Performance assessment of biofuel production via biomass fast pyrolysis and refinery technologies

Biofuels have been identified as one of several GHG emission strategies to reduce the use of fossil fuels in the transport sector. Fast pyrolysis of biomass is one approach to producing second generation biofuels. The bio-oil product of fast pyrolysis can be upgraded into essential gasoline and diesel range products with conventional refinery technologies. Thus, it is important to assess their techno- economic and environmental performance at an early stage prior to commercialisation. This research was conducted with the goal of evaluating and comparing the techno-economic and environmental viability of the production of biofuels from fast pyrolysis of biomass and upgrading of bio-oil via two refinery technologies, viz. hydroprocessing and zeolite cracking. In order to achieve this aim, process models of fast pyrolysis of biomass and bio-oil upgrading via hydroprocessing and zeolite cracking were developed. The fast pyrolysis model was based on multi-step kinetic models. In addition, lumped kinetic models of the hydrodeoxygenation reactions of bio-oil were implemented. The models were verified against experimental measurements with good prediction and formed the foundation for the development of a 72 t/day fast pyrolysis plant model in Aspen Plus®. Several strategies were proposed for the two pathways to enhance energy efficiency and profitability. All in all, the results revealed that the hydroprocessing route is 16% more efficient than the zeolite cracking pathway. Moreover, the hydroprocessing route resulted in a minimum fuel selling price of 15% lower than that from the zeolite cracking pathway. Sensitivity analysis revealed that the techno-economic and environmental performance of the both pathways depends on several process, economic and environmental parameters. In particular, biofuel yield, operating cost and income tax were identified as the most sensitive techno-economic parameters, while changes in nitrogen feed gas to the pyrolysis reactor and fuel yield had the most environmental impact. It was concluded that hydroprocessing is a more suitable upgrading pathway than zeolite cracking in terms of economic viability, energy efficiency, and GHG emissions per energy content of fuel produced

Techno-economic performance analysis of biofuel production and miniature electric power generation from biomass fast pyrolysis and bio-oil upgrading

The techno-economic performance analysis of biofuel production and electric power generation from biomass fast pyrolysis and bio-oil hydroprocessing is explored through process simulation. In this work, a process model of 72 MT/day pine wood fast pyrolysis and bio-oil hydroprocessing plant was developed with rate based chemical reactions using Aspen Plus® process simulator. It was observed from simulation results that 1 kg s−1 pine wooddb generate 0.64 kg s−1 bio-oil, 0.22 kg s−1 gas and 0.14 kg s−1 char. Simulation results also show that the energy required for drying and fast pyrolysis operations can be provided from the combustion of pyrolysis by-products, mainly, char and non-condensable gas with sufficient residual energy for miniature electric power generation. The intermediate bio-oil product from the fast pyrolysis process is upgraded into gasoline and diesel via a two-stage hydrotreating process, which was implemented by a pseudo-first order reaction of lumped bio-oil species followed by the hydrocracking process in this work. Simulation results indicate that about 0.24 kg s−1 of gasoline and diesel range products and 96 W of electric power can be produced from 1 kg s−1 pine wooddb. The effect of initial biomass moisture content on the amount of electric power generated and the effect of biomass feed composition on product yields were also reported in this study. Aspen Process Economic Analyser® was used for equipment sizing and cost estimation for an nth plant and the product value was estimated from discounted cash flow analysis assuming the plant operates for 20 years at a 10% annual discount rate. Economic analysis indicates that the plant will require £16.6 million of capital investment and product value is estimated at £6.25/GGE. Furthermore, the effect of key process and economic parameters on product value and the impact of electric power generation equipment on capital cost and energy efficiency were also discussed in this study

Extension officers’ perception towards accreditation and regulation of extension services in North West Province, South Africa

