Seventh Mediterranean Combustion Symposium

This chapter discusses results of current and future-projected water cycle components over the Mediterranean region. Results are presented from an ensemble of CMIP3 multi-model simulations (here after referred to as Mariotti) and from the Meteorological Research Institute’s (MRI) 20 km grid global climate model. Referred to as CMIP3 results are surprisingly close to MRI. The projected mean annual change in the rate of precipitation (P) across the region (for sea and land), is projected to decrease by the end of the 21st century by −11% and −10%, respectively, for the MRI and Mariotti runs. Projected changes in evaporation (E) are +9.3% (sea) and −3.6% (land) for JMA runs, compared to +7.2% (sea) and −8.1% (land) in Mariotti’s study. However, no significant difference of the projected change in P–E over the sea body is found between these two studies. E over the eastern Mediterranean was projected to be higher than the western Mediterranean, but the P decrease was projected to be lower. The net moisture budget, P–E, shows that the eastern Mediterranean is projected to become even drier than the western Mediterranean. The river model projects significant decreases in water inflow to the Mediterranean of about −36% by the end of the 21st century in the MRI run (excluding the Nile). The Palmer Drought Severity Index (PDSI), which reflects the combined effects of precipitation and surface air temperature (Ts) changes, shows a progressive and substantial drying of Mediterranean land surface over this region since 1900 (−0.2 PDSI units/decade), consistent with a decrease in precipitation and an increase in Ts (not shown). The last section of this chapter reports on components of the hydrological cycle from five climate model projections for the Mediterranean region. Three of these models have an interactive Mediterranean Sea (MPI, ENEA, Meteo-France), and two are versions of the Met Office Hadley Centre regional model (HadRM3-MOSES2, HadRM3-MOSES1) with different land surface schemes. The focus of this section is upon changes in evapotranspiration, and how these changes could be important in controlling available renewable water resources (runoff). These r indicate that rainfall is projected to decline across large areas by over −20% in all of the models, although in the Meteo-France model the central part of the northern Mediterranean domain, ie. southern Italy and Greece, has areas of increase as well as decrease. In pockets of Turkey, the eastern Mediterranean, Italy and Spain, projections from the MPI, HadRM3-MOSES2, HadRM3-MOSES1 and ENEA models are for decreases in summer rainfall of −50% or more. Consistent with the global model projections, each of the five high-resolution models simulate increasing temperatures and decreasing evapotranspiration and precipitation for much of the Mediterranean region by the middle of this century. The strongest and most widespread reductions in precipitation are projected to occur in the spring and summer seasons, while reductions in evapotranspiration are greatest in summer.

Despite the reduced extension and spatial fragmentations of the Mediterranean region, its biogeodiversity (biologic, edaphic, geomorphic, climatic and hydrologic) is among the highest of the planet. Quantitative data published recently show great links between arid and Mediterranean soilscapes. Mediterranean soilscapes are extremely fragile and therefore potential changes due to climatic and anthropic causes may lead to desertification. Thus, future CO2 warming will increase current desertization processes. Land degradation in arid and semiarid Mediterranean regions (rainfall less than 600 mm) is highly analogous to desertification.

Oxy-fuel combustion is a viable technology for new and existing coal-fired power plants, as it facilitates carbon capture and thereby, can reduce carbon dioxide emissions. The use of biomass as an energy source is another popular strategy to reduce carbon dioxide emissions as they are considered nearly carbon dioxide neutral. If the use of biomass is combined with oxy-fuel combustion, negative net emissions of carbon dioxide are possible. This work examined the particulate emissions from combustion of pulverized biomass residues burning in either conventional or oxy-fuel environments. Combustion of three biomasses (olive residue, corn residue, and torrefied pine sawdust) occurred in a laboratory-scale laminar-flow drop tube furnace (DTF) heated to 1400 K. The O2 mole fraction was increased from 20% to 60% in N2 environments while a range of 30% to 60% O2 mole fractions were used in CO2 environments to represent plausible dry oxy-fuel combustion conditions. Submicron particulate matter (PM1) emission yields of all three fuels were typically lower in O2/CO2 environments than in O2/N2 environments. When the oxygen mole fraction was increased, the PM1 yields typically increased. The mass fractions of submicron particulate matter (PM1/PM18) collected from biomass combustion were higher than those of coal combustion. PM1 constituted approximately 50 wt% of the collected ash particles in PM18 in each environment, whereas the corresponding submicron emissions from coal constituted approximately 20 wt%. Changing the background gas had little effect on the chemical composition of the PM1 particles. Unlike the submicron particles collected from coal which contained high amounts of silicon and aluminum, high amounts of alkalis (potassium, calcium, and sodium) and chlorine were the major elements observed in PM1 from the biomasses. In addition, phosphorous and sulfur also existed in high amounts in PM1 of corn residue. Super-micron particles (PM1-18) yields exhibited no clear trend when the background gas was changed or when the oxygen mole fraction was increased. The composition of these particles reflected the bulk ash composition of the parent fuels. Olive residue resulted in by far the largest particulate yields, while torrefied pine sawdust had the lowest. The yields of these two biomasses were analogous with the ash contents of the parent fuels. The particulate yields of corn residue, however, were lower than expected when compared to the parent fuel's ash content. This was attributed to the high phosphorous and sulfur contents of this fuel which might have increased its deposition tendencies in the laboratory furnace.

