Advances in the thermo-chemical production of hydrogen from biomass and residual wastes: Summary of recent techno-economic analyses

Journal Pre-proofs Review Advances in the thermo-chemical production of hydrogen from biomass and residual wastes: Summary of recent techno-economic analyses M. Shahabuddin, Bhavya B. Krishna, Thallada Bhaskar, Greg Perkins PII: DOI: Reference:

S0960-8524(19)31787-0 https://doi.org/10.1016/j.biortech.2019.122557 BITE 122557

To appear in:

Bioresource Technology

Received Date: Revised Date: Accepted Date:

30 September 2019 1 December 2019 2 December 2019

Please cite this article as: Shahabuddin, M., Krishna, B.B., Bhaskar, T., Perkins, G., Advances in the thermochemical production of hydrogen from biomass and residual wastes: Summary of recent techno-economic analyses, Bioresource Technology (2019), doi: https://doi.org/10.1016/j.biortech.2019.122557

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2019 Published by Elsevier Ltd.

1 2

Advances in the thermo-chemical production of hydrogen from biomass and residual wastes: Summary of recent techno-economic analyses M. Shahabuddin1, Bhavya B. Krishna2,3, Thallada Bhaskar2,3 and Greg Perkins4,5,*

3 4 5

1Department

of Chemical Engineering, Monash University, Clayton, 3800, Australia

6

2Academy

7

Dehradun 248005, Uttarakhand, India

8

3Materials

9

Uttarakhand, India

of Scientific and Innovation Research (AcSIR) at CSIR – Indian Institute of Petroleum (IIP),

Resource Efficiency Division (MRED), CSIR-Indian Institute of Petroleum (IIP), Dehradun 248005,

10

4Martin

Parry Technology, Brisbane, 4001, Australia

11

5School

of Chemical Engineering, University of Queensland, Brisbane, 4072, Australia

12 13

*Corresponding

author:

14 15 16 17 18 19 20

Greg Perkins GPO Box 1215 Brisbane 4001 Australia Email: [email protected]

1

21 22

Abstract This article outlines the prospects and challenges of hydrogen production from biomass and residual

23

wastes, such as municipal solid waste. Recent advances in gasification and pyrolysis followed by reforming

24

are discussed. The review finds that the thermal efficiency of hydrogen from gasification is ˜50%. The

25

levelized cost of hydrogen (LCOH) from biomass varies from ˜2.3 - 5.2 USD/kg at feedstock processing

26

scales of 10 MWth to ˜2.8 - 3.4 USD/kg at scales above 250 MWth. Preliminary estimates are that the LCOH

27

from residual wastes could be in the range of ˜1.4 - 4.8 USD/kg, depending upon the waste gate fee and

28

project scale. The main barriers to development of waste to hydrogen projects include: waste pre-

29

treatment, technology maturity, syngas conditioning, the market for clean hydrogen, policies to incentivize

30

pioneer projects and technology competitiveness. The main opportunity is to produce low cost clean

31

hydrogen, which is competitive with alternative production routes.

32 33

Keywords:

34

Hydrogen, municipal solid waste, biomass, gasification, pyrolysis, reforming, syngas

35 36

2

37 38

1. Introduction Today, over 2.0 billion tonnes of municipal solid waste (MSW) is generated each year and is expected to

39

increase to 3.4 billion tonnes annually by 2050 (Kaza et al., 2018). Recyclables such as paper, cardboard,

40

plastic, glass and metals constitute a substantial fraction of the waste generated, ranging from 16% in low-

41

income countries to about 50% in high-income countries. Even when advanced waste schemes that

42

separate the recyclables and organics from MSW are applied, there is still a residual portion of 30%, such

43

as contaminated paper and plastics, that cannot be recycled, and is preferably converted into energy

44

products rather than sent to landfill. The main component of MSW is cellulose, making MSW a largely

45

renewable resource. The plastics in MSW are currently fossil derived and have a high energy content (40

46

MJ/kg vs 20 MJ/kg for cellulose).

47

Hydrogen is a promising future energy source and has the highest specific energy density with a net

48

heating value of 120 MJ/kg, which is at least four times higher than any hydrocarbon fuel and three times

49

higher than gasoline (Parthasarathy and Narayanan, 2014). Furthermore, the combustion of hydrogen is

50

emission-free. The main industrial uses of hydrogen today are for refinery hydrotreating to make cleaner

51

fuels and for ammonia production. Hydrogen can also be used directly in an internal combustion engine,

52

fuel cell or can be used as an intermediate to convert liquid fuels such as gasoline, ethanol and methanol.

53

Nevertheless, a major issue concerning hydrogen is its cost effective storage and transport. Today,

54

hydrogen is mainly produced from natural gas (49%), liquid hydrocarbon (29%), and coal (18%)

55

(Parthasarathy and Narayanan, 2014). In contrast, only a 4% share comes from renewables (i.e., biomass,

56

waste, solar, wind, hydro-power) and other sources (Parthasarathy and Narayanan, 2014). Hydrogen has

57

been identified as an important energy carrier to aid in decarbonisation of the energy system (Bruce et al.,

58

2018).

59

There are different techniques for the production of hydrogen, which include gasification, electrolysis,

60

methane reforming, liquid reforming and biomass fermentation (Balat and Kırtay, 2010). The main

61

disadvantage of electrolysis is its current high cost, while the main disadvantage of fossil derived hydrogen

62

are the CO2 emissions.

63

This review focuses on the production of hydrogen from biomass and residual wastes and is limited to

64

the production of hydrogen from gasification and pyrolysis followed by reforming, which are considered as

65

the most mature and economical routes (Balat and Kırtay, 2010; Bridgwater, 1995). This article is

66

structured as follows – first the main schemes for making hydrogen are outlined, then the state of the art

67

in gasification and pyrolysis with in-line reforming are summarized. The article is distinguished from prior

68

works by including a thorough summary of the techno-economic and lifecycle analyses for producing 3

69

hydrogen from biomass and residual wastes. Finally, the technical and socio-economic barriers to

70

widespread deployment of waste to hydrogen projects are discussed along with the opportunity to

71

produce clean hydrogen at relatively low cost.

72

4

73 74

2. Schemes for making hydrogen from waste 2.1. Waste characterization

75

There are many types of “waste” materials and for the purposes of this work we are concerned with

76

biomass and residual wastes, which are generally not being recycled or reused and are currently being sent

77

to landfill. Residual wastes include domestic municipal solid wastes (MSW) as well as commercial and

78

industrial solid wastes. Residual wastes may also be formed from the sorting of wastes in recovery facilities

79

(both mechanical and/or biological). Error! Reference source not found. Table 1 shows the ultimate

80

analysis of a typical MSW and its main constituents. MSW may contain up to 40 - 50% of biodegradables

81

and 30 - 40% of inert materials, but this depends on location (Mastellone, 2015). MSW from higher socio-

82

economic areas has higher levels of paper, cardboard, plastics, metal and glass and lower amounts of food

83

organics, than MSW from lower socio-economic areas (Kaza et al., 2018). Figure 1 shows the typical

84

composition of MSW for high and low socio-economic areas.

85

Mixed plastics include plastics of varying types which are used as packaging materials and incorporated

86

into many domestic products. Plastics have a high content of carbon and hydrogen, along with a low

87

moisture and oxygen content giving them a high calorific value. However, if the plastic contains

88

polyvinylchloride (PVC) it will have a significant chlorine content. A typical composition of mixed waste

89

plastic in MSW has a carbon content of 80 wt%, hydrogen content of 15 wt% and oxygen content of 4 wt%,

90

being a mixture of 20 wt% high density polyethylene (HDPE), 42 wt% low density polyethylene (LDPE), 10

91

wt% polypropylene (PP), 16 wt% polystyrene (PS) and 12 wt% polyethylene terephthalate (PET) (Saad and

92

Williams, 2016). Residual wastes and mixed plastics are also heterogeneous in size and composition and

93

will likely be contaminated with food organics, glass, metals and even small quantities of aggregates (stone,

94

concrete).

95 96 97

2.2.

Pre-treatment steps for biomass and waste

Biomass and residual wastes may need to be treated before they can be fed to thermo-chemical

98

processes such as gasification and pyrolysis. Drying, size reduction and removal of unwanted materials are

99

the most common treatment steps, though some technologies like melting and plasma gasification can

100

process raw wastes without any pre-treatment (Tanigaki et al., 2013). The pre-treatment step may include

101

mechanical or mechanical-biological treatment. Error! Reference source not found. Figure 2 shows the

102

mechanical treatment process of MSW for fluidized bed application.

5

103

The pre-treatment is mainly carried out in three different stages to separate the heavy metals, no-

104

ferrous and ferrous metal. When these metals are separated, the end product of MSW is the secondary

105

fuel. However, there might be additional steps in the process, depending on the gasifier type. For instance,

106

further shredding and milling will be required for entrained flow gasifiers. Another option is the

107

combination of mechanical and biological treatments, in which bio-stabilisation and composting are added

108

to the process of Figure 2. Depending on the end-use, the composting might be either aerobic or

109

anaerobic. Several groups have used the stabilization pre-treatment technique to decrease the coke and

110

char formation and increase the syngas yield (Fang et al., 2016; Tanksale et al., 2007). The pre-treatment of

111

solid waste can also involve chemical treatment to alter the organic and inorganic structure of the

112

feedstock. Some chemical pre-treatment techniques for waste biomass include (Taylor et al., 2019): (i)

113

ozonolysis for lignin degradation, (ii) Acidic pre-treatment for solubilisation of the solid ingredients (Mosier,

114

2005) (iii) Base pre-treatment for solubilisation of lignin and hemicellulose (Sahoo et al., 2018) , (iv) Ionic

115

liquids for solubilise crystalline cellulose (Datta et al., 2010; Sahoo et al., 2018) and (v) Leaching for

116

extracting inorganic components for valorisation (Tonn et al., 2012). Apart from these common methods,

117

non-conventional methods exist, including: (a) pulsed electric field (PEF) (Hassan et al., 2018), (b) electron

118

beam (Leskinen et al., 2017) and (c) gamma irradiation (Singh et al., 2016).

119 120

2.3. Waste to hydrogen flowsheets

121

Conversion of waste into hydrogen first requires the production of a synthesis gas (syngas), being

122

predominately composed of CO and H2. Gasification is used to directly convert solid waste materials into

123

syngas at high temperatures using controlled conditions. Most waste gasification technologies are

124

autothermal and require a quantity of oxygen to convert the waste. Figure 3Error! Reference source not

125

found. shows a general schematic for producing hydrogen from wastes using gasification or

126

pyrolysis/reforming. In the case of gasification, the waste is pre-treated as required and the char is reacted

127

at high temperature (> 700 oC) to form a mixture of CO and H2:

128

Char + H2O↔H2 + CO

129

Char + CO2↔2CO

130

(ΔH>0)

(1) (ΔH>0)

(2)

Some gasification technologies require minimal pre-treatment, while others such as fluidized bed

131

gasification require sorting and size reduction. Most gasification technologies for municipal solid wastes use

132

(some) pure oxygen to reach temperatures sufficient to slag the ash, while technologies for biomass often

133

use steam or steam/oxygen mixtures (Basu, 2013). Laboratory studies have also been conducted on using

134

CO2 as a gasification agent (Bouraoui et al., 2016; Jeong et al., 2014), but this technique has not yet been 6

135

commercialized. If gasification is undertaken at temperatures between about 800 to 1000 oC, then the

136

syngas may be further reformed to remove tars before being quenched to recover heat for steam

137

production (Basu, 2013). In high temperature processes, such as plasma gasification tar reforming is

138

unnecessary.

