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Life-cycle performance of hydrogen production via indirect biomass gasification with CO2 capture

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Abstract

The implementation of CO2 capture into biohydrogen-production systems is seen as a potential solution for greening the energy sector. However, the performance of biocapture strategies needs to be assessed thoroughly in order to guarantee their suitability. In this work, the Life Cycle Assessment methodology is used to evaluate an energy system producing hydrogen from short-rotation poplar biomass through gasification coupled with carbon dioxide capture. The biomass feedstock is dried and milled before being fed to a low-pressure char-indirect gasifier. The syngas produced is conditioned and undergoes a water gas shift process. Biohydrogen is separated from the rest of compounds in a pressure swing adsorption (PSA) unit. The PSA off-gas is burnt for electricity production and the exhaust gas from this power-generation section goes through a two-stage gas separation membrane process for CO2 capture. The results show that the system succeeds in obtaining a negative (i.e., favourable) global warming impact with a low cumulative non-renewable energy demand. Direct emissions to the air, external electricity production and biomass production are the key processes contributing to the evaluated impacts. When it comes to replacing conventional (fossil-based) hydrogen, the biohydrogen product is found to be a better alternative than biohydrogen without CO2 capture only under global warming aspects.

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... Biomass gasification can be also integrated with CCS to yield a negative carbon balance. The inventory data for both biomass gasification systems without and with CCS are taken from Susmozas et al. [42,43], respectively. Further details on the inventory data of the poplar can be found in Table S3 in the ESI. ...
... Biomass gasification with carbon capture and storage shows the lowest global warming potential value (− 13.11 kg CO 2 -eq/kg H 2 ), as carbon capture and storage leads to a net-negative carbon balance). This global warming potential value is in good agreement with the only LCA study reported for biomass gasification with carbon capture and storage, i.e., − 14.63 kg CO 2 -eq/kg H 2 [43]. This technology is followed by the unabated biomass gasification process (0.65 kg CO 2 -eq/kg H 2 ), where both global warming potential values (biomass gasification and biomass gasification with carbon capture and storage) fit well within the range previously reported [5]. ...
... The obtained results are aligned with previous studies concerning the midpoint impacts, i.e., biomass gasification emits approximately 0.39 kgCO 2 /kgH 2 [42] and − 14.63 kgCO 2 /kgH 2 when equipped with carbon capture and storage [43]. For the ecosystem quality impact, the biomass feedstock is the main contributor to the total impact due to the land utilisation and water consumption in the biomass plantations ( Figure S1c in the ESI). ...
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Hydrogen has been identified as a potential energy vector to decarbonise the transport and chemical sectors and achieve global greenhouse gas reduction targets. Despite ongoing efforts, hydrogen technologies are often assessed focusing on their global warming potential while overlooking other impacts, or at most including additional metrics that are not easily interpretable. Herein, a wide range of alternative technologies have been assessed to determine the total cost of hydrogen production by coupling life-cycle assessments with an economic evaluation of the environmental externalities of production. By including monetised values of environmental impacts on human health, ecosystem quality, and resources on top of the levelised cost of hydrogen production, an estimation of the “real” total cost of hydrogen was obtained to transparently rank the alternative technologies. The study herein covers steam methane reforming (SMR), coal and biomass gasification, methane pyrolysis, and electrolysis from renewable and nuclear technologies. Monetised externalities are found to represent a significant percentage of the total cost, ultimately altering the standard ranking of technologies. SMR coupled with carbon capture and storage emerges as the cheapest option, followed by methane pyrolysis, and water electrolysis from wind and nuclear. The obtained results identify the “real” ranges for the cost of hydrogen compared to SMR (business as usual) by including environmental externalities, thereby helping to pinpoint critical barriers for emerging and competing technologies to SMR.
... The final step of H 2 synthesis is the water gas shift (WGS) reaction (Eq. 21) where CO and H 2 O are transformed into H 2 and CO 2 , so that H 2 production increases [38]. The WGS reactor is considered as a secondary H 2 producer and a primary CO clean-up system. ...
... The shifted syngas had a high concentration of H 2 but it also included a high concentration of CO 2 and H 2 O as well as residual CH 4 and small amounts of CO and N 2 . In order to produce a high quality H 2 , the gas is then purified in a Methyldiethanolamine (MDEA) unit, condensation, and drying unit and PSA (pressure swing adsorption) unit for the removal of CO 2 , moisture and other contaminants, respectively [38]. The separation of H 2 in PSA process, which consists of two stages, needs an adsorbent, which specifically adsorbs H 2 from feed stream. ...
... The CO-rich stream exiting from SMR is then converted into CO 2 and H 2 in the WGS reactor. The WGS reaction takes place in two consecutive reactors, a high-temperature reactor (HTS) at 375°C followed by a low-temperature reactor (LTS) at 200°C [37,38]. The two catalysts considered for the WGS reaction are namely Fe-Cr- based catalyst for HTS and Cu-based catalyst for LTS. ...
... The incorporation of CCS with biomass gasification is one route toward negative GHG emissions, given that the cultivation of biomass removes CO 2 from the atmosphere [58]. The potential contribution of biomass to hydrogen production may be large, dependent on availability of biomass resources. ...
... Estimates of GHG emissions from biomass gasification are lower but more variable, − 371 to 504 gCO 2 eq/kW h H2 [58,77,78,[85][86][87][88][89][90][91][92][93][94]. Key factors associated with emissions estimates are the source of the biomass feedstock, how the carbon sink associated with biomass growth is included, as well as whether CCS is within the scope. ...
... Hydrogen from biomass gasification using CCS is one route to produce negative life cycle GHG emissions in gas production. One study provides an estimate of hydrogen production from biomass gasification using CCS of − 371 gCO 2 eq/kW h H2 [58]. This estimate is comparable to estimates for electricity generation from biomass combustion with CCS, suggesting that hydrogen production from biomass with CCS will be relevant in the second half of this century, when negative emissions become increasingly important [96]. ...
Article
Projections of decarbonisation pathways have typically involved reducing dependence on natural gas grids via greater electrification of heat using heat pumps or even electric heaters. However, many technical, economic and consumer barriers to electrification of heat persist. The gas network holds value in relation to flexibility of operation, requiring simpler control and enabling less expensive storage. There may be value in retaining and repurposing gas infrastructure where there are feasible routes to decarbonisation. This study quantifies and analyses the decarbonisation potential associated with the conversion of gas grids to deliver hydrogen, focusing on supply chains. Routes to produce hydrogen for gas grids are categorised as: reforming natural gas with (or without) carbon capture and storage (CCS); gasification of coal with (or without) CCS; gasification of biomass with (or without) CCS; electrolysis using low carbon electricity. The overall range of greenhouse gas emissions across routes is extremely large, from − 371 to 642 gCO2eq/kW hH2. Therefore, when including supply chain emissions, hydrogen can have a range of carbon intensities and cannot be assumed to be low carbon. Emissions estimates for natural gas reforming with CCS lie in the range of 23–150 g/kW hH2, with CCS typically reducing CO2 emissions by 75%. Hydrogen from electrolysis ranges from 24 to 178 gCO2eq/kW hH2 for renewable electricity sources, where wind electricity results in the lowest CO2 emissions. Solar PV electricity typically exhibits higher emissions and varies significantly by geographical region. The emissions from upstream supply chains is a major contributor to total emissions and varies considerably across different routes to hydrogen. Biomass gasification is characterised by very large negative emissions in the supply chain and very large positive emissions in the gasification process. Therefore, improvements in total emissions are large if even small improvements to gasification emissions can be made, either through process efficiency or CCS capture rate.
... (13)) unit. In this step, carbon monoxide and steam are reacted to produce carbon dioxide and more hydrogen [38]. Accordingly, the carbon monoxide content decreased while hydrogen content increased in the reactor. ...
... Therefore, a hydrogen purification section was employed as a final process step. Here, carbon dioxide and other impurities were removed from the gas stream using various purification methods, such as pressure swing adsorption (PSA), Methyldiethanolamine (MDEA), and condensation processes [38]. Afterwards, the purified hydrogen product was collected at ambient temperature using a water-cooled heat exchanger. ...
... The operation parameters of 850 � C, 20 atm, and S/C ratio of 3 were selected, and it was modelled with RGibbs module (RGibbs reactor) [44]. Afterwards, the WGS reaction takes place in two consecutive reactors, a HTS at 375 � C followed by a LTS at 200 � C [37,38]. The modelling of the WGS unit was carried out using the Aspen REquil module (REquil reactor). ...
... On the contrary, when the microalgae was cultivated with artificial light, the high energy consumption resulted in high CO 2 emissions, i.e. 670 kg CO 2 /MJ H 2 with more than Fig. 11. The GHG emissions (kg CO 2 -eq/kg H 2 ) range distribution of the reviewed three hydrogen production technologies (fermentation [217,218,220], gasification [19,220,224,227,229,[232][233][234][235]239,241] and MEC [243]) and the three conventional technologies (electricity water electrolysis [224,245], coal gasification [224,239,246] and steam methane reforming [224,227,239,247]). ...
... The normalized LCA results showed that steam gasification of wood chips and pyrolysis-gasification of MSW had the lowest environmental impacts. CO 2 capture was also developed in these years coupled with gasification to further reduce GHG emissions and even achieve negative emissions [232,236]. However, it was reported by Susmozas et al. [232] that only the impact of GWP was better when CO 2 capture was implemented, while all the other impacts, such as ozone layer depletion, acidification potential, eutrophication potential, etc., were worse compared to the scenario without CO 2 capture, which indicated that optimization of the CO 2 capture technology is needed in order to achieve an overall improved environmental performance. ...
... CO 2 capture was also developed in these years coupled with gasification to further reduce GHG emissions and even achieve negative emissions [232,236]. However, it was reported by Susmozas et al. [232] that only the impact of GWP was better when CO 2 capture was implemented, while all the other impacts, such as ozone layer depletion, acidification potential, eutrophication potential, etc., were worse compared to the scenario without CO 2 capture, which indicated that optimization of the CO 2 capture technology is needed in order to achieve an overall improved environmental performance. ...
