The management of natural resources is an extremely important tool for strategic planning of the rational and sustainable use of the same, from whose results the measures for the improvement of the soil, water, energy, forestry etc are obtained; and consequently the standard of living of the men and women who produce rises (Altieri 2007).
ENERGY RESOURCES
Natural energy offers
For Arrastía, (2010), the origin of all the changes that occur around us, whether due to natural causes or caused by man, is associated with the term energy. Energy is considered a quantitative measure of the motion of matter that characterizes the ability of systems to change their properties, or the properties of other systems, to bring about change through work, heating, or radiation.
On the other hand, Cruz et al; (2005) consider that photosynthesizing plants and organisms are in charge of producing, in the presence of abiotic factors, all the energy of the other living beings on planet earth and these place them in the group of producers: leaves, flowers, fruits, stems and roots become fuels for the consumer group and, to close the cycle, decomposing and detritivorous organisms in the soil transform all the remains of plants and animals, incorporating them into it. This energy supply of ecosystems consists of energy from natural recycling systems (biomass from crops, forestry operations and the use of residues and renewable or inexhaustible sources offered by the environment (wind, solar, hydraulic energy, etc.).), (Gligo 1984).
Masera and Astier (1996), argue that with the artificialization of the ecosystem to transform them into agrosystems, the energy supply of the environment tends to be wasted, such as natural systems for recycling accumulated energy, mainly biomass, and others. When the systems are based on technologies that are gradually deteriorating them, according to what was stated by Álvarez et al; (2008), present an increasing energy requirement to maintain the expected production rate. Energy subsidies are generally made with the use of direct fossil energy (Diesel and all the inputs used in the technique to execute the technologies of soil preparation, cultivation, irrigation,transportation and even human and animal labor and including sequestered energy for the manufacture of fertilizers and pesticides and all inputs). We must add the impact caused by the combustion and spills of these fossil fuels to the environment (Ayes, 2008) and, furthermore, because the hydrocarbon reserve is limited and its definitive exhaustion is in sight (Arrastra, 2006).
The use of fossil energy and its environmental effect
The most difficult thing to understand is where fossil fuels come from and why they are high environmental pollutants when they degrade differently than nature does in recycling energy (Rojo, 1999 and Serrano, 2006). Man affects the environment since the conquest of fire, but since the first industrial oil well was made in August 1859, there has been an acceleration of the development of humanity based on fossil fuels, without taking into account that this It is a finite resource and that in a few centuries the end of its reserves are in sight.
According to Pérez and González (2009), the situation of fuel shortages is delicate worldwide and especially for Cuba, which currently imports a high percent of these for the vehicles it uses, including those employed in agricultural work; reason why it is necessary to look for technologies with greater energy efficiency, as one of the ways to save these fossil fuels.
The already latent food crisis will follow the energy crisis, as proposed by Vásquez and Montesinos, (2007), whose solution depends directly on access to energy and the sustainability of our common project as a species. Currently, the pressing problems caused by the population explosion and the non-renewable nature of fossil fuels have created a negative environmental effect on the planet, which compromises the future of the human species. (Valles et al; 2002).
On the other hand, the use of fossil fuels, such as oil and its derivatives, stone coal, accompanying gas, etc., emit large amounts of gases that contribute to global warming. Vigil, (2006) shows that a liter of gasoline can emit more than 100 liters of carbon monoxide into the atmosphere; Chamorro (2008) also indicate that one kg of diesel when it combusts emits 3.16 kg of carbon dioxide (CO 2), different gasoline sends an average of 3.20 kg of CO 2 per kilogram of this fuel, or liquefied petroleum gas (LPG), generates an emission of 2.74 kg of carbon dioxide (CO 2) for each kg. of gas, constituting a strong contribution to the atmosphere of greenhouse substances, well above the capacity of the planet's leaf mass to capture and clean the excess of these gases, made harmful by the irrational and indiscriminate action of man by combining the indiscriminate use of fossil fuels and the indiscriminate felling of the planet's forests.
