Life Cycle Assessment and Economic Analysis of an Innovative Biogas Membrane Reformer for Hydrogen Production

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Article Life Cycle Assessment and Economic Analysis of an Innovative Biogas Membrane Reformer for Hydrogen Production

Gioele Di Marcoberardino 1,* , Xun Liao 2, Arnaud Dauriat 2, Marco Binotti 1 and Giampaolo Manzolini 1

1 Politecnico di Milano, Dipartimento di Energia, via Lambruschini 4, 20156 Milano, Italy; [email protected] (M.B.); [email protected] (G.M.) 2 Quantis, EPFL Innovation Park building D, 1015 Lausanne, Switzerland; [email protected] (X.L.); [email protected] (A.D.) * Correspondence: [email protected]; Tel.: +39-02-2399-3935

Received: 21 December 2018; Accepted: 4 February 2019; Published: 8 February 2019

Abstract: This work investigates the environmental and economic performances of a membrane reactor for hydrogen production from raw biogas. Potential benefits of the innovative technology are compared against reference hydrogen production processes based on steam (or autothermal) reforming, water gas shift reactors and a pressure swing adsorption unit. Both biogas produced by landfill and anaerobic digestion are considered to evaluate the impact of biogas composition. Starting from the thermodynamic results, the environmental analysis is carried out using environmental Life cycle assessment (LCA). Results show that the adoption of the membrane reactor increases the system efficiency by more than 20 percentage points with respect to the reference cases. LCA analysis shows that the innovative BIONICO system performs better than reference systems when biogas becomes a limiting factor for hydrogen production to satisfy market demand, as a higher biogas conversion efficiency can potentially substitute more hydrogen produced by fossil fuels (natural gas). However, when biogas is not a limiting factor for hydrogen production, the innovative system can perform either similar or worse than reference systems, as in this case impacts are largely dominated by grid electric energy demand and component use rather than conversion efficiency. Focusing on the economic results, hydrogen production cost shows lower value with respect to the reference cases (4 €/kgH2 vs 4.2 €/kgH2) at the same hydrogen delivery pressure of 20 bar. Between landfill and anaerobic digestion cases, the latter has the lower costs as a consequence of the higher methane content.

Keywords: biogas; hydrogen production; ﬂuidized bed membrane reactor; life cycle assessment; economic analysis

1. Introduction Hydrogen is a promising energy carrier, that can replace fossil fuels in power generation and transports, when produced by renewable sources [1]. Nowadays H2 production mainly comes from steam reforming of natural gas [2], although H2 can be produced from others fossil sources by hydrocarbon reforming and pyrolysis of coal or natural gas, or from renewable feedstocks by biological or thermochemical processing of biomass or water splitting [3]. In Europe, the common biogas (BG) production process is the anaerobic digestion of agricultural waste, manure, and energy crops; then biogas, or biomethane (if the plant has an upgrading step) is currently fed to an internal combustion engine for electricity and heat production [4]. The Fuel Cells and Hydrogen Joint Undertaking (FCH-JU) project BIONICO, ﬁnanced by the European Commission, aims at developing

Processes 2019, 7, 86; doi:10.3390/pr7020086 www.mdpi.com/journal/processes Processes 2019, 7, 86 2 of 14

biogas, that mainly consists of methane and carbon dioxide, was identified as one of the cheapest and promising way for hydrogen production [1]. As shown in Figure 1, the conventional reforming process consists of a steam reformer (SMR) or autothermal reformer (ATR), typically working at 800 °C, followed by two water gas shift (WGS) reactors (high-temperature, HT-WGS, and low-temperature, LT-WGS) and by a pressure swing Processesadsorption2019, 7 ,(PSA) 86 unit for hydrogen separation [5]. The innovative membrane reactor technology,2 of 14 such as the autothermal catalytic membrane reactor (ATR-CMR) in Figure 1, developed within BIONICO, allows the production and separation of hydrogen in a single vessel, with advantages over an innovative concept for green hydrogen production from raw biogas. Steam reforming of raw traditional biogas reforming related to the increase of the overall conversion efficiency and to the biogas, that mainly consists of methane and carbon dioxide, was identified as one of the cheapest and strong decrease of equipment size due to the process intensification [6]. promising way for hydrogen production [1]. Compared to previous works [7,8], this paper starts from the energy and economic consideration As shown in Figure1, the conventional reforming process consists of a steam reformer (SMR) to evaluate the environmental performance of the innovative BIONICO process comparing results or autothermal reformer (ATR), typically working at 800 ◦C, followed by two water gas shift (WGS) with the conventional H2 production processes from raw biogas assumed as references. The reactors (high-temperature, HT-WGS, and low-temperature, LT-WGS) and by a pressure swing combination of conventional techno-economic assessment with environmental assessment is adsorptionnecessary (PSA)when unitdealing for hydrogenwith technologies separation aiming [5]. Theat increasing innovative the membrane overall system reactor efficiency, technology, suchreducing as the the autothermal energy consumption. catalytic membrane Life cycle reactor assessment (ATR-CMR) (LCA) determines in Figure1 ,the developed environmental within BIONICO,impacts including allowsthe all the production system aspects, and separation covering ofmultiple hydrogen indicators, in a single including vessel, water with withdrawal, advantages overecosystems, traditional resources biogas reformingdepletion, related and human to the health, increase with of the detailed overall analysis conversion on the efficiency climate and change to the strongimpact. decrease of equipment size due to the process intensification [6].

Conventional process Off-gas

Landfill SR o r ATR HT-WGS LT-WGS BIOGAS Sulphur PSA PURE H Removal (800°C) (350°C) (200°C) 2 Anaerobic digester

ATR-CM R H O 2 (500-550°C) AIR

Innovative Ret en t at e process

FigureFigure 1.1. Hydrogen producti productionon from from biogas. biogas.

