Silvia A. Nebra

Assessing GHG Emissions, Ecological Footprint, and Water Linkage for Different Fuels

Currently, transport is highly dependent on fossil fuels and responsible for about 23% of world energy-related GHG (greenhouse gas) emissions. Ethanol from sugar cane and corn emerges as an alternative for gasoline in order to mitigate GHG emissions. Additionally, deeper offshore drilling projects such as in the Brazilian Pre-Salt reservoirs and mining projects of nonconventional sources like Tar Sands in Canada could be a solution for supplying demand of fossil fuels in the short and midterm. Based on updated literature, this paper presents an assessment of GHG emissions for four different fuels: ethanol from sugar cane and from corn and gasoline from conventional crude oil and from tar sands. An Ecological Footprint analysis is also presented, which shows that ethanol from sugar cane has the lowest GHG emissions and requires the lowest biocapacity per unit of energy produced among these fuels. Finally, an analysis using the Embodied Water concept is made with the introduction of a new concept, the CO(2)-Water, to illustrate the impacts of releasing carbon from underground to atmosphere and of the water needed to sequestrate it over the life cycle of the assessed fuels. Using this method resulted that gasoline from fossil fuels would indirectly require on average as much water as ethanol from sugar cane per unit of fuel energy produced.

Electricity production from municipal solid waste in Brazil

Brazil has an increasing production of municipal solid waste that, allied to the current waste management system, makes the search for alternatives of energy recovery essential. Thus, this work aims to study the incineration of municipal solid waste and the electricity production through steam cycles evaluating the influence of municipal solid waste composition. Several scenarios were studied, in which it was assumed that some fractions of municipal solid waste were removed previously. The municipal solid waste generated in Santo André city, São Paulo State, Brazil, was adopted for this study. Simulation results showed that the removal of organic matter and inert components impacts advantageously on the cycle performance, improving their parameters in some cases; in addition, there is the possibility of reusing the separated fractions. The separation of some recyclables, as plastic material, showed disadvantages by the reduction in the electricity generation potential owing to the high calorific value of plastics. Despite the high energy content of them, there are other possible considerations on this subject, because some plastics have a better recovery potential by recycling.