Article
The increasing worldwide population and rapid urbanization have led to huge amount of fossil fuels consumption and waste generation. The awareness of living in a sustainable society is pushing people to target a low-carbon energy structure. Hydrogen, a carbon-free energy source, draws more and more attention. Particularly, biohydrogen from organic waste calls great interest by generating hydrogen and disposing waste simultaneously. Therefore, the three main technologies converting waste to biohydrogen: biological fermentation, thermochemical gasification and microbial electrolysis cell, were reviewed in this study from both technological and environmental perspective. The results showed that a variety of waste streams have been tested to produce hydrogen and different production efficiency were reported. The most favourable waste material for fermentation and microbial electrolysis cell were different types of wastewater, and agricultural lignocellulosic waste was also intensively studied in fermentation. Whereas wooden waste and municipal solid waste were the two wastes investigated the most in gasification. Optimization of the operational parameters was proved to improve the hydrogen production. However, researches focusing on scale-up of these technologies are still needed. On the other hand, life cycle assessment demonstrated that waste gasification had a better environmental profile compared to other technologies. However, the majority of the reviewed life cycle assessment studies failed to further explain the robustness due to the lack of sensitivity and uncertainty analysis, indicating high quality life cycle assessment studies are needed in the future.
... When compared to similar processes, differences in the CO2 separation technology can reveal a lower environmental performance. For example, the membrane adsorption system applied in (Susmozas et al., 2016) captures 70% of CO 2 , resulting in higher CO 2 emissions in the flue gas. The sole indirect burden associated to H 2 purification and compression process units is the electricity consumption for pressurisation (4% acidification, 5% climate change, 6% ecotoxicity freshwater, 2% eutrophication and 5% photochemical ozone formation). ...
... HHV of H 2 -in stark contrast to the scenarios where biogenic carbon is captured. The contribution of the biogenic carbon fraction to GWP becomes evident when results are compared to other BECCS system that uses 100% biomass, such as Susmozas et al. (2016). Their results showed a negative contribution to GWP (kg CO 2 eq.) of − 14.63 per kg of H 2 produced, equivalent to − 368.67 kg CO 2 eq. ...
... Even higher benefits could be observed if considering as counterfactual other waste management practises, such as landfill or incineration with no energy recovery. There are currently several studies in literature on the production of hydrogen from first-and second-generation biomass as feedstock source (Bhatia et al., 2021;Cortés et al., 2019;Susmozas et al., 2016;Tian et al., 2019). However, the production of Bio-H 2 , either from biomass or waste feedstock, would still need to be proven at a commercial scale to validate the model assumptions. ...
Article
This study focuses on the production of hydrogen from municipal solid waste (MSW) for applications in transportation. A life cycle assessment (LCA) was conducted on a semi-commercial advanced gasification process for Biohydrogen (Bio-H2) production from MSW to evaluate its environmental impact on five impact categories: Climate Change, Acidification, Eutrophication Fresh Water, Ecotoxicity Freshwater and Photochemical Ozone Formation (human health). The biogenic composition of waste and the effect of carbon sequestration were analysed for Bio-H2, uncovering a net-negative carbon process. The counterfactual case of MSW incineration further bolsters the carbon savings associated to Bio-H2. The production of Bio-H2 from waste is proven to be competitive against alternative hydrogen productions routes, namely blue hydrogen (Blue-H2) produced via steam methane reforming/autothermal reforming coupled with carbon capture and storage (CCS), and green hydrogen (Green-H2) from solar and offshore wind, with respect to climate change. These climate change advantages are shown to carry forward in the context of decarbonisation of electricity grid mix, as analysed by scenarios taken for 2030 and ‘net-zero’ 2050.
... Hydrogen production from renewable sources such as poplar (Susmozas et al., 2016) or willow wood (González- García et al., 2012), sugar cane (Halleux et al., 2008), sweet potato , sorghum (Aguilar-Sánchez et al., 2018) or sugar beet (Luo et al., 2009) have been investigated as the first actions to achieve a significant reduction of environmental impacts (Salkuyeh et al., 2018). Hydrogen can be obtained from different feedstocks through steam reforming (Braga et al., 2016;López et al., 2019;Zheng et al., 2019), autothermal reforming (Khila et al., 2017;Spallina et al., 2018;Xue et al., 2017) and aqueous phase reforming (Coronado et al., 2018;Esteve-Adell et al., 2017;García et al., 2018), among them, steam reforming is the most common, as almost 90% of H 2 is produced by natural gas reforming. ...
... In addition to the basic scheme, a comparison was made with some processes published in the scientific literature. The FU was changed to 1 kg of hydrogen produced in the plant with 99.9 vol% purity by steam reforming (Fig. 6), in agreement with other reforming studies using other raw materials for hydrogen production (Hajjaji et al., , 2013Khila et al., 2016;Susmozas et al., 2016Susmozas et al., , 2015Susmozas et al., , 2013, thus allowing the comparison of the environmental profile of different processes. Therefore, the new facility configuration does not consider the operation of the SOFC, consequently the output stream of the system is led to a purification system: First, the WGS process removes carbon monoxide and produces a small amount of additional hydrogen. ...
... Once in the plant are included all the operations necessary to obtain hydrogen and the production of electricity from the steam produced in the system (Susmozas et al., 2013). PG&C-H 2 : Gasification of poplar biomass, as mentioned above, but includes carbon fixation during the cultivation stage (Susmozas et al., 2016). GSR-H 2 : Glycerol reforming, obtained as a co-product of biodiesel production by transesterification of rapeseed oil. ...
Article
Nowadays, there is an increasing demand for energy in the world. With an energy system still based on fossil fuels, a paradigm shifts towards clean energy production based on available renewable resources is necessary. Hydrogen is a high-quality energy carrier that can be used with great efficiency and is expected to acquire a great importance in the next generation of fuels. This study aims to analyze the potential environmental impacts associated with the steam reforming of alcoholic waste from distilleries to produce clean electricity by using the Life Cycle Assessment methodology. The main findings from this study reported that the global environmental profile is better than other alternatives more common as sanitary landfill or incineration. In terms of some impact categories as Abiotic and Ozone Depletion, Acidification and Eutrophication, steam reforming of alcoholic waste performed better profiles than other processes that produce hydrogen from diverse feedstocks.
... Comparative LCA study has been recently conducted to compare two different gasification systems (downdraft gasifier and CFB gasifier). H 2 production proved that downdraft gasifier delivered better environmental performance over CFB gasifier (Susmozas et al. 2016). In addition, Susmozas et al. (2016) conducted another LCA study of hydrogen production, they focused on direct emission, outer power production, and biomass manufacture to be major practices in determining the environmental impacts, and it has been proved that bio-hydrogen production with CO 2 capture delivers better environmental performance over conventional processes. ...
... H 2 production proved that downdraft gasifier delivered better environmental performance over CFB gasifier (Susmozas et al. 2016). In addition, Susmozas et al. (2016) conducted another LCA study of hydrogen production, they focused on direct emission, outer power production, and biomass manufacture to be major practices in determining the environmental impacts, and it has been proved that bio-hydrogen production with CO 2 capture delivers better environmental performance over conventional processes. Another study proved electricity production from biomass delivered noticeably less CO 2 emissions than coal fired systems (Cambero, Alexandre, and Sowlati 2015;Varun and Bhat 2009b). ...
... Evaluation of co-firing of biomass with coal Alternatives:Wood pellets, coal, and natural gas GHG emissions Zhang, 2009 Evaluation of co-firing of biomass with coal for electricity production Alternatives: Forestry residues, energy crops, and coal GHG emissions Froese, 2010 Heat production through gasification Alternatives: Forestry residues, and recycled wood GHG emissions Puy, 2010 Heat production through gasification Alternatives: Forestry residues, wood pellets, and natural gas GHG emissions Pa, 2011 Heat production through gasification Alternatives: Forestry residues, woody energy crops, and natural gas GHG emissions Pucker, 2012 Production of H 2 through gasification Alternatives: Vine and almond pruning, forest waste from pine, and eucalyptus plantation FU*: production of 1 Nm 3 H 2 Moreno, 2013 Evaluation of technologies Evaluation of integrated gasification combined cycle (IGCC) Alternatives: IGCC with upstream CO 2 adsorption vs. chemical absorption of CO 2 FU: produced energy unit Carpentieri, 2005 Evaluation of H 2 production via biomass gasification Alternatives: Gasification followed by syngas reforming vs. electricity generation GHG emissions Koroneos, 2008 Evaluation of production processes for ethanol production Alternatives: Biochemical vs. thermochemical processes GHG emissions Bright, 2009 Evaluation of CHP plant with different sizes Alternatives: 0.1, 1, and 50 MWe GHG emissions Guest,2011;Kimming,2011 Evaluation of CHP plants for power and heat production in rural areas Alternatives: Biomass fed CHP vs. fossil fuels in a large scale plant FU: 1 year supply of heat and power to a modern village Kimming, 2011 Comparison of different gasifiers for H 2 production Alternatives: Downdraft gasifier and fluidized bed gasifier GHG emissions Kalinci, 2012 Evaluation of energy production systems Alternatives: Electricity via gasification vs. bioethanol through enzymatic hydrolysis FU: the use of biomass chips from 1 ha Susmozas, 2016 Evaluation of potential future energy systems Alternatives: F-T liquid through biomass gasification, rapeseed based biodiesel, and fossil fuels FU: 1 energy unit of diesel fuel Tonini,2012 Evaluation of methanol production (via gasification) based on an autonomous distillery or sugar mill Alternatives: Co-generation plant combined with methanol or biomass integrated gasification/gas turbine (BIG-GT) system 1 MJ of each product Renó, 2014 Evaluation of bioenergy generation alternatives using forest and wood residues Alternatives: Combustion and gasification technologies with different capacities GHG emissions Cambero, 2015 Evaluation of H 2 production through biomass gasification Alternatives: ...
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The exhaustion of fossil fuel resources has instigated a necessity to find new alternatives like biofuels, for heat and power generation. Biofuels are usually generated from the thermal conversion of densified biomass material. Densification systems convert biomass into pellets, and consist of three phases: pre-pelletization, pelletization, and post- pelletization. This article provides an overview of available biomass densification techniques. A detailed discussion has been provided to emphasize the effect of raw material properties on the pellet’s durability and bulk density. A quality parameter (Q) has been proposed to evaluate the quality of pellets considering the factors involved in pellet characterization. Particularly, accounting for pellet compression rather than tensile forces were found to be better when quantifying the pellet quality parameter Q. A discussion regarding the binding mechanisms, types of binders used, and their effect on the pellet’s durability is provided, in addition to the pelletization process by itself with the main parameters that affect its operation. The post-pelletization processes were presented, focusing on three thermal conversion techniques: gasification, pyrolysis, and combustion. A comparison between these techniques has been provided, in addition to recommendations regarding pros and cons of each one. Finally, the environmental footprints of densification systems have been reviewed.