ComparedVarious LCA to previous studies have works been [7, 8performed], this paper on starts biogas from production the energy system and and economic its conversion consideration into tocombined evaluate theelectricity environmental and heat performance (CHP), and ofthey the all innovative provide BIONICOquite similar process insights. comparing Whting results et al. with[9] theshowed conventional that the H global2 production warming processes potentials from (GWP) raw biogasof a CHP assumed system asfed references. with biogas The from combination anaerobic of conventionaldigestion of techno-economicagricultural wastes assessment can be withmuch environmental lower compared assessment with fossil is necessary fuel alternatives: when dealing in withparticular, technologies climate aiming change at increasingimpacts are the influenced overall system by the efficiency, type and reducing source theof feedstock, energy consumption. digestate Lifestorage cycle and assessment its application (LCA) on determines land. Bacenetti the environmental et al. [10] found impacts that feedstock including production all thesystem and digestate aspects, coveringemissions multiple are the indicators, main contributors including to water the withdrawal,impact of agricultural ecosystems, anaerobic resources digestion depletion, plants. and human Van health,Stappen with et detailedal. [11] identified analysis on th theat the climate key determining change impact. factors for LCA are the choices of biogas feedstockVarious and LCA displaced studies marginal have been technologies performed for on biogaselectricity production production system and fertilizers. and its conversion Hijazi et intoal. combined[12] reviewed electricity the LCA and study heat of (CHP), biogas and production they all in provide Europe, quite and similaralso found insights. sourcesWhting of feedstocks et al. [9 ] showedfor biogas that determining the global warming the overall potentials environmental (GWP) impact of a CHP for systembiogas systems. fed with Moreover, biogas from some anaerobic LCA digestionstudies have of agricultural also been wastesperformed can beon much hydrogen lower prod compareduction withfrom fossilbiogas. fuel Hajja alternatives:ji et al. [13] in particular,found a climatecradle changeto grave impacts carbon arefootprint influenced of 5.59 by kg theCO2-eq type per and kg sourceof H2 produced of feedstock, from digestate biogas from storage anaerobic and its applicationdigesters. More on land. than Bacenetti 96% of etthose al. [10impact] found came that from feedstock the biogas production feedstock and production digestate emissions stage, and are theimpact main results contributors are highly to the influenced impact of by agricultural the amount anaerobic of artificial digestion fertilizer plants. displaced Van Stappenby digestate et al. and [11 ] identifiedcredits from that recycling the key determining the plant construction factors for materials LCA are and the choicesequipment. of biogas Valente feedstock et al., [14] and calculated displaced marginalthe harmonized technologies carbon for footprint electricity fr productionom 71 case and studies fertilizers. of green Hijazi H2 production: et al. [12] reviewed the only the case LCA study study ofrelated biogas to production biogas reforming in Europe, [13] and resulted also found in a sourcesharmonized of feedstocks carbon footprint for biogas is determining7.34 kgCO2-eq per the overallkg of environmentalH2 produced. impactBattista foret al., biogas [15] systems.investigated Moreover, an ATR some reforming LCA studies process have finding also that been the performed carbon on hydrogen production from biogas. Hajjaji et al. [13] found a cradle to grave carbon footprint of 5.59 kgCO2-eq per kg of H2 produced from biogas from anaerobic digesters. More than 96% of those impact came from the biogas feedstock production stage, and impact results are highly influenced by the amount of artificial fertilizer displaced by digestate and credits from recycling the plant construction materials and equipment. Valente et al., [14] calculated the harmonized carbon footprint from 71 case studies of green H2 production: the only case study related to biogas reforming [13] resulted in a harmonized carbon footprint is 7.34 kgCO2-eq per kg of H2 produced. Battista et al., [15] investigated Processes 2019, 7, 86 3 of 14 an ATR reforming process finding that the carbon footprint from required material production and the total life cycle stages are 0.08 and 7.24 kgCO2-eq per kg of H2 produced respectively. Major impacts are related to energy consumption of the PSA and air compressors as well as CO2 emitted during the auto-thermal reforming process. Most of the above studies focus on answering the question: “what are the environmental impacts attributed to producing biogas or its derivative product?” Furthermore, they also identified the hotspots influencing impacts are the sourcing of substrates and digestate storage. Admittedly, the biogas production stage is important, however, it is less relevant to our question. In this study, our question is different. The focus is not to debate if we should produce biogas, nor what feedstock of substrates or digestate storage options should be chosen. Instead, the reference condition in this study considers the existing biogas from waste substrates that have been or will be managed for energy production or simply flared without energy recovery. From this reference point, the purpose of our study is to answer the following question: “What technologies are preferable for the environment by diverting the biogas mentioned above for producing hydrogen?” This study aims to provide a techno-economic and environmental life cycle assessment of the ATR-CMR technology and of the reference technology under different configurations (SMR or ATR) and operating conditions.

2. Case Studies Six case studies, that differ in terms of production process and biogas composition, are investigated. The innovative BIONICO system is compared with two conventional fuel processor (SMR and ATR); on the other hand, two raw biogas compositions biogases produced by landﬁll (LF) and anaerobic digestion (AD) are considered. All three systems are designed to produce 100 kg/day of pure hydrogen. Moreover, this work sets a pressure delivery of 20 bar in order to compare the system efﬁciency with the conventional plants (an additional hydrogen compressor is introduced since hydrogen stream is produced at ambient pressure). As shown in Table1, the main biogas differences lie on CH4 and inert (CO2,N2) content.

Table 1. Investigated biogas compositions. LF: landﬁll; AD: anaerobic digestion.

