page 17 of 23

G, FW

H, FW

340 350

320 300

300

280

250

260

200 Energy consumption of ammonia recovery Heat generation efficiency of CHP

240 220 0.6

0.8

1.0

1.2

1.4

150

950

1600 CH4 concentration in biogas

1.6

1400 900 1200 1000

850

800 800

600

750

400


700 0.6

0.8

1.0

1.2

1.4

200


400




360


1 2 3 4 5 6 7 8 9 10 11 12 13 1 14 15 2 16 17 3 18 19 20 4 21 22 23 5 24 25 6 26 27 7 28 29 8 30 31 32 9 33 34 10 35 36 37 11 38 39 40 12 41 42 13 43 44 45 14 46 47 15 48 49 50 16 51 52 53 17 54 55 56 18 57 58 59 60


1.6

Fig. 7. Sensitivity analysis of negative CO2 emission and net profit of BEEF system. x-axis value represents the ratio of variables to the benchmark. The benchmarks (ratio=1.0) of the sensitivity analysis are as follows: CH4 concentration in biogas is 60 vol.%, heat generation efficiency of CHP is 45% and the heat consumption of ammonia recovery in SM- and FW-based BEEF system is 45MJ/kg-N, while the heat consumption is 25 MJ/kg-N and 135 MJ/kg-N in CHM- and CAM-based systems, respectively. 

CONCLUSIONS In this study, aiming to increase the revenue of anaerobic digestion plant and achieve negative CO2 emission

simultaneously, we proposed a novel system called BEEF to treat biogas to generate Bio-Energy, Electricity and Fertilizer (BEEF). In BEEF system, the organic wastes are digested in anaerobic digestion to generate biogas and biogas digestate. Renewable aqueous ammonia is recovered from biogas digestate, and then is used as CO2 absorbent in biogas upgrading unit. Partial biogas is combusted in CHP unit to supply the heat and electricity required in the ammonia recovery and biogas upgrading units. Bio-methane, nearly pure CO2, and NH4HCO3 can be generated from BEEF system during biogas upgrading. An average of ~277 Nm3/h negative CO2 emission and a net profit of ~RMB ¥365 /1000 Nm3-biogas can be acquired using animal manure as the feedstocks. Especially, this system provides a pathway to the sustainable nutrients and carbon management to deal with the climate and environmental problems.

17


ACS Sustainable Chemistry & Engineering 11 2 3 4 52 6 7 8 93 10 11 4 12 13 14 15 5 16 17 6 18 19 20 21 7 22 23 24 25 8 26 27 28 9 29 30 31 32 10 33 34 35 36 11 37 38 39 40 12 41 42 13 43 44 45 14 46 47 15 48 49 50 16 51 52 17 53 18 54 55 19 56 57 58 20 59 60



Page 18 of 23

ASSOCIATED CONTENT

Supporting Information

Vacuum membrane distillation experimental process and results, cost of ammonia recovery, and costs of biogas upgrading.



AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected].

ORCID

Shuiping Yan: 0000-0001-9016-0267

Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENT

The authors thank the financial supports from the National Natural Science Foundation of China (NSFC) (No. 51676080, 51376078), and the Fundamental Research Funds for the Central Universities (No. 2662018PY046, 2662018QD028).



REFERENCES

(1) IEA CO2 emissions from fuel conbustion; 2017. https://webstore.iea.org/co2-emissions-from-fuelcombustion-highlights-2017 18


Page 19 of 23 11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 8 20 21 9 22 23 24 10 25 26 27 11 28 29 12 30 31 32 13 33 34 14 35 36 37 15 38 39 40 16 41 42 17 43 44 45 18 46 47 19 48 49 50 20 51 52 53 21 54 55 22 56 57 58 23 59 60


(2) Monlau, F.; Sambusiti, C.; Ficara, E.; Aboulkas, A.; Barakat, A.; Carrere, H., New opportunities for agricultural digestate valorization: current situation and perspectives. Energy & Environmental Science 2015, 8 (9), 2600-2621. DOI 10.1039/C5EE01633A. (3) Hijazi, O.; Munro, S.; Zerhusen, B.; Effenberger, M., Review of life cycle assessment for biogas production in Europe. Renewable and Sustainable Energy Reviews 2016, 54, 1291-1300. DOI 10.1016/j.rser.2015.10.013. (4) Wulf, S.; Jäger, P.; Döhler, H., Balancing of greenhouse gas emissions and economic efficiency for biogasproduction through anaerobic co-fermentation of slurry with organic waste. Agriculture, Ecosystems & Environment 2006, 112 (2), 178-185. DOI 10.1016/j.agee.2005.08.017. (5) Bui, M.; Fajardy, M.; Mac Dowell, N., Bio-Energy with CCS (BECCS) performance evaluation: Efficiency

enhancement

and

emissions

reduction.