This paper examines extension officers’ perception towards accreditation and regulation of extension services. This is based on the premise that a pluralistic extension service delivery currently prevails in South Africa where public and private service providers exist with differentials in quality of services to clients; which can be overcome through accreditation of providers from end-users’ perspectives. Using a random sampling technique, 69 extension officers were sampled and a questionnaire was used to collect data, which was analysed with the aid of Statistical Package for Social Sciences (SPSS) using frequency counts, percentages and probit regression. Extension officers have high knowledge that accreditation aids periodic quality review (̅ = 1.81, SD = 0.49); improving quality of services (̅ = 3.91, SD = 1.26) and promotes accountability (̅ = 2.49, SD = 0.79). Significant determinants of the perception on accreditation are gender (t = 3.08; p < 0.05); marital status (t = -2.42; p < 0.05); number of children (t = 1.73; p < 0.05); household size (t =-2.03; p < 0.05); residence status (t = 1.78; p < 0.05); distance to clients (t =2.06; p < 0.05); and attitude to accreditation (t = 1.86; p < 0.05).Keywords: accreditation, agricultural extension service, information sources, farmers, service delivery, service provider

Comparative evaluation of GHG emissions from the use of Miscanthus for bio-hydrocarbon production via fast pyrolysis and bio-oil upgrading

This study examines the GHG emissions associated with producing bio-hydrocarbons via fast pyrolysis of Miscanthus. The feedstock is then upgraded to bio-oil products via hydroprocessing and zeolite cracking. Inventory data for this study were obtained from current commercial cultivation practices of Miscanthus in the UK and state-of-the-art process models developed in Aspen Plus®. The system boundary considered spans from the cultivation of Miscanthus to conversion of the pyrolysis-derived bio-oil into bio-hydrocarbons up to the refinery gate. The Miscanthus cultivation subsystem considers three scenarios for soil organic carbon (SOC) sequestration rates. These were assumed as follows: (i) excluding (SOC), (ii) low SOC and (iii) high (SOC) for best and worst cases. Overall, Miscanthus cultivation contributed moderate to negative values to GHG emissions, from analysis of excluding SOC to high SOC scenarios. Furthermore, the rate of SOC in the Miscanthus cultivation subsystem has significant effects on total GHG emissions. Where SOC is excluded, the fast pyrolysis subsystem shows the highest positive contribution to GHG emissions, while the credit for exported electricity was the main ‘negative’ GHG emission contributor for both upgrading pathways. Comparison between the bio-hydrocarbons produced from the two upgrading routes and fossil fuels indicates GHG emission savings between 68% and 87%. Sensitivity analysis reveals that bio-hydrocarbon yield and nitrogen gas feed to the fast pyrolysis reactor are the main parameters that influence the total GHG emissions for both pathways

Heat integration for bio-oil hydroprocessing coupled with aqueous phase steam reforming

AbstractOptimized heat exchanger networks can improve process profitability and minimize emissions. The aim of this study is to assess the heat integration opportunities for a hypothetical bio-oil hydroprocessing plant integrated with a steam reforming process via pinch technology. The bio-oil hydroprocessing plant was developed with rate based chemical reactions using ASPEN Plus® process simulator. The base case is a 1600kg/h bio-oil hydroprocessing plant, which is integrated with a steam reforming process of the bio-oil aqueous phase. The impact of the reformer steam to carbon ratio on energy targets was analysed, revealing that significant energy savings can be achieved at different process variations. Aspen Energy Analyzer™ was employed to design the heat exchanger network. Two heat exchanger network designs are considered. The optimum design reveals that the second hydrodeoxygenation reactor effluent can preheat the bio-oil feed with minimal capital cost implication and achieve similar energy targets compared with the alternative design. The economic and environmental implications of the two heat exchanger network designs on product value were also evaluated

Techno-economic analysis of biofuel production via bio-oil zeolite upgrading: An evaluation of two catalyst regeneration systems