139

Depending upon the feedstock and upstream technologies, gas conditioning may be applied to remove

140

H2S and other contaminants (eg. heavy metals, chlorine, heavy hydrocarbons) and even possibly CO2.

141

Steam is reacted with CO to increase the H2 content of the syngas by water gas shift before the H2 is

142

separated (Higman and Burgt, 2008). Most waste gasification technologies operate at low pressure, so

143

compression will be required upstream of the separation unit which is commonly undertaken using

144

pressure swing adsorption (PSA). In the context of hydrogen production, gasification is well suited to solids

145

like biomass, coal and MSW which have a high fraction of fixed carbon when heated.

146

An alternate approach, also shown in Figure 3Error! Reference source not found., is to partially convert

147

the waste in a pyrolysis unit to produce vapours and char. The char may be combusted separately to

148

provide the energy required for pyrolysis and the volatile vapours can be immediately reformed with steam

149

(or CO2) over a catalyst to produce a H2 rich syngas. This two-step process can be represented as:

150

C𝑥H𝑦O𝑧→Char + Volatiles ( C𝑛H𝑚O𝑘 . . .)

151

C𝑛H𝑚O𝑘 + (𝑛 ― 𝑘)H2O↔𝑛CO + (n +

152

𝑚 2

(ΔH>0)

― 𝑘)H

2

(ΔH>0)

(3) (4)

The syngas is further conditioned to maximize the H2 content using the water gas shift reaction and is

153

then separated. In this scheme the waste is subjected to less severe temperature conditions and a catalyst

154

is used during reforming to maximise syngas production. Thus, this process is better suited to waste

155

feedstocks with lower fixed carbon content, less contaminants (which may poison the catalysts) and

156

feedstocks which can be readily pre-treated to suit pyrolysis technologies. Combined pyrolysis and

157

reforming is potentially a good candidate for converting biomass and mixed waste plastic streams into

158

hydrogen. In principle the pyrolysis and reforming functions may be undertaken separately, for example to

159

process biomass into bio-oil in distributed units and to produce hydrogen from bio-oil in a centralized

160

facility. However, when considering waste streams, pyrolysis and in-line reforming has advantages which

161

are discussed further below.

162 163

7

164 165

3. Gasification Following sections describe different gasification techniques, current status, and their applications.

166 167 168

3.1.

Fixed bed, fluidized bed and entrained flow gasification

Historically, gasifiers are based on the three generic types, which include a fixed (moving) bed, fluidized

169

bed and entrained flow gasifiers. Fluidized bed gasifiers may be of the bubbling, spouted, circulating or

170

transport type. Error! Reference source not found.Table 1 lists the key operating conditions of the

171

different gasifiers. Gasifiers may use a range of oxidants depending upon the desired final product (Perkins

172

and Vairakannu, 2017).

173 174 175

3.2. Plasma gasification Plasma gasification is a relatively new technology, which has advantages over conventional thermal

176

gasification. The plasma is formed using torches and peak temperatures may reach over 5,000 oC. The

177

advantages include lower emission, the formation of inert ash, fuel flexibility, very high-temperatures and

178

lower reaction time (Ibrahimoglu et al., 2017; Rutberg et al., 2011). Also, the very high temperatures result

179

in a clean syngas composed of only CO and H2. Therefore, plasma gasifiers have been used widely in the

180

field of gasifying printed circuit boards (PCB) (Kim et al., 2003), medical wastes, metallurgical wastes,

181

incineration fly ash and low-level radioactive wastes (Cheng et al., 2002). In plasma gasification, the plasma

182

acts as a reforming agent, which helps to breakdown the hydrocarbons present in the solid fuels (Agon et

183

al., 2016). A major advantage is that only minimal feedstock preparation is required due to its ability to

184

gasify particles with lump size (Arena, 2012). Disadvantages of low temperature gasification in fixed and

185

fluidized beds are: unconverted carbon and the formation of tar and inorganic ash, which may require

186

disposal in hazardous landfill sites (Materazzi et al., 2015). However, the carbon conversion in plasma

187

gasification is as high as 100% and the tars are completely converted into gaseous products, consequently

188

increasing the net calorific value of the syngas. Besides, the inorganic ash is transformed into a glass or

189

glass-like substance. A major disadvantage of plasma gasification is its high electricity requirement which

190

can reach ˜15-20% of the gross output of the plant (Arena, 2012; Lombardi et al., 2012). The technology is

191

also expensive due to the severe operating conditions and need for refractory and high strength/corrosion

192

resistant metals in most parts of the gasification unit. Error! Reference source not found. Table 3 outlines

193

the summary of the plasma gasification from literature. A number of commercial plasma gasification plants

194

are currently in operation to convert MSW, medical and hazardous wastes. 8

195 196 197

3.3. Catalytic and supercritical water gasification Despite being a mature technology, gasification, in particular, the low temperature gasification suffers

198

from a variety of issues including low single-pass carbon conversion, tar formation and relatively high

199

greenhouse gas emission and the associated costs (Brar et al., 2012). In an attempt to solve these issues,

200

several studies and some pilot/demonstration plants have been conducted using catalytic gasification (Tang

201

and Wang, 2016; Wood and Sancier, 1984; Yeboah et al., 2003). The results showed that catalytic

202

gasification not only increases the carbon conversion significantly but also reduces tar formation and

203

improves the quality of the synthetic gases. Furthermore, a considerable decrease in the pollutant emission

204

was identified. However, a high cost is associated with catalytic gasification due to the expensive industrial

205

catalyst. In addition, the most effective alkali metal-based catalysts are converted into gaseous form at

206

high-temperatures (Emami Taba et al., 2012).

207

Supercritical water gasification is promising for the production of hydrogen from feedstocks having a

208

moisture content as high as 95% (Guo et al., 2007; Lu et al., 2008; Rodriguez Correa and Kruse, 2018; Yanik

209

et al., 2007). Besides, the agent for the gasification plays a vital role in the production of H2. The

210

supercritical water gasification involves the gasification with the presence of biomass and water, which has

211

a unique characteristic to hinder the production of char and tar (Chuntanapum and Matsumura, 2009). A

212

comprehensive review of factors affecting supercritical water gasification can be found in (Kalinci et al.,

213

2009; Rodriguez Correa and Kruse, 2018).

214 215

3.4. Catalytic reforming

216

One of the major challenges for gasification technologies, like steam gasification in fixed and fluidized

217

beds, conducted at intermediate temperatures (˜700 - ˜1100 oC) is the formation of tars in the syngas in

218

concentrations that range from 1 – 100 g/Nm3 (Anis and Zainal, 2011; Rabou et al., 2009; Valderrama Rios

219

et al., 2018). Tars may be removed via aqueous scrubbing, oil scrubbing, thermal oxidation and thermal and

220

catalytic reforming. Catalytic reforming is considered as a potential future option to remove tars and adjust

221

the H2/CO ratio of syngas produced from the gasification and pyrolysis of wastes (Zhang et al., 2019). It may

222

also increase syngas yields, carbon conversion, overall cold gas efficiency and aid removal of contaminants

223

in the syngas such as phenolics and heavy metals (Zhang et al., 2018).

224

Zhang et al. studied the catalytic reforming of MSW derived syngas at 850 oC using a Ni based catalyst

225

on a carbon support with a Ce promoter (Zhang et al., 2019). When the molar ratio of Ce/Ni was 0.25 in a

9

226

Ce-15Ni/C catalyst, they found that tar content was reduced to 15 g/Nm3, and when molar ratio of Ce/Ni

227

was 0.50 the PAHs in tar almost disappeared (Zhang et al., 2019).

228 229

3.5. Gasification of biomass and residual wastes for H2 production A process for converting MSW into hydrogen using a slurry-fed entrained flow gasifier has been

230

reported by Wallman et al. (1998)Error! Reference source not found.. The MSW is pre-treated in a rotary

231

drum pyrolyzer at 500 oC using hot sand circulated in a combustor fuelled by char and pyrolysis off-gas. The

232

pre-treated feed is then mixed with water to form a slurry and reacted with pure oxygen at 40 bar and

233

˜1300 oC in an entrained flow gasifier. Mineral matter and heavy metals in the feed are removed from the

234

process as a slag. The syngas from the gasifier is conditioned to remove sulphur, HCl, NH3 and reacted with

235

steam in a water gas shift unit to convert CO to H2. The H2 is separated in a PSA unit. Thermal efficiency to

236

H2 is ˜50% when processing MSW and ˜66% when processing a feed of 50% plastic and biomass (Wallman

237

et al., 1998).

238

The European Union recently funded a project to evaluate the production of hydrogen from biomass,

239

called the UNIfHY project (Bocci et al., 2014; Moneti et al., 2016; Sara et al., 2016; Sentis et al., 2016). This

240

project involved building 0.1 MWth and 1 MWth gasifier systems to make H2. Biomass (wood chips) are

241

gasified with steam at 800 – 900 oC in an indirectly heated fluidized bed to form syngas which is filtered of

242

solids before being cooled and undergoing water gas shift to increase the H2 content. Additional syngas is

243

supplied through reforming of off-gases. The syngas is scrubbed to removed residual tars, water and sulfur

244

before being pressurized. Water scrubbing is used for bulk removal of CO2 upstream of a PSA to separate H2

245

(Sentis et al., 2016). The thermal efficiency to H2 is ˜50%.

246

Salkuyeh et al. (2018) recently analysed both entrained flow (EF) and fluidized bed (FB) gasification of

247

biomass for the production of H2 with and without carbon capture (CC) at large scale. For residual wastes

248

the fluidized bed system was considered more appropriate Error! Reference source not found.and is

249

operated at 870 oC and 3 bar, being heated indirectly by a circulating heat carrier, such as sand. Tars in the

250

syngas are reformed separately in a subsequent unit before heat recovery, syngas scrubbing and sulfur

251

removal using the Lo-Cat technology and a ZnO guard bed (Salkuyeh et al., 2018)Error! Reference source

252

not found.. Clean syngas is subjected to water gas shift and then CO2 removal in an amine unit before

253

hydrogen separation using a PSA. Offgas is used for power and steam generation. The thermal efficiency to

254

H2 for FB gasification was estimated at 45% without CC and 41% with CC (Salkuyeh et al., 2018). While

255

processing biomass in an entrained flow gasifier achieved higher thermal efficiency, the process was found

256

to be more expensive, with a higher levelized cost of hydrogen (LCOH).

