• Energy Research

Abstract Portugal relies to a very large extent on imports to meet its energy needs. The predominant energy source is oil, which comes in its entirety from other countries. Renewables now are the second most important energy source being hydropower the most important domestic source of energy. Since more than one third of the territory is forests, biomass is one of the most potential renewable energy sources. This paper presents the scope, potential and technologies related to the use of biomass resources. The study also discusses the biomass projects undertaken by the government and non-government organizations, plans and strategies to promote the biomass. The current status of biomass resources shows that the total potential estimated for various sectors of the country is of 42,489.7 GW h/year. The study also reveals one overexploited biomass resource such as forest biomass (if all the predicted biomass power plants enter into the running phase) and underexploited biomass resources such as municipal solid wastes, waste waters and animal manures. The future prospects for biomass are the embodied in the EU and national strategies for the RES sector, which estimates an average annual growth of 5% for installed capacity and 1% for the power production.

Abstract Portugal relies to a very large extent on imports to meet its energy needs. The predominant energy source is oil, which comes in its entirety from other countries. Renewables now are the second most important energy source being hydropower the most important domestic source of energy. Since more than one third of the territory is forests, biomass is one of the most potential renewable energy sources. This paper presents the scope, potential and technologies related to the use of biomass resources. The study also discusses the biomass projects undertaken by the government and non-government organizations, plans and strategies to promote the biomass. The current status of biomass resources shows that the total potential estimated for various sectors of the country is of 42,489.7 GW h/year. The study also reveals one overexploited biomass resource such as forest biomass (if all the predicted biomass power plants enter into the running phase) and underexploited biomass resources such as municipal solid wastes, waste waters and animal manures. The future prospects for biomass are the embodied in the EU and national strategies for the RES sector, which estimates an average annual growth of 5% for installed capacity and 1% for the power production.

Hydrogen is a versatile energy vector for a plethora of applications; nevertheless, its production from waste/residues is often overlooked. Gasification and subsequent conversion of the raw synthesis gas to hydrogen are an attractive alternative to produce renewable hydrogen. In this paper, recent developments in R&D on waste gasification (municipal solid waste, tires, plastic waste) are summarised, and an overview about suitable gasification processes is given. A literature survey indicated that a broad span of hydrogen relates to productivity depending on the feedstock, ranging from 15 to 300 g H2/kg of feedstock. Suitable gas treatment (upgrading and separation) is also covered, presenting both direct and indirect (chemical looping) concepts. Hydrogen production via gasification offers a high productivity potential. However, regulations, like frame conditions or subsidies, are necessary to bring the technology into the market.

Hydrogen is a versatile energy vector for a plethora of applications; nevertheless, its production from waste/residues is often overlooked. Gasification and subsequent conversion of the raw synthesis gas to hydrogen are an attractive alternative to produce renewable hydrogen. In this paper, recent developments in R&D on waste gasification (municipal solid waste, tires, plastic waste) are summarised, and an overview about suitable gasification processes is given. A literature survey indicated that a broad span of hydrogen relates to productivity depending on the feedstock, ranging from 15 to 300 g H2/kg of feedstock. Suitable gas treatment (upgrading and separation) is also covered, presenting both direct and indirect (chemical looping) concepts. Hydrogen production via gasification offers a high productivity potential. However, regulations, like frame conditions or subsidies, are necessary to bring the technology into the market.

The generation and management of wastes constitute today one of the major challenges of societies due not only to the huge amounts that are produced, but also to the need of implementing new treatments that can be more sustainable at an environmental level. The present work explored the production, management and policies adopted in the treatment of relevant typologies of solid wastes in Portugal, in particular, municipal solid wastes and construction and demolition wastes and sewage sludge, and tried to quantify the energetic potential that can be achieved through gasification processes. In addition, a techno-economic study to evaluate the feasibility of the construction and operation of a small-scale gasification plant was also developed. Results indicated that there are various methods which are considered more sustainable for the treatment of such wastes like bio-digestion, pyrolysis and gasification, and which may replace the current techniques of incineration or landfilling that are largely adopted but have caused a number of problems to communities and also to the environment. It was identified a huge potential to valorise these wastes to obtain electricity through gasification, since a significant portion of them are currently disposed of or eliminated in inadequate ways. The economic analysis revealed that it is possible to implement a small-scale gasification plant with financial viability and possible attractive economic results for investors. Construction of these units located in strategic points over the country may contribute for a more sustainable treatment and valorisation of solid wastes.

The generation and management of wastes constitute today one of the major challenges of societies due not only to the huge amounts that are produced, but also to the need of implementing new treatments that can be more sustainable at an environmental level. The present work explored the production, management and policies adopted in the treatment of relevant typologies of solid wastes in Portugal, in particular, municipal solid wastes and construction and demolition wastes and sewage sludge, and tried to quantify the energetic potential that can be achieved through gasification processes. In addition, a techno-economic study to evaluate the feasibility of the construction and operation of a small-scale gasification plant was also developed. Results indicated that there are various methods which are considered more sustainable for the treatment of such wastes like bio-digestion, pyrolysis and gasification, and which may replace the current techniques of incineration or landfilling that are largely adopted but have caused a number of problems to communities and also to the environment. It was identified a huge potential to valorise these wastes to obtain electricity through gasification, since a significant portion of them are currently disposed of or eliminated in inadequate ways. The economic analysis revealed that it is possible to implement a small-scale gasification plant with financial viability and possible attractive economic results for investors. Construction of these units located in strategic points over the country may contribute for a more sustainable treatment and valorisation of solid wastes.

This paper aims to briefly overview gasification technologies of biomass and heterogeneous wastes as a means for syngas production. For this purpose, an overview of the existing technologies, their main advantages, limitations, and costs, as well as commercial plants and projects (lower TRL) operating with these technologies and syngas applications is presented. The type of technology and operating parameters should be selected considering the quality of the syngas as it will dictate its end use. Syngas quality is determined by the combination of feedstock properties, type of technology and process operating conditions, and the scale of operation. For smaller projects with a capacity of up to 10 MWth, fixed-bed technologies have been a recurring choice, while fluidized bed reactors can have an installed capacity above 100 MWth and are, therefore, more suitable for medium- and large-scale projects. Fluidized bed gasification technology supports feedstock flexibility, has scale-up potential, and presents relatively low cost, making it a suitable solution and a frequent choice for heterogeneous waste gasification in medium- or large-scale projects. Commercializing waste gasification technology is already a reality. However, more efforts need to be made so that pilot and demonstration projects can overcome the technological and economic problems and move towards commercialization.

This paper aims to briefly overview gasification technologies of biomass and heterogeneous wastes as a means for syngas production. For this purpose, an overview of the existing technologies, their main advantages, limitations, and costs, as well as commercial plants and projects (lower TRL) operating with these technologies and syngas applications is presented. The type of technology and operating parameters should be selected considering the quality of the syngas as it will dictate its end use. Syngas quality is determined by the combination of feedstock properties, type of technology and process operating conditions, and the scale of operation. For smaller projects with a capacity of up to 10 MWth, fixed-bed technologies have been a recurring choice, while fluidized bed reactors can have an installed capacity above 100 MWth and are, therefore, more suitable for medium- and large-scale projects. Fluidized bed gasification technology supports feedstock flexibility, has scale-up potential, and presents relatively low cost, making it a suitable solution and a frequent choice for heterogeneous waste gasification in medium- or large-scale projects. Commercializing waste gasification technology is already a reality. However, more efforts need to be made so that pilot and demonstration projects can overcome the technological and economic problems and move towards commercialization.