Species Units LF AD

CH4 44.2 58.1

CO2 34.0 33.9

N2 % mol 16.0 3.8

O2 2.7 1.1

H2 0.0165 - CO 0.0006 -

H2O Saturated Saturated p, T bar, ◦C 1.013, 25 1.013, 25 LHV MJ/kg 12.7 17.8

2.1. System Layouts Figure2 shows layouts for both a conventional system based on steam reforming (Figure2 left) or auto-thermal reforming (Figure2 right), while the innovative plant with auto-thermal membrane reactor and vacuum pump is represented in Figure3. Processes 2019, 7, 86 4 of 14

BGfeed

CMPBG BG brn BGfeed AIRfeed SMR CMP (800 °C) Offgas CMPAIR BG

Flue gas AIR ATR brn (800 °C) AIRbrn Burner HX-4 HT-WGS Reformate HX-4 HT-WGS Reformate Burner Offgas (SH) HX-3

CMPH2 Flue gas H2 HX-3 (EV) HX-2 PSA H2 CMPH2 Exhaust HX-2 PSA LT-WGS Exhaust SEP-2 LT-WGS SEP-2 HX-1 HX-1 SEP-1 SEP-1

H2Ofeed H2Ofeed

Water Water Processes 2019, 7, 86 4 of 14 P-1 Processes 2019, 7, 86 P-1 4 of 14 Figure 2. Reference system layouts: steam reformer (SMR) reforming solution (left) and autothermal BGfeed reformer (ATR) reforming solution (right). CMPBG BG brn BGfeed AIRfeed SMR Offgas CMPBG In the first reference(800 °C) layout (Figure 2, left), a mixtureCMPAIR of compressed BG and steam is fed to the Flue gas AIR ATR SMR reactor. After a first cooling step (HX-4),brn the syngas exiting(800 the°C) reforming reactor is sent to water AIRbrn Burner HX-4 HT-WGS gas shift reactorsReformate to promote the CO conversion in CO2, increasing hydrogen production. The HX-4 HT-WGS Reformate Burner Offgas (SH) resulting streamHX-3 consists of a H2 rich syngas diluted with inert gases that, after the water removal, is

CMPH2 Flue gas H2 2HX-3 sent to a pressure swing adsorption unit to recover a pure H (EV) flow. The heat required by the HX-2 PSA H2 CMPH2 endothermic reaction at the SMR is suppliedExhaust by the combustion of the PSAHX-2 off-gas together with an PSA Exhaust additional amount ofLT-WGS biogas (BGbrn). Regarding the second reference layout (Figure 2, right), the main SEP-2 LT-WGS SEP-2 difference with the previous caseHX-1 relies on the main reactor for biogas to hydrogen conversion. The HX-1 SEP-1 stream at the inlet of the reactor is a mixture of compressed BG, steam and air.SEP-1 In fact, the heat H2Ofeed H2Ofeed required by the endothermic reforming reactionWater is balanced by the partial oxidation of theWater feed fuel with air. The intake of air is always below stoichiometry and it is regulated to control the reactor P-1 operating temperature. Thanks to the partial oxidation, there is no need to supplyP-1 an additional amountFigure of biogas 2. Reference to the system burner: layouts: in the steamATR configurat reformer (SMR)(SMRion,) the reforming burner solution is fed only (left) with and autothermalthe off-gas from the PSA.reformer (ATR)(ATR) reformingreforming solutionsolution (right).(right).

Retentate In the first reference layout (Figure 2, left), a mixture of compressed BG and steam is fed to the HX-2 SMR reactor. After a first cooling step (HX-4), the syngas exiting the reforming reactor is sent to water CMPH2 gas shift reactors to promote the CO conversion in CO2, increasing hydrogen production. The Vac.P. H resulting stream consists of a HATR-CMR2 rich syngas diluted2 withHX-1 inert gases that, after the water removal, is

HX-3 2 sent to a pressure swing adsorption unit to recover a pure HHXD-1 flow. The heat required by the endothermic reaction at the SMR is supplied by the combustion of the PSA off-gas together with an

brn additional amount of biogas (BGBGfeed). Regarding the second reference layout (Figure 2, right), the main

difference with the previous case relies on the main reactorreaction for biogas to hydrogen conversion. The

CMPBG CMPair O 2 stream at the inlet of the reactor is a mixture of compressedH BG,Exhaust steam and air. In fact, the heat required by the endothermic reforming reactionAirATR is balanced by the partial oxidation of the feed fuel Burner HXD-2 with air. The intake of air is always below stoichiometry and it is regulated to control the reactor operating temperature. Thanks to theHX-4 partial oxidation, there is noSep need to supply an additional amount of biogas to the burner: in theAirbrn ATR configuration, the burner is fed only with the off-gas from Sep the PSA. water rec. Retentate

HX-2 P-1 CMPH2 Figure 3. Innovative BIONICO system layouts (autothermal catalyticVac.P. membrane reactor, ATR-CMR). H Figure 3. Innovative BIONICOATR-CMR system layouts2 (autothermHX-1al catalytic membrane reactor, ATR-CMR).

In the ﬁrst reference layout (Figure2, left), a mixtureHX-3 of compressed BG and steam is fed to the HXD-1 SMR reactor. After a ﬁrst cooling step (HX-4), the syngas exiting the reforming reactor is sent to water gas shift reactors to promote the CO conversion in CO2, increasing hydrogen production. The resulting BGfeed stream consists of a H rich syngas diluted with inert gases that, after the water removal, is sent to

2 reaction

CMPBG CMPair O 2

a pressure swing adsorption unit to recover a pure H flow.H The heat required by the endothermic 2 Exhaust reaction at the SMR is supplied by the combustionAirATR of the PSA off-gas together with an additional Burner HXD-2 amount of biogas (BGbrn). Regarding the second reference layout (Figure2, right), the main difference with the previous case relies on the mainHX-4 reactor for biogas to hydrogenSep conversion. The stream at the inlet of the reactor is a mixtureAir of compressed BG, steam and air. In fact, the heat required by the Sep brn endothermic reforming reaction is balanced by the partial oxidation of the feed fuel with air. The intake water of air is always below stoichiometry and it is regulatedrec. to control the reactor operating temperature. Thanks to the partial oxidation, there is no need to supply an additional amount of biogas to the burner: in the ATR configuration, the burner is fed onlyP-1 with the off-gas from the PSA. In the BIONICO layout (Figure2, right), the BG is firstly compressed (CMP BG), then preheated up to 300Figure◦C in 3. HX-4 Innovative and mixed BIONICO with steamsystem and layouts water (autotherm at the inletal catalytic of the ATR-CMR. membrane Atreactor, the ATR-CMR ATR-CMR). outlet,

Processes 2019, 7, 86 5 of 14

two streams, the retentate and the pure H2, leave from the top section of the reactor. The retentate stream, which mainly consists of steam, CO2 and N2 with the remaining CO, CH4 and H2 is cooled down to 200 ◦C and throttled before being combusted in air. The separated hydrogen is cooled down to 30 ◦C and then compressed to the delivery pressure by the vacuum pump/hydrogen compressor. The amount of hydrogen separated in the ATR-CMR is determined so that the thermal power of the retentate closes the energy balance of the system avoiding additional BG supply.