10

257

Other authors have considered the logistics of large scale gasification of biomass, and proposed to first

258

generate a slurry composed of bio-oil and bio-char from distributed pyrolysis and then gasify the slurry in a

259

central plant to make syngas for production of chemicals, fuels and potentially hydrogen (Dahmen et al.,

260

2017; Funke et al., 2016) .

11

261

4. Pyrolysis and in-line reforming

262

Pyrolysis of natural (biomass) and synthetic polymers (plastics etc.) has been gaining a lot of interest over

263

the past two decades due to the simplicity of operating a pyrolysis unit when compared to other thermo-

264

chemical methods of conversion. Pyrolysis is defined as the heating of any polymeric substance in the

265

absence of oxygen and is typically undertaken in the temperature range of 400 to 600 °C (Akhtar and Amin,

266

2012). It generally gives rise to three products, namely, non-condensable gas, oil and a solid residue called

267

char (Perkins et al., 2018). Slow pyrolysis involves very long residence times and yields mostly gas and char.

268

Medium or intermediate pyrolysis is typically undertaken with residence times on the order of tens of

269

seconds and results in higher liquid yields when the products are quenched to atmospheric temperature.

270

Fast pyrolysis refers to residence times which are less than a few seconds and yields maximum liquid yields

271

of up to 75 wt%, with relatively low amounts of gas and char (Akhtar and Amin, 2012). Pyrolysis is typically

272

undertaken in the temperature range of 400 to 600 °C (Akhtar and Amin, 2012)While char yields are

273

minimized using fast pyrolysis, these technologies generally require the feedstock to be reduced in size to a

274

few millimetres, which can be achieved with biomass but may not be practical or economical for many

275

residual waste streams, such as MSW. Such residuals may require processing using slow or intermediate

276

pyrolysis technologies, such as rotating drum pyrolyzers. Mixed plastics may also be suitable for processing

277

in fast pyrolysis technologies such as fluidized beds (bubbling, circulating and spouted), but agglomeration

278

issues need to be managed carefully.

279

There are several reasons for the developing interest in the pyrolytic route with in-line reforming for

280

the production of hydrogen. One of them is the elimination of tar rich stream generally produced during

281

gasification. The pyrolysis vapours are immediately reformed without any need for syngas conditioning and

282

can be carried out at milder conditions when compared to that required in gasification.

283

A team led by Professor Paul T Williams has investigated a system where pyrolysis occurs in one reactor

284

and the reforming is carried out in the second fixed bed reactor and both the reactors could be operated

285

independently (Saad and Williams, 2016; Wu and Williams, 2010a, 2010b, 2009). A continuous system with

286

2 fixed beds, one for pyrolysis and second for reforming was tested which could cause problems during

287

scale up (Namioka et al., 2011; Park et al., 2010). Commercial naphtha reforming catalyst has been used for

288

testing in fluidized bed reactor which is also joined to a fluidized bed pyrolysis reactor in the previous step

289

(Czernik and French, 2006).

290

Erkiaga et al. (2015) used a spouted bed reactor for pyrolysis which was followed by a fixed bed reactor

291

for reforming. But severe coke was formed in a small span of time. Several problems were noticed during

292

the pyrolysis of waste plastics like sticking of the plastic particles when heated to a certain temperature 12

293

leading to agglomeration. The immediate effect of this is the loss of fluidization in the continuous reactor. A

294

spouted bed reactor has better heat transfer and the spout helps in providing cyclic movement to the

295

particles thereby avoiding the agglomeration of particles. Thus the spouted bed reactor has been studied

296

by several researchers (Arabiourrutia et al., 2012; Artetxe et al., 2015, 2010; Mastellone and Arena, 2004).

297

Biomass pyrolysis has also been carried out using the spouted bed reactor (Fernandez-Akarregi et al.,

298

2013; Makibar et al., 2015). Different kinds of waste streams lead to different pyrolysis outlet streams

299

thereby requiring a proper understanding in order to design the reforming catalysts. HDPE and PP pyrolysis

300

products are majorly composed of waxes and hydrocarbons in the diesel range whereas the yield of gases,

301

gasoline and aromatics is very low. Depolymerisation of PS leads to the production of styrene monomer,

302

oligomer and aromatic secondary products. Oxygenates and aromatics are mainly observed during PET

303

pyrolysis (Barbarias et al., 2019a).

304

The operating parameters for the reforming step are temperature, space time velocity, steam/feed

305

ratio and the catalyst used in the process. Hydrogen production using polystyrene as feedstock has been

306

studied by Barbarias et al. (2016) who performed pyrolysis at 500 °C and reforming at 700 °C using

307

commercial Ni catalyst. Initially 29.1% of hydrogen production was observed which later on reduced due to

308

deactivation of the catalyst by aromatic degradation products. Deactivation was severe in the case of HDPE

309

as reported by the authors at similar conditions. Studies to regenerate the catalyst between reactions using

310

by in-situ coke combustion in the reforming reactor showed that it is not possible to recover the initial

311

catalyst activity due to the sintering of Ni0 active sites (Barbarias et al., 2019b).

312

Arregi et al. (2016) have carried out the pyrolysis of pinewood saw dust in a conical spouted bed

313

reactor followed by in-line reforming using Ni commercial catalyst. Hydrogen yields higher than bio-oil

314

reforming or direct steam gasification of 117g per kg of biomass were observed at 600 °C, steam/biomass

315

ratio of 4 and space time of 30 gcat min gvolatiles−1 . A kinetic model to quantify the effect of operating

316

parameters of reforming on product distribution has also been developed (Arregi et al., 2018). Deactivation

317

of the catalyst has been observed and studies have been carried out to understand it better (Ochoa et al.,

318

2018). Deactivation is mainly attributed to the encapsulation of Ni particles by coke and Ni sintering mainly

319

due to the condensation of oxygenates mainly phenols.

320

As commercial Ni catalyst showed deactivation, the effect of different catalyst supports for the

321

reforming step using the same pinewood sawdust has been studied by Santamaria et al. (Santamaria et al.,

322

2019a, 2018). The catalysts prepared are Ni/Al2O3, Ni/SiO2, Ni/MgO, Ni/TiO2 and Ni/ZrO2 each of which has

323

shown different levels of reforming carried out. The catalysts Ni/Al2O3, Ni/ZrO2 and Ni/MgO showed better

324

activity than Ni/TiO2 and Ni/SiO2 (Santamaria et al., 2019a, 2018). The difference in calcination 13

325

conditions had an effect on the deactivation of the catalysts. It was observed that as the

326

calcination temperature was reduced, the spinel phase formation was lower leading to higher

327

reforming activity and on stream stability (Santamaria et al., 2019b). Detailed studies are also

328

being carried out to understand the effect of promoter on the catalysts used for the process to

329

increase its stability (Santamaria et al., 2020).

330

Where the feedstock can be effectively pyrolyzed, the process of pyrolysis followed by in-situ reforming

331

is an effective process for hydrogen production compared to bio-oil reforming and direct steam

332

gasification. The combined process has operational advantages to obtain high hydrogen production as it

333

makes sure there is high catalyst efficiency for tar reduction. One advantage is that operating conditions for

334

both pyrolysis and reforming can be optimized separately, and the entire catalyst bed is available for the

335

vapour coming out of the pyrolysis reactor into the reforming reactor. The need to handle and process an

336

aqueous phase is also eliminated. The temperatures used in the process are lower than for direct steam

337

gasification which also leads to high tar content followed by energy intense tar removal steps. The

338

immediate conversion via in-line reforming also eliminates the problems associated with collecting oil/bio-

339

oil such as storage, ageing and vaporisation (Perkins et al., 2018). In-line reforming is also shown to

340

produce higher quantities of hydrogen than bio-oil reforming where a high rate of catalyst deactivation is

341

observed due to deposition of repolymerised products. In the case of the separation of the bio-oil phases

342

followed by reforming, there is inefficiency due to the steps of cooling and reheating. The conical spouted

343

bed reactor seems to be effective for pyrolysis for fine and sticky solids like plastics where the feed is non-

344

uniform. The impurities contained in the biomass, such as mineral matter can be separated from the

345

vapours and removed before they have any direct contact with the catalyst accelerating deactivation

346

mechanisms, which occurs in the case of catalytic pyrolysis and gasification (Barbarias et al., 2019b;

347

Santamaria et al., 2019a, 2018; Valle et al., 2013; Yildiz et al., 2016).

348

At present, the development of pyrolysis and reforming for the conversion of mixed plastics into

349

hydrogen is focused on laboratory studies and optimization of the operating conditions and catalysts. We

350

could not find any studies which provide a commercial process design, nor could we find any techno-

351

economic analyses. Combining pyrolysis with dry reforming will be beneficial for effective utilisation of CO2,

352

however as mixed plastics are derived from fossil fuels, the lifecycle greenhouse gas (GHG) emissions from

353

the process are expected to be higher than renewable hydrogen production methods. Segregated waste

354

streams are difficult to obtain and hence, robust catalyst systems for processing of commingled waste will

355

be necessary for commercial development.

14

356

The major barrier to the scale-up and deployment to date is in regards to the performance of the

357

catalyst systems to be used for the reforming step. Current catalysts show high levels of deactivation after

358

only a few hours of time on-stream. Sintering of the catalyst has been observed and so is coking due to the

359

repolymerisation products getting deposited on the surface of the catalyst. Improvements in the design of

360

reactor for better control of feedstocks and the ability to use mixed feedstocks is also essential. The design

361

of reactors needs to take into account the heat transfer required for different feedstocks when mixed feeds

362

are used since there should not be any hotspots inside the reactor.

363

From the literature, it can be observed that the combination of pyrolysis and in-line reforming has

364

flexibility in terms of feedstock as it has the ability to process biomass, plastics and a mixture of both

365

biomass and plastics. However, using residual wastes will likely require initial sorting to remove the

366

unsuitable materials. The process development is currently focused at the laboratory scale but several

367

groups have been able to successfully run small units with continuous biomass feeding and hope to make

368

progress soon in terms of pilot scale demonstration.

15

369 370 371

5. Techno-economic and lifecycle analyses 5.1. Techno-economic analyses While a large number of techno-economic analyses (TEAs) have been conducted for biomass

372

gasification, there are very few studies that focus on converting residual wastes into H2. While every TEA

373

has considered a specific case, it is generally found that the levelized cost of hydrogen (LCOH) is most

374

sensitive to the overall plant efficiency (technology selection), the feedstock cost, the processing scale, the

375

total installed capital cost and the financing parameters, such as the cost of capital.

376

In 1998, Wallman et al. (1998) estimated the cost of producing H2 from MSW and a feed of 50% mixed

377

plastics by combining pyrolysis and entrained flow gasification at a processing scale of 2500 tpd. Wallman

378

et al. assumed a cost of capital of 15%. The estimated cost of producing H2 from MSW, inflation adjusted to

379

a 2018 cost base is 3.3 USD/kg, while the estimated cost for converting a feed containing 50% plastics is 1.3

380

USD/kg (1998). The National Renewable Energy Laboratory (NREL) in the USA has conducted several studies

381

into producing H2 using biomass gasification (Kinchin and Bain, 2009; Parks et al., 2011). The 2011 study

382

found a LCOH of 6.3 USD/kg (1st plant) and 3.3 USD/kg (nth plant) when inflated to 2018 dollars for H2

383

production of 12 - 50 ktpa with a learning rate of 11% derived from steam methane reforming experience

384

(Parks et al., 2011). This study assumed a composite cost of capital of 6.4% and a 20 year plant lifetime.

