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Mango (Mangifera indica L.) is one of the most widely cultivated fruits in the tropics as well as other coastal subtropical climate areas, existing around 160 varieties of mangoes in the world, grown in more than 90 countries. Its consumption has greatly increased worldwide over the last decades. The world production of these fruits has been rising in recent years, with a production of more than 46 million tons in 2016, 23% above the production in 2009. India is the largest producer in the world by a very wide margin - more than 28% of the total produced worldwide in 2016. Next, China, Thailand and Indonesia produced 3.61, 2.25 and 1.83 million tons in that same year, respectively. Potential high energy content of the residual biomass produced in the mango sector is barely known. Mango stone weight accounts for 30–45% of the total fruit weight which completely goes off as waste. Hence, the aim of this work is to outline mango stone energy qualities and to assess these parameters to establish its suitability as a solid biofuel for thermal energy production. With a view to achieving this goal, the following analysed parameters were considered: moisture (59.70%), higher heating value (18.05 MJ/kg), lower heating value (1727 MJ/kg), elemental composition (48.26% C, 44.92% O, 3.48% H, 1.041% N, 0.086% S, 0.070% CL), ash content (2.14%), or oil content (3%). These results were compared to other biomass sources, such as olive pit and avocado stone, as well as almond shell, obtaining intermediate but similar readings. Finally, the most accurate model to estimate higher heating value of mango stone has been determined, considering the predictive models of HHV for the biomass submitted by other scientific research studies. As main conclusions, the findings of this work pave the way for using mango stone as biofuel in domestic or industrial heating facilities. On the other hand, this biofuel has proven to be useful in reducing greenhouse gas emissions in producing countries. In relative terms, it has proved to be particularly significant in a large part of Central Africa (Sudan, Nigeria, Tanzania, Kenya or Congo) and Madagascar, being able to reduce above 0.02‰ of their CO2 emissions.

The increasing fossil fuels price is a direct result of a growth in worldwide demand of energy and has become a major concern of many countries. The special conditions of Mediterranean countries, with high dependency on energy imports and energy used mainly from fossil fuels, make these countries users of high carbon energy. On the other hand, the mild environmental conditions which do not need high energy demands in heating, together with the progressive abandonment of forest exploitation as fuel source, have provoked environmental problems, such as increased risk of forest fires. In view of the above arguments, the Mediterranean forest use becomes essential in order to reduce the risk fire as well as the dependence on energy imports of fossil fuels, and lower CO 2 emissions. Nowadays, Biomass District Heating (BDH) is widely used in the North of Europe. The main objective of this work is to establish a methodology for renewable energy resources integration at small urban areas in Mediterranean countries till now with high-energy consumption, and to asses that this methodology could be applied in Mediterranean areas successfully, and the determination of forest needs. For this purpose, a case study is shown, so a BDH network to cover the energy demand in a small urban area in the south of Spain was studied. The study was done in three phases: energy demand survey, BDH calculations, and assessment of technology for both, savings costs and CO 2 emissions. In this case, BDH system offers 100% of CO 2 savings and 68.22% of fuel cost savings versus fossil fuels. Using BDH, CO 2 emissions to the atmosphere have been reduced by 35 tonnes, which is the equivalent of the annual CO 2 sequestration of 700 adult trees approximately. As main conclusion of this work, if used, the available forest biomass, it could be saved more than 68% of the current energy demand in the case study. For this small rural settlement of 3000 inhabitants, 4 ha of forest was found as forest biomass needs every year, this means a total of 40 ha as sustainable energy model based on Mediterranean pine forest. The finds of this work can be used as policy solution that has to be study in the whole Mediterranean areas with forest resources, in order to have more sustainable environment.

The insufficiency of current energy sources, elevated costs and global climate worriment are distinctive factors making of renewable energy an issue of boosting consideration. In this concern, solar energy is viewed as being indefinitely environmental friendly, carbon-free, beneficial nature with appreciated cost potentials and is witnessing fast progressing. Following the Horizon 2020 climate and energy package, the volume of gases emitted by greenhouses has to be cut down by 20% by all the European Union (EU) member countries in order to enhance energy performance by 20% and raise the renewable energy rate to 20% by 2020. Solar energy on building roofs plays a crucial aspect in renewable and sustainable energy consumption of high-density human habitats. A merest energy should be allocated to provide hot water service from solar sources, as other European norms for new buildings by the Spanish Technical Building Code, similarly to other European regulation on achievement objectives. The climate zone and the overall demand of hot water in the building regulate this minimal amount needed. This manuscript use a new methodology for automatic detection of geometric patterns from aerial or space images using a Hierarchical Temporal Memory (HTM) algorithm. In this way, an automatic method for the identification of building roofs in order to assess the opportunities available to install solar thermal systems in small urban areas has been developed. As case of study: a village with 7000 inhabitants was analyzed in the South of Spain. The maximum overall accuracy obtained among the different classifications made was 98.05%, avoiding problems related to the use of images with high spatial resolution, as in the salt-and-pepper noise effect. This approach contributes reducing the generated carbon and GHG emissions and open new perspectives for energy savings strategies to optimize the energy efficiency of buildings. In the case study, implementing the solar thermal systems would come out with a saving of 1.4 tons of CO 2 per inhabitant.

The development of cleaner and renewable energy sources are needed in order to reduce fossil fuel dependence and mitigate global warming by reducing greenhouse gas emissions. Solar dryers are considered as clean technologies and optimal use of these can minimize the use of non-renewable energy, and can play an important role in the world's future. Drying for forest products is one of the most attractive and cost effective application of solar energy because it may be possible to improve forest residues in profitable biomass as biofuel. In this study, a solar greenhouse dryer was used in drying experiments of wood chips of Pinus pinaster in the south of Spain. The environmental conditions were under autumn season with an average daily solar radiation of 13.74 MJ/(m 2 d) during the 15 days of the experiment. The experiment analyzed the drying process under indoor conditions of several piles of wood chips which was compared to the same shaped piles under open sun drying. The results were mathematically modelled to show the advantages of the Solar Greenhouse Dryer for both, to reach the 10% of relative humidity and fewer days were dedicated for this. Thus, these analyses reveal that the Solar Greenhouse Dryer is a useful and vital technology for the improvement of wood chips as biofuel, it reduces moisture, and it can be applied in many countries because of the fact that it only uses solar energy; it is a renewable energy resource which is both free and clean.