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El turismo rural en Costa Rica representa una etapa avanzada del ecoturismo, pues incorpora como protagonista de su desarrollo a las comunidades locales, que se convierten en los encargados de proteger y poner en valor económico el patrimonio natural y cultural. A nivel nacional el sector se articula en dos redes: la Red COOprena R.L. y la Asociación Comunitaria de Turismo Rural, quienes desarrollan programas de apoyo y promoción dirigidos a las asociaciones y cooperativas socias. Con el objetivo de profundizar en el conocimiento del funcionamiento del sector, en este artículo se han identificando y clasificado por tipologías las principales asociaciones locales de turismo rural comunitario y, a partir de un análisis de más de 50 casos, se perfilan las principales características. Todo ello debe permitir entender mejor los mecanismos y factores que permiten o dificultan el éxito de una iniciativa local.

The energetic and environmental performance of production and distribution of the Brassica carinata biomass crop in Soria (Spain) is analysed using life cycle assessment (LCA) methodology in order to demonstrate the major potential that the crop has in southern Europe as a lignocellulosic fuel for use as a renewable energy source. The Life Cycle Impact Assessment (LCIA) including midpoint impact analysis that was performed shows that the use of fertilizers is the action with the highest impact in six of the 10 environmental categories considered, representing between 51 % and 68% of the impact in these categories. The second most important impact is produced when the diesel is used in tractors and transport vehicles which represents between 48% and 77%. The contribution of the R carinata cropping system to the global warming category is 12.7 g CO eq. MJ(-1) biomass produced. Assuming a preliminary estimation of the B. carinata capacity of translocated CO(2) (631 kg CO ha(-1)) from below-ground biomass into the soil, the emissions are reduced by up to 5.2 g CO eq. MJ(-1). The production and transport are as far as a thermoelectric plant of the B. carinata biomass used as a solid fuel consumes 0.12 MJ of primary energy per 1 MJ of biomass energy stored. In comparison with other fossil fuels such as natural gas, it reduces primary energy consumption by 33.2% and greenhouse gas emission from 33.1 % to 71.2% depending on whether the capacity of translocated CO(2) is considered or not. The results of the analysis support the assertion that B. carinata crops are viable from an energy balance and environmental perspective for producing lignocellulosic solid fuel destined for the production of energy in southern Europe. Furthermore, the performance of the crop could be improved,

The object of this work was to determine and model the air exchange rate of greenhouses with insect-proof screens over the vents. Experimental tests were conducted on multi-span tunnel greenhouse with two types of ventilation openings, one with continuous roof vents and the other with an insect-proof screen which was able to replace a flexible roll-up plastic cover. Ventilation rates of the experimental greenhouses were measured using the tracer gas technique. Discharge coefficients were determined in a 1:3 scale model replica of the experimental greenhouses. A simple model that includes the global effect of the wind on the greenhouse ventilation was developed and compared with the measured air exchange values. The main results determine the reduction in the discharge coefficient when an insect-proof screen is incorporated. It was found that vents located in lateral spans have a higher discharge coefficient than those located in central spans. Some practical considerations for the design of more efficient ventilation systems can be derived from this fact. The global wind effect coefficient was found to be dependent on the type of vent, insect-proof screen and wind speed. Some results are not in agreement with others previously published, but obtained under different environmental conditions. This coefficient is derived from empirical measurements which makes its general application questionable. In spite of its simplicity, the theoretical model describes accurately the ventilation rate of the greenhouse with both types of vents. The roll-up roof vent provides a ventilation rate about three times greater than the continuous roof vent. It has an acceptable air exchange, while acting as a barrier against the entrance of undesirable pests. (C) 1999 Silsoe Research Institute

A laboratory method for the physical simulation of natural ventilation by thermal effects in greenhouses is presented. Scale models of a tunnel greenhouse were constructed and immersed in a water tank. A solution of salty water and black dye was injected to produce density differences that simulated the buoyancy flux due to the heating of the greenhouse air. Flow was visualized using a video camera and images were processed in order to relate pixel intensities and density increments. Scaling laws allowed the calculation of the temperature increments associated with relative density increments for each experiment. Experiments with Reynolds numbers Re ranging from 101 to 1350 were carried out in order to estimate the minimum Re necessary to neglect Viscosity effects. For the type of greenhouse under study, this minimum value of Re was determined to be close to 900. The increments of temperature obtained from laboratory experiments were about 25% lower than those obtained by the theoretical model developed by Bruce. The method could be a useful tool for testing ventilation arrangements in greenhouse structures and for comparing results with those obtained by calculation based on models. (C) 1999 Silsoe Research Institute.