385

Elia et al. found the average cost of H2 production from biomass was 3.0 USD/kg in 2018 dollars (2011),

386

while Woo et al. studied biomass gasification to H2 in Korea and estimated a levelized cost of 5.5 USD/kg (in

387

2018 USD) which also included storage and transport infrastructure in the analysis (2016).

388

Recently, Salkuyeh et al. (2018) evaluated fluidized bed (FB) and entrained flow (EF) gasification with

389

and without carbon capture (CC) for producing 165 ktpa of H2. They assumed a 30 year plant life and a

390

composite cost of capital of 11%. The FB configuration without CC gave the lowest levelized cost and this

391

ranged from ˜0.5 USD/kg when the biomass had no cost, to ˜4.3 USD/kg when the biomass feedstock cost

392

was 150 USD/tonne (dry). At a biomass price of 75 USD/tonne (dry) the LCOH was 2.5 USD/kg. Addition of

393

carbon capture in the FB case increased the LCOH by ˜0.4 USD/kg. While EF gasification was found to be

394

more efficient than FB gasification, there is a much higher capital cost penalty which meant that the EF

395

cases were more expensive than FB, except when the biomass was priced above 125 USD/tonne (dry).

396

Several studies have considered small plant sizes producing <1 ktpa of hydrogen. Mohammed et al.

397

(2011) estimated production costs of 2.4 USD/kg (in 2018 USD) for a plant making 2.7 t/yr of H2 from empty

398

fruit bunches, which seems unrealistic given the very small scale. Sara et al. (2016) performed a TEA for H2

399

from the UNIfHY European project at small scale of 0.1 MWth in 2016 and found production costs in the 16

400

range of 8.5 – 11.5 USD/kg for biomass cost of ˜68 USD/tonne, a 20 year plant life and 7% cost of capital.

401

At a larger scale of 1 MWth, the production costs ranged from 7.4 to 10.1 USD/kg depending upon how the

402

gasifier was heated - indirectly or with oxygen (Sentis et al., 2016). The estimated LCOH reduced when

403

surplus offgas was used for electricity generation and ranged from ˜5.0 USD/kg at 1 MWth to ˜2.4 USD/kg

404

at 10 MWth (Sentis et al., 2016). Table 4 shows a summary of the results of TEAs that evaluated producing

405

hydrogen from biomass and waste gasification. TEAs for pyrolysis and inline reforming could not be found.

406 407

The LCOH can also be expressed in USD/litre-gasoline-equivalent. A price of 3 USD/kg represents 0.79 USD/litre-ge and a price of 5 USD/kg represents 1.32 USD/litre-ge.

408 409

5.2. Estimates of the LCOH for waste to H2

410

The TEAs find that the feedstock cost is one of the main drivers of the LCOH. For example, Salkuyeh et

411

al. (2018) found that a 50 USD/tonne reduction in the feed price, translated into a 1.3 USD/kg reduction in

412

the hydrogen production cost, equivalent to a ˜40% reduction. Residual wastes can attract a gate fee that

413

could range anywhere from ˜50 USD/tonne to ˜150 USD/tonne depending upon the location and waste

414

type/composition, with 75 – 100 USD/tonne being a typical fee paid to conventional waste to energy

415

plants. If waste feedstocks could be substituted in the biomass plant of Salkuyeh et al. (2018) then the

416

LCOH would be only ˜0.4 USD/kg. In practice the waste will need either feed pre-treatment and/or a

417

change in gasification technology to melting or plasma gasification which would increase the overall plant

418

capex, thereby increasing the LCOH. In addition, most waste feedstocks have a lower calorific value than

419

biomass, which impacts on plant capacity and efficiency for the gasification section.

420

To make a preliminary estimate of the LCOH from a waste to H2 plant, the techno-economic model of

421

Salkuyeh et al. has been re-created for the case of a fluidized bed gasifier without carbon capture. The

422

capital and operating cost and financial model methodologies reported in Salkuyeh et al. (2018) have been

423

applied in this work. The capital cost has been increased to include an activated carbon bed in the gas clean

424

up section to remove additional contaminants. Furthermore, it is assumed that MSW will be processed and

425

shredded to form a waste feedstock suitable for the fluidized bed gasifier using a process similar to that

426

shown in Figure 2. The waste feed has a lower heating value of 12.5 MJ/kg and an effective waste gate fee

427

for the gasification plant of between 0 and 50 USD/tonne (ie. this is the gate fee available after the pre-

428

treatment step has been applied). The model has been used to estimate the LCOH for processing capacities

429

of 500 and 1000 tpd of waste feedstock, equivalent to approximately 75 MWth and 150 MWth of

430

feedstock, respectively. The capital costs for the plant capacities have been estimated by using a scaling

431

exponent of 0.6 (Salkuyeh et al., 2018). For the 500 tpd plant, the model forecasts that the LCOH varies 17

432

between 2.6 and 4.8 USD/kg, while for the 1000 tpd plant the LCOH, ranges from 1.4 to 3.5 USD/kg. While

433

the calculated LCOHs for the waste to hydrogen configuration are sensitive to the project capital,

434

processing scale and waste gate fee, these preliminary results appear reasonable. For example, the study

435

of Wallman et al. (1998) found a LCOH of 3.3 USD/kg. In addition, the calculated LCOH are of similar

436

magnitude to biomass gasification and can be lower when the waste gate fee becomes substantial. Further

437

work is warranted to develop a more comprehensive techno-economic model for converting waste

438

feedstocks into hydrogen.

439 440 441

5.3. Comparison of the LCOH for different technologies Figure 4Error! Reference source not found. shows the estimated LCOH production for a range of

442

potential pathways using data from (Bruce et al., 2018; Hinkley et al., 2016; Salkuyeh et al., 2018). The

443

production of green hydrogen using solar PV and proton exchange membrane (PEM) electrolyzers has been

444

taken from the work of Hinkley et al. (2016) and shown as +/-10% of the reported values after conversion

445

to USD. Forecasts out to 2030 indicate a LCOH in the range of 6.4 USD/kg. A recent report by the CSIRO in

446

Australia estimated the cost of using variable renewable energy (VRE) sources (ie. wind and solar) with PEM

447

electrolyzers of 7.7 USD/kg (Bruce et al., 2018). The LCOH from renewable energy and electrolysis is

448

sensitive to the levelized cost of electricity from renewables (with or without storage), the capital cost of

449

the electrolyser and the capacity factor (Hinkley et al., 2016). The long term target for the LCOH from

450

renewables is ˜2 USD/kg, which is necessary to be competitive with using fossil fuels combined with carbon

451

capture and storage (CCS). In the Australian context, recent studies estimate that using grid electricity with

452

PEM electrolyzers has a current LCOH of 4.3 – 5.2 USD/kg, with a potential future best case of 1.6 – 2.0

453

USD/kg (Bruce et al., 2018). However, using grid electricity and electrolysis in Australia currently has high

454

emissions – 5 times more than using steam methane reforming and 3 times more than using coal

455

gasification, both without CCS (COAG Energy Council, 2019). Use of renewables with electrolysis has the

456

advantage of modular design and ability to easily increase production over time. Also, there are low

457

operating costs once the plant has been built.

458

Production costs of hydrogen using natural gas steam methane reforming with carbon capture are

459

estimated at less than 2 USD/kg, with black and brown coal having costs in the range 1.5 – 2.2 USD/kg

460

(Bruce et al., 2018). However, fossil derived hydrogen production assumes large scale projects with

461

corresponding high capital costs. Relying on carbon capture and storage to reduce emissions will also limit

462

the locations for suitable project sites.

18

463

The biomass gasification studies described earlier are summarized with LCOHs ranging from about 3

464

USD/kg at large scale to over 5 USD/kg for small scale projects. It can be seen that the preliminary

465

estimates of the LCOH from processing wastes are in the range 1.5 – 5 USD/kg, depending upon project

466

scale and waste gate fee. These estimates are substantially lower than the current costs of producing

467

hydrogen from electrolysis with renewable energy and already approach the long term target range of ˜2

468

USD/kg. While the LCOH from wastes is generally higher than using natural gas or coal, the process does

469

not require carbon sequestration to achieve relatively low lifecycle GHG emissions. Waste gasification is

470

also suitable for distributed production of hydrogen, requiring moderate sized plants. When compared to

471

processing biomass, the LCOH from waste gasification is generally lower, due to the positive impact of the

472

waste gate fees. In this work it has been found that when the effective waste gate fee is 50 USD/tonne or

473

more, the LCOH from waste can be <2 USD/kg.

474 475

5.4. Lifecycle GHG emissions

476

We could not find any specific lifecycle analyses for the production of hydrogen from waste (residuals or

477

mixed plastics). Moreno and Dufour calculated the lifecycle GHG emissions for producing H2 from the

478

gasification of four biomass resources in the Spanish context – pine, eucalyptus, almond and vine pruning

479

(Moreno and Dufour, 2013). They found lifecycle emissions ranged from about -0.07 to 0.55 kg-CO2eq/Nm3-

480

H2 (-0.8 to 6.1 kg-CO2eq/kg-H2), with pine and eucalyptus woods having the lowest lifecycle emissions.

481

Susmozas et al. (2013) estimated that the GHG emissions from producing H2 using indirect gasification of

482

biomass was 0.4 kg-CO2eq/kg-H2. Analyses of the UNIfHY project estimated lifecycle CO2 emissions of 2.4

483

kg-CO2eq/kg-H2 , while Salkuyeh et al. (2018) estimated lifecycle CO2 emissions from pine ranging from -0.1

484

to -0.5 kg-CO2eq/kg-H2 for EF and FB indirect gasification, respectively. When carbon capture was included,

485

the lifecycle emissions became highly negative with -21.9 kg-CO2eq/kg-H2 for entrained flow gasification

486

and -15.8 kg-CO2eq/kg-H2 for fluidized bed gasification (Salkuyeh et al., 2018). For comparison, H2 produced

487

from natural gas using steam methane reforming has a lifecycle emission of ˜8.5 - 11 kg-CO2eq/kg-H2

488

(COAG Energy Council, 2019; Salkuyeh et al., 2018; Susmozas et al., 2013), while coal gasification has

489

emissions of 12.7 – 16.8 kg-CO2eq/kg-H2 (COAG Energy Council, 2019). The gasification of biomass to make

490

hydrogen is therefore generally neutral in terms of its CO2 emissions with specific configurations having

491

slightly positive or slightly negative emission profiles. It is expected that the gasification of residual wastes

492

would have higher lifecycle emissions than pure biomass resources, as they are a mixture of biomass

493

derived materials like paper and cardboard, mixed with fossil hydrocarbons like plastics. The magnitude of

19

494

the increase in the emissions rates over biomass will obviously be related to the composition of the waste

495

and the performance of the conversion technology.