Use of renewable energy sources in agricultural activity.
Renewable energy is the only way to guarantee a promising future, since it allows the independence of fossil fuels by replacing oil and its non-renewable derivatives with renewable and less polluting alternatives to the environment, according to criteria by (Henríquez, 2002).
The eolic energy
Wind energy is the energy that the wind possesses and that can be directly used or transformed to other types of energy, such as electrical energy. The first known use of wind harvesting dates back to 3000 BC, with the first Egyptian sailing ships (Moreno and Canosa, 2007).
This technology has been developed in Cuba since the last fifty years of the 19th century, according to Soltura, Roque, (2007) and Montesino, (2008), starting mainly in the livestock areas, from Camagüey to the east. The Camagüeyan plains, with their possibilities of good exposure to the wind and their gentle breeze, made it a success in this region. However, in the early days it was limited to the use of wind pumps to supply water to people and animals and other very specific purposes (Novo, 2005). Today, in order to promote the use of wind energy, as part of the Energy Revolution, the evaluation of wind resources in the country is a priority (Fauchon, 2006). The subject is of utmost importance for the economy and the environment;to improve living conditions in peri-urban and rural areas and support plans for sustainable agriculture and rural development, for the preservation of the environment and natural resources (Sachs and Lenton 2005). Also UN (2005), indicates that it is important that among the millennium goals for 2015, increase the use of renewable sources by 15%.
Renewable energy source: biogas.
All agricultural residues emit methane (CH 4) and carbon dioxide (CO 2) into the atmosphere), which contribute 33% to global warming and the greenhouse effect (Graedel and Crutzen, 2003). Livestock contributes to the food supply in developing countries, but it causes deforestation, overgrazing leads to desertification, overcharging causes soil erosion, and excreta results in the production of greenhouse gas methane and not only It contaminates the atmosphere, if not also the soil and water, many times with bacteria and parasites that end up in the water table, or are transferred in the excreta that are used in organic fertilization and irrigation water (Arribas, 2006 and Fonte 2006), Excreta production contributes 7% of the greenhouse effect,which will result in an emission of between 20 and 30 million tons of methane per year that is sent to the atmosphere (Kaiser and Povez, 2007). Every M3 methane causes a greenhouse effect equivalent to the greenhouse effect that causes 23 m 3 of CO 2 (Graedel and Crutzen, 2003; Káiser Povez, 2007).
A typical m 3 of biogas, with a 65% methane concentration, contains approximately the equivalent of 0.55 kg of light diesel (0.66 liter) per m 3. With 60% CH4, one m 3 of biogas is sufficient to generate around 6.5 kWh of energy (Castelar and Hilbert, 2005). Typically, the biogas produced by a biodigester can be used directly like any other fuel gas. According to Lugones (2003).
According to Álvarez, Martínez (2005) and Martínez (2007) state that three billion people still use firewood, and they deforest between 16 and 20 million hectares of tropical forest each year to cook and heat water; biogas is used in direct combustion in simple stoves, in cooking food, thus reducing the pressure on forests (firewood, charcoal, etc.). Biogas is an alternative that can also be used for lighting, heating and cooling, as well as fuel for diesel and gasoline engines, from which electrical energy can be produced by means of a generator, according to what was proposed by Carmona et to the; (2007); although in the case of diesel engines, biogas can replace up to 80% of the fuel and, in gasoline engines,biogas can completely replace it.
Díaz Piñón (2008) states that in China there are 6.7 million biodigesters that process the country's organic waste; in Cuba the potential is 78 million m 3 of biogas that can replace 152 thousand tons of conventional fuel per year, taking advantage of only a small percentage. Suárez Riva (2011), characterizes the waste of state livestock residues in Pinar del Río, illustrating how only 43 pig digesters exist in the Swine Company, when conditions allow mounting more than 800, that is, only 5% built and no more than half working. Here neither private producers nor cattle, sheep - goats or other species are considered.