2.2. Techno-Economic Results The innovative fuel processor and the conventional systems, together with their relative balance of plant, are implemented in Aspen Plus® (AspenTech, Bedford, Massachusetts, MA, USA) [16], where mass and energy balances are solved. The methodology adopted is consistent with previous works [8,17]. A phenomenological model of membrane reactor developed in Aspen Custom Modeler®(ACM) was adopted [18]. The scheme of the membrane reactor model and the main membrane features are summarised respectively in Figure A1 and Table A1 in the AppendixA section. All the cases are compared in terms of overall system efficiency, defined in Equation (1) as the ratio of H2 energy output to biogas and auxiliaries’ energy inputs: . mH2 LHVH2 nsys = . . (1) W mBG, f + mBG,aux LHVBG + aux/nel,re f where LHVH2 is equal to 120 MJ/kg [19]; Waux is the sum of the electric consumptions of the system auxiliaries (i.e., compressors, pumps, control system); ηel,ref is set equal to 45% as the average electric efficiency of the power generating park [20]. The main design parameters for the investigated systems are listed in Table2. A sensibility analysis on reactors operating conditions (p, T and steam to carbon S/C), and reactor geometry for the innovative ATR-CMR solution produced more than 400 simulations.

Table 2. Sensibility analysis: design parameters. SMR: steam reformer; ATR: autothermal reformer; CMR: catalytic membrane reactor.

Parameter Units SMR ATR BIONICO ATR-CMR Biogas (BG) - LF-AD LF-AD LF-AD Reactors operating conditions T max reactors ◦C 800 800 550-600 S/C - 4 3 3-3.5 P feed bar 4-20 4-20 8-16 Reactor geometry D reactor m - - 0.44-0.6 Membrane distance m - - 0.01-0.026

Table3 summarizes the thermodynamic and economic results for the two biogas compositions with the highest efficiency [7,8]. The overall system efficiency for the BIONICO system is higher than 65% which is at least 19 and 41 percentage points higher than SMR and ATR cases. Starting from the thermodynamic results, a preliminary economic analysis of the BIONICO system is carried out to compare the cost of produced hydrogen at different operating conditions. Results are also compared with values found for conventional hydrogen production systems from [7]. The total plant cost (TPC) is calculated with a bottom-up approach breaking down the power plant into basic components or equipment, and then adding installation costs, indirect costs and owner’s and contingencies costs [21]. The components costs, obtained from literature, quotes and reports are then scaled and actualized with the CEPCI index. To evaluate the final levelized cost of Processes 2019, 7, 86 6 of 14 hydrogen (LCOH), consumables, auxiliaries variable and fixed costs are added to the TPC, according to the following formulation: (TPC × CCF) + CO&M + Co&Mvar × heq LCOH = f ix (2) MH2 where CCF represents the carrying charge factor [21] and MH2 is the amount of hydrogen produced in one year of operation. The total installation costs were taken equal to 65% and 80% of the total equipment cost for the innovative and conventional systems respectively [22,23]. Fixed operation and maintenance (O & M) costs are represented by maintenance, insurance and operators costs, while variable O&M costs consider consumables such as catalyst, biogas [24], process water, membranes and auxiliaries electric energy consumptions [25]. Palladium membranes on ceramic supports cost is retrieved from the FERRET project [26] and refers to a production at a semi-industrial scale: membrane cost is included both in the capital cost and in the O & M variable costs taking into account a lifetime of 5 years. The complete methodology and the detailed components costs are reported in [7,8].

Table 3. Techno-economic results for reference and innovative BIONICO systems.

BIONICO Parameter Units SMR ATR ATR-CMR BG - LF AD LF AD LF AD T max reactors ◦C 800 800 800 800 550 550 (S/C)/pfeed - 4/14 4/12 3/18 3/18 3/12 3/12 H2 ﬂow/pressure kg/day/bar 100/20 100/20 100/20 100/20 100/20 100/20 BG Input kW 247 229 407 368 154.6 154.8 Tot aux cons. kW 24.3 17.9 73.0 60.0 24.8 24.1 ηsys % 46.2 51.7 24.5 27.8 65.1 66.1 LCOH €/kg 4.29 4.21 6.60 6.41 4.11 4.01

Regarding the economic analysis, hydrogen production cost shows lower value respect to the reference cases (4 €/kgH2 vs 4.2 €/kgH2) at the same hydrogen delivery pressure of 20 bar. Between landﬁll and anaerobic digestion cases, the latter has the lower costs as consequence of the higher methane content.

3. Lifecycle Assessment (LCA) Methodology The life cycle assessment approach considered the standards, ISO 14040 [27] and ISO 14044 [28], and the FC-Hy guide for performing LCAs on hydrogen technologies [29]. The functional unit is ◦ deﬁned as providing 1 kg of H2 (LHV = 120 MJ/kg) at 20 bar, 15 C and 99.99% of purity to satisfy the hydrogen market demand. The system boundary is shown in Figure4 where BIONICO hydrogen production technology is compared to the conventional systems. The biogas production process and the H2 storage, delivery and use are excluded, being equivalent for all the systems. This study considered the impact of the H2 production system on the current biogas availability and utilization where nowadays biogas is fed to an internal combustion engine producing electric and thermal energy. Two LCA scenarios are developed:

1. Biogas availability for H2 production is limited. Under this scenario, a system with a higher biogas conversion efficiency (i.e., BIONICO process) can supply more H2 to the market. Choosing a technology with lower efficiency means it will require a certain amount of H2 produced from conventional process (such as natural gas steam reforming) to meet the same demand, as shown in Figure5. 2. Biogas production is abundant, thus there is a surplus of biogas which is simply flared. In this scenario, biogas utilization is not competing with other potential uses. Processes 2019, 7, 86 7 of 14 ProcessesProcesses 2019 2019, 7, ,7 86, 86 7 7of of 14 14

SystemSystem boundary boundary

WasteWaste substrate substrate supplysupply WaterWater disposal disposal LF LFor orAD AD EquipmentEquipment and and Displaced Marginal auxiliaryauxiliary input input Biogas production Energy recovery Electricity and heat Displaced Marginal Biogas production Energy recovery Electricity and heat energy EmissionsEmissions energy

Displaced artificial Displaced artificial DigestateDigestate fertilizerfertilizer

DisplacedDisplaced animal animal BiogasBiogas purification/ purification/ feedfeed sulphursulphur removal removal EquipmentEquipment and and infrastractureinfrastracture input input

Water and Air NaturalNatural gas gas Water and Air productionproduction

BIONICOBIONICO SMRSMR or orATR ATR ATR-CMRATR-CMR HT-WGSHT-WGS and and RetentateRetentate LT-WGSLT-WGS PSAPSA

Off-gasOff-gas HydrogenHydrogen Pure H2 production Pure H2 production

Delivery LegendLegend Delivery ExistingExisting reference reference conditions conditions for for biogas biogas utilization and H2 production Avoided utilization and H2 production Use Avoided H2 production processes considered in Use production H2 production processes considered in production BIONICOBIONICO project project Excluded activities Excluded activities End of life End of life FigureFigureFigure 4. 4.4. System SystemSystem boundaries boundaries boundaries for for the the for reference reference the reference techno technologies technologieslogies (SMR (SMR and and (SMR ATR) ATR) and and and ATR)BIONICO BIONICO and ATR-CMR BIONICOATR-CMR technology.ATR-CMRtechnology.technology.

Figure 5. Scenario 1: biogas utilization and H2 production from the different systems. FigureFigure 5. 5. ScenarioScenario 1: 1: biogas biogas utilization utilization and and H H22 productionproduction from from the the different different systems. systems.

ForForFor the thethe foreground foreground foreground life life life cycle cycle cycle inventory inventory inventory data, data,data, biogas biogasbiogas electricity electricityelectricity and andand auxiliary auxiliaryauxiliary inputs inputsinputs (water, (water,(water, air) air)air) requiredrequiredrequired for for for the the the H H H22 production2production production stagesstages stages areare are based based based on on on the the the techno-economictechno-economic techno-economic modelling modelling modelling data. data. data. Component Component Component datadatadata (including (including reactors,reactors, reactors, catalyst, catalyst, catalyst, membrane) membrane) membrane) are are collectedare collected collected from from partnersfrom partners partners and also and and data also also from data data a previousfrom from a a previousEuropeanprevious European projectEuropean related project project to related H related2 production to to H H2 2production production [30]. The life [30]. [30]. cycle The The inventory life life cycl cycle also einventory inventory includes also also the includes componentsincludes the the componentsthatcomponents have been that that affected have have been been by affected divertingaffected by by biogasdiverting diverting ﬂux biogas biogas for H flux2 fluxproduction: for for H H2 production:2 production: it starts it from it starts starts potential from from potential potential loss of losselectricloss of of electric andelectric thermal and and thermal thermal energy energy thatenergy could that that becould could produced be be produced produced by the divertedby by the the diverted diverted biogas, biogas, tobiogas, the additionalto to the the additional additional impact impactimpact occurred occurred during during the the H H2 2production production stages. stages. Furthermore, Furthermore, the the following following key key assumptions assumptions are are takentaken into into account: account:

Processes 2019, 7, 86 8 of 14

occurred during the H2 production stages. Furthermore, the following key assumptions are taken intoProcesses account: 2019, 7, 86 8 of 14

• For scenario 1, the energyenergy recoveryrecovery ofof biogasbiogas isis assumedassumed toto bebe cogenerationcogeneration ofof electricityelectricity andand heat. The electric and heat efficiencies efﬁciencies are assumed to be 39% and 46%, respectively, with a total CHP efﬁciencyefficiency ofof 85%85% [[31].31]. The impact of biogas productionproduction isis excludedexcluded fromfrom thethe cogenerationcogeneration impact.impact. TheThe marginalmarginal replacing replacing technology technology for for the the lost lost energy energy resulting resulting from from biogas biogas diversion diversion are assumedare assumed to be to the be Europeanthe European average average for electricityfor electricity generation generation and and natural natural gas gas cogeneration cogeneration for heatfor heat production; production; • The European average grid mix is assumed to be the marginal electricity generation technology demanded forfor hydrogenhydrogen production;production; • • The only relevantrelevant airair emissionemission duringduring thethe HH22 production process isis COCO22, which is considered toto be carbon neutralneutral inin thisthis study;study; • • When naturalnatural gas gas is usedis used as additional as additional feedstock feedstock for H2 production,for H2 production, it is assumed it theis assumed conventional the Hconventional2 production H from2 production the steam from reforming the steam technology reforming is used. technology The inventory is used. and The impact inventory data and are basedimpact on data [30 ,are32]. based on [32] and [30].

The secondarysecondary life life cycle cycle impact impact (LCI) data,(LCI) describing data, describing background background processes (e.g., processes transportation, (e.g., electricitytransportation, production), electricity comes production), from the Ecoinventcomes from database the Ecoinvent v3.4 (Ecoinvent, database Zurich, v3.4 (Ecoinvent, Switzerland) Zurich, [33]. BesidesSwitzerland) climate [33]. change, Besides the climate analysis change, will be focusedthe analysis on human will be health, focused ecosystem on human quality health, and ecosystem resources asquality endpoints. and resources as endpoints.

