Electric Power Based on the Solid Urban Waste: Applied to the District of Bellaterra in Barcelona, Spain

— The high growth of Urban Solid Waste forces to seek measures to handle this waste. Applying advanced Thermochemical technology will take advantage of this waste in order to obtain Sustainable Energy. The objective of this study is to analyze the input, production and output behavior of this type of waste so that it can be transformed and used for energy purposes, based on the needs of the community. It is a quantitative, experimental study; after understanding the residual behavior of the community and applying the appropriate technology, it was obtained the quantified amount of energy (975'000 kWh) required for the different proposed scenarios. These scenarios are the use for public lighting, sale and domestic. The thermochemical method applied is not only efficient to extract energy from these wastes but also provides a compatible and environmentally friendly energy source. This energy source was used to supply a local school and 948 homes. The ideas es to achieve a paradigm shift, to avoid thinking that Urban Solid Waste that is generated from day to day is something useless; on the contrary, it is a vital source to provide a basic service for human beings. From a financial point a view, it is estimated that the initial investment will be recovered in the next 10 years, which, seen in the long term, is the useful life of the Pyrolysis plant due to working with the minimum raw material input standards .


I. INTRODUCTION
The rise in solid urban waste (SUW) production is directly linked to the increase in the community in the urban area and its economic development.Currently, half of the population is located in entrenched urban areas with exponential population growth.With the current demand for goods and services of the world population, it is expected that by 2025 the amount of SUW will be approximately 2,200 million tons per year [1].Therefore, it is necessary and urgent that cities in constant development, which do not have integrated waste management programs (IWM), be implemented immediately to see the SUW can be a source of infinite resources and not as a problem should be removed immediately [2].
It is possible to propose some options for valorizing this waste, for example, recycling, composting, and bio-digestion.However, there is a type of exploitation in which SUW can generate electrical power through biochemical processes that consist of aerobic and anaerobic digestion.There is also the thermochemical process that consists of incineration, gasification, and pyrolysis processes.Of the processes, it should be mentioned that thermochemical processes have a greater energy scope, and their capacity to reduce SUW is much greater.For example, it is estimated that in the world, approximately 130 million tons of SUW are processed in plants ranging from Waste-to-Energy (WtE) and produce around 45GW-h [3].
In the case of waste whose purpose is to occupy a space for final disposal, it leads to a dilemma of why not use a clearly residual material to give it a new use and thus mitigate the pollution generated by them and intervene in such a way as to reduce energy consumption in the Bellaterra neighborhood.The study was welcomed mainly due to the pollution and by providing friendly solutions to solid waste produced by the man.This study serves more than a simple investigation in the residual field.This study also comprises a change in the human mentality of managing its resources and its residues for a variation in favor of the environment, analyzing the current residual model of the neighborhood of Bellaterra [4].The study's main objective is to determine the amount of SUW that can be exploited and used for energy purposes and thus minimize the impact on the environment.

II. MATERIAL AND METHOD
A cross-sectional, experimental, descriptive, and analytical study is presented.This type of study is essential because it is an issue that affects the community, and it will solve a problem related to it.It focuses on SUW, as mentioned above, in the community of Bellaterra.As a theoretical scenario for urban waste, the following was proposed: The classification of waste from the Bellaterra neighborhood includes organic, paper, cardboard, glass, and bulky.Quantify the inputs, production, and outputs of waste and thus rate which are usable from this classification.Mention the technologies available to obtain energy for those wastes, along with its operation.Give this renewable energy a purpose, which is beneficial to the Barcelona-Spain's Bellaterra neighborhood.The waste generated by this community will be treated in such a way that there is no reuse as much as possible, a large part (biodegradable) will be used as compost for community gardens, and the other part (not biodegradable) that interests us, will give it an energy value.
All this situation, as mentioned previously, will be valued to the maximum through the technology to be implemented and possible infrastructure, which, together with a detailed budget, will let to know the feasibility of possible scenarios.Aspects related to SUW with certain characteristics have been considered throughout the study to propose later scenarios that benefit them, whose management will have to provide daily service.Aspects related to demography regarding the generation of SUW may be associated with human activity and the economic status present in said community.A current model of organic matter will provide several guidelines to have a general vision of the waste generated by them, considering the inputs that it covers, the production, and the outputs that are being the SUW [5]- [7] III.RESULTS AND DISCUSSION It began by quantifying the different types of inputs to finally obtain a value determined by the kilograms that enter during a year, as seen in Fig. 1 and its numerical balance of the organic matter model:

A. Entry Phase
Food in Cataluña-2018: A sample of an average diet was taken that will consist of:

4) Furniture (Exclusive of wood):
The lifespan of a piece of furniture is 8 years, and the cost of furniture for one home = 530€, according to the Cetelem consumer observatory in Spain: = furniture cost / furniture lifespan =530/8 € years =66 € per year for furniture This means that each year would be missing the value of 66 euros that we have assumed as the investment equivalent to 6 kg of any wooden furniture would be lost (as if 6 kg of furniture entered a home per year: = (6 kg/dwelling.year)* (948 dwellings/neighborhood) = 6.7 tons/year.neighbourhood[9] 5) Fertilizer for plants: Amount of fertilizer for every 100 m 2 : 6 kg Unbuilt area neighborhood: 966,960 m 2 6) Space for the garden: 50% = (966,960m 2 / 2) = 483,480m 2 = (6kg/100m 2 ) * (483,480m 2 ) = 26 tons/year.neighborhood.

