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2 PhD student, El Colegio de la Frontera Sur [email protected] Date of receipt: March 4, Date of acceptance: July 15, Este estudio detalla la estimación de emisiones de gases de efecto invernadero (GEI) generados por desechos Los resultados revelaron que es posible planear medidas o combinar. The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without. Founded in , Meetic is the dating leader with over 9 million registered users. Why should you join us? High conversion rates; Affiliate commission up to 5.
The second objective is to build as well as to compare feasible strategies to reduce GHG emissions from USW to the medium and long term. Finally, the third objective is to present how the analysis of reduction scenarios could be used into decision-making. In order to achive these objectives this document is comprised of six sections. The first describes the "official" status of USW in Mexico.
The third part details calculation methods and reduction scenario building. The fourth segment shows results, while the fifth discusses them. Finally, conclusions are given in section six. Although each waste category is important on its own right, the USW management is imperious because of its ever-increasing production. Additional factors to focus on the USW management are: This increase was due to factors such as: Inthe Center generated 51 percent of the national grand total, followed by the Northern region with a 16 percent contribution and Mexico City with 12 percent.
The augmentation in USW generation during the period showed noticeable differences; regions that increased the most their USW generation were in decreasing order: However it varied per locality size; for example 90 percent of USW collection happened in metropolitan areas, 80 percent in medium cities, 26 percent in small cities and 13 percent in rural and semi-urban regions. By72 percent of USW was landfilled, 23 percent was disposed illegally in garbage dumps; and only five percent was recycled.
Existing regulation states that USW management is responsibility of municipalities.
It is common that authorities operate under different schemes, mostly under a contract regime for private companies to manage the whole household-landfill or part of either collection or final disposal the process.
According to official statistics Inegi, 2 tpd of USW were collected in Baja California by ; this figure is closed to the volume generated as Municipality contribution to daily tonnage of USW varied as follows: Taking into account the population of Baja California, the average amount collected per person was less than one kilogram per day: However there are marked differences in that figure per municipality; for tourists destinations such as Ensenada and Rosarito, this amount was: Whereas for the three remaining municipalities, the amount collected per person was smaller than the regional rate; for Mexicali was 0.
In general, waste collection is simple in the main cities of Baja California. Then it is transferred to landfills located outside city limits.
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There is not a formal process of waste separation, although there is informal recycling of aluminum cans, metals and other type of items. Currently there are five landfills in the State, one per municipality. These disposal sites partially fulfil the appropriate regulation NOMSemarnat ; the presence of scavengers at rubbish tips usually difficult landfill operations.
As previously mentioned, waste does not stop being a source of concern after being deposited in a landfill site, even "properly" disposed waste is subjected to processes that will end generating two main end products: As the interest of this document is on the relationship between USW and climate change, the following paragraphs aim to elucidate the generation and nature of landfill gas.
Biogas within a landfill is produced by the anaerobic decomposition of domestic refuse USW. It is a mixture of gases and is colourless with an offensive odour due to the traces of organosulphur compounds. Its production varies with time, stars within three months to one year after waste deposition; reaches its peak at years and tapers off over years Porteus, The production of landfill gas, however, is determined by a number of factors; these include but are not limited to the type and age of the waste buried in the landfill, the quantity and type of organic compounds in the disposed waste; and landfill conditions, in particular moisture content and temperature whose levels are influenced by the surrounding weather conditions.
Figure 2 depicts three main factors that influence landfill gas generation: As seen in Figure 2the "typical" composition of USW in Baja California is rich in carbon and hence likely to generate landfill gas by anaerobic decomposition of domestic refuse USW Semarnat, Given variations between municipalities over time, one may wonder if USW composition changes to the point of not being carbon rich.
But after careful revision observation holds. For example, by the composition of USW in Ensenada was: Whereas for Tijuana, it was reported that the main component of USW was: As seen, there is plentiful substrate to generate landfill gas in the end disposal sites of Baja California.
Excess of substrate is not enough, as gas generation will occur if the following landfill conditions are met Haug, From the annual environmental factors shown in Figure 2 is not easy to discern if anaerobic conditions will be achieved at regional landfills.
In the northwestern side of the State, maximum rates happen during winter November to March. In the oriental side of the region, rain also occurs during summer.