4. Results and Discussion Figure6 6 (left) (left) illustratesillustrates thethe climateclimate changechange impactimpact ofof thethe scenarioscenario 11 whenwhen biogasbiogas isis aa limitinglimiting factor. BIONICOBIONICO ATR-CMRATR-CMR technology technology performs performs better better than than reference reference systems systems (SR (SR or or ATR), ATR), thanks thanks to itsto its higher higher efficiency efficiency of of converting converting biogas biogas to to H H2.2 The. The carbon carbon footprint footprint of of the the CMRCMR technologytechnology couldcould be 45-46%45‒46% lowerlower thanthan thethe conventionalconventional hydrogenhydrogen productionproduction metho3333dmetho3333d usingusing steam reforming of fossil natural gas.gas. In this scenar scenario,io, the impact due to the electrical electrical and thermal energy production loss (biogas(biogas isis notnot feedingfeeding aa cogenerationcogeneration system)system) isis equivalentequivalent forfor allall scenarioscenario asas thethe maximummaximum amountamount of biogas for the conventional process is fixed.fixed. As shown in Figure7 7 (left), (left), thethe totaltotal thermalthermal inputinput ofof the BIONICO system is always lower respect to the other processes thanks to the reduced amount of biogas, while the electric consumption is really highhigh only for the ATR case.case. The key factors are the carbon footprint of thethe electricityelectricity inputinput andand ofof thethe additionaladditional demanddemand forfor HH22 using fossil natural gas feedstock fromfrom lowerlower biogasbiogas conversionconversion efficiencyefficiency systems,systems, asas representedrepresented inin FigureFigure7 7(right). (right).

Scenario 1 Scenario 2

Energy production loss H2H2 with biogas feedstock H2H2 with NG feedstock Conventional HH22 (SMR NG) 18 18 16 16 14 14 ) 12 12 H2 10 10 /kg 8 8 CO2 6 6 (kg 4 4 2 2 Climate change impact 0 0 SMR LF ATR LF CMR LF SMR AD ATR AD CMR AD SMR LF ATR LF CMR LF SMR AD ATR AD CMR AD

Figure 6. Climate change impact of thethe investigatedinvestigated systemssystems againstagainst thethe conventionalconventional HH22 production fromfrom naturalnatural gasgas steamsteam reforming.reforming.

Processes 2019, 7, 86 9 of 14

ProcessesProcesses 20192019, 7, ,7 86, 86 9 9of of 14 14 SMR ATR CMR LF AD

SMR ATR CMR LF AD

10 500 ) 9

450 H2 ) 8 th 10 500400 /kg 7 ) 9 CO2 450350 H2 6 ) 8 th

/kg 5 400300 7

CO2 4 350250 6 3 300200 5

Biogas input (kW input Biogas 2 150 4 250 1 3 200100 (kg fuel NG fossil 0 Climate change from H2 H2 with from change Climate Biogas input (kW input Biogas 0 20 40 60 80 100 120 140 160 180 200 2 150 01234 1 Primary source for Electric input (kWth) 100 (kg fuel NG fossil 0 Climate change from H2 with biogas (kgCO2/kgH2)

H2 with from change Climate 0 20 40 60 80 100 120 140 160 180 200 01234 Primary source for Electric input (kWth) Climate change from H2 with biogas (kgCO2/kgH2)

Figure 7. Scenario 1 results: thermal power inputs (electric auxiliary and require biogas) for the three Figure 7. Scenario 1 results: thermal power inputs (electric auxiliary and require biogas) for the three H2 production systems (left) and climate change impact of H2 production from biogas and fossil fuel H2 production systems (left) and climate change impact of H2 production from biogas and fossil Figure(right). 7. Scenario 1 results: thermal power inputs (electric auxiliary and require biogas) for the three fuel (right). H2 production systems (left) and climate change impact of H2 production from biogas and fossil fuel (right).On the other hand, when biogas is not a limitinglimiting factor (scenario 2), the use of higher or lower amount ofof biogasbiogas doesdoes notnot causecause additionaladditional impacts, impacts, thus thus the the energy energy production production loss loss is is zero. zero. Figure Figure6 On the other hand, when biogas is not a limiting factor (scenario 2), the use of higher or lower (right)6 (right) shows shows that that climate climate change change impact impact is dominated is dominated by the by amountthe amount of electricity of electricity input input required required from amount of biogas does not cause additional impacts, thus the energy production loss is zero. Figure thefrom grid, the asgrid, the as principle the principle source source for hydrogen for hydrogen production. production. The carbon The carbon footprint footprint of both of CMRboth CMR or SMR or 6 (right) shows that climate change impact is dominated by the amount of electricity input required technologySMR technology are quite are quite similar similar as can as be can seen be fromseen from the electric the electric auxiliary auxiliary consumptions consumptions in Figure in Figure8 and 8 from the grid, as the principle source for hydrogen production. The carbon footprint of both CMR or Tableand Table3: both 3: theboth systems the systems can achieve can achieve large carbon large carbon footprint footprint reduction reduction compared compared to the ATR to the system ATR SMR technology are quite similar2 as can be seen from the electric auxiliary consumptions in Figure 8 andsystem the and conventional the conventional H2 production. H production. and Table 3: both the systems can achieve large carbon footprint reduction compared to the ATR system and the conventional H2 production. SMR ATR CMR LF AD SMR ATR CMR LF AD 4 10

) 43 10 9 H2 ) /kg 32 98 H2 CO2 /kg

(kg 21 87 Climate change CO2 0 6

(kg 1 7

Climate change 10 20 30 40 60 70 80 90 0 6 Electric inputElectric (kW) input (kW)Electric input (kW) 10 20 30 40 60 70 80 90 Figure 8. Scenario 2 results:Electric climate change input impact(kW) as a functionElectric of the input auxiliary (kW) electric consumptions Figure 8. Scenario 2 results: climate changeElectric impact as input a function (kW) of the auxiliary electric consumptions for the three investigated systems. for the three investigated systems. FigureLastly, 8. Scenario Figure9 2compared results: climate the change climate impact change as a impact function of of thethe auxiliary two investigated electric consumptions scenarios with respectfor the to thethree levelized investigated cost systems. of hydrogen conﬁrming that ATR system has the highest impact both from economic and environmental point of view while conventional SR process is similar to the BIONICO

technology just in the second scenario where biogas availability is not a constraint. The results of the other environmental factors are shown in Figure 10, where both SMR and CMR

technology performs better than ATR; however, the difference between SMR and BIONICO ATR-CMR systems is not signiﬁcant due to the uncertainties associated with the impact modelling. Process

contribution analysis indicates that, for all scenarios, all endpoint categories are highly influenced by the required electricity input and its impact for hydrogen production. For Scenario 1 specifically, the impacts are also influenced by the lost credits of electricity and heat generation due to biogas diversion and also by the additional natural gas required as feedstock to meet H demand by systems 2