Appl.

Energ.

2017,

195,

289-302.

DOI

10.1016/j.apenergy.2017.03.063. (6) Corsten, M.; Ramírez, A.; Shen, L.; Koornneef, J.; Faaij, A., Environmental impact assessment of CCS chains – Lessons learned and limitations from LCA literature. Int. J. Greenh. Gas Con. 2013, 13, 59-71. DOI 10.1016/j.ijggc.2012.12.003. (7) Abatzoglou, N.; Boivin, S., A review of biogas purification processes. Biofuel. Bioprod. and Bior. 2009, 3 (1), 42-71. DOI 10.1002/bbb.117. (8) Ryckebosch, E.; Drouillon, M.; Vervaeren, H., Techniques for transformation of biogas to biomethane. Biomass Bioenerg. 2011, 35 (5), 1633-1645. DOI 10.1016/j.biombioe.2011.02.033. (9) Shen, Y.; Linville, J. L.; Urgun-Demirtas, M.; Schoene, R. P.; Snyder, S. W., Producing pipeline-quality biomethane via anaerobic digestion of sludge amended with corn stover biochar with in-situ CO2 removal. Appl. Energ. 2015, 158, 300-309. DOI 10.1016/j.apenergy.2015.08.016. (10) Yan, S.; He, Q.; Zhao, S.; Zhai, H.; Cao, M.; Ai, P., CO2 removal from biogas by using green amino acid 19



Page 20 of 23

salts: Performance evaluation. Fuel Process. Technol. 2015, 129, 203-212. DOI 10.1016/j.fuproc.2014.09.019. (11) Yan, S.; He, Q.; Zhao, S.; Wang, Y.; Ai, P., Biogas upgrading by CO2 removal with a highly selective natural amino acid salt in gas–liquid membrane contactor. Chem. Eng. Process. 2014, 85 (0), 125-135. DOI 10.1016/j.cep.2014.08.009. (12) Crolla, A.; Kinsley, C.; Pattey, E., 13 - Land application of digestate. In The Biogas Handbook, Wellinger, A.; Murphy, J.; Baxter, D., Eds. Woodhead Publishing: 2013. DOI 10.1533/9780857097415.2.302. (13) Drosg, B.; Fuchs, W.; Al Seadi, T.; Madsen, M.; Linke, B., Nutrient Recovery by Biogas Digestate Processing.

IEA

Bioenergy

2015.

http://task37.ieabioenergy.com/files/daten-

redaktion/download/Technical%20Brochures/NUTRIENT_RECOVERY_RZ_web2.pdf (14) Li, K.; Yu, H.; Feron, P.; Tade, M.; Wardhaugh, L., Technical and Energy Performance of an Advanced, Aqueous Ammonia-Based CO2 Capture Technology for a 500 MW Coal-Fired Power Station. Environ. Sci. Technol. 2015, 49 (16), 10243-10252. DOI 10.1021/acs.est.5b02258. (15) He, Q.; Yu, G.; Tu, T.; Yan, S.; Zhang, Y.; Zhao, S., Closing CO2 loop in biogas production: recycling ammonia as fertilizer. Environ. Sci. Technol. 2017, 51 (15), 8841-8850. DOI 10.1021/acs.est.7b00751. (16) He, Q.; Yu, G.; Wang, W.; Yan, S.; Zhang, Y.; Zhao, S., Once-through CO2 absorption for simultaneous biogas upgrading and fertilizer production. Fuel Process. Technol. 2017, 166, 50-58. DOI 10.1016/j.fuproc.2017.05.027. (17) He, Q.; Xi, J.; Wang, W.; Meng, L.; Yan, S.; Zhang, Y., CO2 absorption using biogas slurry: Recovery of absorption performance through CO2 vacuum regeneration. Int. J. Greenh. Gas Con. 2017, 58, 103-113. DOI 10.1016/j.ijggc.2017.01.010. (18) Hakawati, R.; Smyth, B. M.; McCullough, G.; De Rosa, F.; Rooney, D., What is the most energy efficient route for biogas utilization: Heat, electricity or transport? Appl. Energ. 2017, 206, 1076-1087. DOI 10.1016/j.apenergy.2017.08.068. 20


Page 21 of 23 11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 8 20 21 9 22 23 24 10 25 26 27 11 28 29 12 30 31 32 13 33 34 14 35 36 37 15 38 39 40 16 41 42 17 43 44 45 18 46 47 19 48 49 50 20 51 52 53 21 54 55 22 56 57 58 23 59 60