496

20

497 498

6. Challenges and opportunities 6.1. Technical challenges

499

The main technical challenges in the thermo-chemical conversion of residuals and mixed plastics to

500

hydrogen are related to the waste feed. The material handling and pre-treatment of the residual waste to

501

make it suitable for feeding into pyrolysis and gasification technologies are significant issues, which have

502

led to project failures in the past. If pyrolysis, entrained flow or fluidized bed gasification are chosen, then

503

the pre-treatment step will need to include removal of glass, metals and aggregates and size reduction.

504

Most melting and plasma gasification technologies can handle MSW without pre-treatment. Tars from

505

gasification and pyrolysis present a major issue for low temperature gasification systems, while

506

contaminants such as heavy metals, chlorine and sulfur also need to be removed in the syngas conditioning

507

section. For processes that propose to use a catalyst – catalytic gasification, catalytic pyrolysis and

508

reforming – most current catalysts do not perform well enough with residual wastes. The main issues relate

509

to poisoning and deactivation, coking and poor carbon conversion and hydrogen yields. Catalysts for

510

fluidized bed systems also need to be attrition resistant. Optimization and scale-up of catalysts is a major

511

technical challenge for processes that propose to use a catalyst.

512 513 514

6.2. Barriers for waste to hydrogen deployment In addition to the technical challenges, the main barriers to the adoption and scale-up of waste to

515

hydrogen are typical for most new energy technologies, including securing the waste feedstock supply,

516

finding customers willing to make long term commitments to buy the hydrogen and policy frameworks that

517

incentivize and support the scale-up of projects to an economic scale. As shown in the TEAs small-scale

518

projects will have higher LCOHs, yet demonstration and small scale commercial projects are necessary

519

before larger sale projects with better economics can be built.

520

Due to the variability of residual waste (and low calorific value) thermal efficiency to hydrogen is ˜50 %,

521

impacting costs. For mixed plastics, overall thermal efficiency is higher. Project capacities will likely need to

522

be scaled-up (>10 MWth) to achieve competitive hydrogen costs, see TEAs.

523

Clean syngas from gasification/reforming can be used to synthesize many products including fuels (jet

524

fuel, ethanol), chemicals (methanol, DME) and hydrogen. Current waste gasification projects are favouring

525

the production of fuels and chemicals due to their higher value and more mature offtake markets

526

(“Enerkem,” 2019; “Fulcrum Bioenergy,” 2019).

21

527

There is considerable investment going into producing H2 from the electrolysis of water using solar PV,

528

wind and other renewable electricity sources. While these approaches are still expensive, they have no

529

requirement for feedstock, are module in nature, and built using electro-chemical physics which makes

530

them attractive for long-term hydrogen supply at scale.

531 532 533

6.3. Opportunities Despite the technical challenges and socio-economic barriers, the production of hydrogen from

534

biomass and residual wastes is technically and economically feasible given the current state of technology

535

and economic conditions in many developed countries which have gate fees to incentivise diversion of

536

wastes from landfill. The application of gasification is mature with entrained flow, fluidized bed, plasma and

537

melting gasification systems in commercial operation processing various types of residual wastes. While

538

residual wastes have significant inerts and moisture content and a relatively low heating value of (8 – 12

539

MJ/kg), with an effective waste gate fee on the order of 0 – 50 USD/ton, the estimated levelized cost of

540

hydrogen production can reach ˜1.4 – 4.8 USD/kg, making it competitive with emerging pathways to

541

produce hydrogen from renewable energy sources. The lifecycle GHG emissions of biomass to H2 are

542

neutral, and while the lifecycle GHG emissions from MSW to H2 are expected to be somewhat higher, they

543

should be significantly lower than the current emissions profiles of fossil fuels (natural gas, coal and

544

petcoke). Therefore, wastes can be converted into hydrogen with low lifecycle emissions and at costs

545

currently below that of renewables paired with electrolysis.

546

Residual wastes are available globally and converting waste to hydrogen can be undertaken in locations

547

that do not have indigenous resources of fossil fuels or high quality solar and wind resources. However, the

548

clean syngas produced from biomass and waste gasification can also be used to produce renewable fuels

549

and chemicals with little additional cost and these products are being favoured in recent projects by

550

Enerkem and Fulcrum Bioenergy. As the demand for clean hydrogen grows and the market matures, there

551

is an opportunity for wastes, which are a disposal problem in most countries, to capture a share of the

552

clean H2 market.

553 554

22

555 556

7. Conclusions The most promising methods of producing hydrogen from biomass and wastes are using gasification

557

and pyrolysis followed by in-line reforming. The LCOH from biomass gasification ranges from ˜2.8 - 3.4

558

USD/kg. In this work preliminary estimates of gasifying residual wastes yield a LCOH of ˜1.4 – 4.8 USD/kg at

559

feedstock processing scales of 75 – 150 MWth, with waste gate fees of 0 – 50 USD/tonne, after pre-

560

treatment. Production of H2 from wastes could aid in solving global waste problems and enable a rapid

561

scale-up of the production of clean H2.

562 563 564

23

565

References

566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615

Agon, N., Hrabovský, M., Chumak, O., Hlína, M., Kopecký, V., Mas̆láni, A., Bosmans, A., Helsen, L., Skoblja, S., Van Oost, G., Vierendeels, J., 2016. Plasma gasification of refuse derived fuel in a single-stage system using different gasifying agents. Waste Manag. 47, 246–255. https://doi.org/10.1016/j.wasman.2015.07.014 Akhtar, J., Amin, N.S., 2012. A review on operating parameters for optimum liquid oil yield in biomass pyrolysis. Renew Sus Energy Rev 16, 5101–5109. https://doi.org/10.1016/j.rser.2012.05.033 Anis, S., Zainal, Z.A., 2011. Tar reduction in biomass producer gas via mechanical, catalytic and thermal methods: A review. Renew. Sustain. Energy Rev. 15, 2355–2377. https://doi.org/10.1016/j.rser.2011.02.018 Arabiourrutia, M., Elordi, G., Lopez, G., Borsella, E., Bilbao, J., Olazar, M., 2012. Characterization of the waxes obtained by the pyrolysis of polyolefin plastics in a conical spouted bed reactor. J. Anal. Appl. Pyrolysis 94, 230–237. https://doi.org/10.1016/j.jaap.2011.12.012 Arena, U., 2012. Process and technological aspects of municipal solid waste gasification. A review. Waste Manag. 32, 625–639. https://doi.org/10.1016/j.wasman.2011.09.025 Arregi, A., Lopez, G., Amutio, M., Barbarias, I., Bilbao, J., Olazar, M., 2016. Hydrogen production from biomass by continuous fast pyrolysis and in-line steam reforming. RSC Adv. 6, 25975. https://doi.org/10.1039/c6ra01657j Arregi, A., Lopez, G., Amutio, M., Barbarias, I., Santamaria, L., Bilbao, J., Olazar, M., 2018. Kinetic study of the catalytic reforming of biomass pyrolysis volatiles over a commercial Ni/Al2O3 catalyst. Int. J. Hydrog. Energy 43, 12023–12033. https://doi.org/10.1016/j.ijhydene.2018.05.032 Artetxe, M., Lopez, G., Amutio, M., Barbarias, I., Arregi, A., Aguado, R., Bilbao, J., Olazar, M., 2015. Styrene recovery from polystyrene by flash pyrolysis in a conical spouted bed reactor. Waste Manag. 45, 126–133. https://doi.org/10.1016/j.wasman.2015.05.034 Artetxe, M., Lopez, G., Amutio, M., Elordi, G., Olazar, M., Bilbao, J., 2010. Operating Conditions for the Pyrolysis of Poly-(ethylene terephthalate) in a Conical Spouted-Bed Reactor. Ind. Eng. Chem. Res. 49, 2064–2069. https://doi.org/10.1021/ie900557c Balat, H., Kırtay, E., 2010. Hydrogen from biomass – Present scenario and future prospects. Int. J. Hydrog. Energy 35, 7416–7426. https://doi.org/10.1016/j.ijhydene.2010.04.137 Barbarias, I., Arregi, A., Artetxe, M., Santamaria, L., Lopez, G., Cortazar, M., Amutio, M., Bilbao, J., Olazar, M., 2019a. Waste Plastics Valorization by Fast Pyrolysis and in Line Catalytic Steam Reforming for Hydrogen Production, in: Pyrolysis [Working Title]. IntechOpen. https://doi.org/10.5772/intechopen.85048 Barbarias, I., Artetxe, M., Lopez, G., Arregi, A., Santamaria, L., Bilbao, J., Olazar, M., 2019b. Catalyst Performance in the HDPE Pyrolysis-Reforming under Reaction-Regeneration Cycles. Catalysts 9, 414. https://doi.org/10.3390/catal9050414 Barbarias, I., Lopez, G., Artetxe, M., Arregi, A., Santamaria, L., Bilbao, J., Olazar, M., 2016. Pyrolysis and inline catalytic steam reforming of polystyrene through a two-step reaction system. J. Anal. Appl. Pyrolysis 122, 502–510. https://doi.org/10.1016/j.jaap.2016.10.006 Basu, P., 2013. Biomass Gasification, Pyrolysis and Torrefaction, Second. ed. Academic Press, London, United Kingdom. Bocci, E., Sisinni, M., Moneti, M., Vecchione, L., Carlo, A.D., Villarini, M., 2014. State of Art of Small Scale Biomass Gasification Power Systems: A Review of the Different Typologies. Energy Procedia 45, 247–256. http://dx.doi.org/10.1016/j.egypro.2014.01.027 Bouraoui, Z., Dupont, C., Jeguirim, M., Limousy, L., Gadiou, R., 2016. CO2 gasification of woody biomass chars: The influence of K and Si on char reactivity. Comptes Rendus Chim. 19, 457–465. https://doi.org/10.1016/j.crci.2015.08.012 Brar, J.S., Singh, K., Wang, J., Kumar, S., 2012. Cogasification of Coal and Biomass: A Review. Int. J. For. Res. 2012, 1–10. https://doi.org/10.1155/2012/363058 Bridgwater, A.V., 1995. The technical and economic feasibility of biomass gasification for power generation. Fuel 74, 631–653. https://doi.org/10.1016/0016-2361(95)00001-L