Biofuels have been identified as a mid-term greenhouse gas (GHG) emissions abatement solution for decarbonising the transport sector. This study examines the techno-economic analysis of biofuel production via biomass fast pyrolysis and subsequent bio-oil upgrading via zeolite cracking. The aim of this study is to compare the techno-economic feasibility of two conceptual catalyst regeneration configurations for the zeolite cracking process: (i) a two-stage regenerator operating sequentially in partial and complete combustion modes (P-2RG) and (ii) a single stage regenerator operating in complete combustion mode coupled with a catalyst cooler (P-1RGC). The designs were implemented in Aspen Plus® based on a hypothetical 72 t/day pine wood fast pyrolysis and zeolite cracking plant and compared in terms of energy efficiency and profitability. The energy efficiencies of P-2RG and P-1RGC were estimated at 54% and 52%, respectively with corresponding minimum fuel selling prices (MFSPs) of £7.48/GGE and £7.20/GGE. Sensitivity analysis revealed that the MFSPs of both designs are mainly sensitive to variations in fuel yield, operating cost and income tax. Furthermore, uncertainty analysis indicated that the likely range of the MFSPs of P-1RGC (£5.81/GGE − £11.63/GGE) at 95% probability was more economically favourable compared with P-2RG, along with a penalty of 2% reduction in energy efficiency. The results provide evidence to support the economic viability of biofuel production via zeolite cracking of pyrolysis-derived bio-oil

Environmental and economic assessment of the formic acid electrochemical manufacture using carbon dioxide: Influence of the electrode lifetime

This paper focuses on the study of the environmental and economic feasibility of the formic acid (FA) synthesis by means of electrochemical reduction (ER) of carbon dioxide (CO2) with special emphasis on the cathode lifetime. The study has used a Life Cycle Assessment (LCA) approach in order to obtain the environmental indicators as Global Warming Potential (GWP) and Abiotic Depletion (ADP) (both elements and fossil resources ADPs). The values of the indicators obtained in the assessment were representative of the Carbon Footprint (CF) and resource savings of this fabrication process. The commercial/conventional process for FA production was used as benchmark. The novelty of the study is the incorporation into the Life Cycle Inventory (LCI) of those materials and chemicals that are used in the fabrication of an ER cell, and in particular in the cathode. Hence, the lifetime of the cathode was used as a main parameter. The results obtained for a baseline case demonstrated that cathode lifetimes over 210 h would be enough to neglect the influence of the cathode fabrication from an environmental perspective. A first approach to the utility costs of CO2 ER process was also proposed in the study. Cost of utilities ranged between 0.16 € kg and 1.40 € kg-1 of FA in an ER process compared with 0.21 € kg-1 and 0.43 € kg-1 of FA in the conventional process depending on the market prices. This study demonstrated that the ER-based process could be competitive under future conditions if a reasonable electrocatalytic performance (in terms of cell voltage, current density, and faradaic efficiency) is achieved within a reasonable medium or long-term horizon. The results obtained aim to provide useful insights for decision-makers on the future developments within a decarbonized chemical industry.Authors thank to Spanish Ministry of Economy and Competitiveness (MINECO) for the financial support through the project CTQ2016-76231-C2-1-R. We would like also to thank MINECO for providing Marta Rumayor with a Juan de la Cierva postdoctoral contract (FJCI-2015-23658)

Decarbonisation of olefin processes using biomass pyrolysis oil

An imperative step toward decarbonisation of current industrial processes is to substitute their petroleum-derived feedstocks with biomass and biomass-derived feedstocks. For decarbonisation of the petrochemical industry, integrated catalytic processing of biomass pyrolysis oil (also known as bio-oil) is an enabling technology. This is because, under certain conditions, the reaction products form a mixture consisting of olefins and aromatics, which are very similar to the products of naphtha hydro-cracking in the conventional olefin processes. These synergies suggest that the catalytic bio-oil upgrading reactors can be seamlessly integrated to the subsequent separation network with minimal retrofitting costs. In addition, the integrated catalytic processing provides a high degree of flexibility for optimization of different products in response to market fluctuations. With the aim of assessing the techno-economic viability of this pathway, five scenarios in which different fractions of bio-oil (water soluble/water insoluble) were processed with different degrees of hydrogenation were studied in the present research. The results showed that such a retrofit is not only economically viable, but also provides a high degree of flexibility to the process, and contributes to decarbonisation of olefin infrastructures. Up to 44% reductions in greenhouse gas emissions were observed in several scenarios. In addition, it was shown that hydrogen prices lower than 6 $/kg will result in bio-based chemicals which are cheaper than equivalent petrochemicals. Alternatively, for higher hydrogen prices, it is possible to reform the water insoluble phase of bio-oil and produce bio-based chemicals, cheaper than petrochemical equivalents

