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  • Writer's pictureHydroPhos Team

The Connection between Eutrophication and Greenhouse Gas Emissions

Greenhouse gas (GHG) reductions play a critical role in climate change mitigation and adaptation strategies. While carbon gets most of the attention, it is important to understand the impact of all GHGs. These gases, including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), are central to  Earth's climate system, as they trap heat and contribute to the greenhouse effect. In this article, we will delve into the the scopes and sources of GHGs, with a specific focus on the connection between methane emissions and the environmentally destructive algal blooms known as eutrophication. 

Scopes of Greenhouse Gases

To comprehensively understand GHGs and how emissions are calculated, it's important to consider their scopes. Organizations calculating their GHG footprint can decide which scopes to track depending on the data available and their emissions reductions goals. GHGs are categorized into three distinct scopes based on emission sources and implications:

Scope 1 GHGs: These are direct emissions produced by an entity. They include emissions from combustion processes, on-site transportation, and other activities under the control of the organization. Think about the emissions coming directly from an organization’s chimney. 

Scope 2 GHGs: Scope 2 emissions are indirect emissions associated with utilities - the generation of electricity, heat, or steam that an organization consumes. These emissions are typically linked to the use of fossil fuels. Scope 2 emissions reductions include using cleaner energy sources and increasing energy efficiency. 

Scope 3 GHGs: Scope 3 emissions are indirect emissions that occur along the entire value chain of an organization from mining to manufacturing to disposal. Examples of scope 3 emissions include activities such as raw material extraction, product distribution, and end-use of products as well as business travel, employee commuting, and investments. This scope is often the most challenging to address but can also have the most significant environmental impact. For many industries - such as financial services -  scope 3 emissions are the bulk of their GHG footprint.  

Types and Sources of Greenhouse Gas Emissions

       EPA 2021

GHGs come in various forms, with each contributing differently to the greenhouse effect. The primary GHGs include:

Carbon Dioxide (CO2): Carbon dioxide is the most abundant GHG -  contributing to 79.4% of emissions  - and is primarily released through the burning of fossil fuels in energy production (i.e coal, oil, natural gas, etc.), combustion of gas and diesel in transportation, deforestation, and other land-use changes. CO2 emissions are the leading driver of man-made climate change

Methane (CH4): Methane makes up 11.5% of total emissions but has roughly 80 times the heat trapping potential of carbon for the first 20 years it’s in the atmosphere. It is released from various sources, including livestock digestion, rice paddies, natural gas production, landfills, and eutrophication. The impact of methane emissions is particularly concerning due to its high warming potential. Given its warming potential and shorter lifespan in the atmosphere, reducing methane emissions is the fastest opportunity to slow global warming

Nitrous Oxide (N2O): Nitrous oxide is emitted from agricultural practices, industrial activities such as chemical manufacturing and cement production, and the combustion of fossil fuels. At 6.2% of emissions, N2O is less abundant than CO2 or CH4, but it is a potent greenhouse gas with 265 times the warming power of CO2.

Methane Emissions and Eutrophication

Now, with a base understanding of GHGs and the role they play in climate change, we will look more closely at the role of eutrophication in methane emissions. Eutrophication occurs when excessive nutrients, such as nitrogen and phosphorus, enter bodies of water, leading to increased algal growth. This excessive algal growth can have several detrimental effects including oxygen depletion leading to “dead zones” in aquatic ecosystems, harmful algal blooms, toxins released that pose risk to aquatic and human health, and general biodiversity loss. 

In addition to these negative impacts, eutrophication also produces methane emissions. According to ScienceDaily, eutrophication in our lakes and rivers will increase the emission of methane into the atmosphere by 30 to 90 percent during the next 100 years. To provide some context for the impact of this increase, it is equivalent to 18-33 percent of annual carbon dioxide emissions from burning fossil fuels. There are also significant costs associated with these emissions; an estimated present value of global climate change costs from eutrophication-caused methane emissions for 2015–2050 range from $7.5 to 81 trillion. Reducing eutrophication and the associated methane emissions would require decreasing nutrient runoff at the sources. This ties back to the importance of the 3 scopes of emissions; entities being held accountable for all scopes of their emissions could lead to a more accurate calculation and subsequent reduction in the sources of eutrophication. 


GHGs are a critical factor in the complex web of environmental challenges facing our planet. Understanding the different scopes, types, and sources of GHG emissions is essential for designing effective strategies to combat climate change. Additionally, recognizing eutrophication as a significant source of methane emissions highlights the importance of reducing nutrient runoff that leads to these harmful algal blooms. As we work toward a sustainable future, reducing the sources of GHG emissions and mitigating their impact will be paramount for preserving the health of our planet and the well-being of future generations.

More information 

More information on GHGs can be found here

More information on methane can be found here


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