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In 2017, deadly wildfires flared across central and north of Portugal. Following these events, the Government released a set of forestry policies promoting the increase of the currently installed forest biomass combustion thermal power plant capacity. In this study, we conduct a techno-economic analysis of an 11 MW gasification power plant, as a cleaner alternative to traditional combustion plants, dealing with forest biomass blends in Portugal central region. The analysis is built based on existing literature review and evaluation reports concerning investment projects in biomass-to-energy power plants. A spreadsheet economic model combining net present value (NPV), internal rate of return (IRR) and payback period (PBP) is developed over the plant’s lifetime period of 25 years. Cost factors incurred in initial investment, amortizations, fixed assets and working capital investments, financial income, operation and maintenance costs, employees and structure costs. Revenues are generated from selling electricity to the grid. A Monte Carlo sensitivity analysis is employed to gauge the economic model performance and investment risk. Lastly, an assessment of the environmental impact, noxious emissions and future prospects to this biomass-based energy conversion process are addressed. Results predict the feasibility of the project, with an NPV of 2.367 M€, an IRR of 8.66% and PBP of 23.1 years. Sensitivity analysis foresees affordable risks for investors, and that the project’s NPV is highly sensitive to the electricity sales price and electricity production. Despite the viability of the project delivered by the economic model, the economic performance is strongly reliant on revenues from electricity sales regulated by uncertain tariffs and reimbursements. Thus, special concerns must be considered regarding the project attractiveness to potential investors.

A 2-D numerical simulation approach was implemented to describe the gasification process of olive pomace in a bubbling fluidized bed reactor. The numerical model was validated under experimental gasification runs performed in a 250 kWth quasi-industrial biomass gasifier. The producer gas composition, H2/CO ratio, CH4/H2 ratio, cold gas efficiency and tar content were evaluated. The most suitable applications for the potential use of olive pomace as an energy source in Portugal were assessed based on the results. A techno-economic study and a Monte Carlo sensitivity analysis were performed to assess the feasibility and foresee the main investment risks in conducting olive pomace gasification in small facilities. Results indicated that olive pomace gasification is more suitable for domestic purposes. The low cold gas efficiency of the process (around 20%) turns the process more appropriate for producer gas production in small cogeneration facilities. Olive pomace gasification solutions showed viable economic performance in small cogeneration solutions for agriculture waste-to-energy recovery in olive oil agriculture cooperatives. However, the slender profitability may turn the project unattractive for most investors from a financial standpoint.

A mathematical model approach was employed to simulate olive pomace gasification in a bubbling fluidized bed reactor. To validate the model a set of gasification experiments were performed in a 250 kW quasi-industrial gasifier. The cold gas efficiency of the th gasifier and tar production were evaluated to assess the energy potential of olive pomace while determining its most suitable end-use applications. A techno-economic analysis addressing the comparison of two different commercially manufactured gasifying unit sizes (100 kW and 1000 kW) and a Monte-Carlo sensitivity analysis were employed to assess both the feasibility of each application size and also foresee the main investment risks in conducting olive pomace gasification in small rural facilities. Olive pomace gasification showed to be more suitable for personal household purposes. The low cold gas efficiency (around 20%) makes this producer gas more appropriate for small cogeneration facilities applications. The use of olive pomace residues in gasification showed viable economic performance in small cogeneration solutions at a scale of 1000 kW for agriculture waste-to-energy recovery in olive oil agriculture cooperatives, while 100 kW showed to be unable to reach an economically sustainable scenario. Final remarks point out that despite the feasibility of the venture at a scale of 1000 kW special concerns must be considered regarding the study attractiveness to potential investors.

Computational fluid dynamics (CFD) analysis has recently been applied to study the performance of waste-to-energy systems, with a broad literature range dedicated to this topic. However, there is still a lack of guidance, particularly for new researchers, concerning a broad and detailed discussion on the current routes available to appropriately make use of these numerical models to describe waste combustion and gasification processes.

Refuse-derived fuel (RDF) is generated by selected Municipal Solid Waste (MSW) fractions. Due to MSW composition changes by location, it is challenging to sell RDF as a product in the market. This article compiles the significant standards and rules governing RDF manufacture and usage. Additionally, it emphasizes the key actors that have already made a business of its commercialization and energy production through thermochemical processes. Combustion is the most often utilized thermochemical process, and this paper gathers information from several works on the combustion of RDF and RDF blends. Pyrolysis and gasification are also discussed, along with the primary benefits and drawbacks of RDF usage. Finally, the market's potential and significant constraints are examined. The primary constraint is the RDF price due to commercialization fees. However, RDF is aligned with the circular economy, sustainable development goals, and CO2 reductions by avoiding the extraction of new fossil fuels.

