Assessment of hydrogen production from municipal solid wastes as competitive route to produce low-carbon H2.

An economic and CO2 emission impact assessment of the production of H2 from municipal solid waste in the two configurations of retrofitting an existing waste to energy plant with an electrolysis unit (WtE + El) and of hydrogen production via waste gasification (WtH2) is made with respect to reference cases of H2 production by steam reforming of methane (SMR) or of water electrolysis (El). The results are analyzed with reference to two scenarios depending on whether the fate of waste disposal emissions for SMR and El is accounted. The costs of H2 production as a function of waste gate fee and CO2 taxation as well as the CO2 emissions for both scenarios and the four cases of H2 production analyzed are reported. The results show that produce H2 from a WtE plant hybridized with an electrolyzer could be economic only when the plant is free from depreciation costs and no CO2 taxation exists. Conversely, WtH2 solution results preferable when CO2 taxation will be applied to the non-biogenic fraction of waste. Conditions when WtH2 may results competitive to SMR are defined, in terms of both cost of production and CO2 emissions. With respect to El case, WtH2 results more competitive under the assumption made in terms of combined costs and CO2 emissions.

Application of Pd-Based Membrane Reactors: An Industrial Perspective.

The development of a chemical industry characterized by resource efficiency, in particular with reference to energy use, is becoming a major issue and driver for the achievement of a sustainable chemical production. From an industrial point of view, several application areas, where energy saving and CO2 emissions still represent a major concern, can take benefit from the application of membrane reactors. On this basis, different markets for membrane reactors are analyzed in this paper, and their technical feasibility is verified by proper experimentation at pilot level relevant to the following processes: (i) pure hydrogen production; (ii) synthetic fuels production; (iii) chemicals production. The main outcomes of operations in the selected research lines are reported and discussed, together with the key obstacles to overcome.

Waste to Chemicals for a Circular Economy.

The implementation of a circular economy is a fundamental step to create a greater and more sustainable future for a better use of resources and energy. Wastes and in particular municipal solid waste represent an untapped source of carbon (and hydrogen) to produce a large range of chemicals from methane to alcohols (as methanol or ethanol) or urea. The waste to chemical process and related economics are assessed in this concept article to show the validity of such solution both from an economic point of view and from an environmental perspective considering the sensible reduction in greenhouse gas emissions with respect to conventional production from fossil fuels.

Waste-to-methanol: Process and economics assessment.

The waste-to-methanol (WtM) process and related economics are assessed to evidence that WtM is a valuable solution both from economic, strategic and environmental perspectives. Bio-methanol from Refuse-derived-fuels (RdF) has an estimated cost of production of about 110€/t for a new WtM 300t/d plant. With respect to waste-to-energy (WtE) approach, this solution allows various advantages. In considering the average market cost of methanol and the premium as biofuel, the WtM approach results in a ROI (Return of Investment) of about 29%, e.g. a payback time of about 4years. In a hybrid scheme of integration with an existing methanol plant from natural gas, the cost of production becomes a profit even without considering the cap for bio-methanol production. The WtM process allows to produce methanol with about 40% and 30-35% reduction in greenhouse gas emissions with respect to methanol production from fossil fuels and bio-resources, respectively.

Waste-to-Chemicals for a Circular Economy: The Case of Urea Production (Waste-to-Urea).

The economics and environmental impact of a new technology for the production of urea from municipal solid waste, particularly the residue-derived fuel (RdF) fraction, is analyzed. Estimates indicate a cost of production of approximately €135 per ton of urea (internal rate of return more than 10 %) and savings of approximately 0.113 tons of CH4 and approximately 0.78 tons of CO2 per ton of urea produced. Thus, the results show that this waste-to-urea (WtU) technology is both economically valuable and environmentally advantageous (in terms of saving resources and limiting carbon footprint) for the production of chemicals from municipal solid waste in comparison with both the production of urea with conventional technology (starting from natural gas) and the use of RdF to produce electrical energy (waste-to-energy). A further benefit is the lower environmental impact of the solid residue produced from RdF conversion. The further benefit of this technology is the possibility to realize distributed fertilizer production.

Catalytic partial oxidation and membrane separation to optimize the conversion of natural gas to syngas and hydrogen.

The multistep integration of hydrogen-selective membranes into catalytic partial oxidation (CPO) technology to convert natural gas into syngas and hydrogen is reported. An open architecture for the membrane reactor is presented, in which coupling of the reaction and hydrogen separation is achieved independently and the required feed conversion is reached through a set of three CPO reactors working at 750, 750 and 920 °C, compared to 1030 °C for conventional CPO technology. Obtaining the same feed conversion at milder operating conditions translates into less natural gas consumption (and CO(2) emissions) and a reduction of variable operative costs of around 10 %. It is also discussed how this energy-efficient process architecture, which is suited particularly to small-to-medium applications, may improve the sustainability of other endothermic, reversible reactions to form hydrogen.

Can we afford to waste carbon dioxide? Carbon dioxide as a valuable source of carbon for the production of light olefins.

Concerns about climate change have increased the amount of activity on carbon capture and sequestration (CCS) as one of the solutions to the problem of rising levels of CO(2) in the troposphere, while the reuse of CO(2) (carbon capture and recycling; CCR) has only recently received more attention. CCR is focused on the possibility of using CO(2) as a cheap (or even negative-value) raw material. This Concept paper analyzes this possibility from a different perspective: In a sustainable vision, can we afford to waste CO(2) as a source of carbon in a changing world faced with a fast depletion of natural carbon sources and in need of a low-carbon, resource-efficient economy? One of the points emerging from this discussion concerns the use of CO(2) for the production of olefins (substituting into or integrating with current energy-intensive methodologies that start from oil or syngas from other fossil fuel resources) if H(2) from renewable resources were available at competitive costs. This offers an opportunity to accelerate the introduction of renewable energy into the chemical production chain, and thus to improve resource efficiency in this important manufacturing sector.

Reformer and membrane modules for methane conversion: experimental assessment and perspectives of an innovative architecture.

An innovative concept for steam methane reforming (SMR), based on reformer and membrane modules (RMMs), has been developed and tested to investigate its performance, in terms of feed conversion, on an industrial scale. A major benefit of the proposed RMM configuration is a shift of the chemical equilibrium of SMR reactions, achieved by removing the hydrogen produced at high temperature through the integration of highly selective palladium-based membranes, which enhances the yield of product. In this manner the process can operate at temperatures as low as 600-650 °C, compared to the 850-880 °C range used in conventional plants, and allows for the use of a low-temperature heat source. This Full Paper discusses experimental data on feed conversion at different operating parameters, gathered during 1000 h of testing, and processes these data to optimize the overall architecture, defining the maximum achievable feed conversion. An overall conversion of 59% is achieved with two-step reactions at a reforming temperature of 620 °C. A conversion as high as 90% can be obtained with a three-step architecture at 650 °C by properly extending the design parameters within reasonable limits.