MATERIALS AND METHODS
Geographical situation: The Finca "La Rosita" is located in the Municipality "Habana del Este" in the Popular Council of Campo Florido. It limits to the North with the Town of Guanabo, to the South with the town of Arango, to the east with that of Campo Florido and to the West with the Municipality of Guanabacoa. The Farm is surrounded by areas belonging to the Bacuranao Livestock Company.
Methodology to evaluate fossil energy expenditure on the farm.
Methodology for evaluating electrical energy expenditure and its environmental effect (Vigil 2006, Moreno and Canosa 2007).
All the electricity consumed by the La Rosita farm is from the national electrical system (SEN) and is used to generate it, fossil fuels such as light oil, Diesel and others, depending on the fuel used by the source in its generation.
The primary information was obtained from the data of the total consumption of the Farm in 2010, according to its statistics. To determine the fossil energy expenditure in liters equivalent diesel or other, that the thermoelectric or the generator sets demand to generate the electricity, the index used by the National Electric System (SEN) is used. (Vigil 2006, Moreno and Canosa 2007).
The expression represents the expenditure of all electrical energy in kiloWatt hours per year (kWh / year) consumed at the La Rosita farm.
E t = E Inst.A + E bombeoa + E housing and int + E Inst. P + E vaquería + E skirt + E others (kWh / year)
To determine the fossil energy expenditure in liters equivalent diesel or other, that the thermoelectric or the generator sets demand to generate the electricity, E Leq = 0.263 G ekWh E t (L eq.)
Where:
E Leq . - equivalent liters of diesel or fuel used to generate the electricity consumed in the period (L eq).
G ekWh - consumption rate in kilogram of diesel fuel to generate one kiloWatt hour of electricity in the national electrical system
E t - Total electricity consumed in the period evaluated ; in this case it is in kiloWatt hour in the period of one year.
What pollutes the atmosphere is not electricity, but the fuel used to generate it. To determine the emission of atmospheric pollutants generated by all the fuels used to generate the electricity consumed by the La Rosita farm, the pollutant indices of the Danish Wind Industry Association were used. (Moreno2008)
E Ca = G ekWh. E t. I C in kgCO 2
Where
E Ca - Emission of CO 2 sent to the atmosphere, (in kg of CO 2)
G ekWh - fuel consumption index per kiloWatt of electricity generated (Kg / kWh).
E t - amount of kilowatt of electrical energy consumed.
I C - Emission rate in kilograms of CO 2 per kilogram of fuel consumed (CO 2 / kg) of fuel, see table 3.1 Danish wind industry association (Moreno2008)
Methodology to evaluate the consumption of diesel, gasoline and liquefied gas (LPG) fuels and their environmental effect ( Vigil 2006, Moreno and Canosa 2007).
The information on the total consumption of Diesel fuel, gasoline and liquefied gas consumed by the Farm in 2010 was taken.
With the previous information, the environmental emission of each of the energy carriers was determined. Pollution rates in kilograms of CO 2 per kilogram of each fuel consumed by the Farm in 2010 were used, using the 2003 Danish Wind Industry Association and Serrano et al; (2006).
Methodology to determine the potential and management of livestock waste from La Rosita farm.
In compliance with the “Economic and Social Policy Guidelines”, La Granja Management has included, in its 2011-2015 strategy, the use of livestock residues for the production of biogas, high-quality organic fertilizers, the reduction of air pollution, the substitution of non-renewable energy imports for renewable ones (Participatory workshop held in La Granja, in September 2010).
To determine the potential of the residuals of the La Rosita farm, we start from the characteristics of each species. For this, the methodology of Guardado, Martínez 2007 and Gómez 2009 was considered.
Calculation of the excreta and biogas potential of the Farm. Daily quantity of excreta and biomass available.