24

616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668

Bruce, S., Temminghoff, M., Hayward, J., Schmidt, E., Munnings, C., Palfreyman, D., Hartley, P., 2018. National Hydrogen Roadmap. CSIRO, Canberra, Australia. Cheng, T.W., Ueng, T.H., Chen, Y.S., Chiu, J.P., 2002. Production of glass-ceramic from incinerator fly ash. Ceram. Int. 28, 779–783. https://doi.org/10.1016/S0272-8842(02)00043-3 Chuntanapum, A., Matsumura, Y., 2009. Formation of Tarry Material from 5-HMF in Subcritical and Supercritical Water. Ind. Eng. Chem. Res. 48, 9837–9846. https://doi.org/10.1021/ie900423g COAG Energy Council, 2019. Australia’s National Hydrogen Strategy. Commonwealth of Australia. Czernik, S., French, R.J., 2006. Production of Hydrogen from Plastics by Pyrolysis and Catalytic Steam Reform. Energy Fuels 20, 754–758. https://doi.org/10.1021/ef050354h Dahmen, N., Abeln, J., Eberhard, M., Kolb, T., Leibold, H., Sauer, J., Stapf, D., Zimmerlin, B., 2017. The bioliq process for producing synthetic transportation fuels. WIREs Energy Env. 6, e236. https://doi.org/10.1002/wene.236 Datta, S., Holmes, B., Park, J.I., Chen, Z., Dibble, D.C., Hadi, M., Blanch, H.W., Simmons, B.A., Sapra, R., 2010. Ionic liquid tolerant hyperthermophilic cellulases for biomass pretreatment and hydrolysis. Green Chem. 12, 338. https://doi.org/10.1039/b916564a Elia, J.A., Baliban, R.C., Xiao, X., Floudas, C.A., 2011. Optimal energy supply network determination and life cycle analysis for hybrid coal, biomass, and natural gas to liquid (CBGTL) plants using carbon-based hydrogen production. Comput. Chem. Eng. 35, 1399–1430. https://doi.org/10.1016/j.compchemeng.2011.01.019 Emami Taba, L., Irfan, M.F., Wan Daud, W.A.M., Chakrabarti, M.H., 2012. The effect of temperature on various parameters in coal, biomass and CO-gasification: A review. Renew. Sustain. Energy Rev. 16, 5584–5596. https://doi.org/10.1016/j.rser.2012.06.015 Enerkem [WWW Document], 2019. . Enerkem. URL https://enerkem.com/ (accessed 3.31.19). Erkiaga, A., Lopez, G., Barbarias, I., Artetxe, M., Amutio, M., Bilbao, J., Olazar, M., 2015. HDPE pyrolysissteam reforming in a tandem spouted bed-fixed bed reactor for H2 production. J. Anal. Appl. Pyrolysis 116, 34–41. https://doi.org/10.1016/j.jaap.2015.10.010 Fang, S., Yu, Z., Lin, Yan, Lin, Yousheng, Fan, Y., Liao, Y., Ma, X., 2016. Effects of additives on the co-pyrolysis of municipal solid waste and paper sludge by using thermogravimetric analysis. Bioresour. Technol. 209, 265–272. https://doi.org/10.1016/j.biortech.2016.03.027 Fernandez-Akarregi, A.R., Makibar, J., Lopez, G., Amutio, M., Olazar, M., 2013. Design and operation of a conical spouted bed reactor pilot plant (25 kg/h) for biomass fast pyrolysis. Fuel Proc Tech 112, 48– 56. https://doi.org/10.1016/j.fuproc.2013.02.022 Fulcrum Bioenergy [WWW Document], 2019. . Fulcrum Bioenergy. URL http://fulcrum-bioenergy.com/ (accessed 3.31.19). Funke, A., Niebel, A., Richter, D., Abbas, M.M., Muller, A.-K., Radloff, S., Paneru, M., Maier, J., Dahmen, N., Sauer, J., 2016. Fast pyrolysis char – Assessment of alternative uses within the bioliq concept. Bioresour. Tech 200, 905–913. https://doi.org/10.1016/j.biortech.2015.11.012 Gray, Dr.D., 2017. Major gasifiers for IGCC systems, in: Integrated Gasification Combined Cycle (IGCC) Technologies. Elsevier, pp. 305–355. https://doi.org/10.1016/B978-0-08-100167-7.00008-1 Guo, L., Lu, Y., Zhang, X., Ji, C., Guan, Y., Pei, A., 2007. Hydrogen production by biomass gasification in supercritical water: A systematic experimental and analytical study. Catal. Today 129, 275–286. https://doi.org/10.1016/j.cattod.2007.05.027 Hassan, S.S., Williams, G.A., Jaiswal, A.K., 2018. Emerging technologies for the pretreatment of lignocellulosic biomass. Bioresour. Technol. 262, 310–318. https://doi.org/10.1016/j.biortech.2018.04.099 Higman, C., 2017. GSTC Syngas Database: 2017 Update. Higman, C., Burgt, M. van der, 2008. Gasification, Second. ed. Gulf Professional Publishing, Burlington, MA, USA. Hinkley, J., Hayward, J., McNaughton, R., Gillespie, R., Matsumoto, A., Watt, M., Lovegrove, K., 2016. Cost assessment of hydrogen production from PV and electrolysis (No. Project A-3018). CSIRO, Canberra, Australia. Ibrahimoglu, B., Cucen, A., Yilmazoglu, M.Z., 2017. Numerical modeling of a downdraft plasma gasification reactor. Int. J. Hydrog. Energy 42, 2583–2591. https://doi.org/10.1016/j.ijhydene.2016.06.224 25

669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721

Jeong, H.J., Park, S.S., Hwang, J., 2014. Co-gasification of coal–biomass blended char with CO2 at temperatures of 900–1100°C. Fuel 116, 465–470. https://doi.org/10.1016/j.fuel.2013.08.015 Kalinci, Y., Hepbasli, A., Dincer, I., 2009. Biomass-based hydrogen production: A review and analysis. Int. J. Hydrog. Energy 34, 8799–8817. https://doi.org/10.1016/j.ijhydene.2009.08.078 Kaza, S., Yao, L., Bhada-Tata, P., Woerden, F.V., 2018. What a Waste 2.0: A Global Snapshot of Solid Waste Management to 2050. International Bank for Reconstruction and Development, The World Bank, Washington, DC, USA. Kim, S.-W., Park, H.-S., Kim, H.-J., 2003. 100kW steam plasma process for treatment of PCBs (polychlorinated biphenyls) waste. Vacuum 70, 59–66. https://doi.org/10.1016/S0042207X(02)00761-3 Kinchin, C.M., Bain, R.L., 2009. Hydrogen Production from Biomass via Indirect Gasification: The Impact of NREL Process Development Unit Gasifier Correlations (No. NREL/TP-510-44868, 956891). https://doi.org/10.2172/956891 Lemmens, B., Elslander, H., Vanderreydt, I., Peys, K., Diels, L., Oosterlinck, M., Joos, M., 2007. Assessment of plasma gasification of high caloric waste streams. Waste Manag. 27, 1562–1569. https://doi.org/10.1016/j.wasman.2006.07.027 Leskinen, T., Kelley, S.S., Argyropoulos, D.S., 2017. E-beam irradiation & steam explosion as biomass pretreatment, and the complex role of lignin in substrate recalcitrance. Biomass Bioenergy 103, 21– 28. https://doi.org/10.1016/j.biombioe.2017.05.008 Lombardi, L., Carnevale, E., Corti, A., 2012. Analysis of energy recovery potential using innovative technologies of waste gasification. Waste Manag. 32, 640–652. https://doi.org/10.1016/j.wasman.2011.07.019 Lu, Y., Jin, H., Guo, L., Zhang, X., Cao, C., Guo, X., 2008. Hydrogen production by biomass gasification in supercritical water with a fluidized bed reactor. Int. J. Hydrog. Energy 33, 6066–6075. https://doi.org/10.1016/j.ijhydene.2008.07.082 Makibar, J., Fernandez-Akarregi, A.R., Amutio, M., Lopez, G., Olazar, M., 2015. Performance of a conical spouted bed pilot plant for bio-oil production by poplar flash pyrolysis. Fuel Proc Tech 137, 283– 289. https://doi.org/10.1016/j.fuproc.2015.03.011 Mastellone, M.L., 2015. Waste Management and Clean Energy Production from Municipal Solid Waste. Nova Publishers, New York, NY, USA. Mastellone, M.L., Arena, U., 2004. Bed defluidisation during the fluidised bed pyrolysis of plastic waste mixtures. Polym. Degrad. Stab. 85, 1051–1058. https://doi.org/10.1016/j.polymdegradstab.2003.04.002 Materazzi, M., Lettieri, P., Mazzei, L., Taylor, R., Chapman, C., 2015. Reforming of tars and organic sulphur compounds in a plasma-assisted process for waste gasification. Fuel Process. Technol. 137, 259– 268. https://doi.org/10.1016/j.fuproc.2015.03.007 Mohammed, M.A.A., Salmiaton, A., Wan Azlina, W.A.K.G., Mohammad Amran, M.S., Fakhru’l-Razi, A., 2011. Air gasification of empty fruit bunch for hydrogen-rich gas production in a fluidized-bed reactor. Energy Convers. Manag. 52, 1555–1561. https://doi.org/10.1016/j.enconman.2010.10.023 Moneti, M., Di Carlo, A., Bocci, E., Foscolo, P.U., Villarini, M., Carlini, M., 2016. Influence of the main gasifier parameters on a real system for hydrogen production from biomass. Int. J. Hydrog. Energy 41, 11965–11973. https://doi.org/10.1016/j.ijhydene.2016.05.171 Mora, M., del Carmen García, M., Jiménez-Sanchidrián, C., Romero-Salguero, F.J., 2010. Transformation of light paraffins in a microwave-induced plasma-based reactor at reduced pressure. Int. J. Hydrog. Energy 35, 4111–4122. https://doi.org/10.1016/j.ijhydene.2010.01.149 Moreno, J., Dufour, J., 2013. Life cycle assessment of hydrogen production from biomass gasification. Evaluation of different Spanish feedstocks. Int. J. Hydrog. Energy 38, 7616–7622. https://doi.org/10.1016/j.ijhydene.2012.11.076 Mosier, N., 2005. Features of promising technologies for pretreatment of lignocellulosic biomass. Bioresour. Technol. 96, 673–686. https://doi.org/10.1016/j.biortech.2004.06.025 Moustakas, K., Fatta, D., Malamis, S., Haralambous, K., Loizidou, M., 2005. Demonstration plasma gasification/vitrification system for effective hazardous waste treatment. J. Hazard. Mater. 123, 120–126. https://doi.org/10.1016/j.jhazmat.2005.03.038 26