Processes 2019, 7, 86 10 of 14

SMR ATR CMR LF AD

) 10 ) H2 H2 16 9 /kg /kg 8 CO2 14 CO2 7 12 6 5 10 4 8 3 Climate change (kg change Climate 6 (kg change Climate 2 Processes3456782019, 7, 86 34567810 of 14

LCOH (€/kgH2) LCOH (€/kgH2) with lower biogas conversion efﬁciency. The results also show a higher overall energy conversion efﬁciencyProcessesFigure 2019 does 9., 7 Comparison, 86 not necessarily of the climate lead to change better impact human of both health scenario andecosystems. 1 (left) and scenario A trade-off 2 (right) of with climate10 of 14 changerespect and to other the cost impact of hydrogen. categories should always be investigated.

Lastly, Figure 9 compared theSMR climateATR changeCMR impactLF of theAD two investigated scenarios with respect to the levelized cost of hydrogen confirming that ATR system has the highest impact both from economic and environmental point of view while conventional SR process is similar to the 18

) 10 BIONICO technology just in the second scenario) where biogas availability is not a constraint. H2 H2 16 9

/kg The results of the other environmental factors are shown in Figure 10, where both SMR and CMR /kg 8 CO2 14 CO2 technology performs better than ATR; however, the7 difference between SMR and BIONICO ATR- CMR12 systems is not significant due to the uncertaint6 ies associated with the impact modelling. Process 5 contribution10 analysis indicates that, for all scenarios, all endpoint categories are highly influenced by 4 the required8 electricity input and its impact for hydrogen production. For Scenario 1 specifically, the 3 impacts are also influenced by the lost credits of electricity and heat generation due to biogas Climate change (kg change Climate 6 (kg change Climate 2 diversion345678 and also by the additional natural gas required345678 as feedstock to meet H2 demand by systems with lower biogas conversionLCOH (€/kgH2) efficiency. The results also show a higherLCOH (€/kgoverallH2) energy conversion efficiencyFigure does 9. Comparison not necessarily of the climate lead to change better impact human of bothhealth scenario and 1ecosystems (left) and scenario. A trade-off 2 (right) of with climate changerespectFigure and toother9. theComparison cost impact of hydrogen. categoriesof the climate should change always impact be of bothinvestigated. scenario 1 (left) and scenario 2 (right) with respect to the cost of hydrogen. Scenario 1 Scenario 2 SMR LF ATR LF CMR LF SMR AD ATR AD CMR AD 100Lastly, Figure 9 compared the climate change 100impact of the two investigated scenarios with respect90 to the levelized cost of hydrogen confirming90 that ATR system has the highest impact both 80 80 from 70economic and environmental point of view wh70ile conventional SR process is similar to the BIONICO60 technology just in the second scenario where60 biogas availability is not a constraint. 50 50 The40 results of the other environmental factors are40 shown in Figure 10, where both SMR and CMR 30 30

technologyEnvironmental performs better than ATR; however, the difference between SMR and BIONICO ATR-

Factor Impact (%) 20 20 CMR10 systems is not significant due to the uncertainties10 associated with the impact modelling. Process contribution0 analysis indicates that, for all scenarios, all0 endpoint categories are highly influenced by Human health Ecosystem quality Resources Human health Ecosystem quality Resources the required electricity input and its impact for hydrogen production. For Scenario 1 specifically, the Figure 10. Comparison of endpoint environmental impact of different systems under different scenarios. impactsFigure are 10. also Comparison influenced of endpointby the lost envi creditsronmental of electricityimpact of differand entheat systems generation under duedifferent to biogas 5.diversion Conclusionsscenarios. and also by the additional natural gas required as feedstock to meet H2 demand by systems with lower biogas conversion efficiency. The results also show a higher overall energy conversion This work investigates the environmental and economic performances of an innovative membrane 5.efficiency Conclusions does not necessarily lead to better human health and ecosystems. A trade-off of climate reformerchange and for hydrogenother impact production categories from should raw always biogas. be The investigated. introduction of palladium membranes in a reformingThis work reactor investigates allows ther simultaneousthe environmental hydrogen and productioneconomic andperformances separation. of This an conceptinnovative has beenmembrane developed reformer within for the hydrogen BIONICOScenario 1 production project. The fr performanceom raw biogas. of the The BIONICO introductionScenario concept 2 of is palladium compared againstmembranes two availablein a reforming technologies reactor basedallowsSMR LF on therATR reforming, LF simultaneousCMR LF waterSMR AD hydrogen gasATR shift AD reactors CMRproduction AD and and pressure separation. swing 100 100 adsorptionThis concept90 for has hydrogen been developed purification. within the BIONICO90 project. The performance of the BIONICO concept80 is compared against two available technologies80 based on reforming, water gas shift reactors The70 system simulations performed with Aspen considered70 two different biogas compositions, oneand frompressure60 landfill swing and adsorption one from anaerobicfor hydrogen digestion. purification. The60 BIONICO system outperforms the reference cases by50 40–50% points achieving a hydrogen production50 efficiency around 69% assuming a delivery 40 40 pressure30 of 20 bara. Afterwards, the economic assessment30 for the investigated cases was carried Environmental

