Greenhouse gas emissions from production and use of used cooking oil methyl ester as transport fuel in Thailand

Biodiesel, produced from various vegetable and/or animal oils, is one of the most promising alternative fuels for transportation in Thailand. Currently, the waste oils after use in cooking are not disposed adequately. Such oils could serve as a feedstock for biodiesel which would also address the waste disposal issue. This study compares the life cycle greenhouse gas (GHG) emissions from used cooking oil methyl ester (UCOME) and conventional diesel used in transport. The functional unit (FU) is 100 km transportation by light duty diesel vehicle (LDDV) under identical driving conditions. Life cycle GHG emissions from conventional diesel are about 32.57 kg CO₂-eq/FU whereas those from UCOME are 2.35 kg CO₂-eq/FU. The GHG emissions from the life cycle of UCOME are 93% less than those of conventional diesel production and use. Hence, a fuel switch from conventional diesel to UCOME will contribute greatly to a reduction in global warming potential. This will also support the Thai Government's policy to promote the use of indigenous and renewable sources for transportation fuels.     

Air pollutant emissions from rice straw open field burning in India, Thailand and the Philippines

Rice is a widely grown crop in Asia. China (30%) and India (21%) contribute to about half of the world's total rice production. In this study, three major rice-producing countries in Asia are considered, India, Thailand and the Philippines (the later two contributing 4% and 2% of the world's rice production). Rice straw is one of the main field based residues produced along with this commodity and its applications vary widely in the region. Although rice production practises vary from one country to another, open burning of straw is a common practice in these countries.In this study, an approach was followed aiming at (a) determining the quantity of rice straw being subject to open field burning in those countries, (b) congregating pollutant specific emissions factors for rice straw burning, and (c) quantifying the resulting air pollutant emissions. Uncertainties in the results obtained as compared to a global approach are also discussed.     

Spatial patterns reveal negative density dependence and habitat associations in tropical trees

Understanding how plant species coexist in tropical rainforests is one of the biggest challenges in community ecology. One prominent hypothesis suggests that rare species are at an advantage because trees have lower survival in areas of high conspecific density due to increased attack by natural enemies, a process known as negative density dependence (NDD). A consensus is emerging that NDD is important for plant-species coexistence in tropical forests. Most evidence comes from short-term studies, but testing the prediction that NDD decreases the spatial aggregation of tree populations provides a long-term perspective. While spatial distributions have provided only weak evidence for NDD so far, the opposing effects of environmental heterogeneity might have confounded previous analyses. Here we use a novel statistical technique to control for environmental heterogeneity while testing whether spatial aggregation decreases with tree size in four tropical forests. We provide evidence for NDD in 22% of the 139 tree species analyzed and show that environmental heterogeneity can obscure the spatial signal of NDD. Environmental heterogeneity contributed to aggregation in 84% of species. We conclude that both biotic interactions and environmental heterogeneity play crucial roles in shaping tree dynamics in tropical forests.     

Analyzing the spatial structure of a Sri Lankan tree species with multiple scales of clustering

Clustering at multiple critical scales may be common for plants since many different factors and processes may cause clustering. This is especially true for tropical rain forests for which theories explaining species coexistence and community structure rest heavily on spatial patterns. We used point pattern analysis to analyze the spatial structure of Shorea congestiflora, a dominant species in a 25-ha forest dynamics plot in a rain forest at Sinharaja World Heritage Site (Sri Lanka), which apparently shows clustering at several scales. We developed cluster processes incorporating two critical scales of clustering for exploring the spatial structure of S. congestiflora and interpret it in relation to factors such as competition, dispersal limitation, recruitment limitation, and Janzen-Connell effects. All size classes showed consistent large-scale clustering with a cluster radius of approximately 25 m. Inside the larger clusters, small-scale clusters with a radius of 8 m were evident for recruits and saplings, weak for intermediates, and disappeared for adults. The pattern of all trees could be divided into two independent patterns: a random pattern (nearest neighbor distance > 8 m) comprising approximately 12% of the trees and a nested double-cluster pattern. This finding suggests two independent recruitment and/or seed dispersal mechanisms. Saplings were several times as abundant as recruits and may accumulate several recruit generations. Recruits were only weakly associated with adults and occupied about half of the large-scale clusters, but saplings almost all. This is consistent with recruitment limitation. For approximately 70% (95%) of all juveniles the nearest adult was less than 26 m away (53 m), suggesting a dispersal limitation that may also be related to the critical large-scale clustering. Our example illustrates the manner in which the use of a specific and complex null hypothesis of spatial structure in point pattern analysis can help us better understand the biology of a species and generate specific hypotheses to be further investigated in the field.     