In-situ upgrading of Napier grass pyrolysis vapour over microporous and hierarchical mesoporous zeolites

This study presents in-situ upgrading of pyrolysis vapour derived from Napier grass over microporous and mesoporous ZSM-5 catalysts. It evaluates effect of process variables such catalyst–biomass ratio and catalyst type in a vertical fixed bed pyrolysis system at 600 °C, 50 °C/min under 5 L/min nitrogen flow. Increasing catalyst–biomass ratio during the catalytic process with microporous structure reduced production of organic phase bio-oil by approximately 7.0 wt%. Using mesoporous catalyst promoted nearly 4.0 wt% higher organic yield relative to microporous catalyst, which translate to only about 3.0 wt% reduction in organic phase compared to the yield of organic phase from non-catalytic process. GC–MS analysis of bio-oil organic phase revealed maximum degree of deoxygenation of about 36.9% with microporous catalyst compared to the mesoporous catalysts, which had between 39 and 43%. Mesoporous catalysts promoted production olefins and alkanes, normal phenol, monoaromatic hydrocarbons while microporous catalyst favoured the production of alkenes and polyaromatic hydrocarbons. There was no significant increase in the production of normal phenols over microporous catalyst due to its inability to transform the methoxyphenols and methoxy aromatics. This study demonstrated that upgrading of Napier grass pyrolysis vapour over mesoporous ZSM-5 produced bio-oil with improved physicochemical properties

The role of catalyst acidity and shape selectivity on products from the catalytic fast pyrolysis of beech wood

The catalytic fast pyrolysis (CFP) of biomass represents an efficient integrated process to produce deoxygenated stable liquid fuels and valuable chemical products from lignocellulosic biomass. The zeolite ZSM-5 is a widely studied catalyst for the CFP process. However, its microporous structure may limit the diffusion of high molecular weight pyrolysis intermediates to its active sites. Mesoporous aluminosilicates such as Al-SBA-15 are promising materials with larger pore sizes that can overcome these diffusional limitations. Previous comparisons between mesoporous aluminosilicates and ZSM-5 for the CFP process have neglected the disproportionately high acidity of ZSM-5. In this study, an Al-SBA-15 catalyst has been synthesised with high acidity, comparable to that of a ZSM-5 catalyst with a Si:Al ratio of 15:1. The synthesised Al-SBA-15 catalyst was characterised by N2 physisorption, XRD and propylamine-TPD, and was compared to a ZSM-5 catalyst and a typical industrial equilibrium fluid catalytic cracking catalyst (e-FCC). All three catalysts were used at three different catalyst to biomass (C/B) ratios, to investigate the effect of varying concentrations of acid sites on the product distribution from the catalytic fast pyrolysis of beech wood. Interestingly, despite their dissimilar structural architectures, all three solid acid catalysts displayed similar reaction pathways towards the cracking of high molecular weight products such as levoglucosan and formation of intermediates including phenolics and furans. However, the selectivity towards the final catalytic products was dictated mainly by the structure of the catalysts. Despite their very similar surface area and acidity, the ZSM-5 exhibited high selectivity for the formation of desirable aromatic hydrocarbon products due to its shape-selective micropore structure, while Al-SBA-15 instead shifted the selectivity towards the formation of undesirable coke. The results highlighted the importance of catalyst shape-selectivity in the catalytic fast pyrolysis of biomass for the conversion of pyrolysis vapours into desirable products and the suppression of undesirable solid byproduct formation