Elaboración de un documento guía para la aplicación de la Norma NTE

The world demand for petroleum and natural gas is increasing relative to world supplies. Fossil fuel energy can be either replaced with new sources of energy, or optimized in an applied manner (Kitani, 1999; Pimentel et al., 2007). It is predicted that even with the use of more efficient technologies and new energy sources, due to population and economic growth and improving quality of life in developing countries, the fossil fuel demand will increase in the coming years. Higher prices for petrol, diesel, and natural gas are making renewable sources of energy more attractive, economically, suggesting agriculture‘s role as an energy producer (Outlaw et al., 2005).

Energy consumption and carbon dioxide emissions are increasing at alarming rates (Ramanathan, 2005). Continued carbon dioxide (CO2) emissions are likely to lead to

catastrophic problems (Patterson, 1991; Smil, 2008). Energy activities are either contributing factors, or the main causes, of a significant number of environmental concerns. Major energy-related issues include global climate change, acid deposition, and deterioration of urban air quality (Patterson, 1991). Currently, renewable energy sources are more expensive than fossil fuel generation; however, if the environmental impacts and technical limitations are solved, it is possible to use more bioenergy resources in the future (Mallon, 2006; Tester, 2005; Warren, 2007). Since some thirty years ago, in some countries, such as Brazil, biofuels have been blended with fossil fuels. In these countries, cheap agricultural production, especially sugar, helps the use of biofuels in vehicles (Biofuels in Brazil : realities and prospects, 2007; Boyle, 2004; Gerin et al., 2008; Kitani, 1999; Mallon, 2006; Nersesian, 2007; Warren, 2007).

3.3.1.1

Fundamentals of Biomass

Green plants use sunlight to convert carbon dioxide and water into energy in the form of rich starches, cellulose, and sugars through the photosynthesic process; as yet, we do not understand fully how they do it. Biomass is defined as all material that was, or is, part of a living organism. Humans use biomass as the second energy source, after solar energy, for heating and cooking (Boyle, 2004; Mielenz, 2009; Tester, 2005). Biomass, still is the largest renewable energy source available (Randolph & Masters, 2008). Due to the need to find a substitute for fossil fuels and to reduce net CO2

emissions, the use of biomass from natural materials, such as wood, waste, and alcohol fuels has increased in recent years (Sims, 2004).

Biomass can be used as solid fuels like wood, liquid fuels like ethanol and biodiesel, and gaseous fuels like methane and biogas (Boyle, 2004; Randolph & Masters, 2008). Biomass is commonly plant matter grown to generate electricity or produce heat. A wide range of biomass is available. For example, forest residues (such as dead trees, branches, and tree stumps), yard clippings, wood chips, by-products of industrial processes, and urban rubbish can be used as biomass (Biofuels in Brazil : realities and prospects, 2007; Mielenz, 2009; Pimentel et al., 2009).

It is possible to categorize biomass as extractives, carbohydrates, starch, cellulose, hemicelluloses, pectin, lignin, protein, and ash. Each one on the above list contains different materials and is used in different ways (Mielenz, 2009). Due to land limitations, increasing yields and using more plant residues are the best ways to increase biomass production (Boyle, 2004; FAO, 2000a; Pimentel & Pimentel, 2008; Randolph & Masters, 2008; Vlek et al., 2004). Carbon dioxide is one of the main by- products of biomass production; also, burning biomass releases CO2 into the

atmosphere. However, the system is sustainable and the carbon dioxide is absorbed by the next crop of biomass products. Therefore, biomass combustion is considered to be greenhouse gas natural (Nersesian, 2007; Randolph & Masters, 2008).

Biofuels like ethanol, biodiesel, and methanol contain somewhat less energy per litre than petrol; however, they can do the job as well as fossil fuels (Patterson, 1991; Warren, 2007). Most of the fossil fuel energy is used in the transportation sector and cars consume around half of all oil produced. Replacing petroleum with biofuels, such

as ethanol and biodiesel, produces low amount of GHG emissions (Biofuels in Brazil : realities and prospects, 2007). If suitable solutions for some technical problems like the percentage of fibre and octane degree are found, biofuels can be used widely instead of fossil fuels.

The concept of using vegetable oil as an engine fuel dates back to 1895, when Dr Rudolf Diesel developed the first diesel engine to run on vegetable oil. Diesel introduced his engine at the World Exhibition in Paris in 1900 using peanut oil as fuel. Until the 1940s, vegetable oils were used in heavy-duty vehicles, but only in emergency situations. Biodiesel is still not very common and it is mixed with diesel in blends and this range from B-2 to B-100 (Boyle et al., 2003; Ghobadian et al., 2009; Kitani, 1999; Ministry of Commerce. & Eden Resources Ltd., 1993; Randolph & Masters, 2008; Reijnders & Huijbregts, 2009; Soetaert & Vandamme, 2009; Warren, 2007). Also, Henry Ford introduced the first Model T (Tin Lizzy) automobile based on 100% ethanol fuel in 1908; however, due to cheap oil resources in the middle decades of the twentieth century, the use of ethanol reduced until the first oil shock (Reijnders & Huijbregts, 2009; Soetaert & Vandamme, 2009). World ethanol production is increasing by about 20% annually. Interest in ethanol and other biofuels depends on global oil prices (Randolph & Masters, 2008; Warren, 2007) and increasing oil prices would make the ethanol production more economical.