... [34]. c [50][51][52]. d [53]. ...
... c Lower values for CO 2 were based on the assumption of direct or indirect carbon and capture. Other values were based on [50][51][52]. d [53]. e [63,64]. ...
Article
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This study analyzes the road freight sector of São Paulo state to identify the best options to reduce greenhouse gases emissions and local pollutants, such as particulate matter, nitrogen oxides, carbon monoxide, and hydrocarbons. Additionally, the investment cost of each vehicle is also analyzed. Results show that electric options, including hybrid, battery, and hydrogen fuel-cell electric vehicles represent the best options to reduce pollutants and greenhouse gases emissions concomitantly, but considerable barriers for their deployment are still in place. With little long-term planning on the state level, electrification of the transport system, in combination with increased renewable electricity generation, would require considerable financial support to achieve the desired emissions reductions without increasing energy insecurity
... In the case of global warming potential (Fig. 3c), the direct emission of CO 2 and methane to the air was diagnosed as the main contributors which were in accordance with the report of Petrakopoulou et al. (2015) and Susmozas et al. (2016). A 10% decrement in global warming was associated with methane emission during the membrane production, whereas the CO 2 overshadowed the effect of other indicators on greenhouse emission. ...
... It can be concluded that more than 14% of energy saving could be attained by investing in scenario 2. The specification per substance showed the major contribution of natural gas and crude oil for generating DMF and electricity which correspond with the finding of Petrakopoulou et al. (2015). Furthermore, a significant relationship among the CED with natural gas, crude oil, and uranium was discovered by Susmozas et al. (2016). Generally, the total score of CED depends strongly on the energy supply for materials and processes which varied based on implemented technology and the detail of strategic principles adopted in the overall system. ...
Article
The life cycle assessment analysis of polymeric membranes, namely polyacrylonitrile (PAN), polyvinylimidazole (PVIM), and copolymer P(AN-co-VIM): 50:50 ratio utilized for CO2 sequestration is presented in this work for the first time. The Center of Environmental Science (CML) baseline 2000, cumulative energy demand, ecological footprint, and greenhouse gas protocol methods were applied to attain comprehensive information regarding the originated environmental burdens from the synthesis of the membrane. The PVIM membrane manifested the minimum environmental impacts, comparatively. The global warming, marine ecotoxicity, and human toxicity categories belonged to the P(AN-co-VIM) as the polymeric membrane with the highest environmental impact were accounted for 1.20, 1.36, and 1.18, greater than PVIM, respectively. These impacts were augmented in the range of 16.88%–27.59% for P(AN-co-VIM), predominantly derived from dimethylformamide (DMF) consumption and electricity demand. The P(AN-co-VIM) energy usage was 3799 MJ with a 92% contribution of fossil fuels, 1.2 times more than the PVIM. The CO2 emission (kg CO2 eq) from fossil fuels was as follows: P(AN-co-VIM) (146.2)> PAN (123.3)> PVIM (121.8). Besides, the sensitivity of PAN, PVIM, and P(AN-co-VIM) regarded a ±20% fluctuation in the DMF was estimated as 14.41-17.71%, 13.45-19.08%, and 11.08-16.78% for PAN, PVIM, and P(AN-co-VIM), respectively. Accordingly, the PVIM was recognized as the membrane with the highest environmental compatibility.
... Recent studies concerning biomass gasification are summarised in Table 6. Recent LCA studies concerning biomass gasification are categorised into four groups: (i) biomass-based hydrogen (bio-H 2 ) production [33][34][35][36][37][38], (ii) biomass gasification combined heat and power (CHP) [39][40][41][42][43][44], (iii) other energy systems [45][46][47][48], and (iv) dynamic LCA [49]. This chapter covers the review of the LCA studies about biomass gasification. ...
... To evaluate the environmental performance of H 2 production via indirect gasification of short-rotation poplar, a LCA was implemented using process simulation for normal BG processes [33] and for BG with CO 2 capture by pressure swing adsorption [34]. From a life-cycle perspective, H 2 from poplar gasification generally arose as a good alternative to conventional, fossil-derived H 2 produced via steam methane reforming. ...
... A comparative LCA study of two different gasification systems (downdraft gasifier and CFB gasifier) for H2 production proved that downdraft gasifier delivered better environmental performance over CFB gasifier (Kalinci et al., 2012). According to the LCA study of hydrogen production by Susmozas et al. (2016), direct emission to air, external electricity production, and biomass production are the key processes contributing to environmental impacts, while bio-hydrogen production with CO2 capture delivers superior environmental performance over conventional processes. ...
... Summary of LCA studies on biomass gasification. Heat production through gasification Alternatives: Forestry residues, woody energy crops, and natural gas GHG emissions Pucker et al. (2012) Production of H2 through gasification Alternatives: Vine and almond pruning, forest waste from pine, and eucalyptus plantation FU*: production of 1 Nm 3 H2 Moreno and Dufour (2013) Evaluation of technologies Evaluation of integrated gasification combined cycle (IGCC) Alternatives: IGCC with upstream CO2 adsorption vs. chemical absorption of CO2 FU: produced energy unit Corti and Lombardi (2004) Evaluation of H2 production via biomass gasification Alternatives: Gasification followed by syngas reforming vs. electricity generation GHG emissions Koroneos et al. (2008) Evaluation of production processes for ethanol production Alternatives: Biochemical vs. thermochemical processes GHG emissions Bright and Strømman (2009) Evaluation of CHP plant with different sizes Evaluation of CHP plants for power and heat production in rural areas Alternatives: Biomass fed CHP vs. fossil fuels in a large scale plant FU: 1 year supply of heat and power to a modern village Kimming et al. (2011) Comparison of different gasifiers for H2 production Alternatives: Downdraft gasifier and fluidized bed gasifier GHG emissions Kalinci et al. (2012) Evaluation of energy production systems Alternatives: Electricity via gasification vs. bioethanol through enzymatic hydrolysis FU: the use of biomass chips from 1 ha González-García et al. (2012) Evaluation of potential future energy systems Alternatives: F-T liquid through biomass gasification, rapeseed based biodiesel, and fossil fuels Evaluation of methanol production (via gasification) based on an autonomous distillery or sugar mill Alternatives: Co-generation plant combined with methanol or biomass integrated gasification/gas turbine (BIG-GT) system 1 MJ of each product Renó et al. (2014) Evaluation of bioenergy generation alternatives using forest and wood residues Alternatives: Combustion and gasification technologies with different capacities GHG emissions Cambero et al. (2015)Evaluation of H2 production through biomass gasification Alternatives: Bio-H2 with/without CO2 capturing vs. fossil based H2 FU: 1 kg H2 producedSusmozas et al. (2016) ...
Article
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Gasification is an efficient process to obtain valuable products from biomass with several potential applications, which has received increasing attention over the last decades. Further development of gasification technology requires innovative and economical gasification methods with high efficiencies. Various conventional mechanisms of biomass gasification as well as new technologies are discussed in this paper. Furthermore, co-gasification of biomass and coal as an efficient method to protect the environment by reduction of GHG emissions has been comparatively discussed. The increasing attention to renewable resources is driven by the climate change due to GHG emissions caused by conventional fossil fuels, while biomass gasification is considered as a potentially sustainable and environmentally friendly technology. Social and environmental aspects should also be taken into account in the design, to guarantee the sustainable use of biomass. This paper also reviews life cycle assessment studies on the biomass gasification, considering different technologies and various feedstocks.
... The studies reviewed in various publications are mainly focused on very specific aspects of bio-hydrogen production, such as biomass gasification [82], reactor design [83], molecular tools [84], and production pathway [85], etc. However, this article has exclusively reviewed the biological production of hydrogen and its sustainability as an economical clean fuel currently and has also discussed its future perspective. ...
Article
Depleting fuel resources and global warming potential of fossil fuel raise a concern over its sustainability. Among the four strategically important alternative fuel sources viz. biofuels, hydrogen (H2), natural gas and syngas (synthesis gas), hydrogen emerges as a superior fuel. For the reasons, that hydrogen gas is renewable, free from greenhouse gases emission and liberates large amount of energy per unit weight during combustion, and it also gets converted into electricity by fuel cell easily. The utilization of biohydrogen as an energy source could be able to provide environmental safety as it does not liberate GHGs during combustion. The biohydrogen production could be economical with the latest developments and society will be benefitted with pollution control, which is added into environment during the combustion of other energy sources. The present review discusses various aspects with conclusions that considering social, economic and environmental benefits, biohydrogen energy could be considered as a sustainable source of future clean energy.
... The studies reviewed in various publications are mainly focused on very specific aspects of bio-hydrogen production, such as biomass gasification [82], reactor design [83], molecular tools [84], and production pathway [85], etc. However, this article has exclusively reviewed the biological production of hydrogen and its sustainability as an economical clean fuel currently and has also discussed its future perspective. ...
Article
Depleting fuel resources and global warming potential of fossil fuel raise a concern over its sustainability. Among the four strategically important alternative fuel sources viz. biofuels, hydrogen (H2), natural gas and syngas (synthesis gas), hydrogen emerges as a superior fuel. For the reasons, that hydrogen gas is renewable, free from greenhouse gases emission and liberates large amount of energy per unit weight during combustion, and it also gets converted into electricity by fuel cell easily. The utilization of biohydrogen as an energy source could be able to provide environmental safety as it does not liberate GHGs during combustion. The biohydrogen production could be economical with the latest developments and society will be benefitted with pollution control, which is added into environment during the combustion of other energy sources. The present review discusses various aspects with conclusions that considering social, economic and environmental benefits, biohydrogen energy could be considered as a sustainable source of future clean energy.
... The process involves using a gasifying medium such as air, steam, and O 2 under certain temperatures and pressures to convert the solid biomass into a gas mixture. Typically, the gasification products are a mixture of CO, H 2 , CH 4 , CO 2 , tar, char, ash, etc. [8]. Investigation on biomass gasification has attracted many researchers [9][10][11]. ...