The amount of excreta available daily by the animals of the Farm (C E) is calculated by the following expression :
C E = m 1 E d1 + m 2 E d2 + m 3 Ed 3 + m 4 Ed 4 + m 5 Ed 5, in kg / day
Where:
m 1 Ed 1 - Amount of excreta from cattle, kg / day
m 2 Ed 2 - Daily amount of excreta of pigs, kg / day.
m 3 Ed 3 - Daily amount of excreta of sheep; kg / day.
m 4 Ed 4 - Daily amount of excreta produced by poultry, kg / day
m 5 Ed 5 - Daily amount of excreta produced by horses, kg / day
After calculating the amount of excreta available daily, the potential for biogas and its polluting effect are calculated, which generates said amount of excreta daily for all the livestock on the Farm using the methodology of Castelar, Sosa 2003), Martínez, (2007) and Gómez 2009.
Results and Discussion
Use of fossil energy at La Rosita farm.
Energy is the fundamental basis for carrying out all production and service processes on the Farm. The fossil fuels used on the Farm are : Electricity taken from the National Electric System (SEN) ,Diesel, gasoline, and liquefied gas (LPG), on which it depends. Since the beginning of the Energy Revolution, knowledge about the role of energy in the social development of the country has increased and, along with this, the immense need to save it by using it efficiently. The results of this study allow us to quantify the extent to which the activity of the Farm contributes, with its emissions, to climate change, and above all, to global warming of the earth. The most important aspect for the Farm is not to avoid the expenditure of energy, but rather that all the energy expended is efficiently used. In the increase in savings based on energy efficiency in all aspects that correspond to this important farm that produces food for life, is the success of its management ; In addition, it will fully comply with what is stated in the Economic and Social Guidelines of the Party and the Government of Cuba (December, 2010).
Use of electricity and its environmental effect.
Electricity is used in all administrative and service infrastructure , as well as in pumping water for agricultural processes and livestock facilities. Table 1 contains a summary of the energy and environmental cost of electricity consumption at the Farm.
Table 1 Electricity consumed in one year at La Rosita farm, the fossil fuel spent to generate it and the CO 2 emission sent to the atmosphere for this concept .
| Year | Electricity consumed
(KWh year) |
Fossil fuel Liters / year) (L / year) | CO 2 emission (tons / year) (t / year) |
| 2010 | 13 971 | 3 668 | 9,712 |
Note . MW / year - means megawatt year. A megawatt has 1000 kWh
The most significant thing about this result is that the Farm consumes during the year 13,971 kWh / year. 3,668 L liters of fossil fuel are needed to generate it, and 9,712 tons of carbon dioxide (CO 2) will be emitted into the atmosphere.
Use of Diesel fuel.
The Diesel fuel received by the Farm is used in the tractor to prepare the soil and transport materials for livestock and other services for a total consumption of 28,700 liters of diesel per year (table 2).
Table 2 Diesel fuel consumed in La Granja in one year (in Liters and kg), and the emission of CO 2 sent to the atmosphere for this concept in tons of CO 2.
| Year | Diesel consumed (L / year) | Diesel consumed (kg / year.) | Emission into the atmosphere (t.CO 2 / year) |
| 2010 | 28,700 | 24 051 | 76, 001 |
The selected emission factor was 3.16 kg of CO 2 per kilogram of fuel (See Materials and methods: Danish Wind Industry Association, 2003).
Use of Gasoline
Gasoline fuel: this is used, fundamentally, in light transport for the attention of the services and administrative activities of the Farm. Table 3 shows the results of the expenditure and emission into the atmosphere of CO 2 from the combustion of gasoline used in any internal combustion engine.
Table3. Gasoline consumed at La Rosita farm in one year and CO 2 emission sent to the atmosphere for this concept.
| Year | Gasoline (L / year) | Gasoline (kg / year) | CO 2 emission (t / year) |
| 2010 | 13 600 | 9 832 | 31, 462 |
- Gasoline density is 0,723 kg / L.
- The emission factor is 3.20 kg CO 2 / kg of gasoline.
The most important result is that the use of gasoline generates more than 31.46 tons of CO 2 to the environment in the period considered.