3.3.1.2

Benefits and Limitations of using Biomass

A major attraction of biomass as an energy source is its domestic availability. There is a wide range of options to produce biomass in different areas. The raw materials, water, and carbon dioxide for biomass production are available and cheap in most areas. Furthermore, many forms of energy products can be made from biomass (Tester, 2005). However, some studies show that burning biomass is more harmful than burning natural gas. Furthermore, about 550 Mha of land are needed to produce enough transportation fuel from ethanol. This amount of land is one–third of the world‘s cultivated land or approximately all agricultural land in the tropical areas (Ghobadian et al., 2009; Smil, 2008). It is important to note that land covers only 27% of the earth, but around 57% of the earth‘s total biomass is produced in terrestrial systems. The average biomass production from crops is about 15 tonnes/ha.

The average biomass production in wheat production in North America is about 7 tonnes/ha (Pimentel & Pimentel, 2008). The rest of the biomass is produced in aquatic systems. However, using more biomass can increase some environmental impacts, such as soil erosion, water pollution, and air pollution (Biofuels in Brazil : realities and prospects, 2007; Pimentel & Pimentel, 2008). Additionally, it is important to note that every year, 15 million hectares of global forests are removed; around 60% of the forest is used for industrial roundwood and 40% is used for fuelwood. Furthermore, around 90% of fuelwood consumed in developing countries is used in an inefficient way, for cooking and heating (Pimentel et al., 2009).

The important economic benefit of biomass systems is the much lower investment cost per job created compared to industrial projects, petrochemical industries, and hydropower plants. Additionally, biomass production would enhance resource allocation related to rural infrastructure and services, such as rural settlement systems, communications, input distribution, extension, transportation, and marketing networks. Their link with regional agricultural growth is well established. ―The decentralised and modular nature of bioenergy systems provides a unique opportunity for phased-in investment to allow a more regional distribution of wealth and equity in development between rural and urban areas. It also offers new frontiers to facilitate the process of reducing the present large rural-urban energy gap‖ states Oikawa (1995).

There are different ways to extract energy from agricultural production and wastes, such as biogas, combustion, gasification and pyrolysis (Dell et al., 2004). Moreover, petrol is still cheaper than biofuel. A litre of ethanol is around $0.83; while, the cost of petrol at the refinery is around $0.15. Also, due to its lower thermal value, for each litre of petrol, 1.5 litres of ethanol would be needed (Pimentel & Pimentel, 2008). It seems that energy use for cultivation and energy gain of ethanol from some crops, such as corn is very similar; therefore, ethanol fuel from corn in some conditions is an energy loser (Pimentel & Patzek, 2005; Tester, 2005). In addition, some studies show energy output from ethanol fuel is higher than energy input (Shapouri et al., 2004). This difference may be due to different methods of energy input estimation and different farming systems.

There is a consensus that the substantial expansion of bioenergy is a win-win proposition for developed and developing countries alike; it provides opportunities for poverty eradication and for satisfying energy needs in rural and remote regions; it helps generate employment and local economic development opportunities; it helps curb global warming and contributes to the improvement of human health by decreasing air pollution (El.Ashry, 2006; Sims, 2004). However, when 60% of the world‘s population is malnourished and the corn needed to make enough ethanol to fill the tank of a car is enough to feed one person for one year, consuming crops for biofuel instead of food can have negative consequences on human calorific intake. Moreover, deforestation to provide enough land for producing ethanol causes major environmental damage, not only by reducing the global capacity to absorb carbon dioxide, but also by increasing the release of carbon dioxide from the soil. At present, deforestation causes 18% of global green gas emissions. It is important to note that reduction in the growth of food production, in contrast to increases in population growth, creates a serious conflict between energy and food production and decreases the land available for biomass production. This means that the use of biomass, especially grains, as fuel must be limited because food supports essential and diverse needs of human activities. Even the use of crop residues as biofuel considerably reduces soil fertility and carbon stocks on farm soils considerably (Boyle, 2004; Gillingham et al., 2008; Hood et al., 2007; Kitani, 1999; Murphy & Power, 2008; Pimentel & Pimentel, 2008; Pimentel et al., 2009; Sauerbeck, 2001).