Article
In this work, three biomass gasification based hydrogen and power co‐production processes are modelled and examined. Case 1 is the conventional biomass gasification coupled with shift reactor while cases 2 and 3 involves integration of biomass gasification with iron‐based and calcium‐based chemical looping systems respectively. The three cases are modelled using Aspen Plus V 7.2 and the sensitivity analyzes are conducted to investigate the effect of the important process parameters on the performance indicators such as hydrogen yield and efficiencies. These parameters include gasification temperature, molar ratio of steam to biomass in the gasifier, molar ratio of Fe2O3 to syngas in the fuel reactor, molar ratio of Fe/FeO to steam in the steam reactor, molar ratio of CaO to CO and molar ratio of steam to CO in the carbonator. In addition, the energy and exergy balance distribution analyzes for the above three cases are also comprehensively discussed and compared. Furthermore, techno‐economic assessments are performed to evaluate the three cases in terms of capital cost, operating cost and leveled cost of energy.
... 53 The PEI values are positive for each gasification process due to the use of environmentally friendly feedstocks. Susmozas et al. 54 reported that the impacts of biomass gasification are higher than the gas reforming process. Figure 19 depicts global results per PEI/kg and PEI/h in order to study the influence of product mass flowrate on environmental performance. ...
Article
Currently, the production of alternative fuels from renewable sources such as biomass has been increased in order to meet energy policies and reduce the environmental impacts of fossil fuels. This work is focused on hydrogen production from oil palm empty fruit bunches using different biomass gasification methods (direct gasification, indirect gasification, and supercritical water gasification) and purification technologies (selexol-based absorption and pressure swing adsorption). Six routes were selected based on these technologies and simulated using Aspen Plus software. Possible operating process improvements were suggested based on parametric sensitivity analysis by studying the effect of several variables on hydrogen production: gasification temperature, gasifying agent-to-biomass ratio, steam-to-carbon monoxide ratio, temperature of a high-temperature step reactor, and pressure in a hydrogen purification unit. The methodology of waste reduction algorithm was performed to assess the environmental impacts of each route. Results showed that hydrogen production was improved by increasing the gasification reaction temperature to 900 °C, oxygen-to-biomass ratio to 1.5, and pressure of purification stage to 10 atm for all routes. However, routes 1 and 2 presented a slight increase up to 0.7% in hydrogen yield using 1.5 mol O2/mol biomass. The environmental assessment revealed that routes 3 and 4 exhibited the lowest toxicological and atmospheric environmental impacts because of the use of char generated in the gasification reaction for energy production. These results indicated that route 4 exhibited the best performance for producing hydrogen from an environmental viewpoint.
... The vast majority of hydrogen is produced from fossil fuels, with CO2 emission intensities depending on the feedstock and conversion efficiency [225]. Carbon capture and storage (CCS) could be feasible for large centralised production and could potentially deliver negative CO2 emissions when using bioenergy feedstocks [226,227]. This relies on CCS maturing to the point of widespread rollout after 'a lost decade' [228,229] and on wider sustainability issues surrounding bioenergy supplychains being carefully managed [230,231]. ...
Preprint
Hydrogen technologies have experienced cycles of excessive expectations followed by disillusion. Nonetheless, a growing body of evidence suggests these technologies form an attractive option for the deep decarbonisation of global energy systems, and that recent improvements in their cost and performance point towards economic viability as well. This paper is a comprehensive review of the potential role that hydrogen could play in the provision of electricity, heat, industry, transport and energy storage in a low-carbon energy system, and an assessment of the status of hydrogen in being able to fulfil that potential. The picture that emerges is one of qualified promise: hydrogen is well established in certain niches such as forklift trucks, while mainstream applications are now forthcoming. Hydrogen vehicles are available commercially in several countries, and 225,000 fuel cell home heating systems have been sold. This represents a step change from the situation of only five years ago. This review shows that challenges around cost and performance remain, and considerable improvements are still required for hydrogen to become truly competitive. But such competitiveness in the medium-term future no longer seems an unrealistic prospect, which fully justifies the growing interest and policy support for these technologies around the world.
... Environmental impact assessment of each of the processes for hydrogen-rich syngas production differs in accordance with the operating conditions such as reaction temperature, pressure, reactor configuration, heating rates, the nature of microorganism, the types of catalyst and so on. It can be seen that amongst the thermo-catalytic processes for hydrogen-rich syngas production, biomass pyrolysis has the highest CO 2 equivalent emissions compared to other processes (Iribarren et al., 2012;Susmozas et al., 2016). Although, there is no unify bases to compare all these process in terms of the environmental impact of the production activities due to the differences in equipment, process conditions and feedstocks. ...
Article
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The thermo-catalytic and biochemical conversion of biomass to hydrogen-rich syngas has been widely reported with less emphasis on the environmental implications of the processes. This mini-review presents an overview of different thermo-catalytic route of converting biomass to hydrogen-rich syngas as well as their environmental impact investigated using life cycle assessment methodology. The review revealed that most of the authors employed, biomass gasification, biomass pyrolysis, reforming and fermentative processes for the hydrogen-rich syngas production. Global warming potential was observed as the most significant environmental impact reported in the reviewed articles. The CO2 equivalent emissions were found to varies with each of the processes and the type of feedstock used. Trends from literature shows that both thermo-catalytic and biochemical processes have competitive advantages and potential to compete favorable with the existing technology used for hydrogen production. Nevertheless, it cannot be ascertained that these technologies should be excluded from environmental burdens. This mini-review could be a quick guide to future research interest in environmental impact of hydrogen-rich syngas production by thermo-catalytic and biochemical conversion of biomass.
... materials, phenol-based aromatic compounds, biofertilizers, biotextiles, or bioplastics (Galanakis, 2012;Beres et al., 2017;Cao et al., 2018;Pathak et al., 2018). Prior to the implementation of new biorefinery plants, lifecycle and technoeconomic assessments are also required to guarantee the environmental standards and profitability of the developed processes (Susmozas et al. 2016(Susmozas et al. , 2019. ...
... Some conversion pathways lead to carbon-free end-products, such as biomass combustion with CCS to electricity and heating. Similarly, biomass gasification with CCS leads to syngas composed mainly of hydrogen, carbon monoxide, and CO 2 [68][69][70]. Hydrogen is a carbon-free energy carrier that receives a lot of research and development efforts. It can be used as fuel, burned to deliver electricity or heating, or converted to other transport fuels. ...
Article
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Carbon dioxide removal (CDR) will be a key component of the climate change mitigation efforts to achieve the carbon-neutrality goals. Hence, a comprehensive assessment of the CDR potential at national and local levels is crucial to identify regional opportunities and deploy practical actions timely. This study focuses on the potential function of olive agroecosystems in delivering CDR in the European Mediterranean countries. Relying on a geospatial assessment of existing olive groves (and associated residual biomass) combined with statistical, process systems engineering, and life cycle emissions data, the CDR potential considering five promising actions linked with the olive agroecosystems was here estimated. These actions are i) conservation measures protecting tree carbon sequestration, ii) agricultural practices increasing soil carbon sequestration, iii) biochar production and utilization, iv) biomass conversion routes coupled with carbon capture and storage (CCS), and v) development of bio-based and CO2-based materials. Overall, the bottom-up assessment highlights the value of the olive groves, currently storing around 0.22 Gt CO2-eq in standing trees and potentially sequestering 0.03 Gt CO2-eq annually in soils. Moreover, exploiting the abundant biomass wastes in biorefineries coupled with CCS could deliver gigatonne-scale CDR while producing various value-added products, achieving above 0.01 Gt CO2-eq per year only using prunings for biochar or power, while other pathways show lower potential (e.g., 0.52 MtCO2eq yr⁻¹ for fermentation). These results may promote the large-scale deployment of CDR actions, stimulate new policy initiatives to exploit opportunities associated with the olive groves, and ultimately contribute to the transition toward the net-zero targets.
... Key aspects determining the life cycle performance of hydrogen production systems are the source of energy driving the hydrogen production process and the raw material that contains hydrogen Susmozas et al. 2016). On the one hand, since the electrochemical category is widely dominated by case studies of water electrolysis, the environmental performance of this type of system strongly depends on the energy source. ...
Article
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Purpose As a first step towards a consistent framework for both individual and comparative life cycle assessment (LCA) of hydrogen energy systems, this work performs a thorough literature review on the methodological choices made in LCA studies of these energy systems. Choices affecting the LCA stages “goal and scope definition”, “life cycle inventory analysis” (LCI) and “life cycle impact assessment” (LCIA) are targeted. Methods This review considers 97 scientific papers published until December 2015, in which 509 original case studies of hydrogen energy systems are found. Based on the hydrogen production process, these case studies are classified into three technological categories: thermochemical, electrochemical and biological. A subdivision based on the scope of the studies is also applied, thus distinguishing case studies addressing hydrogen production only, hydrogen production and use in mobility and hydrogen production and use for power generation. Results and discussion Most of the hydrogen energy systems apply cradle/gate-to-gate boundaries, while cradle/gate-to-grave boundaries are found mainly for hydrogen use in mobility. The functional unit is usually mass- or energy-based for cradle/gate-to-gate studies and travelled distance for cradle/gate-to-grave studies. Multifunctionality is addressed mainly through system expansion and, to a lesser extent, physical allocation. Regarding LCI, scientific literature and life cycle databases are the main data sources for both background and foreground processes. Regarding LCIA, the most common impact categories evaluated are global warming and energy consumption through the IPCC and VDI methods, respectively. The remaining indicators are often evaluated using the CML family methods. The level of agreement of these trends with the available FC-HyGuide guidelines for LCA of hydrogen energy systems depends on the specific methodological aspect considered. Conclusions This review on LCA of hydrogen energy systems succeeded in finding relevant trends in methodological choices, especially regarding the frequent use of system expansion and secondary data under production-oriented attributional approaches. These trends are expected to facilitate methodological decision making in future LCA studies of hydrogen energy systems. Furthermore, this review may provide a basis for the definition of a methodological framework to harmonise the LCA results of hydrogen available so far in the literature.