Effectiveness of participatory planning for community management of fisheries in Bangladesh

This study provides statistical evidence that support for community-based management of resources was more effective when initiated through a process known as participatory action plan development (PAPD). Thirty-six sites were studied where community management of fisheries was facilitated by NGOs. All involved community participation and establishing local fisheries management institutions. However, communities were able to take up more conservation-related interventions and faced fewer conflicts in the 18 sites where a PAPD was the basis for collective action and institution development. This indicates the value and effectiveness of adopting good practice in participatory planning, such as PAPD, which helps diverse stakeholders find common problems and solutions for natural resource management.     

Effects of 10% biofuel substitution on ground level ozone formation in Bangkok,Thailand

The Thai Government's search for alternatives to imported petroleum led to the consideration of mandating 10% biofuel blends (biodiesel and gasohol) by 2012. Concerns over the effects of biofuel combustion on ground level ozone formation in relation to their conventional counterparts need addressing. Ozone formation in Bangkok is explored using a trajectory box model. The model is compared against O₃, NO, and NO₂ time concentration data from air monitoring stations operated by the Thai Pollution Control Department. Four high ozone days in 2006 were selected for modeling. Both the traditional trajectory approach and a citywide average approach were used. The model performs well with both approaches but slightly better with the citywide average. Highly uncertain and missing data are derived within realistic bounds using a genetic algorithm optimization. It was found that 10% biofuel substitution will lead to as much as a 16 ppb peak O₃ increase on these four days compared to a 48 ppb increase due to the predicted vehicle fleet size increase between 2006 and 2012. The approach also suggests that when detailed meteorological data is not available to run three dimensional airshed models, and if the air is stagnant or predominately remains over an urban area during the day, that a simple low cost trajectory analysis of O₃ formation may be applicable.     

Photolysis of oxyfluorfen in aqueous methanol

Photolysis of oxyfluorfen, an herbicide of the nitrodiphenyl ether class, was studied in aqueous methanol under UV and sunlight. UV irradiation was carried out in a borosilicate glass photoreactor (containing 250 ppm oxyfluorfen in 50% aqueous methanol) equipped with a quartz filter and 125 watt mercury lamp (maximum output 254 nm) at 25 ± 1°C. Sunlight irradiation was conducted at 28 ± 1°C in borosilicate Erlenmeyer flasks containing 250 ppm oxyfluorfen in 50% aqueous methanol. The samples from both the irradiated conditions were withdrawn at a definite time interval and extracted to measure oxyfluorfen content by gas chromatography-flame ionization detector for rate study. The half-life values were 20 hours and 2.7 days under UV and sunlight exposure, respectively. Photolysis of oxyfluorfen yielded 13 photoproducts of which three were characterized by infrared spectrophotometer and ¹H NMR and ¹³C NMR spectroscopy. The rest of the photoproducts were identified by gas chromatography-mass spectrometry (GC-MS) and thin layer chromatography (TLC). An ionization potential 70 eV was used for electron impact-mass spectrometry (EI-MS) and methane was used as reagent gas for chemical ionization-mass spectrometry (CI-MS). Two of the photoproducts were also synthesized for comparison. The main phototransformation pathways of oxyfluorfen involved nitro reduction, dechlorination, and hydrolysis as well as nucleophiles displacement reaction.