a b s t r a c tThe Power-to-Gas (PtG) process chain could play a significant role in the future energy system. Renewable electric energy can be transformed into storable methane via electrolysis and subsequent methanation.This article compares the available electrolysis and methanation technologies with respect to the stringent requirements of the PtG chain such as low CAPEX, high efficiency, and high flexibility.Three water electrolysis technologies are considered: alkaline electrolysis, PEM electrolysis, and solid oxide electrolysis. Alkaline electrolysis is currently the cheapest technology; however, in the future PEM electrolysis could be better suited for the PtG process chain. Solid oxide electrolysis could also be an option in future, especially if heat sources are available.Several different reactor concepts can be used for the methanation reaction. For catalytic methanation, typically fixed-bed reactors are used; however, novel reactor concepts such as three-phase methanation and micro reactors are currently under development. Another approach is the biochemical conversion. The bioprocess takes place in aqueous solutions and close to ambient temperatures.Finally, the whole process chain is discussed. Critical aspects of the PtG process are the availability of CO 2 sources, the dynamic behaviour of the individual process steps, and especially the economics as well as the efficiency.

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Fossil fuels have to be substituted by climate neutral fuels to contribute to CO 2 reduction in the future energy system. Pyrolysis of natural gas is a well-known technical process applied for production of, e. g., carbon black. In the future it might contribute to carbon dioxide-free hydrogen production. Production of hydrogen from natural gas pyrolysis has thus gained interest in research and energy technology in the near past. If the carbon by-product of this process can be used for material production or can be sequestrated, the produced hydrogen has a low carbon footprint. This article reviews literature on the state of the art of methane / natural gas pyrolysis process developments and attempts to assess the technology readiness level (TRL).

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Single crystalline ammonium trivanadate NH4V3O8 with variable morphologies, including shuttles, flowers, belts, and plates, was synthesized by the hydrothermal treatment of NH4VO3 with acetic acid. The crystals optimally grow under gentle conditions of 140 °C for 48 h. The resulting NH4V3O8 microcrystals were characterized by means of X-ray diffraction, scanning electron microscopy, infrared and Raman spectroscopy, static magnetization studies, and thermal analysis. The key factors to control the size and morphology of the crystals are the pH value and the vanadium concentration. A tentative microscopic growth mechanism is proposed and it is demonstrated how shape and morphology of the resulting microcrystalline material can be tuned by appropriate synthesis parameters.

Synthetic fuels from biomass (also referred to as BTL, biomass to liquids) may contribute to the future motor fuel consumption to a considerable extent. To overcome the logistical hurdles connected with the industrial use of large quantities of biomass, the de‐central‐centralized bioliq® concept has been developed. It is based on a regional pretreatment of biomass for energy densification by fast pyrolysis. The intermediate referred to as biosyncrude allows for economic long‐range transportation. Collected from a number of those plants, the biosyncrude is converted into synthesis gas, which is cleaned, conditioned, and further converted to fuels or chemicals in an industrial plant complex of reasonable size. Gasification is performed in a high‐pressure entrained flow gasifier at pressures adjusted to those of the subsequently following chemical syntheses. For increased fuel flexibility and conversion of ash rich feed materials, the gasifier is equipped with a cooling screen operated in slagging mode. At Karlsruhe Institute of Technology (KIT), a pilot plant has been erected for process demonstration along the whole process chain. The two MWth fast pyrolysis plant is already in operation since 2009; the five MWth gasifier, the hot gas cleaning section, and a gasoline synthesis via dimethylether are to be finished in 2011. Commissioning of that plant complex will follow in 2012. The technology applied in the bioliq® process chain and on the state of construction of the pilot plant is presented. © 2012 American Institute of Chemical Engineers Environ Prog, 2012

Biofuels of the second generation can contribute significantly to the replacement of the currently used fossil energy carriers for transportation fuel production. The lignocellulosic biomass residues used do not compete with food and feed production, but have to be collected from wide‐spread areas for industrial large‐scale use. The two‐stage gasification concept bioliq offers a solution to this problem. It aims at the conversion of low‐grade residual biomass from agriculture and forestry into synthetic fuels and chemicals. Central element of the bioliq process development is the 2–5 MW pilot plant along the complete process chain: fast pyrolysis for pretreatment of biomass to obtain an energy dense, liquid intermediate fuel, high‐pressure entrained flow gasification providing low methane synthesis gas free of tar, hot synthesis gas cleaning to separate acid gases, and contaminants as well as methanol/dimethyl ether and subsequent following gasoline synthesis. After construction and commissioning of the individual process steps with partners from industry, first production of synthetic fuel was successfully achieved in 2014. In addition to pilot plant operation for technology demonstration, a research and development network has been established providing the scientific basis for optimization and further development of the bioliq process as well as to explore new applications of the technologies and products involved. WIREs Energy Environ 2017, 6:e236. doi: 10.1002/wene.236 This article is categorized under: Bioenergy > Science and Materials Bioenergy > Systems and Infrastructure

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