... Case studies in the libraries of harmonised carbon [12], energy [13], and acidification [14] footprints. BMG1 Biomass gasification (short-rotation poplar) GWP, CED, AP [28] BMG2 Biomass gasification (willow) GWP, AP [33] BMG3 Biomass gasification (wood chips) GWP [23] BMG4 Biomass gasification (poplar) GWP, CED, AP [34] BMG5 Biomass gasification (woody biomass) GWP, AP [35] BMG6 Biomass gasification (woody biomass) GWP [36] BMG7 Biomass gasification (vine pruning waste) GWP, AP [37] BMG8 Biomass gasification (woody biomass) GWP, CED [38] BMG9 Biomass gasification with CO 2 capture (short-rotation poplar) GWP, AP [39] WPE1 Water electrolysis (wind power) GWP [40] WPE2 Water electrolysis (wind power) GWP [41] WPE3 Water electrolysis (wind power) GWP [42] WPE4 Water electrolysis (wind power) GWP [43] WPE5 Water electrolysis (wind power) GWP [44] WPE6 Water electrolysis (wind power) GWP [45] WPE7 Water electrolysis (wind power) GWP [35] WPE8 Alkaline water electrolysis (wind power) GWP, CED [46] WPE9 Alkaline water electrolysis (asbestos membrane) (wind power) GWP, AP [46] WPE10 Alkaline water electrolysis (advanced membrane) (wind power) GWP, AP [46] WPE11 Alkaline water electrolysis (advanced membrane; optimised system) (wind power) GWP, AP [47] WPE12 Alkaline water electrolysis (Na-Cl cell) (wind power) GWP [48] WPE13 Alkaline water electrolysis (wind power) GWP [49] WPE15 PEM water electrolysis (wind power) GWP [50] WPE16 High-temperature water electrolysis (wind power) GWP, CED, AP [51] WPE17 Alkaline water electrolysis (wind power) GWP [50] WPE18 High-temperature electrolysis (wind power) GWP, CED, AP [50] WPE19 High temperature electrolysis (wind + biogas back-up) GWP, CED, AP [35] PVE1 Alkaline water electrolysis (PV power) GWP, CED [45] PVE2 Water electrolysis (PV power) GWP [39] PVE3 Water electrolysis (PV power) GWP [40] PVE4 Water electrolysis (PV power) GWP [42] PVE5 Water electrolysis (PV power) GWP [47] PVE6 Alkaline water electrolysis (Na-Cl cell) (PV power) GWP [49] PVE7 PEM water electrolysis (PV power) GWP [51] PVE8 Alkaline water electrolysis (PV power) GWP [52] PVE9 Alkaline water electrolysis (PV power) GWP [51] CSE1 Alkaline water electrolysis (thermal solar power) GWP [35] CSE2 Alkaline water electrolysis (thermal solar power) GWP, CED [35] HE1 Alkaline water electrolysis (hydropower) GWP, CED Table A1. Cont. ...
Article
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The Life Cycle Assessment (LCA) methodology is often used to check the environmental suitability of hydrogen energy systems, usually involving comparative studies. However, these comparative studies are typically affected by inconsistent methodological choices between the case studies under comparison. In this regard, protocols for the harmonisation of methodological choices in LCA of hydrogen are available. The step-by-step application of these protocols to a large number of case studies has already resulted in libraries of harmonised carbon, energy, and acidification footprints of hydrogen. In order to foster the applicability of these harmonisation protocols, a web-based software for the calculation of harmonised life-cycle indicators of hydrogen has recently been developed. This work addresses-for the first time-the validation of such a tool by checking the deviation between the available libraries of harmonised carbon, energy, and acidification footprints of hydrogen and the corresponding tool-based harmonised results. A high correlation (R 2 > 0.999) was found between the library-and tool-based harmonised life-cycle indicators of hydrogen, thereby successfully validating the software. Hence, this tool has the potential to effectively promote the use of harmonised life-cycle indicators for robust comparative LCA studies of hydrogen energy systems, significantly mitigating misinterpretation.
... With total CO 2 emissions almost twice as high compared to SMR [18], we exclude coal gasification from the list of potential technologies due to its poor environmental performance and likely limited role in future hydrogen supply scenarios. Hydrogen production via gasification of biomass, on the other hand, may be seen as an attractive technology considering its potential to deliver net-negative carbon emissions, particularly when coupled with the capture and storage of the emitted CO 2 [65]. But while several pilot plants are in operation today, this technology is not yet considered fully developed, and there are open issues regarding biomass availability in the UK at the scale required [18]. ...
Article
The world-wide sustainability implications of transport technologies remain unclear because their assessment often relies on metrics that are hard to interpret from a global perspective. To contribute to filling this gap, here we apply the concept of planetary boundaries (PBs), i.e., a set of biophysical limits critical for operating the planet safely, to address the optimal design of sustainable fuel supply chains (SCs) focusing on hydrogen for vehicle use. By incorporating PBs into a mixed-integer linear programming model (MILP), we identify SC configurations that satisfy a given transport demand while minimising the PBs transgression level, i.e., while reducing the risk of surpassing the ecological capacity of the Earth. On applying this methodology to the UK, we find that the current fossil-based sector is unsustainable as it transgresses the energy imbalance, CO2 concentration, and ocean acidification PBs heavily, i.e., five to 55-fold depending on the downscale principle. The move to hydrogen would help to reduce current transgression levels substantially, i.e., reductions of 9–86% depending on the case. However, it would be insufficient to operate entirely within all the PBs concurrently. The minimum impact SCs would produce hydrogen via water electrolysis powered by wind and nuclear energy and store it in compressed form followed by distribution via rail, which would require as much as 37 TWh of electricity per year. Our work unfolds new avenues for the incorporation of PBs in the assessment and optimisation of energy systems to arrive at sustainable solutions that are entirely consistent with the carrying capacity of the planet.
... In contrast, their side-effects and co-benefits beyond global warming have often been overlooked. Some studies have quantified the environmental impacts of DACCS and BECCS, but their results are hard to interpret from an absolute sustainability viewpoint [15][16][17][18][19] . Only recently, the impacts of BECCS were assessed against the Earth's biophysical limits 20,21 , i.e., the Planetary Boundaries (PBs) within which humanity could safely operate 22 . ...
Article
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Meeting the 1.5 °C target may require removing up to 1,000 Gtonne CO 2 by 2100 with Negative Emissions Technologies (NETs). We evaluate the impacts of Direct Air Capture and Bioenergy with Carbon Capture and Storage (DACCS and BECCS), finding that removing 5.9 Gtonne/year CO 2 can prevent <9·10 ² disability-adjusted life years per million people annually, relative to a baseline without NETs. Avoiding this health burden—similar to that of Parkinson’s—can save substantial externalities (≤148 US$/tonne CO 2 ), comparable to the NETs levelized costs. The health co-benefits of BECCS, dependent on the biomass source, can exceed those of DACCS. Although both NETs can help to operate within the climate change and ocean acidification planetary boundaries, they may lead to trade-offs between Earth-system processes. Only DACCS can avert damage to the biosphere integrity without challenging other biophysical limits (impacts ≤2% of the safe operating space). The quantified NETs co-benefits can incentivize their adoption.
... Those include analyses of the life cycle carbon intensity of electricity [95,96] or heat [97][98][99] production through gasification of biomass, and combustion of the resulting synthesis gas. Other studies focus on the production of hydrogen [73,[100][101][102][103][104][105], the conversion of synthesis gas to liquids [106][107][108], the use of methane from gasification in transportation [59], or combinations of the above mentioned technologies [66,[109][110][111]. Furthermore, the environmentally optimal use of the processed biomass is in the scope of LCA studies [66,[109][110][111]. ...
Article
Natural gas is an energy carrier of predominant significance for today’s electricity and heating sectors. However, science heavily discusses the actual environmental burden of natural gas mainly due to the uncertainty in up- stream methane losses during its extraction and transportation. In this context, numerous technologies pave the way for the production of renewable methane to replace natural gas: biomethane from anaerobic digestion of biomass, substitute natural gas (bio-SNG) from gasification and Power-to-Gas via water electrolysis and subse- quent methanation. In recent years, numerous studies aimed at analysing the life cycle carbon intensity of those renewable gases. Given the high degree of freedom in the methodology of life cycle assessment (LCA) however, the studies are highly dependent on the respective boundary conditions and assumptions. To summarise and discuss the different findings, this review identifies and quantitatively analyses 30 life cycle assessment studies on the greenhouse gas emissions of renewable gases, comparing their results and deriving the main determinants on their environmental friendliness. A comparison between the results for renewable gases and existing literature reviews on the LCA of fossil natural gas shows the considerable emission reduction potential of renewable gases. This however requires the consideration and right implementation of the main influencing factors (inter alia the storage of digestate in closed tanks for biomethane, heat extraction of excess heat for bio-SNG, or the use of renewable electricity for Power-to-Gas) and is not a mere result of the technologies per se.
... As H 2 sources, we consider SMR, 39 indirect BG, 40,41 and electrolytic water splitting. 42,43 The scenarios discussed herein are assumed to be deployed separately, that is, no integration in terms of material and energy inputs between different scenarios was considered. ...
Article
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At present, the synthesis of ammonia through the Haber–Bosch (HB) process accounts for 1.2% of the global carbon emissions, representing roughly one-fourth of the global fossil consumption from the chemical industry, which creates a pressing need for alternative low-carbon synthesis routes. Analyzing seven essential planetary boundaries (PBs) for the safe operation of our planet, we find that the standard HB process is unsustainable as it vastly transgresses the climate change PB. In order to identify more responsible strategies from this integrated perspective, we assess the absolute sustainability level of 34 alternative routes where hydrogen (H2) is supplied by steam methane reforming with carbon capture and storage, biomass gasification, or water electrolysis powered by various energy sources. We found that some of these scenarios could substantially reduce the global impact of fossil HB, yet alleviating the impact on climate change could critically exacerbate the impacts on other Earth-system processes. Furthermore, we identify that reducing the cost of electrolytic H2 is the main avenue toward the economic appeal of the most sustainable routes. Our work highlights the need to embrace global impacts beyond climate change in the assessment of decarbonization routes of fossil chemicals. This approach enabled us to identify more suitable alternatives and associated challenges toward environmental and economically attractive ammonia synthesis.
... We have recently developed different vacuum pressure swing adsorption (VPSA) cycles, that overcome the shortcomings of both Gemini 8/9 and [31]'s one-train process [42,43]. The VPSA process requires a single train only, needs no re-compression, but only a vacuum pump, and allows for the co-purification of both products at high recovery: over 90% of the H 2 can be separated at high purity sufficient for industrial application (99.9% purity, [47]) or even fuel cells (99.97% purity, [19,47]) whilst CO 2 is co-produced at over 90% recovery and 96% purity, thus reaching the target typically set for CCS applications [26,46]. ...