(19) Weiland, P., Biogas production: current state and perspectives. Appl. Microbiol. Biot. 2010, 85 (4), 849860. DOI 10.1007/s00253-009-2246-7. (20) Dalkılıc, K.; Ugurlu, A., Biogas production from chicken manure at different organic loading rates in a mesophilic-thermopilic two stage anaerobic system. J. Biosci. Bioeng. 2015, 120 (3), 315-322. DOI 10.1016/j.jbiosc.2015.01.021. (21) Jimenez, J.; Lei, H.; Steyer, J.-P.; Houot, S.; Patureau, D., Methane production and fertilizing value of organic waste: Organic matter characterization for a better prediction of valorization pathways. Bioresour. Technol. 2017, 241, 1012-1021. DOI 10.1016/j.biortech.2017.05.176. (22) Zhang, W.; Heaven, S.; Banks, C. J., Continuous operation of thermophilic food waste digestion with side-stream

ammonia

stripping.

Bioresour.

Technol.

2017,

244

(Pt

1),

611-620.

DOI

10.1016/j.biortech.2017.07.180. (23) Criscuoli, A.; Carnevale, M. C.; Drioli, E., Evaluation of energy requirements in membrane distillation. Chem. Eng. Process. 2008, 47 (7), 1098-1105. DOI 10.1016/j.cep.2007.03.006. (24) Bonmatı́, A.; Flotats, X., Air stripping of ammonia from pig slurry: characterisation and feasibility as a pre- or post-treatment to mesophilic anaerobic digestion. Waste Manage. 2003, 23 (3), 261-272. DOI 10.1016/S0956-053X(02)00144-7. (25) Zhao, Q.-B.; Ma, J.; Zeb, I.; Yu, L.; Chen, S.; Zheng, Y.-M.; Frear, C., Ammonia recovery from anaerobic digester effluent through direct aeration. Chem. Eng. J. 2015, 279, 31-37. DOI 10.1016/j.cej.2015.04.113. (26) Lee, J.-G.; Kim, W.-S., Numerical study on multi-stage vacuum membrane distillation with economic evaluation. Desalination 2014, 339, 54-67. DOI 10.1016/j.desal.2014.02.003. (27) Xing, Y.-L.; Qi, C.-H.; Feng, H.-J.; Lv, Q.-C.; Xu, G.-R.; Lv, H.-Q.; Wang, X., Performance study of a pilot-scale multi-effect vacuum membrane distillation desalination plant. Desalination 2017, 403, 199-207. DOI 10.1016/j.desal.2016.07.008. 21


ACS Sustainable Chemistry & Engineering 11 2 3 42 5 63 7 8 94 10 11 5 12 13 14 6 15 16 7 17 18 19 8 20 21 9 22 23 24 10 25 26 27 11 28 29 12 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 23

(28) Scholwin, F.; Nelles, M., 9 - Energy flows in biogas plants: analysis and implications for plant design. In The Biogas Handbook, Wellinger, A.; Murphy, J.; Baxter, D., Eds. Woodhead Publishing: 2013. DOI 10.1533/9780857097415.2.212. (29) Verbeeck, K.; Buelens, L. C.; Galvita, V. V.; Marin, G. B.; Van Geem, K. M.; Rabaey, K., Upgrading the value of anaerobic digestion via chemical production from grid injected biomethane. Energ. Environ. Sci. 2018, 11 (7), 1788-1802. DOI 10.1039/c8ee01059e. (30) Beil, M.; Beyrich, W., 15 - Biogas upgrading to biomethane. In The Biogas Handbook, Wellinger, A.; Murphy, J.; Baxter, D., Eds. Woodhead Publishing: 2013. DOI 10.1533/9780857097415.3.342. (31) Yan, S.; Zhang, L.; Ai, P.; Wang, Y.; Zhang, Y.; Li, S., CO2 absorption by using a low-cost solvent: biogas slurry produced by anaerobic digestion of biomass. Energy Procedia 2013, 37, 2172-2179. DOI 10.1016/j.egypro.2013.06.096.

22


Page 23 of 23

For Table of Contents Use Only

Negative CO2 emission CO2 utilization

CO2 output

BEEF Biogas Biogas storage

Biogas upgrading

NH4HCO3 output

Biogas 0

Biogas 100%

Combined heat and power (CHP)

Livestock and poultry wastes input

Profit increasing

Bio-methane output

NH3

11 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 2 28 3 29 30 4 31 32 5 33 34 6 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Electricity output

Biogas digestate Anaerobic digestion

Ammonia recovery

Synopsis： This novel BEEF system used all the resources from renewable organic wastes to achieve negative CO2 emission and increase of profit simultaneously based on anaerobic digestion.

23


B.E.E.F: A Sustainable Process Concerning Negative CO2 Emission

Recommend Documents