The liquefied gas used in the kitchen (Table 4)
The energy cost for food processing is also relevant, even though the liquefied gas (LPG) used for cooking is slightly less polluting compared to the other fuels previously treated, mainly hydrocarbons such as oil, Diesel, gasoline and others, but also this fuel emits 2.74kg of CO 2 per kg of LPG (Danish Wind Industry Association 2003).
Table 4. Liquefied gas (LPG) for cooking on the Farm
| Year | LPG (kg / year) | CO 2 emission (kg / year) | CO 2 emission .
(tCO 2 / year) |
| 2010 | 540 | 1 479 | 1, 48 |
- LPG emission factor is 2.74 kg of CO 2 per kilogram of liquefied gas. (Danish Wind Industry Association 2003). Here it was considered that the Farm consumes a monthly balloon of 45 kilograms.
Tables 5 6 summarize the Farm's fuel consumption and atmospheric emissions due to the use of fossil fuels to generate electricity, Diesel and gasoline to perform the service, administrative and agricultural work, as well as liquefied gas for cooking workers' food.
Table 5. Fossil energy equivalent liters consumed in 2010 at the La Rosita farm.
| Year | Liters of fuel to generate electricity (L / year) | Diesel liters consumed on the Farm (L / year) | Liters of gasoline consumed (L / year) | Liters of liquefied gas consumed (L / year) | Total liters of fossil fuel
(L / year) |
| 2010 | 3 668 | 28,700 | 13 600 | 1 479 | 80 447 |
Table 6. CO 2 Emission into the Atmosphere
| Year | CO 2
emitted in electricity generation. (t / year) |
CO 2
Issued for Diesel consumption. (t / year) |
CO 2
emitted by gasoline consumption (t / year) |
CO 2
emitted by LPG consumption (t / year) |
CO 2
total of issue (t / year) |
| 2010 | 9.36 | 76, 001 | 31, 462 | 1, 48 | 118.30 |
It is important to clarify that these energy and environmental costs are only due to the use of fossil energy, these results are basic to be able to assess the effect of the strategy of saving and efficient use of fuels, including electricity. In the workshop carried out on the Farm, the technical and completion state of the technique and facilities is presented as a weakness, since as they age due to the years of operation, specific consumption increases, breaks and leaks, being spent more fuel than necessary for the same operation.
Management of livestock residues at La Rosita farm.
Residual and biogas potential of La Rosita farm.
La Rosita farm has a diversified livestock, where it produces more than 15.5 tons of meat per year and more than 13,000 liters of milk and including 200,000 eggs, so all this production makes an important contribution of energy and protein to the feeding the population within the Food Security program developed by the country .
Cattle raising generates an enormous quantity of excreta a year; Which La Rosita farm uses as organic matter, replacing the use of chemical fertilizers. This strategy is correct, especially since organic matter is a natural fertilizer that does not consume energy for its manufacture and is more compatible with nature. However, livestock residues contribute more than 30% of pollutant emissions worldwide (FAO, 2007). This allows the orientation of a study of the residuals of the Farm.
Table 7 highlights the different species that are raised on the Farm, the potential of excreta and biogas daily and annually that they can generate (Castelar, 2005).
Table 7. Escrest volume and energy value of different species.
| Species | Quantity
(OR) |
Excreta rates (kg / day) | Total kg excreta daily | m 3 - biogas / kg excreta | Total m 3 of biogas daily |
| Bovine | 49 | 8 | 392 | 0.037 | 14.5 |
| Pigs in category | 193 | 2.3 | 444 | 0.064 | 28.5 |
| 83 | 0.9 | 75 | 0.064 | 5.0 | |
| Sheep | 130 | 2.5 | 325 | 0.03 | 9.75 |
| Equine | two | 10 | twenty | 0.04 | 0.8 |
| Chickens | 204 | 0.18 | 36.72 | 0.05 | 1.8 |
| Laying hens | 1711 | 0.18 | 308 | 0.05 | 15.4 |
| Total | 1600 | 75.75 |
Among all the cattle on the Farm, 1,600 kg of excreta are generated daily, and 584,000 kg / year, for a production of 27,648 m 3 of biogas annually, using the rate of 0.60 liters of light Diesel per cubic meter of biogas According to Castellar (2005) and Chamorro (2008), the Farm has an energy potential in the excreta of its livestock, equivalent to 16 589 liters of light Diesel. Even when only 50% is used, it would be more than 8294 liters of clean and renewable fuel, and it will be fully complying with the Economic and Social Guidelines of the Party and the Government of Cuba.