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Reforming of fossil fuels coupled with carbon capture and storage has the potential to produce low-carbon H2 at large scale and low cost. Adsorption is a potentially promising technology for two key separation tasks in this process: H2 purification and CO2 capture. In this work, we present equilibrium adsorption data of H2 and CH4 on zeolite 13X, in addition to the already established CO2 isotherms. Further, we carry out binary (CO2–CH4) and ternary (H2–CO2–CH4) breakthrough experiments at various pressures and temperatures to estimate transport parameters, assess the predictive capacity of our 1D column model, and compare different multi-component adsorption models. CO2 adsorbs strongly on zeolite 13X, CH4 adsorbs less, and H2 adsorbs very little. Thus, H2 breaks through first, CH4 second (first in the binary breakthrough experiments) and CO2 last. Linear driving force (LDF) mass transfer coefficients are estimated based on a single breakthrough experiment and mass transfer is found to be fast for H2, slower for CH4, and slowest for CO2. The LDF parameters can be used in a predictive manner for breakthrough experiments at varying pressures, temperatures, flows, and, though with lower accuracy, even compositions. Heat transfer inside the column is described well with a literature correlation, thus yielding an excellent agreement between simulated and measured column temperatures. Ideal and real adsorbed solution theories (IAST and RAST, respectively) both model the observed breakthrough composition profiles well, whereas extended isotherms are inferior for predicting the competitive behavior between CH4 and CO2 adsorption. This study provides the groundwork necessary for full cyclic experiments and their simulation.
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Hydrogen technologies have experienced cycles of excessive expectations followed by disillusion. Nonetheless, a growing body of evidence suggests these technologies form an attractive option for the deep decarbonisation of global energy systems, and that recent improvements in their cost and performance point towards economic viability as well. This paper is a comprehensive review of the potential role that hydrogen could play in the provision of electricity, heat, industry, transport and energy storage in a low-carbon energy system, and an assessment of the status of hydrogen in being able to fulfil that potential. The picture that emerges is one of qualified promise: hydrogen is well established in certain niches such as forklift trucks, while mainstream applications are now forthcoming. Hydrogen vehicles are available commercially in several countries, and 225 000 fuel cell home heating systems have been sold. This represents a step change from the situation of only five years ago. This review shows that challenges around cost and performance remain, and considerable improvements are still required for hydrogen to become truly competitive. But such competitiveness in the medium-term future no longer seems an unrealistic prospect, which fully justifies the growing interest and policy support for these technologies around the world.
Article
An increasing number of studies addressing the Life Cycle Assessment (LCA) of hydrogen energy systems is found in the scientific literature. Most of these studies are comparative and show significant differences in terms of methodological choices. These differences significantly affect the results of the LCA studies and hamper their robust interpretation, especially when comparing results from different studies. Hence, harmonisation of the results under a consistent methodological framework is needed. This article defines a protocol for the harmonisation of the life-cycle global warming impact of hydrogen. Furthermore, the protocol is applied to renewable hydrogen based on a thorough literature survey of relevant LCA case studies classified by hydrogen-production technological category: thermochemical, electrochemical, and biological. In this sense, the two main outcomes of the study are the harmonisation protocol and the initial library of harmonised carbon footprints of renewable hydrogen for 71 case studies. Key methodological choices subject to harmonisation include (i) attributional approach, (ii) functional unit, (iii) system boundaries, and (iv) multifunctionality approach. Harmonisation is found to affect more significantly the thermochemical and biological categories than the electrochemical one. Nevertheless, risk of misinterpretation is found and exemplified in every technological category. The sources of potential misinterpretation are found to be usually linked to inconsistencies in terms of system boundaries (e.g., hydrogen compression) and, when applicable, multifunctionality approaches. Future LCA practitioners are highly recommended to use the proposed protocol to provide, along with their own results, the harmonised global warming impact of hydrogen in order to enhance current and future result interpretation when comparisons are made.
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Co-processing methanol and ethanol in bio-char steam gasification was investigated in a fixed-bed reactor. The effect of reaction temperature, steam flow rate and additives content on gas composition and H2 yield were evaluated. The results showed that bio-char is an ideal material for H2 production, and the maximum H2 yield (233.3 g/kg bio-char) was obtained in the absence of additives at 950 °C, 0.5 g/min steam flow rate, meantime, producing hydrogen-rich gas with slight formation of methane. Methanol and ethanol blended with steam, and subsequently introduced in reactor have positive effect on H2 yield. However, taking the economy and char conversion rate into consideration, 5 vol%–8 vol% may be suitable contents, and H2 yield increased to 342 g/kg and 308.9 g/kg with 5 vol% of methanol and ethanol added in gasifying agent at 950 °C and 0.5 g/min steam flow rate. Furthermore, the proposed catalytic gasification of hydrogen-rich gas for high purity hydrogen and synthetic natural gas may be a promising way for using the produced gases.
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The need to significantly reduce emissions from the steelmaking sector requires effective and ready-to-use technical solutions. With this aim, different decarbonization strategies have been investigated by both researchers and practitioners. To this concern, the most promising pathway is represented by the replacement of natural gas with pure hydrogen in the direct reduced iron (DRI) production process to feed an electric arc furnace (EAF). This solution allows to significantly reduce direct emissions of carbon dioxide from the DRI process but requires a significant amount of electricity to power electrolyzers adopted to produce hydrogen. The adoption of renewable electricity sources (green hydrogen) would reduce emissions by 95–100% compared to the blast furnace–basic oxygen furnace (BF–BOF) route. In this work, an analytical model for the identification of the minimum emission configuration of a green energy–steel system consisting of a secondary route supported by a DRI production process and a renewable energy conversion system is proposed. In the model, both technological features of the hydrogen steel plant and renewable energy production potential of the site where it is to be located are considered. Compared to previous studies, the novelty of this work consists of the joint modeling of a renewable energy system and a steel plant. This allows to optimize the overall system from an environmental point of view, considering the availability of green hydrogen as an inherent part of the model. Numerical experiments proved the effectiveness of the model proposed in evaluating the suitability of using green hydrogen in the steelmaking process. Depending on the characteristics of the site and the renewable energy conversion system adopted, decreases in emissions ranging from 60% to 91%, compared to the BF–BOF route, were observed for the green energy–steel system considered It was found that the environmental benefit of using hydrogen in the secondary route is strictly related to the national energy mix and to the electrolyzers’ technology. Depending on the reference context, it was found that there exists a maximum value of the emission factor from the national electricity grid below which is environmentally convenient to produce DRI by using only hydrogen. It was moreover found that the lower the electricity consumption of the electrolyzer, the higher the value assumed by the emission factor from the electricity grid, which makes the use of hydrogen convenient.
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Utilization of renewable energy has become a current energy development trend. In this study, the water footprints of a fuel cell electric vehicle (FCEV) and a compressed natural gas vehicle (CNG) under different fuel scenarios were evaluated. The FCEV exhibits a low water footprint of 27.2 L/100 km under steam methane reforming hydrogen production technology. Hydrogen production using steam methane reforming and water electrolysis via wind can enable the FCEV industry to save more water resources. The percentage difference between different metallic materials in automobiles was analyzed. The water consumption by steel accounted for 73.6% and 80.5%, respectively. The fluctuation law of the water footprint was analyzed based on different power structures and steel water consumption coefficients. It was found that for low steel water consumption coefficient, wind power generation is conducive to slowing down the water consumption during the entire life cycle. In addition, a sensitivity analysis was performed for the FCEV and CNG under different fuel scenarios. Fuel technology and material structure have a significant impact on the total water footprint. The results of this study can provide guidance for the layout of the automobile industry and for water-saving measures in the future.
Chapter
Hydrogen energy systems are expected to play a significant role in achieving a sustainable energy sector. This requires that sustainable hydrogen options are actually available and implemented. In order to check the suitability of hydrogen under sustainability aspects, the life cycle assessment methodology is often used. In particular, global warming (i.e., carbon footprint) and cumulative energy demand (CED or energy footprint) are among the most common life-cycle indicators evaluated for hydrogen energy systems. This chapter provides a complete library of consistent (i.e., harmonised) CED values for a high number of hydrogen production options belonging to different technological categories (thermochemical, electrochemical, and biological). Overall, 71 case studies of renewable hydrogen are benchmarked—in terms of CED—against the reference case of conventional (fossil-based) hydrogen from steam reforming of natural gas. Furthermore, a correlation equation between CED and carbon footprint is calculated and applied for the estimation of harmonised CED values. The use of harmonised values allows sound comparisons by mitigating the risk of misinterpretation. The results show that electrochemical hydrogen generally performs better than thermochemical hydrogen, while biological systems show a high dispersion of values. Especially, the use of wind power as the driving energy for electrochemical hydrogen production tends to be associated with a favourable performance.
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Steam crackers convert hydrocarbon feedstock (e.g., natural gas liquids) to light olefins via thermal cracking and produce hydrogen as a by-product during the process. Benefiting from the shale gas boom in recent years, the overall production capacity of U.S. steam crackers, as well as the potential of by-product hydrogen production, is continuously growing. We estimate that 3.5 million tonne/year of by-product hydrogen can be produced from steam crackers, almost doubling the size of the existing U.S. merchant hydrogen market. We also find that producing hydrogen from steam crackers creates less (15%–91%) life-cycle greenhouse gas emissions than the conventional centralized steam methane reforming (SMR) pathway. For criteria air pollutants, life-cycle emissions reduction benefits vary greatly (−75% – +85%), depending on the co-product treatment scenario (substitution or allocation) and air pollutant type. The substitution scenario generally results in an increase of criteria air pollutants emissions, mainly due to the requirement of substitutive natural gas fuel. We estimate that the cost of purified by-product hydrogen fuel from steam crackers is $0.9–1.1/kg, reducing hydrogen production costs by 30% compared to the conventional central SMR pathway. Furthermore, using by-product hydrogen from steam crackers can generate credits of $1.8–2.5/kg under California's low-carbon fuel standard.
