L. Tarelho

Critical aspects of biomass ashes utilization in soils: composition, leachability, PAH and PCDD/F

Bottom and fly ashes streams collected along a year in several biomass thermal plants were studied. The bulk composition of ashes and other chemical characteristics that may impact soil application showed a high variability depending on the ash stream, combustion technology and ash management practice at the power plants. The acid neutralization capacity (ANC) and metals availability for leaching at fixed pH 7 and 4 was performed according with EA NEN 7371, as a quick evaluation method to provide information on the long-term behavior of ashes, regarding heavy metals and also plant nutrients release. Also the pH dependence leachability study was performed according to CEN/TS 14429 for predicting the leaching behavior under different scenarios. Leachability profiles were established between pH 3 and 12, allowing to distinguish different solubility control phenomena of toxic heavy metals (Cu, Cr, Mn, Ni, Zn, Pb) as well as other salts (Ca, K, Mg, Na, Cl). The ANC of fly ashes at pH 4 (3.6-9.6 molH(+)/kg) were higher than that observed for the bottom ashes (1.2-2.1 molH(+)/kg). Ashes were also characterized for persistent organic pollutants (POP), such as polycyclic aromatic hydrocarbons (PAH) and paradibenzodioxines and furanes (PCDD/F). Contents were found to be much higher in fly ash than in bottom ash streams. None of the PAH levels did reach the current national limit value of sewage sludge application in soils or the guide value for ash in north European countries. However, PCDD/F contents, which are not regulated, varied from non-detectable levels to high amounts, regardless the level of loss on ignition (LOI) or unburned carbon content in fly ashes. Given the current ash management practices and possible use of blends of bottom and fly ash streams as soil conditioners resembles clear the urgent need to regulate ash utilization in soils, incorporating limit values both for heavy metals, PAH and PCDD/F.

Impact of forest biomass residues to the energy supply chain on regional air quality.

The increase of the share of renewable energy in Portugal can be met from different sources, of which forest biomass residues (FBR) can play a main role. Taking into account the demand for information about the strategy of FBR to energy, and its implications on the Portuguese climate policy, the impact of energy conversion of FBR on air quality is evaluated. Three emission scenarios were defined and a numerical air quality model was selected to perform this evaluation. The results reveal that the biomass thermal plants contribute to an increment of the pollutant concentrations in the atmosphere, however restricted to the surrounding areas of the thermal plants, and most significant for NO₂ and O₃.

Emissions from the combustion of eucalypt and pine chips in a fluidized bed reactor.

Interest in renewable energy sources has increased in recent years due to environmental concerns about global warming and air pollution, reduced costs and improved efficiency of technologies. Under the European Union (EU) energy directive, biomass is a suitable renewable source. The aim of this study was to experimentally quantify and characterize the emission of particulate matter (PM2.5) resulting from the combustion of two biomass fuels (chipped residual biomass from pine and eucalypt), in a pilot-scale bubbling fluidized bed (BFB) combustor under distinct operating conditions. The variables evaluated were the stoichiometry and, in the case of eucalypt, the leaching of the fuel. The CO and PM2.5 emission factors were lower when the stoichiometry used in the experiments was higher (0.33±0.1 g CO/kg and 16.8±1.0 mg PM2.5/kg, dry gases). The treatment of the fuel by leaching before its combustion has shown to promote higher PM2.5 emissions (55.2±2.5 mg/kg, as burned). Organic and elemental carbon represented 3.1 to 30 wt.% of the particle mass, while carbonate (CO3(2-)) accounted for between 2.3 and 8.5 wt.%. The particulate mass was mainly composed of inorganic matter (71% to 86% of the PM2.5 mass). Compared to residential stoves, BFB combustion generated very high mass fractions of inorganic elements. Chloride was the water soluble ion in higher concentration in the PM2.5 emitted by the combustion of eucalypt, while calcium was the dominant water soluble ion in the case of pine.