B. Production Phase 1) Forest Biomass:
This data y according to the composition of the forest in Bellaterra proposed by a platform of the Diputació Barcelona, as shown in Fig. 2.
Forest area = 68.15ha (measured from the AutoCAD plan of Bellaterra) = (68.15ha) * (3.5 ton/ha) = 238.52ton/year.neighborhoodNote: All this quantity is part of the stock, which means it does not add up, but remains there for possible use.

C. Outgoing Phase
For the outgoing phase, in which a general audit was carried out, and the classification and quantification of urban solid waste that is generated in it is immersed, as shown in the following Table I   It is essential to know the calorific value of the waste that will be used in order to have an estimate of the energy scope that can be obtained from them.For this reason, it is important to know the components to be analyzed together with their PCI expressed in Kilocalories/kilogram and another value of ash with another type of rejection that would generate mentioned residues.We proceed to quantify how much energy can be extracted from the aforementioned waste in the General Model of Organic Matter, in mass per unit to get an idea of how much is the energy use, taking into account that 1 kcal = 0.00116222 kWh the following Table III shows: Quantity of raw material supplied: Production of raw material in ton = 1340 ton/year Production of raw material in ton = 4 ton/day Production capacity of raw material in m 3 = 13660 m 3 / year Production capacity of raw material in m 3 = 37.4 m 3 / day Table IV shows the gross net energy used from the SUW shown, giving a value of around 3,000,000 kWh.The amount of material collected is 4 tons per day, and pyrolysis will be chosen and, as its application range is 10 to 100 tons per day, it possible to apply it on this occasion.Pyrolysis is that thermal technique or thermochemical process that leads to the degradation of the material, in this case, SUW in an inert atmosphere, that is, in the absence of oxygen.This process can be applied to almost all materials such as domestic, urban and industrial waste (although this is not the case), mentioning with emphasis that in the Pyrolysis process, there is no incineration.In addition, there are dangerous gases that are the product of the pyrolysis process, as well as: PCDD: polychlorinated dibenzodioxins and PCDF: polychlorinated dibenzofurans.Whose mandate establishes control measures for the mentioned harmful gases, through the implementation of chimneys capable of containing them and thus preventing them from polluting the environment.
As previously established, the applied technology would be thermal conversion by pyrolysis, taking into account, according to the calculations of the Organic Matter Model, that around 4 tons / day would be administered.It would be recommended to implement a small continuous pyrolysis plant.It is a reliable technology if the construction standards are followed properly, its cost compared to other plants is low and it has no environmental problems.It has durability and ease maintenance and components that are present in the pyrolysis system.As can be seen in Fig. 3, and 4, and in Table V and VI, the pyrolysis plant (and the costs it generates) to be implemented is described, and its characteristics are presented below:  Brand: Jinpeng   Regarding the available energy, although data of the amount of gross net energy of the SUW was given at 3'000,000 kWh, and due to the losses, that occur in the Pyrolysis process, the energy that will be obtained at the end of the process is equivalent to 1,500,000 kWh.The useful energy is the result of the remainder of the Pyrolysis plant, the liquid waste being a type of Biofuel where there are hydrocarbons, that energy must be extracted from that material by means of a Generating Set.As mentioned above, we start with gross energy of 3,000,000 kWh, and due to the Pyrolysis processes, the reduction is almost 50%, which is why we obtain the energy of 1,500,000 kWh, now with the generator set that will be capable of transforming the Bio-fuel into energy will have a loss of around 35% of loss due to operation so that as a result the own energy to be implemented in future scenarios would be around 975'000 kWh [11].Price of electricity for sale = € 0.1198 / kWh.Recovered Investment: (975,000 kWh) * (€ 0.1198 / kWh) = € 117,000 / year Therefore, the price of electricity in kWh, together with useful energy production, can be recovered from the initial investment in 10 years, which coincidentally is almost the lifetime of the pyrolysis plant.First, it is worth mentioning that the land to implement the Pyrolysis plant had to be strategically located in order to provide the energy obtained by the fuel so that it is not too far from the benefited area (Fig. 5 and 6).Therefore, a land of around 1500 m 2 was found, an area spacious enough to locate the structure of the plant together with the raw material warehouses [12], [13]

D. Environmental Impact Assessment
This type of assessment that is used by Leopold's matrices is a type of instrument that will allow foreseeing negative aspects of the activities carried out in any project such as the construction phase, operation phase, and completion phase, stating the most important in the study area.[14], [15].As a point of comparison, the impacts generated by each action carried out in the project are verified, whether it generates impacts on the socio-economic, physical or biological environment and what type of environmental impact they are immersed.For this reason, the following main activities to be carried out once the study is applied will be enunciated:  Educational-social impact The methodology is based on a set of matrices with different quantifications that will be used to use an environmental impact assessment, and this will indicate which action is the one that generates the most impact on the environment and thus take preventive measures.

