The maritime industry needs sustainable, low-emission fuels to reduce the environmental impact. Ammonia is one of the most promising alternative fuels because it can be produced from renewable energy, such as wind and solar. Furthermore, ammonia combustion does not emit carbon. This review article covers the advantages and disadvantages of using ammonia as a sustainable marine fuel. We start by discussing the regulations and environmental concerns of the shipping sector, which is responsible for around 2% to 3% of global energy-related CO₂ emissions. These emissions may increase as the maritime industry grows at a compound annual growth rate of 4.33%. Next, we analyze the use of ammonia as a fuel in detail, which presents several challenges. These challenges include the high price of ammonia compared to other fossil fuels, the low reactivity and high toxicity of ammonia, NOx, and N₂O emissions resulting from incomplete combustion, an inefficient process, and NH₃ slipping. However, we emphasize how to overcome these challenges. We discuss techniques to reduce NOx and N₂O emissions, co-combustion to improve reactivity, waste heat recovery strategies, the regulatory framework, and safety conditions. Finally, we address the market trends and challenges of using ammonia as a sustainable marine fuel.

A computational fluid dynamics (CFD) model was coupled with an advanced statistical strategy combining the response surface method (RSM) and the propagation of error (PoE) approach to optimize and test the robustness of the co-firing of ammonia (NH₃) and coal in a fluidized bed reactor for coal phase-out processes. The CFD model was validated under experimental results collected from a pilot fluidized bed reactor. A 3^k full factorial design of nine computer simulations was performed using air staging and NH₃ co-firing ratio as input factors. The selected responses were NO, NH₃ and CO₂ emissions generation. The findings were that the design of experiments (DoE) method allowed for determining the best operating conditions to achieve optimal operation. The optimization process identified the best-operating conditions to reach stable operation while minimizing harmful emissions. Through the implementation of desirability function and robustness, the optimal operating conditions that set the optimized responses for single optimization showed not to always imply the most stable set of values to operate the system. Robust operating conditions showed that maximum performance was attained at high air staging levels (around 40%) and through a balanced NH₃ co-firing ratio (around 30%). The results of the combined multi-optimization process performance should provide engineers, researchers and professionals the ability to make smarter decisions in both pilot and industrial environments for emissions reduction for decarbonization in energy production processes.

Millions of tons of forest residues, agricultural residues, and municipal solid waste are generated in Latin America (LATAM) each year. Regularly, municipal solid waste is diverted to landfills or dumpsites. Meanwhile, forest and agricultural residues end up decomposing in the open air or burnt, releasing greenhouse gases. Those residues can be transformed into a set of energy vectors and organic/chemical products through thermochemical conversion processes, such as pyrolysis and gasification. This book chapter provides information on current examples of gasification on large scale in the world, which typically operate at 700°C, atmospheric pressure, and in a fluidized bed reactor. The produced gas is used for heat and energy generation. Whereas pyrolysis at a large scale operates around 500°C, atmospheric pressure, and in an inert atmosphere, using a fluidized bed reactor. The produced combustible liquid is used for heat and energy generation. The decision of using any of these technologies will depend on the nature and availability of residues, energy carries, techno-socio-economic aspects, and the local interest. In this regard, the particular situation of Brazil and Mexico is analyzed to implement these technologies. Its implementation could reduce the utilization of fossil fuels, generate extra income for small farmers or regions, and reduce the problem derived from the accumulation of residues. However, it is concluded that it is more convenient to use decentralized gasification and pyrolysis stations than full-scale processes, which could be an intermediate step to a large-scale process. The capabilities of numerical models to describe these processes are also provided to assess the potential composition of a gas produced from some biomass species available in these countries.

This comprehensive techno-economic analysis focuses on a proposed power plant that uses cleaner alternatives to traditional combustion methods. The study meticulously examines ternary blends of ammonia, refuse-derived fuels (RDFs), and coal. Utilizing an Aspen Plus simulation equilibrium model, a thorough review of the relevant literature, and evaluation reports on biomass-to-energy power plants and ammonia combustion, the analysis spans 20 years. It considers vital financial metrics such as the net present value (NPV), internal rate of return (IRR), and payback period (PBP). The findings indicate that the combustion of pure coal is the most energy-efficient but has the highest global warming potential (GWP). In contrast, ammonia and RDF blends significantly reduce GWP, with ammonia showing a 3215% lower GWP than coal. Economically, pure coal remains the most attractive option. However, blends of 80% coal, 10% ammonia, and 10% RDF also show promise with a PBP of 11.20 years at a 15% discount rate. These results highlight the potential of ammonia and RDF blends to balance environmental and economic considerations in power generation.

Despite the advantages of gasification over combustion, some elements remain to improve. Fortunately, it is not necessary to reinvent the wheel to improve efficiency and quality because there are already methodologies that have been proven successful with other processes, like the Six Sigma DMAIC methodology. Therefore, this chapter explores the synergies between gasification and Six Sigma DMAIC to improve gas quality and hydrogen production, using RDF and wood as feedstock. Furthermore, the blends and equivalence ratio influence the produced gas is explored.