Use of a geographic information system to find areas for locating of municipal solid waste management facilities

Municipal solid waste (MSW) management is a pressing concern for Goiás State, Brazil. Of the states 246 municipalities, only 16 send their waste to licensed landfills. This means that 93% of the cities in Goiás dispose of their MSW inappropriately, in dumps or unlicensed landfills. This practice poses a danger to both the environment and to public health. On this basis, the goal of this study was to survey potential landfill sites in Goiás. A geographic information system tool was used to first identify Goiás landfills and dumps and then examine them, to check whether they are located in legally restricted areas. This tool cross-references morphology, land use and occupancy, conservation of the environment, public health and population projections for 2040. It then outputs restriction-free areas that are suitable for landfill construction. The results indicate that, by 2040, Goiás will have 59,500 km2 available for landfills, i.e., 17% of the states total area. Conversely, 60% of the states geographical area will be off limits for landfill construction. The most urgent need is in the Goiânia Metropolitan area, which will be producing about 40%, of 6,850 t⋅day-1, of the MSW generated in the state by 2040. This metropolitan area will have the smallest restriction-free area for landfill construction (832 km2). A total of 235 MSW final disposal facilities were identified in Goiás: 15 licensed landfills, 23 unlicensed landfills and 197 dumps. Of these, 15 are in permitted areas, 38 are in areas subject to approval and 182 are in restricted areas. These numbers highlight the need for Goiás municipalities to terminate and/or readjust landfills and unlicensed dumps and to set up new MSW management facilities that conform to the legal and environmental requirements and the expected population growth.

Atmospheric emissions from pellet energy supply chain: a Portuguese case study

The increased knowledge and awareness of the impacts of climate change on global environment and its linkage to the greenhouse gases emissions (GHG) has resulted in an expansion of a set of European policies during the past decades. Since the energy sector is one of the major contributors of GHG emissions, the need to mitigate the climate change impacts has led to a diversification of the world’s energy mix, promoted by an increased demand for renewable energy sources. The Portuguese government considers the use of biomass for pellet production as a key factor to accomplish the national goals established in the energy strategy for renewable energy sources. However, few studies have evaluated the potential impact of this type of bioenergy on air quality. In this context, a case study was selected to estimate the atmospheric emissions of the pellet energy supply chain in Portugal. A comparison of both pellet and forest biomass residue energy supply chain in terms of atmospheric emissions was performed. Results show that the pellet production is the process with the largest contribution to CO2e and SOx emissions (with a contribution higher than 90%); the domestic combustion is mainly responsible for total suspended particle and CO emissions; NOx is a result of both production and combustion processes, and non-methane volatile organic compound is a result of the forest exploitation. Compared with the forest biomass residue energy supply chain, the pellet energy supply chain produces higher atmospheric emissions.

Characterization of Exhaust Emissions from A EURO 5 Light Passenger Vehicle Using Biodiesel Blends

The authors have performed experiments using a EURO 5 light passenger vehicle, operated over the New European Driving Cycle (NEDC). Fuel blends containing 7% (B7) and 20% (B20) of biodiesel (84% soyabean/16% palm) in petroleum-based diesel were tested and compared with a diesel fuel (B0). The exhaust gases emissions were assessed for NO, NO₂, SO₂ and volatile organic compounds (VOC), including a speciation analysis of VOC. The experiment reveals that biodiesel blends improve the combustion efficiency, NO and SO₂ emissions, and increasing NO₂ and total VOC emissions. The VOC speciation analysis suggests that the type and fraction of VOC existent in exhausted gases is fuel dependent, changing their presence and concentrations according to the fuel used. Additionally, the concentration of the three main VOC species in exhaust gases from B0 (benzene, toluene and octane) decrease 60-80% if a B20 blend is used. This experimental study contributes to a better characterization of the emission factors of EURO 5 light passenger vehicles using diesel/biodiesel blends and to a better understanding of the impact of the use of biodiesel blends on pollutant emissions.