The contribution of this chapter is to deepen and widen existing knowledge on municipal solid waste (MSW) management by analyzing different energy recovery routes for MSW. The main aspects related to the composition of waste are addressed, as well as the technological routes for thermochemical and biochemical energy usage. Within the thermochemical route, incineration is currently the most utilized technology for energy recovery of waste, with generation of electricity and heat and also a decrease in the volume of the produced waste. Gasification and pyrolysis are alternatives for the production of chemical products from wastes. The biological route is an interesting alternative for the utilization of the organic fraction of MSW, as aerobic or anaerobic processes enable the production of biogas and of a compound that can be utilized as a fertilizer. Depending on the size of the population, composition of waste, and products to be obtained (energy or chemical), more than one technology can be combined for a better energy usage of waste.

In this work, an energetic and environmental evaluation of the electricity generation process through refuse-derived fuel (RDF) gasification coupled to a gas microturbine (GM) was performed. Two scenarios are considered with different gasification agents in RDF gasification modeling: air and air enriched with oxygen. A thermodynamic chemical equilibrium approach was used to analyze the gasification parameters. The results of RDF gasification indicate a maximum value of syngas low heating value (LHV) equal to 8.0 MJ/Nm³, obtained for an equivalence ratio of 0.3. The use of these syngas in the gas microturbine produces 79.6 kW of electrical power. For the environmental evaluation of gasification and electricity generation systems, the Life Cycle Assessment methodology was employed. The calculated environmental impacts indicate that the emission of contaminants from fossil fuel combustion (in the stage of transport by heavy load vehicles) and that the electricity consumption for equipment operation (in the stage of municipal solid waste pretreatment) contributes to environmental pollution. On the other hand, electricity generation through GM presented lower environmental impact for all analyzed categories, suggesting that the electricity generation from gas obtained from gasification could be a viable option for thermochemical conversion of RDF and its subsequent energetic use.

In Brazil, specify in isolated areas, the connection to the conventional electric energy distribution grid becomes restrictied due to financial and geographical factors. Then the main option for supplying the energy demand is fossil fuel driven thermal systems. With the purpose of providing an alternative option for power generation, this study presents an analysis of biomass‐based energy systems for isolated communities, in special Bonfim city, in Roraima state. The technologies applied were conventional Rankine cycle, organic Rankine cycle (ORC) and gasification system with an internal combustion engine. All systems are operated with agricultural wastes (rice straw and rice husk). The modelled systems produced electricity with a conversion efficiency of 10.78, 17.78 and 14% for ORC, conventional Rankine cycle and gasification systems, respectively. With these results and with a production of 35,667 tons of waste per year, the systems can supply the energetic demand of Bonfim city (536.40 kW). With relation to costs, currently the generation costs in isolated communities of Bonfim city are in a range of 390.31–475.85 US$/MWh. The proposed cases have a generation costs of 197.11 US$/MWh (conventional Rankine cycle), 324.77 US$/MWh (ORC) and 336.49 US$/MWh (gasification system).

Brazil is a country of agricultural culture, and for over a hundred years has been the largest coffee producer. Thus, the work proposes alternatives for the use of agricultural residues from coffee production, analyzing them from an environmental and economic point of view. A coffee crop was selected from the municipality of Santa Rosa da Serra (Minas Gerais, Brazil), and three scenarios were established. Scenario 1: husk is discarded outdoors; scenario 2: energy use of the husk for gasification and subsequent production of electricity; scenario 3: use of the husk as an organic fertilizer. An economic and environmental analysis was conducted from these three scenarios. The gasification technology with the coffee husk, although technically feasible, according to the economic analysis becomes unfeasible, since the value of this electric generation was higher than the other generation values. Scenarios 2 and 3 that applied sustainable practices resulted in negative values for the environmental impacts of water depletion and depletion of fossil fuels, proving the benefits of such practices. The gasification process needs technological development to make the enterprise economically viable. Sustainable practices in coffee cultivation bring environmental benefits in the short and long terms.