Acronym Key and Definitions
Landfill Gas Renewable Energy
Biogas is produced by processing of various types of organic waste. Digestion carried out by microorganisms creates methane, which can be used as it is locally or upgraded to biogas. The biogas quality is equivalent to natural gas and can be transported over longer distances.
Compressed Natural Gas (CNG)
Compressed natural gas is a fuel that can be used in place of gasoline, diesel fuel and liquefied petroleum gas (LPG). CNG combustion produces fewer undesirable gases than the aforementioned fuels. In comparison to other fuels, natural gas poses less of a threat in the event of a spill because it is lighter than air and disperses quickly when released. CNG is made by compressing natural gas, which is mainly composed of methane (CH4), to less than 1% of the volume it occupies at standard atmospheric pressure. It can be stored and distributed in hard containers at a pressure of 20–25 MPa (2,900–3,600 psi), usually in cylindrical or spherical shapes.
Global Warming Potential (GWP)
Greenhouse gases (GHGs) warm the Earth by absorbing energy and slowing the rate at which the energy escapes to space. They act like a blanket insulating the Earth. Different GHGs can have different effects on the Earth's warming. Two key ways in which these gases differ from each other are their ability to absorb energy (radiative efficiency) and their lifetime in the atmosphere. The Global Warming Potential (GWP) was developed to allow comparisons of the global warming impacts of different gases. Specifically, it is a measure of how much energy the emissions of one ton of a gas will absorb over a given period of time, relative to the emissions of one ton of carbon dioxide (CO2). The larger the GWP, the more that a given gas warms the Earth compared to CO2 over that time period. The time period usually used for GWPs is 100 years. GWP provides a common unit of measure, which allows analysts to add up emissions estimates of different gases and allows policymakers to compare emissions reduction opportunities across sectors and gases.
• CO2, by definition, has a GWP of one regardless of the time period used because it is the gas being used as the reference. CO2 remains in the climate system for a very long time: CO2 emissions cause increases in atmospheric concentrations of CO2 that will last thousands of years.
• Methane (CH4) is estimated to have a GWP of 28–36 over 100 years. CH4 emitted today lasts about a decade on average, which is much less time than CO2. But CH4 also absorbs much more energy than CO2. The net effect of the shorter lifetime and higher energy absorption is reflected in the GWP. The CH4 GWP also accounts for some indirect effects, such as the fact that CH4 is a precursor to ozone and ozone is itself a GHG.
A kilowatt (kW) is 1,000 watts of energy. A kilowatt-hour (kWh) is a unit that measures electrical energy used over a period of time. For example, if you use a 2,300 watt oven, it would be using 2.3 kWh for every hour it is running.
Methane is a chemical compound with the chemical formula CH4 (one atom of carbon and four atoms of hydrogen) and is the main constituent of natural gas. The relative abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it poses technical challenges due to its gaseous state under normal temperature and pressure conditions.
Metric Tons of Carbon Dioxide Equivalent (MTCO2e)
The measurement of greenhouse gasses (in metric tons) that have been saved from entering our atmosphere. Each type of greenhouse gas has been standardized based on its atmospheric impact and global warming potential (GWP) to be represented as a unit of carbon dioxide equivalent (CO2e). For example, saving the atmosphere from one metric ton of methane would be equivalent to roughly 25 metric tons of carbon dioxide.
Million British Thermal Units (MBTU)
A standard unit of measurement used to denote both the amount of heat energy in fuels and the ability of appliances and air conditioning systems to produce heating or cooling. A BTU is the amount of heat required to increase the temperature of 16 ounces of water by one degree Fahrenheit. Since BTUs are measurements of energy consumption, they can be converted directly to kilowatt-hours (3412 BTUs =1 kWh) or joules (1 BTU =1,055.06 joules). A wooden kitchen match produce approximately 1 BTU and household air conditioners typically produce between 5,000 and 15,000 BTU. MBTU stands for one million BTUs. MBTU is occasionally used as a standard unit of measurement for natural gas and provides a convenient basis for comparing the energy content of various grades of natural gas and other fuels. One cubic foot of natural gas produces approximately 1,000 BTUs or 1 MBTU.
Biogas and landfill gas can contain one or more species of siloxanes depending on the organic feedstock used to produce biogas in the landfill. When biogas containing siloxanes is combusted in gas turbines, boilers or combustion engines, deposits of solid silica will adhere to cylinder heads, pistons, turbine blades, and heat exchanger surfaces, causing wear, imbalance, fouling, and other serious problems. Siloxane removal from biogas is imperative to guarantee a consistent performance of frequently used machinery.
Standard Cubic Feet per Minute (SCFM)
Standard cubic feet per minute measures the flow rate of gas under standard pressure and temperature conditions. The accepted standards of temperature and pressure are 68 degrees Fahrenheit and 36 percent humidity at sea level.
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