Response Surface Methodology (RSM) when combined with the Propagation of Error (PoE) approach offers an efficient robust design able to find the best operating conditions to simultaneously maximize power density and reduce normal operation variability in a hydrogen-fed Proton Exchange Membrane Fuel Cell (PEMFC). To proceed with the statistical analysis, a central composite design with 20 experimental runs (6 central points were used to assess the experimental error) was adopted to inspect which factors have significant effects and how they interact each other. This allowed generating a polynomial function to determine the maximum power density at 1415 mW/cm 2 . Taking advantage of the desirability concept and using the PoE measure as a response, a multiple optimization under different restrictions was carried out defining a new set of operating conditions able to target the maximum possible power density at the most robust conditions (1074 mW·cm −2 at 55 °C, 50% RHC and 25 Psi). Then, actions were carried out to narrow even more the tolerance intervals towards more ambitious standards. Reducing the standard deviation from input factors through the use of adequate controlling measures led to a decrease of almost 50% in the tolerance intervals. This is an useful methodology to help the PEMFC normal operation more repeatable and predictable under its lifetime by combing both optimization and robustness goals.

A 2-D multiphase CFD model was coupled with advanced statistical methods to find the best operating conditions to maximize a set of selected responses that characterize the normal operation of a pilot scale fluidized bed gasifier running Municipal Solid Waste. After using CFD simulations to compute 7 responses at 27 different operating conditions, a single response optimization based on the response surface method was carried out to identify the best operating conditions. Then, the desirability concept was advantageously used to proceed with a multiple optimization where all the responses were targeted under normal industrial conditions. The operating conditions that set the optimized responses not always coincide with the most stable process. To target both optimized and robust conditions a multiple optimization combining the response surface and the propagation of error methods were employed. Finally, the tolerance intervals were reduced to increase the process Cpk and six sigma standards about 20%. New measures to further increase the process performance were identified and the transmitted variation to the response from input factors was computed.

Ammonia and hydrogen carry great potential as carbon-free fuels with promising applications in energy systems. Hydrogen, in particular, has been generating massive expectations as a carbon-free economy enabler, but issues related to storage, distribution, and infrastructure deployment are delaying its full implementation. Ammonia, on the other hand, stands as a highly efficient energy vector delivering high energy density and an established and flexible infrastructure capable of mitigating hydrogen’s key drawbacks. This mature infrastructure together with the possibility of producing ammonia through renewable energy sources triggered an exploring route to the transition of ammonia as the next sustainable fuel solution for power generation. In this regard, the transportation sector as one of the main culprits for carbon emissions can benefit from ammonia-powered internal combustion engines. However, the use of pure ammonia as fuel still presents important constraints leading researchers to develop strategies such as dual-fuel concepts or novel combustion approaches. Therefore, this review covers these issues by delving into the underpinning mechanisms required for developing pure ammonia combustion in internal combustion engines. To do so, fundamentals, technical, environmental, and economic aspects associated with the use of ammonia as a transportation fuel are broadly addressed. While the emphasis is given to pure ammonia and ammonia fuel blends operation, NOx emissions control, current challenges related to the detailed and accurate understanding of the ammonia chemistry, and the lack of high-fidelity numerical models are also deeply discussed on their role into aiding the commercial deployment of this technology.

The present work assesses the energetic valorisation of forest biomass blends in the archipelago of the Azores, to do so, a multiphase 2-D Eulerian-Eulerian model was employed to simulate forest biomass gasification in a pilot-scale fluidized bed reactor. The numerical model was validated under experimental gasification runs performed in a 250 kWth quasi-industrial biomass gasifier. The potential use of the produced syngas as a complementary energy source for small-scale power production in the Azores was assessed based on the results. The exergy efficiency and tar production of the process were determined. A techno-economic study combining the net present value (NPV), internal rate of return (IRR), and payback period (PBP) followed by a Monte Carlo sensitivity analysis was comparatively performed for two distinct application sizes (100 and 1000 kW) so to gauge which unit size carries enhanced operative feasibility and foresee the main investment risks in conducting forest biomass blends gasification for power production in small facilities. Results revealed that the 100 kW unit was economically impracticable under current market conditions, while the 1000 kW unit showed to be economically feasible with an NPV of 486 k€, IRR of 17.44% and PBP of 7.4 years. The sensitivity analysis predicted a higher risk of failure in the NPV, being highly sensitive to the electricity sales tariff and electricity production. Indeed, forest biomass gasification projects carry great potential when applied to small facilities with economic viability in some economies of scales, withal, special concerns must always be considered regarding the project attractiveness to potential investors.