This precipitation patters could result in percolation and storage of rainwater in landfill sites, this could enhance moisture contents levels in time. As observed, environmental conditions are likely to propitiate anaerobic conditions inside local landfills in Baja California. Finally, the waste management options shown in Figure 2 are a brief summary of the conditions officially reported Inegi, During the period studied, many changes happened in the ways waste was handled in the Baja California municipalities.
For example, Tijuana disposed its waste in a dumpsite from until when it was transformed to a controlled dumpsite under private management. This controlled dumpsite reached the end of its useful life in Bythe local government bought a piece of land and put it under private management to built and run a landfill site for a lease of 20 years. The beginning of the new landfill operations brought many changes in particular limited operation due to access to the site because of an unpaved and rough roadpartial abandonment of transfers stations and shortages of garbage trucks; these and further changes caused a crisis in same that was resolved in ; in that year it was reported that 70 illegal dumping sites were closed and 3 tonnes of waste were collected; at the same time it was announced the opening of a recycling center Cuoto, As noticed, the generation of gas is likely to occur in the ways waste has been and is managed in Baja California.
Population data were taken from the National Censuses Inegi,, Population for the in-between years was calculated by interpolation. Data on the amount and composition of waste were obtained from Semarnat In order to compute the carbon content in USW, first its average composition was estimated using official data reported from to results are shown in Figure 2.
Then the different percentages of organic substances in USW were multiplied by their appropriate default factor and summed up, such multiplication was equal to 0.
Methane emissions were transformed to equivalent units of CO2, by multiplying them times The waste management options identified for Baja California are three: For the period studied tothe MCF was taken as 1; this was decided in a way to balance the variability of waste management options used in the municipalities of Baja California. This assumption is likely to overestimate in nearly 20 percent methane emissions in the first third of the period; however, this amount aims to compensate for known but not quantified open pit burning activities.
Despite this assumption, it is likely that the methane emissions in Baja California for the period are conservative estimations. For the period to population data was extrapolated using the linear model shown in Equation 2: Once population projections were ready, the USW expected volume was computed using the multiplicative Winters model; this was chosen because fairly describes seasonal changes that are not constant; in addition it is appropriate to apply when dealing with growing seasonal trends.
To apply the Winters model the Equation 3 was used: Series random factor, volume of USW at t Series trend slope of the trend componentincrement of the USW volume at t Once USW volumes were forecasted from to in five-year periods. The expected GHG emissions were calculated applying Equation 1. It was assumed that USW composition remain constant for the forecasted period. However, changes in the constitution of USW compounds could be used to update the degradable organic carbon fraction in USW.
Reduction Scenarios of GHG from USW To build reduction scenarios, selected technologies and strategies were chosen after careful review to identified the best and more suitable alternatives for the region in terms of low technical needs, accessible costs and feasibility of implementation. In USW generated 5.
In methane emissions reached Forecasted methane emissions tended to growth at a rate of 0. Projection results indicated that By methane emissions will reach Forecasted results defined the BAU or inertia scenario; these computations were used as the baseline to compare reductions brought by mitigation actions considered in the other seven scenarios.
Results for estimated and forecasted methane emissions are depicted in Figure 3. The former are shown in silver and the latter in graphite. Radiative energy losses become increasingly important higher in the atmosphere, largely because of the decreasing concentration of water vapor, an important greenhouse gas.
It is more realistic to think of the greenhouse effect as applying to a "surface" in the mid- tropospherewhich is effectively coupled to the surface by a lapse rate. The simple picture also assumes a steady state, but in the real world, there are variations due to the diurnal cycle as well as the seasonal cycle and weather disturbances.
Solar heating only applies during daytime. During the night, the atmosphere cools somewhat, but not greatly, because its emissivity is low. Diurnal temperature changes decrease with height in the atmosphere. Within the region where radiative effects are important, the description given by the idealized greenhouse model becomes realistic.
It reradiates in all directions, both upwards and downwards; in equilibrium by definition the same amount as it has absorbed. This results in more warmth below. Increasing the concentration of the gases increases the amount of absorption and reradiation, and thereby further warms the layers and ultimately the surface below. Greenhouse gases Main article: Greenhouse gas By their percentage contribution to the greenhouse effect on Earth the four major gases are: