Jaime Filipe Borges Puna

A gestão integrada de resíduos sólidos urbanos - perspectiva ambiental e económico-energética

The importance of urban solid waste integrated systems is characterized by the several components of these systems, which are, basically, formed by physical, chemical and biological methods. This article, characterizes these methods and, which is also important, identifies the several and potential environmental impacts of those techniques. Its also extremely important to make a study of the economic rentability of those infrastructures and, also, characterize the quantitative energetic contributions of some components of these systems. This study was analysed and their results are presented in this article.

Status of biodiesel production using heterogeneous alkaline catalysts

This paper describes biodiesel production using heterogeneous alkaline catalysts instead of the conventional homogenous alkaline catalysts, such as NaOH, KOH or sodium methoxide, for the methanolysis reaction, in the search for more profitable and sustainable alternatives regarding biodiesel production. The heterogeneous catalytic process has many differences from that currently used in industrial homogeneous processes. The main advantage is that it requires lower investment costs, as there is no need for separation steps such as methanol/catalyst, biodiesel/catalyst and glycerine/catalyst. This paper also describes experimental work towards the development of new heterogeneous alkaline catalysts able to produce biodiesel from vegetable oils. The research has resulted in the selection of CaO and CaO modified with alkaline and alkaline earth metal catalysts. They show very good catalytic performances with high activity and stability. In fact, biodiesel (FAME) yields higher than 94% were observed in several consecutive reaction batches without expensive intermediate reactivation procedures. Therefore, those catalysts appear to be suitable for biodiesel production.

Thermal Conversion Technologies for Solid Wastes: A New Way to Produce Sustainable Energy

The solid waste generation is an important environmental problem, because it grows at a rate that exceeds the ability of natural environment assimilation and the treatment capacity available. Nowadays we need to reduce the consumption of raw materials and to increase the rate of recovery and reuse of waste materials. An essential component in many integrated solid waste management systems is thermal conversion. This kind of technology allow to obtained volume reduction and energy recovery. The energy produce by solid waste treatment contribute for the use of less fossil fuels and can help meet renewable energy targets, as a consequence of global warning problem, and contribute significantly to achieving Kyoto Protocol objectives. As it is knowledge of the scientific community, the integrated solid waste treatment follows a hierarchic management strategy, which is sequential and obeys to some steps, in decreasing order of waste best destination (Puna, 2002). In the nineties the waste management hierarchy usually was composed by: source reduction, recycling, waste combustion and landfilling. Nowadays waste management hierarchy is more complete because the use of chemical and biological treatments (aerobic and anaerobic). The development of a proper waste management system depends on the availability data on the characteristics of the waste stream, performance specifications for alternative technologies and cost information. (Tchobanoglous et al., 1993). The United Kingston and United State of America often disregard waste incineration on future waste management systems, but other countries like Switzerland, Japan and Denmark incinerate more than 65% of municipal solid waste (Damgaard et al., 2007). There are advantages and disadvantages with all treatment options. As mentioned before, the wastes have to be submitted to one or more waste solid treatment methods and technologies. These treatment methods actually available and suitable to treat those solid wastes are classified attempting to their dangerousness (no dangerous and dangerous wastes) (Puna, 2002).