Factor Impact (%) 20 20 out accounting10 for both the capital and operating costs10 to determine the hydrogen production costs. The hydrogen0 cost production of the BIONICO case ranges0 from 4 to 4.2 €/kgH2, while the reference Human health Ecosystem quality Resources Human health Ecosystem quality Resources case resulted 4.21 €/kgH2 and 6.4 €/kgH2 for the SMR and ATR respectively. With respect to the steam reforming reference case, the BIONICO one has lower biogas and capital costs, but higher Figure 10. Comparison of endpoint environmental impact of different systems under different electricity costs (as a consequence of the hydrogen compression consumptions), while it has lower scenarios. biogas and electricity cost with respect to the ATR case. Between the landﬁll and anaerobic digestion cases, the latter has the lower costs as a consequence of the higher methane content and same price 5. Conclusions assumed. These results outline the fact that membrane reactors are a promising technology for green hydrogenThis productionwork investigates starting fromthe biogas.environmental and economic performances of an innovative membrane reformer for hydrogen production from raw biogas. The introduction of palladium membranes in a reforming reactor allows ther simultaneous hydrogen production and separation. This concept has been developed within the BIONICO project. The performance of the BIONICO concept is compared against two available technologies based on reforming, water gas shift reactors and pressure swing adsorption for hydrogen purification.

Processes 2019, 7, 86 11 of 14

For environmental life cycle assessment, this shows that the BIONICO case performs better than reference systems for climate change and resource indicators, when biogas becomes a limiting factor for H2 production to satisfy market demand, as the results are more influenced by the additional hydrogen production. For a healthy human ecosystem, the results are more influenced by the amount and environmental profile of direct electricity input. However, when biogas is not a limiting factor for H2 production, the innovative system can perform either similarly or worse than reference systems, as impacts are dominated by grid electric energy demand. This study highlights the technology deployment should be carefully examined considering local reference conditions, and type and efficiency of displaced or required marginal technologies for electricity production.

Author Contributions: M.B., G.D.M. and X.L. conceived the study. X.L. performed the Life cycle analysis starting from the thermodynamic system results made by G.D.M. G.D.M. and M.B. wrote the manuscript with support of X.L. G.M. and A.D. supervised the project. All authors discussed the results and contributed to the final version of the manuscript. Acknowledgments: The BIONICO project leading to this application has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 671459. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme, Hydrogen Europe and N.ERGHY. Conflicts of Interest: The authors declare no conflict of interest.

Nomenclature p Pressure (bar) T Temperature (◦C) Acronyms AD Anaerobic digester ATR Autothermal reformer ATR-CMR Autothermal catlytic membrane reformer BG Biogas CCF Carrying charge factor CHP Combined heat and power GWP Global warming potential HT High temperature HX Heat exchanger LCA Life cycle assessment LCOH Levelised cost of hydrogen LF Landﬁll LHV Low heating value LT Low temperature MR Membrane reactor NG Natural Gas O/C Oxygen to carbon molar ratio P Pump PSA Pressure swing adsorption S/C Steam to carbon molar ratio SMR Steam methane reformer WGSR Water gas shift reformer Greek letters ηsys System efﬁciency in terms of LHV of hydrogen

Appendix A

LT Low temperature MR Membrane reactor NG Natural Gas O/C Oxygen to carbon molar ratio P Pump PSA Pressure swing adsorption S/C Steam to carbon molar ratio SMR Steam methane reformer WGSR Water gas shift reformer Greek letters

ηsys System efficiency in terms of LHV of hydrogen

Appendix

Membrane Reactor The membrane reactor model includes reforming reactions (different kinetic schemes or chemical equilibrium), detailed hydrodynamics of bubble-emulsion phases and different options on Processes 2019, 7, 86 12 of 14 the permeate side (vacuum or co-counter flow sweep gas, including gas diffusion limitations in the porous support) [18]. Membrane reactor bed is divided into three main regions, which lengths can be (vacuumset by the or user: co-counter the first flow region sweep at gas, the including bottom of gas th diffusione reactor limitations is dedicated in the to porous the oxidation support) and [18]. reforming Membrane reactorreactions, bed the is dividedmiddle intoregion three is mainoccupied regions, by whichthe membranes lengths can (permeation be set by the zone); user: thethe firstlast regionsection at is the a bottom of the reactor is dedicated to the oxidation and reforming reactions, the middle region is occupied by the membranesbuffer region (permeation that mainly zone); corresponds the last section with is the a buffer free-board region thatregion. mainly The corresponds schematic withof Aspen the free-board Custom region.Modeler The fluidized schematic bed of Aspen membrane Custom reactor Modeler model fluidized is depi bedcted membrane in Figure reactor A1 model while is the depicted main infeatures Figure A1of whilereactor the design main features are reported of reactor in Table design A1. are reported in Table A1.

Sweep Permeate Permeate

Free board region

H 2 perm H2 perm Membranes region

Bubble phase

Emulsion phase

b-e Bottom region b-e

Feed Feed

Figure A1. Scheme of ﬂuidized bed membrane reactor developed in ACM for vacuum pump and sweepFigure gasA1. case.Scheme of fluidized bed membrane reactor developed in ACM for vacuum pump and sweep gas case. Membranes consist of a Pd-Ag layer deposited onto a ceramic multilayer porous support. Parameters of the permeationMembranes law consist (pre-exponential of a Pd-Ag factor layerk0, apparent deposited activation onto energya ceramiEa andc multilayer exponential porous factor n), support. listed in Table2, comes from experimental analysis of [34]. Parameters of the permeation law (pre-exponential factor k0, apparent activation energy Ea and exponential factor n), listed in TableTable 4, A1.comesMembrane from experimental reactor features. analysis of [34].

ParameterTable A1. Membrane reactor features. Units Value Membrane reactor geometry Parameter Units Value L reactor m 1 L bottom region (from distributor to membrane) m 0.1 L free board region m 0.45 D reactor m 0.44-0.6 Membrane distance m 0.01-0.026 Membrane parameters OD/ID m 0.014/0.007 Support thickness m 0.0035 Length m 0.45 Membrane thickness (δ) µm 4.5 −1 −1 −n −8 k0 mol s m Pa 3.93 × 10 -1 Ea kJ mol 9.26 n - 0.5 Processes 2019, 7, 86 13 of 14

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