When these wastes are improperly managed, they pose a significant risk to the environment and public health. Pathogens, chemicals, antibiotics, and nutrients present in wastes can contaminate surface and ground waters through runoff or by leaching into soils. Excess nutrients cause algal blooms, harm wildlife, and infect drinking water. Drinking water with high levels of nitrates is linked to hyperthyroidism and blue-baby syndrome.
Municipal water utilities treat drinking water to remove nitrates, but it is costly to do so. Organic wastes also generate large amounts of methane as they decompose. Methane is a powerful greenhouse gas that traps heat in the atmosphere more efficiently than carbon dioxide. Given equal amounts of methane and carbon dioxide, methane will absorb 86 times more heat in 20 years than carbon dioxide.
To reduce greenhouse gas emissions and the risk of pollution to waterways, organic waste can be removed and used to produce biogas, a renewable source of energy. When displacing fossil fuels, biogas creates further emission reductions, sometimes resulting in carbon negative systems.
Despite the numerous potential benefits of organic waste utilization, including environmental protection, investment and job creation, the United States currently only has 2, operating biogas systems, representing less than 20 percent of the total potential. Biogas is produced after organic materials plant and animal products are broken down by bacteria in an oxygen-free environment, a process called anaerobic digestion.
Biogas systems use anaerobic digestion to recycle these organic materials, turning them into biogas, which contains both energy gas , and valuable soil products liquids and solids. Anaerobic digestion already occurs in nature, landfills, and some livestock manure management systems, but can be optimized, controlled, and contained using an anaerobic digester. Biogas contains roughly percent methane, percent carbon dioxide, and trace amounts of other gases.
The liquid and solid digested material, called digestate, is frequently used as a soil amendment. Some organic wastes are more difficult to break down in a digester than others. Food waste, fats, oils, and greases are the easiest organic wastes to break down, while livestock waste tends to be the most difficult. Mixing multiple wastes in the same digester, referred to as co-digestion, can help increase biogas yields.
Warmer digesters, typically kept between 30 to 38 degrees Celsius Fahrenheit , can also help wastes break down more quickly. After biogas is captured, it can produce heat and electricity for use in engines, microturbines, and fuel cells.
Biogas can also be upgraded into biomethane, also called renewable natural gas or RNG, and injected into natural gas pipelines or used as a vehicle fuel. The United States currently has 2, operating biogas systems across all 50 states, and has the potential to add over 13, new systems. Stored biogas can provide a clean, renewable, and reliable source of baseload power in place of coal or natural gas.
Baseload power is consistently produced to meet minimum power demands; renewable baseload power can complement more intermittent renewables. Similar to natural gas, biogas can also be used as a source of peak power that can be rapidly ramped up. Using stored biogas limits the amount of methane released into the atmosphere and reduces dependence on fossil fuels. The reduction of methane emissions derived from tapping all the potential biogas in the United States would be equal to the annual emissions of , to 11 million passenger vehicles.
Please click here to see any active alerts. As of September , there are operational LFG energy projects in the United States and landfills that are good candidates for projects. Landfill gas LFG is a natural byproduct of the decomposition of organic material in landfills. LFG is composed of roughly 50 percent methane the primary component of natural gas , 50 percent carbon dioxide CO 2 and a small amount of non-methane organic compounds. Methane is a potent greenhouse gas 28 to 36 times more effective than CO 2 at trapping heat in the atmosphere over a year period, per the latest Intergovernmental Panel on Climate Change IPCC assessment report AR5.
Learn more about methane emissions in the United States. Municipal solid waste MSW landfills are the third-largest source of human-related methane emissions in the United States, accounting for approximately The methane emissions from MSW landfills in were approximately equivalent to the greenhouse gas GHG emissions from more than At the same time, methane emissions from MSW landfills represent a lost opportunity to capture and use a significant energy resource.
When MSW is first deposited in a landfill, it undergoes an aerobic with oxygen decomposition stage when little methane is generated.
Then, typically within less than 1 year, anaerobic conditions are established and methane-producing bacteria begin to decompose the waste and generate methane. The following diagram illustrates the changes in typical LFG composition after waste placement. Bacteria decompose landfill waste in four phases. Gas composition changes with each phase and waste in a landfill may be undergoing several phases of decomposition at once.
The time after placement scale total time and phase duration varies with landfill conditions. Chapter 2: Landfill Gas Basics. Figure , pp. Biogas can be produced from various raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste while LFG is the product of anaerobic degradation of the organic fraction of solid urban waste within a Landfill.
These gases are primarily methane CH4 and carbon dioxide CO2 — both of which are greenhouse gases — and may have small amounts of hydrogen sulphide H2S , moisture and other volatile organic compounds VOCs. Capturing biogas and LFG avoids the release into the atmosphere of environmental-harmful compounds. In terms of global warming potential, methane is over 25 times more detrimental to the atmosphere than carbon dioxide.
Landfills are esteemed to be the third largest source of methane in the US. Thus, a landfill can essentially act as a large biogas plant. An added benefit to landfills is the mix of bio waste that is found there. Studies reveal that mixing different types of bio waste speeds up the anaerobic process and increases green gas production levels. It will come as no surprise to you that a major part of human waste is methane gas.
For this reason, wastewater treatment facilities also offer a surprising opportunity for green gas development as, much like landfills, wastewater treatment facilities are already part of our current infrastructure. While most wastewater treatment facilities already capture green gas , many do not have the infrastructure in place to correctly use it and sadly decide to simply burn it.
As you have already heard, green gas is largely methane-based. However, some other gases do appear in trace amounts. Green gas or biogas are the blanket terms used to describe any gas made from organic waste.
However, green gas is not pure enough to be used in all instances due to the high amounts of CO2 it contains. In other words, biomethane is the purer form of green gas which means it has reached the same level of purity as natural gas from fossil fuels. Raw biogas, or the green gas that is produced before being refined to create biomethane, can be burned in a boiler and used to heat buildings.
Likewise, green gas is often reutilised at the biogas plant to power the operations and the biogas digester. Green gas can also be converted into electricity through a combustion engine, turbine or fuel cell and sent back to the electricity grid. If green gas is refined or upgraded to biomethane , It can also be used as an exact replacement for natural gas or liquid propane gas LPG and sent to homes to be used for cooking and heating.
In some places, it can also be compressed and used as fuel to power automobiles, such as hybrid cars. For one, green gas is less harmful to the environment as it helps deal with the problem of properly disposing of, and recycling , organic waste. Green gas is also a renewable and sustainable resource that will always be around as long as living organisms exist, meaning it is a good tool for fighting climate change. While green gas still emits CO2 into the atmosphere, it emits considerably less than natural gas making it more ecological.
Green gas can also easily be substituted for fossil fuels , versus other forms of renewable energy, as it can be used on existing infrastructure , such as the natural gas grid.
Find an offer that best suits your needs! Call Selectra and our energy experts will help answer all your questions. The UK is home to many green gas plants or anaerobic digestion plants.
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