E. Scenario Benefited
1) Scenario 1: Destined to the equipment located next to the Pyrolysis plant, the Ramón Fuster School, together with the public lighting and finally to sell the surplus energy to a market to recover the investment of the Pyrolysis plant.
2) Scenario 2: As it is solid waste generated by all the houses in the neighborhood, allocate the final product to benefit these houses.

F. Energy Demands of Each Scenario 1)
Scenario 1: In the Ramón Fuster School case, the energy obtained by the Pyrolysis plant will be implemented in heating as a priority need.For this, it is necessary to know the useful spaces that are intended for heating, taken from the cadastral headquarters (Table VII).According to the CTE standard, around 20are needed kWh / m 2 annually, so it should cover an area of approximately 3,378 m 2 , as described in Table VII; therefore, the heating demand would be 67,560 kWh / annual.Since that around the area are needed 70,000 kWh to heat the Ramón Fuster School 100% during the winter days, another suggestion would be to benefit or provide energy to public lighting.Giving an approximate total of 550,000 kWh as the demand for Public lighting (Table VIII).Moreover, with the surplus energy, to be able to sell it to the highest bidder to recover the pyrolysis plant's initial investment.With this sale of 355,000 kWh, the investment of the plant will be recovered in the useful time of the plant, which is 10 years; of course, it is worth mentioning that the Ramón Fuster School and the public lighting of the neighborhood will be benefited (See Fig. 7).2) Scenario 2: Another option would be that each of the authors who provide the raw material for obtaining energy is those who benefit from it.That is why it is necessary to know the energy demand of the homes in the Bellaterra neighborhood and an estimate of how much it will cover according to the total kWh generated by the Pyrolysis plant and thus be able to allocate this energy for a common good, covering (Table IX).The best option to use the energy produced by the Pyrolysis plant It would be used for lighting that would cover 50% of it, and even for hot water that would cover almost 30% and to be bio-fuel the product generated by the plant this would be the best option (See Fig. 8).However, you can think of different alternatives in order to make the most of all the energy for a common good.Thermal conversion plants such as pyrolysis solve and mitigate two major problems: efficiently recovering the energy extracted from solid urban waste (SUW) and controlling the emissions of the main polluting gases.In addition to providing a compatible and stable energy source to the environment (See Fig. 9), it is acquired from the waste that the Bellaterra neighborhood generates for its benefit; It is important to emphasize that both scenarios were presented to the city government for them to decide which is the best option.
Heating being a big problem in this neighborhood, either due to a large amount of consumption or the high prices that it entails, that is why the energy acquired by waste is directed to this end.From a financial point of view, the initial investment in this project will be recovered within the following 10 years, which, seen in the long term, is the Pyrolysis plant's useful life due to working with the minimum raw material input standards.
This mechanism complies with the Kyoto Protocol in which Spain is committed, which consists of any means or project that includes a considerable reduction in greenhouse gases harmful to the environment.Both alternatives are feasible; one, on the one hand, satisfies an educational entity and at the same time the neighborhood itself with electric lighting; on the other hand, alternative 2 provides those people who contributed the raw material to make this possible, contributing directly to their homes, both scenarios they are beneficial depending on the public or private point of view.
As a key point and of utmost importance is to be able to implement a paradigm shift for the people of this community, to stop thinking that solid waste from day to day is something useless and without any other use, generating energy from it is a great challenge not only for society but also for private companies and the government itself.

Fig. 2
Fig. 2 Illustrative plan of Bellaterra, forest area and residential complex

Fig. 3
Fig. 3 Pyrolysis plant to be implemented in the study

Fig. 5
Fig. 5 Superior view of the Bellaterra neighbourhood scoring the Ramón Fuster School


Fencing the land  Cleaning and clearing the land. Installation of the plant (Pyrolysis)  Selection of waste to use. Transport of waste to the plant  Maintenance of the plant Pyrolysis  Transport of ashes to landfill  Gases produced by the plant.

TABLE I SOLID
URBAN WASTE IN THE BELLATERRA NEIGHBORHOOD

TABLE II BALANCE
SHEET OF THE ORGANIC MATTER MODEL

TABLE VI DETAILED
INVESTMENT OF THE PYROLYSIS PLANT PROJECT

TABLE VII USEFUL
AREA OF THE RAMÓN FUSTER SCHOOL

TABLE VIII ENERGY
DEMAND FOR PUBLIC LIGHTING IN BELLATERRA

TABLE IX ENERGY
DEMAND OF THE HOUSES IN THE BELLATERRA NEIGHBORHOOD