Pollutant effect of the livestock of the La Rosita farm.
Although the 584,000 kg of excreta generated annually at La Rosita farm can be a considerable contribution to natural organic fertilization for pastures and temporary and permanent crops, the decomposition of excreta and urine in open conditions in the field and in oxidation ponds, they emit into the atmosphere, in this specific case, more than 16 588 m 3 of methane (CH 4) per year, whose polluting power, according to Kaiser and Povez (2007), is 21 times higher than carbon dioxide, whose concrete contribution is 348 348 m 3 of carbon dioxide, for non-use of methane, plus 40% of CO 2 that accompanies biogas, that is, (11,000 m 3 of CO 2), for a total of359 348 m 3 of CO 2, being the total emission made by the livestock of the Farm and which affects global warming of the earth.
The polluting effect produced by the excreta of most animals must be added to the water, the water table and the soil, when wastewater is used for irrigation and other human activities, and even by the infiltration and dragging that occurs. with the water used in cleaning the facilities, and with the dragging caused by rainwater.
Justification of a proposal for the management of excreta
residuals from livestock on the La Rosita farm.
Braun and Wellinger 2003; Arribas, 2006; Fonte, A, 2006 and Sánchez et al; 2007, considered that obtaining methane from organic matter is an activity whose environmental balance is clearly positive. This benefit can be analyzed at three levels: the one associated with the process of obtaining or capturing biogas, the one associated with the use of biogas as fuel, as well as the decontamination of these residual pathogen vectors and improving the quality of the effluent for fertilization. and improvement of the soils where they are applied.
The Farm has several main sources that generate excreta, these are: the dairy with 49 animals and a potential of 14.5 m 3 of biogas per day. As the cattle remain half the time grazing in the field, 50% of the excreta will be the accumulated and available to process it in a biodigester, with the possibility of obtaining a minimum of 7m 3 of biogas daily from the bovine cattle it has the farm.
The 130 sheep also accumulate 50% of the excreta in the stable, so the real possibility is to obtain a maximum of 5m 3 of biogas from said sheep.
The laying hens accumulate all the excreta in the house, so here there is a real possibility of obtaining 308 kg of manure daily with a potential of 15m 3 of biogas every day, according to the indicators in the table.
The first proposal is based on what was proposed by FAO (2002) and Chamorro (2008), who consider that raw material mixtures of varied nature give better results in the production of biogas than raw material from a single source. These criteria support the proposal for the construction of a biodigester to process the excreta of cattle, sheep and laying hens.
For the proposal of a second biodigester to elaborate the residual offer of the pigs, it is assumed that a third of the total are piglets in reproduction (83), and 193 adults, who deposit 519 kg of excreta every day, which must be clean with abundant pressurized water towards a lagoon where it oxidizes and sends methane and carbon dioxide to the atmosphere, without taking advantage of the biogas.
By way of summary on the beneficial effect of the management of the residuals of the livestock of the Farm.
- The beneficial effect is concretized, using biodigesters for waste management, since methane and carbon dioxide are no longer emitted, which in natural conditions is always emitted into the atmosphere.
- The methane that is retained in the biodigester can be used to replace fossil energy (Diesel, gasoline, LPG)
- The third important benefit is that more than tons of high quality organic fertilizers are obtained, which constitutes a strong contribution to soil improvement and enhances the clean fertilizer effect and the sustainability of the Farm. It should be noted that the La Rosita farm takes this important aspect into account in its 2011-2015 Strategy, in correspondence with the Economic and Social Policy Guidelines (Article 229).
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