What are Anthropogenic Methane Emissions?
Anthropogenic methane emissions refer to the release of methane caused by human activities, such as livestock farming, landfills, natural gas production, and oil extraction. Livestock farming and landfills are considered renewable methane sources, as their methane emissions result from the breakdown of organic materials. On the other hand, natural gas production and oil extraction are categorized as non-renewable methane sources, as the methane is extracted from ancient deposits of fossil fuels.
Anthropogenic methane is released into our atmosphere as a direct result of human activity, so efforts to capture and utilize this methane are one potential solution. The benefits extend beyond simply removing an extremely potent gas, however. Captured methane is also a dense energy source.
Tapping into the Hidden Potential of Landfills
As organic waste decomposes in landfills, it releases methane and other gases, commonly called landfill gas or biogas. While some of this gas inevitably escapes into the atmosphere, a significant amount can be captured through specially designed systems installed at the landfill site. This gas can be sold for use as heat or fuel or be converted and sold on the energy market as renewable "green" power.
Not only does capturing landfill gas help to reduce the amount of methane entering the atmosphere, but it also presents a financial opportunity for many municipalities. The cost of buying and installing the necessary equipment for a gas capture system is often offset by income generated from selling captured methane, meaning that local governments can return a profit.
The capture of landfill gas (LFG) offers significant benefits to local communities even beyond job creation. About one percent of landfill gas contains organic or inorganic compounds that emit unpleasant odors. Moreover, certain compounds in LFG can react with sunlight and contribute to the formation of ground-level ozone, also known as smog. Additionally, uncontrolled LFG has been found to contain nearly 30 organic hazardous air pollutants, including benzene, toluene, ethyl benzene, and vinyl chloride. These pollutants pose significant health risks to nearby communities.
When LFG is utilized as a source of energy, the harmful pollutants undergo degradation, resulting in the formation of water vapor, CO2, and other less hazardous compounds. This positive impact on air quality is a significant ancillary advantage in pursuing economic sustainability in waste management.
Harnessing Energy from Waste
A well-designed gas collection system is central to harnessing methane emissions. It consists of a network of extraction wells strategically drilled into the landfill and connected via a series of pipes. These wells are carefully placed around the landfill, accounting for waste composition and the size of the landfill. By installing impermeable liners to isolate landfill cells and create a vacuum-like effect, methane gas generated from the decomposing organic waste is drawn up from these wells with pumps.
The system is equipped with a blower or compressor to enhance gas extraction. It also incorporates condensate knockout tanks to eliminate moisture and a flare or energy recovery system to burn or harness the captured methane gas. This captured methane can then be converted into electricity or heat, marketed as renewable natural gas, or flared to minimize any negative impacts.
Tackling Methane: A Sustainable Approach to Agriculture and Livestock Farming
Agricultural and Livestock Biogas
Agriculture and livestock farming contributes significantly to methane emissions, primarily through enteric fermentation in ruminant animals and the decomposition of organic waste. According to the Environmental Protection Agency (EPA), our livestock and agricultural practices directly account for 37% of methane emissions resulting from human activity.
Ruminant animals, such as cows, sheep, and goats, possess a unique digestive system that produces biogas as a byproduct. When these animals belch or release gases, they emit this potent gas into the air.
However, despite the outcry over the burden of "cow burps," it's important to note that animals are not the sole source of agricultural methane. For example, rice cultivation contributes another 8% of methane emissions to the atmosphere, most of which comes from flooded paddies.
Still, manure and other organic waste from livestock is the most significant producer of agricultural and livestock emissions.
Manure collected from livestock operations is collected and placed in sealed tanks called anaerobic digesters, or in liquid form, in wastewater ponds or lagoons. Ponds and lagoons can be equipped with covers that trap methane, much like landfills. As the organic matter breaks down, it produces biogas consisting of about 60% methane, with the balance comprising CO2, water vapor, and other gases.
The captured biogas is processed and converted into methane. This renewable energy source can be used for heat, electricity, or even as vehicle fuel, creating a win-win situation where farmers can efficiently manage waste while generating valuable energy.
Methane Capture in Fossil Fuel Extraction
While agriculture remains the primary contributor to anthropogenic methane emissions, fossil fuel extraction runs a close second. The extraction, transportation, and processing of non-renewable fossil fuels - including coal, oil, and natural gas - account for approximately 30% of global methane emissions. However, unlike renewable sources, such as biogenic methane, this originates from fossil fuels and is not currently being generated. Instead, it is released through venting, leakage, or flaring during oil and gas extraction.
Coal mining, in particular, releases substantial amounts of methane trapped within coal seams and surrounding rock strata. The escape of this gas is not only a waste of a potentially valuable energy resource but also poses a significant safety hazard.
Capturing methane during fossil fuel extraction is critical to reducing greenhouse gas loads and combating climate change. In the oil and gas industry, methane has traditionally been released as a waste product by burning it off or gas flaring. However, technological advancements allow us to harness and convert this waste product into usable energy. Captured methane can generate electricity, providing an additional source revenue stream for the industry and contributing to sustainable energy practices. This process reduces methane released into the atmosphere and maximizes the utility of extracted fossil fuels.
The Remarkable Effectiveness of Methane Capture
The effectiveness of methane capture varies based on the technology used and the source of the emissions. For example, closed and engineered landfills can capture 85% or more of their methane.
Similarly, methane capture from agricultural and livestock sources can be highly effective with proper management and equipment. Anaerobic digesters, for example, have been reported to capture around 60-80% of the methane produced from manure
Methane capture represents a potent solution to the rising demand for renewable energy sources. Its implementation in landfills, farms, and other methane-producing sectors showcases its versatility and potential for wide-scale application. And, more technological innovation is needed to enhance methane capture systems' efficiency and economic viability.