722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775

Namioka, T., Saito, A., Inoue, Y., Park, Y., Min, T., Roh, S., Yoshikawa, K., 2011. Hydrogen-rich gas production from waste plastics by pyrolysis and low-temperature steam reforming over a ruthenium catalyst. Appl. Energy 88, 2019–2026. https://doi.org/10.1016/j.apenergy.2010.12.053 Ochoa, A., Arregi, A., Amutio, M., Gayubo, A.G., Olazar, M., Bilbao, J., Castaño, P., 2018. Coking and sintering progress of a Ni supported catalyst in the steam reforming of biomass pyrolysis volatiles. Appl. Catal. B Environ. 233, 289–300. https://doi.org/10.1016/j.apcatb.2018.04.002 Park, Y., Namioka, T., Sakamoto, S., Min, T., Roh, S., Yoshikawa, K., 2010. Optimum operating conditions for a two-stage gasification process fueled by polypropylene by means of continuous reactor over ruthenium catalyst. Fuel Process. Technol. 91, 951–957. https://doi.org/10.1016/j.fuproc.2009.10.014 Parks, G.D., Curry-Nkansah, M., Hughes, E., Sterzinger, G., 2011. Hydrogen Production Cost Estimate Using Biomass Gasification: Independent Review (No. NREL/BK-BA10-51726). National Renewable Energy Laboratory, Golden, CO, USA. Parthasarathy, P., Narayanan, K.S., 2014. Hydrogen production from steam gasification of biomass: Influence of process parameters on hydrogen yield – A review. Renew. Energy 66, 570–579. https://doi.org/10.1016/j.renene.2013.12.025 Perkins, G., Bhaskar, T., Konarova, M., 2018. Process development status of fast pyrolysis technologies for the manufacture of renewable transport fuels from biomass. Renew. Sustain. Energy Rev. 90, 292– 315. https://doi.org/10.1016/j.rser.2018.03.048 Perkins, G., Vairakannu, P., 2017. Considerations for oxidant and gasifying medium selection in underground coal gasification. Fuel Process. Technol. 165, 145–154. https://doi.org/10.1016/j.fuproc.2017.05.010 Rabou, L.P.L.M., Zwart, R.W.R., Vreugdenhil, B.J., Bos, L., 2009. Tar in Biomass Producer Gas, the Energy research Centre of The Netherlands (ECN) Experience: An Enduring Challenge. Energy Fuels 23, 6189–6198. https://doi.org/10.1021/ef9007032 Rodriguez Correa, C., Kruse, A., 2018. Supercritical water gasification of biomass for hydrogen production – Review. J. Supercrit. Fluids 133, 573–590. https://doi.org/10.1016/j.supflu.2017.09.019 Rutberg, Ph.G., Bratsev, A.N., Kuznetsov, V.A., Popov, V.E., Ufimtsev, A.A., Shtengel’, S.V., 2011. On efficiency of plasma gasification of wood residues. Biomass Bioenergy 35, 495–504. https://doi.org/10.1016/j.biombioe.2010.09.010 Saad, J.M., Williams, P.T., 2016. Pyrolysis-Catalytic-Dry Reforming of Waste Plastics and Mixed Waste Plastics for Syngas Production. Energy Fuels 30, 3198–3204. https://doi.org/10.1021/acs.energyfuels.5b02508 Sahoo, D., Ummalyma, S.B., Okram, A.K., Pandey, A., Sankar, M., Sukumaran, R.K., 2018. Effect of dilute acid pretreatment of wild rice grass (Zizania latifolia) from Loktak Lake for enzymatic hydrolysis. Bioresour. Technol. 253, 252–255. https://doi.org/10.1016/j.biortech.2018.01.048 Salkuyeh, Y.K., Saville, B.A., MacLean, H.L., 2018. Techno-economic analysis and life cycle assessment of hydrogen production from different biomass gasification processes. Int. J. Hydrog. Energy 43, 9514–9528. https://doi.org/10.1016/j.ijhydene.2018.04.024 Santamaria, L., Artetxe, M., Lopez, G., Cortazar, M., Amutio, M., Bilbao, J., Olazar, M., 2020. Effect of CeO2 and MgO promoters on the performance of a Ni/Al2O3 catalyst in the steam reforming of biomass pyrolysis volatiles. Fuel Process. Technol. 198, 106223. https://doi.org/10.1016/j.fuproc.2019.106223 Santamaria, L., Lopez, G., Arregi, A., Amutio, M., Artetxe, M., Bilbao, J., Olazar, M., 2019a. Stability of different Ni supported catalysts in the in-line steam reforming of biomass fast pyrolysis volatiles. Appl. Catal. B Environ. 242, 109–120. https://doi.org/10.1016/j.apcatb.2018.09.081 Santamaria, L., Lopez, G., Arregi, A., Amutio, M., Artetxe, M., Bilbao, J., Olazar, M., 2019b. Effect of calcination conditions on the performance of Ni/MgO–Al 2 O 3 catalysts in the steam reforming of biomass fast pyrolysis volatiles. Catal. Sci. Technol. 9, 3947–3963. https://doi.org/10.1039/C9CY00597H Santamaria, L., Lopez, G., Arregi, A., Amutio, M., Artetxe, M., Bilbao, J., Olazar, M., 2018. Influence of the support on Ni catalysts performance in the in-line steam reforming of biomass fast pyrolysis derived volatiles. Appl. Catal. B Environ. 229, 105–113. https://doi.org/10.1016/j.apcatb.2018.02.003 27

776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829

Sara, H.R., Enrico, B., Mauro, V., Andrea, D.C., Vincenzo, N., 2016. Techno-economic Analysis of Hydrogen Production Using Biomass Gasification -A Small Scale Power Plant Study. Energy Procedia 101, 806– 813. https://doi.org/10.1016/j.egypro.2016.11.102 Sentis, L., Rep, M., Barisano, D., Bocci, E., Sara Rajabi, H., Pallozzi, V., Tascioni, R., 2016. Techno-economic analysis of UNIFHY hydrogen production system (No. SP1- JTI- FCH.2011.2.3). Shin, D.H., Hong, Y.C., Lee, S.J., Kim, Y.J., Cho, C.H., Ma, S.H., Chun, S.M., Lee, B.J., Uhm, H.S., 2013. A pure steam microwave plasma torch: Gasification of powdered coal in the plasma. Surf. Coat. Technol. 228, S520–S523. https://doi.org/10.1016/j.surfcoat.2012.04.071 Singh, R., Krishna, B.B., Kumar, J., Bhaskar, T., 2016. Opportunities for utilization of non-conventional energy sources for biomass pretreatment. Bioresour. Technol. 199, 398–407. https://doi.org/10.1016/j.biortech.2015.08.117 Susmozas, A., Iribarren, D., Dufour, J., 2013. Life-cycle performance of indirect biomass gasification as a green alternative to steam methane reforming for hydrogen production. Int. J. Hydrog. Energy 38, 9961–9972. https://doi.org/10.1016/j.ijhydene.2013.06.012 Tang, J., Wang, J., 2016. Catalytic steam gasification of coal char with alkali carbonates: A study on their synergic effects with calcium hydroxide. Fuel Process. Technol. 142, 34–41. https://doi.org/10.1016/j.fuproc.2015.09.020 Tanigaki, N., Fujinaga, Y., Kajiyama, H., Ishida, Y., 2013. Operating and environmental performances of commercial-scale waste gasification and melting technology. Waste Manag. Res. 31, 1118–1124. https://doi.org/10.1177/0734242X13502386 Tanksale, A., Wong, Y., Beltramini, J., Lu, G., 2007. Hydrogen generation from liquid phase catalytic reforming of sugar solutions using metal-supported catalysts. Int. J. Hydrog. Energy 32, 717–724. https://doi.org/10.1016/j.ijhydene.2006.08.009 Tanner, J., 2015. High Temperature Entrained Flow Gasification of Victorian Brown Coals and Rhenish Lignites (PhD). Monash University, Melbourne, Australia. Taylor, Alabdrabalameer, Skoulou, 2019. Choosing Physical, Physicochemical and Chemical Methods of PreTreating Lignocellulosic Wastes to Repurpose into Solid Fuels. Sustainability 11, 3604. https://doi.org/10.3390/su11133604 Tonn, B., Thumm, U., Lewandowski, I., Claupein, W., 2012. Leaching of biomass from semi-natural grasslands – Effects on chemical composition and ash high-temperature behaviour. Biomass Bioenergy 36, 390–403. https://doi.org/10.1016/j.biombioe.2011.11.014 Valderrama Rios, M.L., González, A.M., Lora, E.E.S., Almazán del Olmo, O.A., 2018. Reduction of tar generated during biomass gasification: A review. Biomass Bioenergy 108, 345–370. https://doi.org/10.1016/j.biombioe.2017.12.002 Valle, B., Remiro, A., Aguayo, A.T., Bilbao, J., Gayubo, A.G., 2013. Catalysts of Ni/α-Al2O3 and Ni/La2O3αAl2O3 for hydrogen production by steam reforming of bio-oil aqueous fraction with pyrolytic lignin retention. Int. J. Hydrog. Energy 38, 1307–1318. https://doi.org/10.1016/j.ijhydene.2012.11.014 Wallman, P.H., Thorsness, C.B., Winter, J.D., 1998. Hydrogen production from wastes. Energy 23, 271–278. https://doi.org/10.1016/S0360-5442(97)00089-3 Woo, Y., Cho, S., Kim, J., Kim, B.S., 2016. Optimization-based approach for strategic design and operation of a biomass-to-hydrogen supply chain. Int. J. Hydrog. Energy 41, 5405–5418. https://doi.org/10.1016/j.ijhydene.2016.01.153 Wood, B.J., Sancier, K.M., 1984. The Mechanism of the Catalytic Gasification of Coal Char: A Critical Review. Catal. Rev. 26, 233–279. https://doi.org/10.1080/01614948408078065 Wu, C., Williams, P.T., 2010a. A novel Ni–Mg–Al–CaO catalyst with the dual functions of catalysis and CO2 sorption for H2 production from the pyrolysis–gasification of polypropylene. Fuel 89, 1435–1441. https://doi.org/10.1016/j.fuel.2009.10.020 Wu, C., Williams, P.T., 2010b. Investigation of coke formation on Ni-Mg-Al catalyst for hydrogen production from the catalytic steam pyrolysis-gasification of polypropylene. Appl. Catal. B Environ. 96, 198– 207. https://doi.org/10.1016/j.apcatb.2010.02.022 Wu, C., Williams, P.T., 2009. Investigation of Ni-Al, Ni-Mg-Al and Ni-Cu-Al catalyst for hydrogen production from pyrolysis–gasification of polypropylene. Appl. Catal. B Environ. 90, 147–156. https://doi.org/10.1016/j.apcatb.2009.03.004 28

830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847

Yanik, J., Ebale, S., Kruse, A., Saglam, M., Yuksel, M., 2007. Biomass gasification in supercritical water: Part 1. Effect of the nature of biomass. Fuel 86, 2410–2415. https://doi.org/10.1016/j.fuel.2007.01.025 Yeboah, Y.D., Xu, Y., Sheth, A., Godavarty, A., Agrawal, P.K., 2003. Catalytic gasification of coal using eutectic salts: identification of eutectics. Carbon 41, 203–214. https://doi.org/10.1016/S00086223(02)00310-X Yildiz, G., Ronsse, F., Duren, R. van, Prins, W., 2016. Challenges in the design and operation of processes for catalytic fast pyrolysis of woody biomass. Renew Sus Energy Rev 57, 1596–1610. https://doi.org/10.1016/j.rser.2015.12.202 Yoon, S.J., Lee, J.-G., 2012. Hydrogen-rich syngas production through coal and charcoal gasification using microwave steam and air plasma torch. Int. J. Hydrog. Energy 37, 17093–17100. https://doi.org/10.1016/j.ijhydene.2012.08.054 Zhang, L., Wu, W., Siqu, N., Dekyi, T., Zhang, Y., 2019. Thermochemical catalytic-reforming conversion of municipal solid waste to hydrogen-rich synthesis gas via carbon supported catalysts. Chem. Eng. J. 361, 1617–1629. https://doi.org/10.1016/j.cej.2018.12.115 Zhang, L., Wu, W., Zhang, Y., Zhou, X., 2018. Clean synthesis gas production from municipal solid waste via catalytic gasification and reforming technology. Catal. Today 318, 39–45. https://doi.org/10.1016/j.cattod.2018.02.050

29

848

Tables

849 850 851

Table 1: Ultimate analysis and main constituents (wt%) of municipal solid waste from a high socioeconomic area (Mastellone, 2015).