Surface water bodies are constantly exposed to pollutant inputs of different origin. Wastewater effluents discharge directly on the receiving natural streams, and are among the main entrance pathways for sulfonamides. Strong contrast between seasons, with the consequent fluctuations in the flow rates, and heavy contamination pressures from extensive urban, industrial, and agricultural activities are characteristics of water courses located in the Mediterranean area. The low base flows of Mediterranean rivers makes their hydrology cycle heavily dependent on wastewater inputs, and therefore removal efficiencies of wastewater treatment plants are key to the health of the aquatic ecosystem.

The paper describes the U.S. EPA`s biomass fuel analytical laboratory at its Environmental Research Center in Research Triangle Park, NC. There is increasing interest in utlizing biomass-based fuels in thermal energy systems as an effective means for global warming remediation. The laboratory is examining biomass fuels and the variation in products of incomplete combustion (PICs) with combustion conditions. The objectives are to evaluate the kinetics of combustion and emission characteristics (e.g., structure and composition) of representative samples of relevant types of biomass fuels by studying (1) the local pyrolysis and combustion processes and products, and (2) the overall degradation rate as influenced by heat transmission. Biomass fuel samples will be examined by thermogravimetric analysis with an on-line Fourier transform infrared spectrometer (TGA-FTIR). EPA has built a prototype TGA, capable of handling a 100 g sample with 1 microgram resolution for this laboratory. This instrument is capable of heating the sample to 1200 C. Samples can be pyrolyzed and combusted sequentially by automated gas switching.

An experimental study was undertaken to assess the combustion characteristics and emissions of SO{sub 2}, NO{sub x} and CO{sub 2} gases from ground waste tires. Results were contrasted with those obtained from burning pulverized coal. Laboratory bench-scale experiments were conducted in a drop-tube, laminar-flow furnace, in air at fuel-lean conditions, at gas temperatures ranging from 1300 K to 1600 K. Two particle size cuts were burned from both materials, 75-90 {mu}m and 180-212 {mu}m. Blends of coal and tire particles, at equal weight ratios, were also burned. Pyrometric and cinematographic observations revealed that the coal particles exhibited distinct volatile and char combustion phases, while tire particles exhibited a distinct primary volatile phase followed by a char combustion phase, which was accompanied by burning of secondary pyrolysis products. SO{sub 2} emissions of burning ground tires increased from 160 to 500 ppm as the temperature increased from 1300 K to 1600 K. Combustion of coal produced SO{sub 2} emissions in the neighborhood of 200-300 ppm (corresponding to 40 to 60 wt% of its sulfur content) independent of the gas temperature. The blend of coal and tire particles (equal mass ratios) exhibited SO{sub 2} values which fell in between the above. NO{sub x}more » emissions were constant at approximately 175 ppm for tire crumb (corresponding to approximately 45 wt% of its fuel nitrogen content) and 625 ppm for coal (corresponding to 55 wt% of its fuel nitrogen content) in the temperature range studied. CO{sub 2} emissions from tire were 8-9 molar %, while for coal particles they were 5-7 molar %; the upper limits corresponded to approximately 100% combustion efficiency. As a means to reduce the SO{sub 2} emissions, pulverized coal and tire crumb were fluidized together with particles of a calcium bearing sorbent - calcium magnesium acetate (CMA). CMA has been identified as an effective SO{sub 2} scrubbing agent in previous studies.« less

Three wood burning stoves were modified by the addition of preheated secondary air systems to keep burn volatile gases given off during the initial stage of combustion. This report describes the modifications and the performance of the stoves after modification. Stoves tested during the year's study included a Jotul 118, a Garrison IV and a Hearthstone I. After modification, total particulate emissions decreased in the three stoves by 56%, 69% and 4%, respectively. Flue gas CO/sub 2/ (a by-product of combustion and an indicator of the completeness of combustion) increased by 15%, 15% and 17%, respectively. Temperatures in the secondary combustion zones increased by 17%, 50% and 6%. On the basis of these measurements, other internal temperatures and visual observations, we believe the modifications significantly increased the combustion efficiencies of the Jotul and the Garrison. No improvement was discerned in the Hearthstone's performance (possibly due to unrealistic burn rate compared to firebox size). The design concepts developed, refined and tested under this year's study should be readily applicable to the majority of residential wood stoves on the market.