but residues throughout the rest of the year are minimal. Biomass facilities that depend significantly on agricultural residues must either be able to adjust output to follow the seasonal variation, or have the capacity to stockpile a significant amount of fuel.
Dry animal manure, which is typically defined as having a moisture content less than 30% w/w, is produced by feedlots and livestock corrals, where the manure is collected and removed only once or twice a year. Manure that is scraped or flushed on a more frequent schedule can also be separated, stacked, and allowed to dry. Dry manure can be composted or can fuel a biomass-to-energy combustion project. Animal manure does have value to farmers as fertilizer, and a biomass-to-energy project would need to compete for the manure. However, the total volume of manure produced in many livestock operations exceeds the amount of fertilizer required for the farmlands and, in some areas/countries, nutrient management plans are beginning to limit the over-fertilization of farmlands. Therefore, although there are competitive uses for the manure and low-cost disposal options at this time, manure disposal is going to become more costly over time, and the demand for alternative disposal options, including biomass-to-energy, will only increase.
Biomass technologies present attractive options for mitigating many of the environmental challenges of manure wastes. The most common biomass technologies for animal manures are combustion, anaerobic digestion, and composting. Moisture content of the manure and the amount of contaminants, such as bedding, determine which technology is most appropriate.
Urban wastes include municipal solid waste that is generated by household and commercial activities and liquid waste or sewage. Most municipal solid waste is currently disposed of in landfill sites. However, the disposal of this waste is a growing problem worldwide. Much of the waste could be used for energy production though incineration and processes. Japan currently incinerates more than 80% of the available municipal solid waste. It is also possible to use the methane produced in landfill sites for energy production.
Urban wood and yard wastes are similar in nature to agricultural residues in many regards. A biomass facility will rarely need to purchase urban wood and yard wastes, and most likely can charge a tipping fee to accept the fuel. Many landfills are already sorting waste material by isolating wood waste. This waste could be diverted to a biomass project, and although the volume currently accepted at the landfills would not be enough on its own to fuel a biomass project, it could be an important supplemental fuel and could provide more value to the community in which the landfill resides through a biomass project than it currently does as daily landfill cover.
Municipal solid wastes are produced and collected each year with the vast majority being disposed of in open fields. The biomass resource in municipal solid waste comprises the putrescible materials, paper and plastic and averages 80% of the total municipal solid waste collected. Municipal solid waste can be converted into energy by direct combustion, or by natural anaerobic digestion in the engineered landfill. At the landfill sites the gas produced by the natural decomposition of municipal solid waste (approximately 50% methane and 50% carbon dioxide) is collected from the stored material and scrubbed and cleaned before feeding into internal combustion engines or gas turbines to generate heat and power. The organic fraction of municipal solid waste can be anaerobically stabilized in a high-rate digester to obtain biogas for electricity or steam generation.
1.4 Energy Supply
Energy supply (energy flow) is the delivery of fuels or transformed fuels to point of consumption and the term potentially encompasses the extraction, transmission, generation distribution, and storage of fuels. This supply of energy can be disrupted by several factors, including imposition of higher energy prices due to action by OPEC (in the case of crude oil) or other cartel, war, political disputes, economic disputes, or physical damage to the energy infrastructure due to terrorism. The security of energy supply is a major concern of national security and energy independence.
1.4.1 Economic Factors
Crude oil economics is, as might be expected if the peak oil theory is true, dominated by the so-called occurrence of the remaining reserves that are to be depleted in the very near future. While there may be varied volatility in the price of crude oil, when there is a belief that the price in the future will be higher than the price for immediate delivery there will be a flurry of economic activity in the form of the purchase of short-term contracts. This, in turn, leads to a so-called equilibrium price level that is invariable higher than the previous price level which can influence producers to defer production activities in anticipation of a rise in price (Fleming, 2000). In actual fact, the price circle is indeed a vicious circle insofar as one arc of the price circle affects the other arcs (of the price circle) leading to what might be called economic anarchy. This anarchy might easily be laid at the feet of the peak oil theorists who base their theory on faulty or uncertain data and speculation. Moreover, the economic principles, which explain how a market economy works, tend to break down when applied to natural resources such as oil. In fact, there are two ways in which the principles of market economics do not apply to crude oil: (i) the current price of oil has virtually no influence on the rate at which it is discovered and (ii) the rules of supply and demand do not always hold, and (iii) a rise in the price of crude oil does not always lead to an increase in production.
While current high oil prices may encourage development and adoption of alternatives to oil, if high oil prices are not sustained, efforts to develop and adopt alternatives may fall by the wayside. The high oil prices and fears of running out of oil in the 1970s and early 1980s encouraged investments in alternative energy sources (including synthetic fuels made from coal and oil shale) but when oil prices decreased, investments in these alternatives became uneconomic. In fact, the development of renewable energy systems needs to be supported by decisive, well-coordinated action by governments, in sustained multi-decade programs. Many oil-consuming nations are moving to alternate fuel development rather than be faced with a destabilizing energy gap.
1.4.2 Geopolitical Factors
The true picture of oil supply may never be known. Difficult as it is because of a variety of factors, reporting data on oil production or oil reserves is a political act (Laherrère, 2001). The United States Securities and Exchange Commission (SEC) obliges the oil companies listed on the US stock market to report only proved reserves and to omit probable reserves that are reported in the rest of the world. This practice of reporting only proved reserves can lead to a strong reserve growth since 90% of the annual reserves oil addition come from revisions of old fields, showing that the assessment of the fields was poorly reported. In fact, reporting of production is not much better and may give a false impression of oil abundance (Simmons, 2000) – technical data do exist and must be included in any peak theory model.
1.4.3 Physical Factors
Crude oil reserves (Speight, 2011a, 2014a) are the estimated quantities of oil that are claimed to be recoverable under existing operating and economic conditions. However, because of reservoir characteristics and the limitations of current recovery technologies only a fraction of this oil can be brought to the surface; it is this producible fraction that is considered to be reserves. Crude oil recovery varies greatly from oil field to oil field based on the character of the field and the operating history as well as in response to changes in technology and economics.
According to current estimates, more than three-quarters of the oil reserves of the world are located in OPEC countries. The bulk of OPEC oil reserves is located in the Middle East, with Saudi Arabia, Iran and Iraq contributing 41.8% to the OPEC total. OPEC member countries have made significant contributions to their reserves in recent years by adopting best practices in the industry. As a result, OPEC proven reserves currently stand at 1214.2 billion barrels (1214.2 x 109 bbls) which represented 71.9% of the total crude oil reserves (BP, 2019).
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