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Low-carbon hydrogen is an essential element in the transition to net-zero emissions by 2050. Hydrogen production from biomass is a promising bio-energy with carbon capture and storage (BECCS) scheme that could produce low-carbon hydrogen and generate the carbon dioxide removal (CDR) envisioned to be required to offset hard-to-abate emissions. Here, we design a BECCS supply chain for hydrogen production from biomass with carbon capture and storage and quantify, at high spatial resolution, the technical potential for hydrogen production and CDR in Europe. We consider sustainable biomass feedstocks that have minimal impacts on food security and biodiversity, namely agricultural residues and waste. We find that this BECCS supply chain can produce up to 12.5 Mtons of H2 per year (currently ∼10 Mtons of H2 per year are used in Europe) and remove up to 133 Mtons CO2 per year from the atmosphere (or 3% of European total greenhouse gas emissions). We then perform a geospatial analysis to quantify transportation distances between where biomass feedstocks are located and potential hydrogen users, and find that 20% of hydrogen potential is located within 25 km from hard-to-electrify industries. We conclude that BECCS supply chains for hydrogen production from biomass represent an overlooked near-term opportunity to generate carbon dioxide removal and low-carbon hydrogen.
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Hydrogen is a fuel with immense potential of satisfying the need for environmentally benign energy sources, and waste-derived hydrogen is promising in diverting waste streams away from landfills and other costly treatment. Nonetheless, many waste-to-hydrogen pathways are incipient and require significant efforts to be established as an indispensable element of the path towards sustainability. This review comprehensively evaluates waste-to-hydrogen technologies from technological, economic, environmental, and societal viewpoints. State-of-the-art of five technologies was summarized, focusing on emerging trends in published literature. Several knowledge gaps, future research prospects, and possible improvements related to performance, greenhouse gas emissions, production costs, hydrogen-based transportation, and public acceptance were also identified. Fulfilling the lack of techno-economic and environmental studies of waste-to-hydrogen routes, incorporation of renewable energy into processes, and necessities of scaling-up and production cost reduction are prominent among research needs recognized through this review. Conclusions of this study will be beneficial towards sustainably integrating hydrogen into large-scale energy systems.
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Chapter
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This article addresses the life-cycle assessment of an energy conversion system for the coproduction of fuels and electricity from a gasification-based biosyngas feedstock via Fischer–Tropsch synthesis coupled with a combined-cycle process. Inventory data obtained mainly through process simulation are used to evaluate the environmental performance of the system in terms of abiotic depletion, global warming, ozone layer depletion, photochemical oxidant formation, land competition, acidification, and eutrophication. Furthermore, the cumulative non-renewable energy demand of the system is quantified and used in the calculation of the life-cycle energy balance of the system, which is found to be positive.Biosyngas generation arises as the main source of impact, with a much higher contribution than the rest of processes (production of catalysts, waste treatment, etc.). Electricity, diesel, gasoline and surplus hydrogen are the products of the system. The environmental profiles of these bioproducts are calculated and compared with those of fossil diesel, rapeseed biodiesel, soybean biodiesel, fossil gasoline, corn bioethanol, steam-methane reforming hydrogen, and the EU electrical grid. Overall, the bioproducts from the evaluated system are found to be promising alternatives to current energy products from a life-cycle environmental perspective.
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Exergy efficiency analysis tool is used to evaluate sorption enhanced steam reforming in comparison with the industrial hydrogen production route, steam reforming. The study focuses on hydrogen production for use in high pressure processes. Thermodynamic sensitivity analysis (effect of reforming temperature on hydrogen yield and reforming enthalpy) was performed to indicate the optimum temperature (650 °C) for the sorption enhanced reforming. The pressure was selected to be, for both cases, 25 bar, a typical pressure used in the industrial (conventional) process. Atmospheric pressure, 1000 °C and CO2 as inert gas were specified as the optimum operating parameters for the regeneration of the sorbent after performing exergy efficiency analysis of three realistic case scenarios. Aspen Plus simulation process schemes were built for conventional and sorption enhanced steam reforming processes to attain the mass and energy balances required to assess comparatively exergy analysis. Simulation results showed that sorption enhanced reforming can lead to a hydrogen purity increase by 17.3%, along with the recovery of pure and sequestration-ready carbon dioxide. The exergy benefit of sorption enhanced reforming was calculated equal to 3.2%. Analysis was extended by adding a CO2 separation stage in conventional reforming to reach the hydrogen purity of sorption enhanced reforming and enable a more effective exergy efficiency comparison. Following that analysis, sorption enhanced reforming gained 10.8% in exergy efficiency.
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This study evaluates the environmental and thermodynamic performance of six coal-fired power plants with CO2 capture and storage. The technologies examined are post-combustion capture using monoethanolamine, membrane separation, cryogenic fractionation and pressure swing adsorption, pre-combustion capture through coal gasification, and capture performing conventional oxy-fuel combustion. The incorporation of CO2 capture is evaluated both on its own and in combination with CO2 transport and geological storage, with and without beneficial use.Overall, we find that pre-combustion CO2 capture and post-combustion through membrane separation present relatively low life-cycle environmental impacts and high exergetic efficiencies. When accounting for transport and storage, the environmental impacts increase and the efficiencies decrease. However, a better environmental performance can be achieved for CO2 capture, transport and storage when incorporating beneficial use through enhanced oil recovery. The performance with enhanced coal-bed methane recovery, on the other hand, depends on the impact categories evaluated. The incorporation of methane recovery results in a better thermodynamic performance, when compared to the incorporation of oil recovery. The cumulative energy demand shows that the integration of enhanced resource recovery strategies is necessary to attain favourable life-cycle energy balances.
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The objective of the Biomass to Methanol Systems Analysis Project is the determination of the most economically optimum combination of unit operations which will make the production of methanol from biomass competitive with or more economic than traditional processes with conventional fossil fuel feedstocks. This report summarizes the development of simulation models for methanol production based upon the Institute of Gas Technology (IGT) ''Renugas'' gasifier and the Battelle Columbus Laboratory (BCL) gasifier. This report discusses methanol production technology, the IGT and BCL gasifiers, analysis of gasifier data for gasification of wood, methanol production material and energy balance simulations, and one case study based upon each of the gasifiers.
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This analysis developed detailed process flow diagrams and an Aspen Plus{reg_sign} model, evaluated energy flows including a pinch analysis, obtained process equipment and operating costs, and performed an economic evaluation of two process designs based on the syngas clean up and conditioning work being performed at NREL. One design, the current design, attempts to define today's state of the technology. The other design, the goal design, is a target design that attempts to show the effect of meeting specific research goals.
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This report provides an assessment of the state of the biopower industry and the technology for producing electricity and heat from biomass. Biopower (biomass-to-electricity generation), a proven electricity generating option in the United States and with about 11 GW of installed capacity, is the single largest source of non-hydro renewable electricity. This 11 GW of capacity encompasses about 7.5 GW of forest product industry and agricultural industry residues, about 3.0 GW of municipal solid waste-based generating capacity and 0.5 GW of other capacity such as landfill gas based production. The electricity production from biomass is being used and is expected to continue to be used as base load power in the existing electrical distribution system. An overview of sector barriers to biopower technology development is examined in Chapter 2. The discussion begins with an analysis of technology barriers that must be overcome to achieve successful technology pathways leading to the commercialization of biomass conversion and feedstock technologies. Next, an examination of institutional barriers is presented which encompasses the underlying policies, regulations, market development, and education needed to ensure the success of biopower. Chapter 3 summarizes biomass feedstock resources, characteristics, availability, delivered prices, requirements for processing, and the impediments and barriers to procurement. A discussion of lessons learned includes information on the California biomass energy industry, lessons from commercial biopower plants, lessons from selected DOE demonstration projects, and a short summary of the issues considered most critical for commercial success is presented in Chapter 4. A series of case studies, Chapter 5, have been performed on the three conversion routes for Combined Heat and Power (CHP) applications of biomass--direct combustion, gasification, and cofiring. The studies are based on technology characterizations developed by NREL and EPRI. Variables investigated include plant size and feed cost, and both cost of electricity and cost of steam are estimated using a discounted cash flow analysis. The economic basis for cost estimates is given. Environmental considerations are discussed in Chapter 6. Two primary issues that could create a tremendous opportunity for biomass are global warming and the implementation of Phase II of Title IV of the Clean Air Act Amendment of 1990 (CAAA). The environmental benefits of biomass technologies are among its greatest assets. Global warming is gaining greater salience in the scientific community and among the general population. Biomass use can play an essential role in reducing greenhouse gases, thus reducing the impact on the atmosphere. Cofiring biomass and fossil fuels and the use of integrated biomass gasification combined cycle systems can be an effective strategy for electric utilities to reduce their emissions of greenhouse gases. The final chapter reviews pertinent Federal government policies. U.S. government policies are used to advance energy strategies such as energy security and environmental quality. Many of the benefits of renewable energy are not captured in the traditional marketplace economics. Government policies are a means of converting non-economic benefits to an economic basis, often referred to as ''internalizing'' of ''externalities.'' This may be accomplished by supporting the research, development, and demonstration of new technologies that are not funded by industry because of projected high costs or long development time lines.
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Two energy production systems using short rotation coppice (SRC) willow chips were evaluated: bioethanol production via enzyme-catalyzed hydrolysis and electricity production following a biomass integrated gasification combined cycle scheme. The most relevant input and output flows of each renewable energy system were identified and quantified throughout the life cycle from the SRC willow plantation to the bioenergy plant gate. Both bioenergy systems were found to be feasible from an energy perspective. Moreover, they entailed environmental benefits when compared to conventional energy practices. However, improvements relating to not only willow biomass production but also bioenergy conversion-related activities should be considered. In this respect, the process steps that provided the highest environmental impacts have been highlighted. Furthermore, well-to-wheels environmental characterization results were estimated and compared for the bioethanol and bioelectricity scenarios. In this sense, the identification of the most appropriate processing route for willow chips was found to be highly dependent on the impact category under assessment. In particular, global warming and energy parameters led to opposite conclusions. While the bioethanol scenario arose as the potentially best choice from an energy perspective, the bioelectricity scenario seems to be a more suitable alternative when global warming is the decisive factor.
