During the past decade, there has been substantial interest in recovering energy from many unwanted byproducts from industries and municipalities. Co-combustion of these products with coal seems to be the most cost-effective approach. The combustion process typically results in emissions of pollutants, especially fine particles and trace elements. This paper presents the results of an experimental study of particulate emission and the fate of 13 trace elements (arsenic [As] [Zn]) during combustion tests of recovered paint solids (RPS) and coal. The emissions from combustions of coal or RPS alone were compared with those of co-combustion of RPS with subbituminous coal. The distribution/partitioning of these toxic elements between a coarse-mode ash (particle diameter [d p ] Ͼ 0.5 m), a submicrometer-mode ash (d p Ͻ 0.5 m), and flue gases was also evaluated. Submicrometer particles generated by combustion of RPS alone were lower in concentration and smaller in size than that from combustion of coal. However, co-combustion of RPS and coal increased the formation of submicrometer-sized particles because of the higher reducing environment in the vicinity of burning particles and the higher volatile chlorine species. Hg was completely volatilized in all cases; however, the fraction in the oxidized state increased with co-combustion. Most trace elements, except Zn, were retained in ash during combustion of RPS alone. Mo was mostly retained in all samples. The behavior of elements, except Mn and Mo, varied depending on the fuel samples. As, Ba, Cr, Co, Cu, and Pb were vaporized to a greater extent from cocombustion of RPS and coal than from combustion of either fuel. Evidence of the enrichment of certain toxic elements in submicrometer particles has also been observed for As, Cd, Cr, Cu, and Ni during co-combustion. INTRODUCTIONEnergy is an issue of great importance in the current times. This concern has not only called for extensive research and development in renewable energy and energy-efficient technologies, but has also increased interest in recovering energy from many unwanted byproducts from municipal and industrial sources to reduce consumption of fossil fuels. [1][2][3][4][5] Recovered paint solids (RPS) from automobile paint operations are one such industrial byproduct that has high energy content (ϳ24.9 MJ/kg) and are currently disposed into a landfill. Paint solids are generated from overspray liquid paint and clear-coating during the spraying process of an automobile paint operation. The overspray paint and overspray clear-coating are collected in a water solution, which contains a defoamer and a detackifier for charge neutralization of the overspray. The content is then solidified via flocculation, skimming, and dewatering processes. For a standard size vehicle, approximately 2.5 kg of paint solids

Studies show that agricultural and animal feeding operations (AFOs) contribute a considerable amount of ammonia (NH 3 ) to the atmosphere. Agricultural NH 3 emissions are recognized as an important air quality issue. Biological decomposition of manure from dairy operations results in emissions of NH 3 and other gases. There is a need to determine NH 3 emission factors (EFs) to compile annual NH 3 inventories. NH 3 emissions should be estimated from different ground-level area sources (GLAS) including open-lots (cows on earthen corrals), free-stalls (cows in barns), manure composting sites, primary and secondary lagoons, separated solids, and milking parlors. A protocol using flux chambers was used to determine NH 3 EFs from different GLAS of a free-stall dairy in central Texas. Data including NH 3 emissions from GLAS were collected during winter and summer seasons. NH 3 concentration measurements were made using chemiluminescence-based analyzers. The EFs for the free-stall dairy were estimated as 11 Ϯ 4.9 (confidence interval [CI]) kg-NH 3 ⅐ yr Ϫ1 ⅐ head Ϫ1 for summer and 4.7 Ϯ 4.9 kg-NH 3 ⅐ yr Ϫ1 ⅐ head Ϫ1 for winter. The estimated annual NH 3 EF was 8.4 Ϯ 4.9 kg-NH 3 ⅐ yr Ϫ1 ⅐ head Ϫ1 for this free-stall dairy. This seasonal difference was attributed to temperature, loading rate of dairy waste, and manure bacterial activity of GLAS. In winter, composted manure and free-stalls contributed nearly 77% of the total NH 3 emissions for the dairy; however, in summer, two lagoons at the dairy contributed 65% of the overall NH 3 emissions.