24.92

Food and green wastes 27.00

29.60

12.00

3.14

4.00

4.64

25.60

9.02

15.06

25.00

18.94

Nitrogen

0.16

0.90

0.73

1.00

0.67

Chlorine

0.27

3.38

0.41

0.40

0.78

Sulfur

0.16

0.34

0.18

0.02

0.12

36.80

4.2

33.40

30.00

25.07

5.85

6.59

22.16

12.58

10.19

Component

Paper

Plastic

Other

Carbon

27.40

63.57

3.76

Oxygen

Hydrogen

Moisture Mineral Matter

852 853 854 855 856

30

MSW

857 858

Table 2: Summary of the generic gasifier characteristics (Gray, 2017; Higman and Burgt, 2008; Tanner, 2015). Operating conditions

Fixed bed

Fluidized bed

dry

slagging

dry

Feed conditions

dry

dry

dry

agglomer ating dry

Typical reactor temp (°C) Syngas exit temp (°C)

1000

1800

1050

425-650

425-650

water

water

Ash conditions

Syngas cooling Pressure (MPa) Residence time (s) Oxidant type Oxidant requirement Steam requirement Gas Flow Typical particle size (mm) Commercial Gasifier

Preferred Feedstock Moisture content limit (%) Typical Ash Content (%) Typical Ash Fusion Temp (°C) Conversion Typical Cold gas efficiency (%)

Entrained flow

Plasma

slagging

slagging

slagging

dry

slurry

1050

1600

1600

dry 1500 5500 (peak)

925-1040

925-1040

1400 – 1600

1200 – 1400

1000

syngas cooler

syngas cooler

water/syngas cooler

water/syngas cooler

varies

Up to 2.5 900 – 3600 air / oxygen

Up to 3

1–3

2.5 – 3

2.5 – 3

0.1

10 – 100

10 – 100

1.5-4

1.5

-

air / oxygen

air / oxygen

oxygen

oxygen

plasma

low

low

moderate

moderat e

high

high

low / moderat e

high

low

moderate

moderat e

low

low

none

up or down

up

up

up

up or down

up or down

up or down

5 - 80

5 - 80

<6

<6

< 0.1

< 0.1

any

HTW, KBR, IDGCC

KRW, UGas

Shell, PRENFLO, EAGLE, Siemens, MHI

GE, E-Gas

Hitachi Metals, Alter NG, Westingh ouse Plasma Corp

coal, coke, biomass, waste, petcoke

coal, coke, biomass, waste , petcoke

Any

Up to 3 900 – 3600 air / oxygen

Lurgi (coal) Various for biomass

BGL Nippon DMS

coal, biomass, waste

coal, waste

coal, waste

coal, coke, biomass waste

any

<28

any

any

any

limited

any

<15

<25

<40

<40

2 – 25

<25

any

no limit

no limit

>1100

>1100

<1300

<1300

no limit

>99

96

95

98-99

100

100

~88

~85

70 – 80

~80

74-77

varies up to 99 varies up to ~88

859 860 861 862 31

863

Table 3: Summary of plasma gasification technologies. 

Gasifier type Pilot scale plasma plant

Feedstoc k hazardou s waste

Medium

Microwave

Light paraffin

Microwave

Coal and charcoal

Steam and air

Microwave

Coal

Steam

Microwave plasma with integrated down-draft coal gasifier Fluid bed integrated with plasma gasification

Coal

Air and steam

RDF

steam/oxygen

Downdraft gasification

Wood residues

Air

Fixed bed

Textile waste RD F

Air

Air and steam

Purpose Conversion of valuable combustible by product

Transformation of light paraffin for the production of H2 and ethylene Change in syngas composition based on operating parameters and corresponding performance Water molecular disintegration and effect of gas temperature on plasma gasification characteristics were tested Effect of operating conditions on gasification performance via numerical modelling Focused primarily on converting tars and organic sulfur compounds into valuable combustible products. Synthesis of fuel and its heating value analysis Production and improvement of syngas quality and slag characterisation

864

32

Key finding

Ref.

Heat recovery from product gases are required to improve the efficiency. Typical gas composition includes (Vol.%) H2: 24– 43%; CO: 25–44%; CO2 and N2: 10–26%. For higher production of H2 low power with a range 100–150 W is found to be effective.

(Moustaka s et al., 2005)

Carbon conversion increased with increasing O2/fuel ratio and Cold gas efficiency (CGE) was maximum when O2/fuel ratio was 0.272. The syngas composition using steam to coal ratio of 9:1 was: H2: 48%; CO: 23% and CO2: 25%.

(Yoon and Lee, 2012)

The syngas composition was: H2: 18.4% and CO: 37.2%. The cold gas efficiency (CGE) was determined to be 55.3%. The sulfur compounds converted into H2S by 5060%, while other organic compounds reduced to CO, H2 and H2S with an efficiency of 96%. The heating value of the product gases was determined to be 13.8–14.3 MJ kg−1. Plasma gasification offers suitable syngas quality along with acceptable building materials from slag. The syngas composition (vol.%) was: H2: 8.1% and CO: 17.6% and CO2: 3.6%.

(Ibrahimog lu et al., 2017)

(Mora et al., 2010)

(Shin et al., 2013)

(Materazzi et al., 2015)

(Rutberg et al., 2011) (Lemmens et al., 2007)

Table 4: Summary of techno-economic analyses for producing hydrogen from waste and biomass gasification. Note: Originally reported prices have been adjusted to 2018 USD dollars using United States inflation rates. Study

Year

Feedstock

Feedstock price

Process configuration

(USD/tonne) Wallman et al. (1998)

1998

MSW

Wallman et al. (1998)

1998

50% plastic

NREL (Parks et al., 2011)

2011

Biomass

60

NREL (Parks et al., 2011)

2011

Biomass

Sentis et al. (2016)

2016

Sentis et al. (2016)

2016

Sentis et al. (2016)

Process scale

H2 Production

Capex

O&M OPEX

Thermal efficiency

LCOH

CO2 Emissions

(MWth feedstock)

(ton/yr)

(Million USD)

(% of CAPEX)

(%)

(USD/kg)

(kg-CO2eq/kg-H2)

89

Pyrolyzer and EF gasification

347

nd

nd

nd

50.0

3.3

nd

156

Pyrolyzer and EF gasification

347

nd

nd

nd

66.0

1.3

nd

FB indirect gasification, 1st plant

87

12,000

250

3.4

48.8

6.3

nd

80

FB indirect gasification, nth plant

347

50,000

403

3.9

50.8

3.3

nd

Biomass

75

FB indirect gasification

0.1

10.5

0.8

2.0

50.0

9.2

nd

Biomass

75

FB indirect gasification

1

105

1.9

2.0

50.0

5.5

2.4

2016

Biomass

75

FB indirect gasification

10

1,050

6.6

2.0

50.0

2.4

nd

Salkuyeh et al. (2018)

2018

Biomass

100

EF gasifier, w/o CC

1,049

165,564

1229

5.0

55.7

3.4

-0.1

Salkuyeh et al. (2018)

2018

Biomass

100

EF gasifier, with CC

1,180

165,564

1340

5.0

49.5

3.5

-21.9

Salkuyeh et al. (2018)

2018

Biomass

100

FB indirect gasifier, w/o CC

1,298

165,564

647

5.0

45.0

3.1

-0.5

Salkuyeh et al. (2018)

2018

Biomass

100

FB indirect gasifier, with CC

1,425

165,564

852

5.0

41.0

3.5

-15.8

nd = not disclosed

33

Figures

(a)

(b) Figure 1: Typical composition of MSW by constituent for: (a) high and (b) low incomes (from Kaza et al. (2018)).

34

MSW

Mechanical Procession

Percussing (slow running shredder): Size ≤ 150 mm

Output

Air shifter

Heavy content (glass, stone, ceramic)

FM-separator (Over belt magnetic separator)

Ferrous metals (FM)

NFM-separator (eddy current separator): Size ≤ 50 mm

Non-ferrous metals (NFM)

Secondary crushing (fast running shredder)

Secondary fuel

Figure 2: MSW mechanical treatment process (adapted from Higman (Higman, 2017)).

35

Gasification line up Feedstock Gasification

Tar Reformer (optional) Syngas Conditioning

Pretreatment (as required)

Pyrolysis

Volatiles Reforming

Water Gas Shift

Separation

H2S, CO2

Hydrogen

Pyrolysis and reforming line up

Figure 3: General scheme for producing hydrogen from wastes using gasification and pyrolysis/reforming.

36

15 14

Levelized Cost of Hydrogen (USD/kg)

13 12 11 10 9 8 7 6 5 4 3 2

Long Term Target Range

1 0

Solar PV + PEM (2015)

VRE + PEM (2018)

Solar PV + PEM (2030)

NG SMR + CCS

Black Coal + Brown Coal + Biomass CCS CCS gasification (10 MWth)

Biomass gasification (250 MWth)

Waste gasification (75 MWth)

Waste gasification (150 MWth)

Figure 4: Estimated levelized costs of clean hydrogen production (USD/kg) from a variety of common production pathways. (Data from (Bruce et al., 2018; Hinkley et al., 2016; Salkuyeh et al., 2018); range for PEM cases taken as +/-10% of reported values; waste gasification to H2 estimates from this work; MWth refers to energy in the feedstock).

Declaration of interests

☐ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

☒The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

One author, Dr Greg Perkins, is a co-inventor of a gasification technology for biomass and wastes (see www.wildfireenergy.com.au). This may be perceived to be a competing interest. However, as this technology is immature and only at pilot scale there is no reference or promotion of it in the paper; only verifiable literature sources have been used in the paper, most of which has been written by Mr Ahmmad and Dr. Krishna.

None of the other authors, Dr. Bhaskar, Dr. Krishna 37 and Mr. Ahmmad, declare any known or perceived competing interests.

Highlights:  Recent advances in gasification and pyrolysis followed by reforming are reviewed  The levelized cost of hydrogen (LCOH) from biomass is ˜2.3 to 5.2 USD/kg  The LCOH from residual wastes are estimated to be ˜1.4 to 4.8 USD/kg  Technical barriers are waste pre-treatment, syngas conditioning, technology scale  Socio-economic barriers are hydrogen market, technology competitiveness, policies

38