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New processes under development for producing hydrogen have been assessed using a life cycle methodology and compared to conventional ones. The aim of this paper is to determine the main obstacles to be beaten or the critical aspects to be addressed to ensure the feasibility of these processes. Water photosplitting, solar two-step thermochemical cycles and automaintained methane decomposition with different lay-outs were studied. They have been compared to methane steam reforming with CCS and electrolysis with different electricity sources.The results show the good behaviour of the automaintained methane decomposition. This process is one of the best options when the greenhouse effect emissions are evaluated. Nevertheless, the consumption of a great amount of a non-renewable resource, i.e., natural gas, as reagent can be negative. The two-step thermochemical cycles based on NiFe2O4 is also an interesting option, but its behaviour depends largely on the infrastructure materials employed on the installations. The most promising option is photosplitting with CdS as catalysts. This process shows the best performance.
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This paper discusses environmentally benign and sustainable, as green, methods for hydrogen production and categorizes them based on the driving sources and applications. Some potential sources are electrical, thermal, biochemical, photonic, electro-thermal, photo-thermal, photo-electric, photo-biochemical, and thermal-biochemical. Such forms of energy can be derived from renewable sources, nuclear energy and from energy recovery processes for hydrogen production purposes. These processes are analyzed and assessed for comparison purposes. Various case studies are presented to highlight the importance of green hydrogen production methods and systems for practical applications.
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The poplar bioenergy system has been analysed applying life cycle assessment (LCA) to compare its environmental performance to: Ethiopian mustard bioenergy system and natural gas. The life cycle impact assessment (LCIA) shows that the use of fertilizers is the highest impact in four of the 10 environmental categories, representing between 39% and 67% of the impact in them. The diesel used in transport vehicles and agricultural tractors also has a significant impact in another five of the 10 analysed categories 40–85%. The poplar bioenergy system contributes to global warming with 1.90–1.98gCO2eqMJ−1 biomass produced. The production and transport as far as the thermoelectric plant of the poplar biomass consumes 0.02MJ of primary energy per 1MJ of biomass stored. In comparison with Ethiopian mustard and natural gas, it reduces primary energy consumption by 83% and 89% and the greenhouse gas emission by 84% and 89%, respectively. The results of the analysis support that the poplar bioenergy system is viable from an energy balance and environmental perspective for producing energy in southern Europe, as long as it is cultivated in areas where water is available. This latter point and the better environmental performance of both crops in comparison to natural gas allows us to affirm that the combination of several crops adapted to the local agro-climatic conditions of the territory will be the most suitable strategy in Mediterranean areas that wish to reach the global energy production targets in terms of biomass established by the European Union (EU).
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This paper presents the results of a theoretical investigation whose aim was the development of a simulation tool for performance prediction of a steam reforming hydrogen production plant, and particularly of its overall energetic efficiency. A 1500 Nm3/h hydrogen production plant was simulated. Field data coming from an industrial plant were used for model validation in both design and off design operating conditions. To evaluate the plant performances in terms of energetic efficiency, a particular attention was paid to the simulation of all plant auxiliaries consumptions. Nevertheless the large uncertainty in most of the field data values, the model was able to capture all the relevant phenomena taking place in all the plant components, from reformer reactor up to CO2 sequestration unit, in the investigated plant capacity range (40–100%).
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Steam methane reforming (SMR) is one of the most promising processes for hydrogen production. Several studies have demonstrated its advantages from the economic viewpoint. Nowadays process development is based on technical and economical aspects; however, in the near future, the environmental impact will play a significant role in the design of such processes. In this paper, an SMR process is studied from the viewpoint of overall environmental impact, using an exergoenvironmental analysis. This analysis presents the combination of exergy analysis and life cycle assessment. Components where chemical reactions occur are the most important plant components from the exergoenvironmental point of view, because, in general, there is a high environmental impact associated with these components. This is mainly caused by the exergy destruction within the components, and this in turn is mainly due to the chemical reactions. The obtained results show that the largest potential for reducing the overall environmental impact is associated with the combustion reactor, the steam reformer, the hydrogen separation unit and the major heat exchangers. The environmental impact in these components can mainly be reduced by improving their exergetic efficiency. A sensitivity analysis for some important exergoenvironmental variables is also presented in the paper.
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Recent developments in the production of semipermeable plastic tubing could make gas separation by tube bundles competitive with existing gas separation methods. In order to explore this possibility research was conducted on a variety of tubular gaseous diffusion cells. The results permitted the development of a predictive model for the outputs of tube bundles and the optimum operating conditions.
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When designing steam reformers, important parameters help to define optimum capital cost for the amount of hydrogen produced and the types of feedstocks and fuels available. These parameters include: pressure, temperature, heat flux, steam to carbon ratio, catalyst type, furnace tubes (metallurgy, diameter, length, thickness, and pitch), burners, flow distribution, and heat recovery. The paper discusses the cost effectiveness of steam reforming, feedstocks, fuels, and the above design considerations.
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Hydrogen is considered to be an ideal energy carrier in the foreseeable future and can play a very important role in the energy system. A variety of technologies can be used to produce hydrogen. One of the most remarkable methods for large-scale hydrogen production is thermo-chemical water decomposition using heat energy from nuclear, solar and other sources. Detailed simulations of the two most promising water splitting thermo-chemical cycles (the Westinghouse cycle and the Sulphur–Iodine cycle) were performed in Aspen Plus code and obtained results were used for life cycle analysis. They were compared with two different processes for hydrogen production (coal gasification and coal pyrolysis). Some of the results obtained from LCA are also reported in the paper.
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The use of hydrogen as an alternative fuel is gaining more and more acceptance as the environmental impact of hydrocarbons becomes more evident. Hydrogen production is accomplished by steam reforming of natural gas and other fossil primary energy at approximately 97% of total. Thus, less than 3% is based on renewable energy sources. This work presents the environmental feasibility and efficiency of producing hydrogen from biomass via two processes. Biomass gasification followed by reforming of the syngas is compared to gasification followed by electricity generation and electrolysis. The technical and environmental performance of such systems is examined using the life cycle assessment (LCA) methodology. The systems under investigation are assumed to be located in an agricultural region of Greece. The classification of the inventory data to impact categories was made using the EcoIndicator 95 methodology. Although the gasification-steam reforming-PSA route is the most energy efficient the LCA study of the two biomass to hydrogen systems, indicates that the biomass-gasification-electricity-electrolysis route has a better environmental performance.
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Biomass is expected to become an important energy source in U.S. electricity generation under state-lead renewable portfolio standards. This paper investigated the greenhouse gas (GHG) emissions for energy generated from forest resources through pyrolysis-based processing. The GHG emissions of producing pyrolysis bio-oil (pyrolysis oil) from different forest resources were first investigated; logging residues collected from natural regeneration mixed hardwood stands, hybrid poplar cultivated and harvested from abandoned agricultural lands, short rotation forestry (SRF) willow plantations and waste wood available at the site of the pyrolysis plant. Effects of biomass transportation were investigated through a range of distances to a central pyrolysis facility through road transport by semi-truck. Pyrolysis oil is assumed to be converted to electrical power through co-combustion in conventional fossil fuels power plants, gas turbine combined cycle (GTCC) and diesel generators. Life cycle GHG emissions were compared with power generated using fossil fuels and power generated using biomass direct combustion in a conventional Rankine power plant. Life cycle GHG savings of 77%–99% were estimated for power generation from pyrolysis oil combustion relative to fossil fuels combustion, depending on the biomass feedstock and combustion technologies used. Several scenario analyses were conducted to determine effects of pyrolysis oil transportation distance, N-fertilizer inputs to energy crop plantations, and assumed electricity mixes for pyrolysis oil production.
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The adequacy and feasibility of methods recommended for allocation by the current international standard on life cycle inventory analysis (LCI) are reviewed. The review is based on the view that an LCI should provide information on the environmental consequences of manipulating technological systems. On this basis, subdivision and allocation based on physical, causal relationships are adequate methods to deal with allocation problems for certain multifunction processes where the production volume of exported functions are unaffected. Further research is needed to develop methods that can deal with a broader range of processes. System expansion is an adequate method when exported functions are affected if data can be obtained for the competing production of the exported function, and if the data uncertainties are not too large. In LCI practice, system expansion is often based on inaccurate data on the effects on the exported functions as well as on the indirect effects of changes in the exported functions. Further research is needed to establish what data should be used at system expansion. Other approaches to the allocation problems are adequate only where the effects on the LCI results are small. The ISO procedure should be revised to take into account the type of information provided by the different methods.
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This paper investigates various usages of natural gas (NG) as an energy source for different hydrogen production technologies. A comparison is made between the different methods of hydrogen production, based on the total amount of natural gas needed to produce a specific quantity of hydrogen, carbon dioxide emissions per mole of hydrogen produced, water requirements per mole of hydrogen produced, and a cost sensitivity analysis that takes into account the fuel cost, carbon dioxide capture cost and a carbon tax. The methods examined are the copper–chlorine (Cu–Cl) thermochemical cycle, steam methane reforming (SMR) and a modified sulfur–iodine (S–I) thermochemical cycle. Also, an integrated Cu–Cl/SMR plant is examined to show the unique advantages of modifying existing SMR plants with new hydrogen production technology. The analysis shows that the thermochemical Cu–Cl cycle out-performs the other conventional methods with respect to fuel requirements, carbon dioxide emissions and total cost of production.
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Since the hydrogen movement started in 1974, there has been progress in research, development, demonstration and commercialization activities, covering all aspects of the hydrogen energy system. In order to solve the interrelated problems of depletion of fossil fuels and the environmental impact of the combustion products of fossil fuels, it is desirable to speed up the conversion to the hydrogen energy system. Most established industries have joined the hydrogen movement. There is one exception: the fossil fuel industry. A call is made to the fossil fuel industry to join the hydrogen movement. It is also proposed to change the present economic system with a sustainability economics in order to account for environmental damage, recyclability and decommissioning, and thus, ensure a sustainable future.
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In this paper, the results of an exergetic well-to-wheels analysis of a number of hydrogen production and hydrogen storage systems for automotive applications are given. A total of eight different fuel chains is exergetically analysed. Exergy analysis is shown to have considerable additional value compared to conventional energetic well-to-wheels analyses based on the lower or higher heating value of fuels under consideration. Exergy can be used for both fuel and non-fuel resources and can play an important role in the quantification of resource depletion in fuel chains. With exergy analysis, it is possible to determine thermodynamic limits of processes and to locate and interpret process losses. Exergy analysis is therefore a useful tool in process improvement and process comparison. Furthermore, exergy can play a role in the quantification of the effort it would take to abate or recycle waste streams.